I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
phil
:Hello folks,
:I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
:
:This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
:
:
VDC and drops to 90 volts in about two minutes. Sounds like a bad resistor to me, so I replaced R35 and R36 with little change.
To clarify, while the plate voltage drops, the filter cap voltage remains at 277 VDC.
:what voltage do you have at the + side of 11a,the 8mfd cap?
:phil
:
::Hello folks,
::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
::
::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
::
::
this issue shouldn't affect reception,do you kave another tube to sub?
phil
:Phil, I get 277 on the plus side of that cap. The tube plate gets 201
:VDC and drops to 90 volts in about two minutes. Sounds like a bad resistor to me, so I replaced R35 and R36 with little change.
:
:To clarify, while the plate voltage drops, the filter cap voltage remains at 277 VDC.
:
::what voltage do you have at the + side of 11a,the 8mfd cap?
::phil
::
:::Hello folks,
:::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
:::
:::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
:::
:::
:just to make sure,you replaced the coupling cap at the plate?
:this issue shouldn't affect reception,do you kave another tube to sub?
:phil
:
::Phil, I get 277 on the plus side of that cap. The tube plate gets 201
::VDC and drops to 90 volts in about two minutes. Sounds like a bad resistor to me, so I replaced R35 and R36 with little change.
::
::To clarify, while the plate voltage drops, the filter cap voltage remains at 277 VDC.
::
:::what voltage do you have at the + side of 11a,the 8mfd cap?
:::phil
:::
::::Hello folks,
::::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
::::
::::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
::::
::::
:Hello folks,
:I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
:
:This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
:
:
: Wade, the only component between the B+ and plate of 6K5 is the 99K resistor. The .015 mfd cap (C34)if leaky or shorted would pull that voltage down. If resistor correct value and cap and tube OK, something is mis-wired. One side of 99K (R36) to tube socket pin 3 and the other side to + on 8 mfd (C11 A)or downstream terminal of field coil or terminal stripe (block) that white wire to speaker goes to or any combination thereof. PL
:
:
::Hello folks,
::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
::
::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
::
::
:I checked the arrangement of those components and they are all as they should be. I'll check and see if maybe the cap I put in to replace c34 was just a bad sub. I just noticed: both the field coil and audio transformer are replacements. Both have impedances higher than on the schematic: field coil at 1300 ohms and transformer primary at 500 ohms. Shouldn't be a problem, shouldn't it?
:
:: Wade, the only component between the B+ and plate of 6K5 is the 99K resistor. The .015 mfd cap (C34)if leaky or shorted would pull that voltage down. If resistor correct value and cap and tube OK, something is mis-wired. One side of 99K (R36) to tube socket pin 3 and the other side to + on 8 mfd (C11 A)or downstream terminal of field coil or terminal stripe (block) that white wire to speaker goes to or any combination thereof. PL
::
::
:::Hello folks,
:::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
:::
:::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
:::
:::
phil
: Wade, if the voltages are at or close tyo those called for the resistance of the field coil and transformer not critical. Your field coil is only 160 ohms over the schematic value. Primary is puzzling, schematic calls for 5 Ohms? Again, are voltages correct? PL
:
:
::I checked the arrangement of those components and they are all as they should be. I'll check and see if maybe the cap I put in to replace c34 was just a bad sub. I just noticed: both the field coil and audio transformer are replacements. Both have impedances higher than on the schematic: field coil at 1300 ohms and transformer primary at 500 ohms. Shouldn't be a problem, shouldn't it?
::
::: Wade, the only component between the B+ and plate of 6K5 is the 99K resistor. The .015 mfd cap (C34)if leaky or shorted would pull that voltage down. If resistor correct value and cap and tube OK, something is mis-wired. One side of 99K (R36) to tube socket pin 3 and the other side to + on 8 mfd (C11 A)or downstream terminal of field coil or terminal stripe (block) that white wire to speaker goes to or any combination thereof. PL
:::
:::
::::Hello folks,
::::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
::::
::::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
::::
::::
You've given me quite a bit to go on here. The wire run from that 99k resistor to the plate is a very long one-from literally one side of the chassis to the other. This nine inch piece of wire is only visible for maybe half of its length as it disappears behind a baffle along the front of the radio. Quite a bit could be happening with this connection. I will also check for cold solder joints and other sloppiness as well. Perhaps most importantly, I will monitor voltage on both sides of that 99k resistor during warmup.
I mentioned in the first post that this is a Radiobar. I've seen quite a few examples of these, but never one with the large dial of a 38-7. Has anyone ever seen an instance where this chassis was used by Radiobar?
:does the voltage drop on the low side of the 99k resistor? can you monitor voltage there on warmup and see it drop like the plate voltage?
:phil
:
:: Wade, if the voltages are at or close tyo those called for the resistance of the field coil and transformer not critical. Your field coil is only 160 ohms over the schematic value. Primary is puzzling, schematic calls for 5 Ohms? Again, are voltages correct? PL
::
::
:::I checked the arrangement of those components and they are all as they should be. I'll check and see if maybe the cap I put in to replace c34 was just a bad sub. I just noticed: both the field coil and audio transformer are replacements. Both have impedances higher than on the schematic: field coil at 1300 ohms and transformer primary at 500 ohms. Shouldn't be a problem, shouldn't it?
:::
:::: Wade, the only component between the B+ and plate of 6K5 is the 99K resistor. The .015 mfd cap (C34)if leaky or shorted would pull that voltage down. If resistor correct value and cap and tube OK, something is mis-wired. One side of 99K (R36) to tube socket pin 3 and the other side to + on 8 mfd (C11 A)or downstream terminal of field coil or terminal stripe (block) that white wire to speaker goes to or any combination thereof. PL
::::
::::
:::::Hello folks,
:::::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
:::::
:::::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
:::::
:::::
Bill
: Wade, if the voltages are at or close tyo those called for the resistance of the field coil and transformer not critical. Your field coil is only 160 ohms over the schematic value. Primary is puzzling, schematic calls for 5 Ohms? Again, are voltages correct? PL
:
:
::I checked the arrangement of those components and they are all as they should be. I'll check and see if maybe the cap I put in to replace c34 was just a bad sub. I just noticed: both the field coil and audio transformer are replacements. Both have impedances higher than on the schematic: field coil at 1300 ohms and transformer primary at 500 ohms. Shouldn't be a problem, shouldn't it?
::
::: Wade, the only component between the B+ and plate of 6K5 is the 99K resistor. The .015 mfd cap (C34)if leaky or shorted would pull that voltage down. If resistor correct value and cap and tube OK, something is mis-wired. One side of 99K (R36) to tube socket pin 3 and the other side to + on 8 mfd (C11 A)or downstream terminal of field coil or terminal stripe (block) that white wire to speaker goes to or any combination thereof. PL
:::
:::
::::Hello folks,
::::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
::::
::::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
::::
::::
:There's nothing wrong with the power transformer primary reading 5 ohms. Wade you got the wrong resistor value for R36 or a big glob of soder or additional resistance between field coil and plate. The field coil at 1300 ohms resistance (that's not impedance)wouldn't make that much difference in plate voltage.
:Bill
:
:: Wade, if the voltages are at or close tyo those called for the resistance of the field coil and transformer not critical. Your field coil is only 160 ohms over the schematic value. Primary is puzzling, schematic calls for 5 Ohms? Again, are voltages correct? PL
::
::
:::I checked the arrangement of those components and they are all as they should be. I'll check and see if maybe the cap I put in to replace c34 was just a bad sub. I just noticed: both the field coil and audio transformer are replacements. Both have impedances higher than on the schematic: field coil at 1300 ohms and transformer primary at 500 ohms. Shouldn't be a problem, shouldn't it?
:::
:::: Wade, the only component between the B+ and plate of 6K5 is the 99K resistor. The .015 mfd cap (C34)if leaky or shorted would pull that voltage down. If resistor correct value and cap and tube OK, something is mis-wired. One side of 99K (R36) to tube socket pin 3 and the other side to + on 8 mfd (C11 A)or downstream terminal of field coil or terminal stripe (block) that white wire to speaker goes to or any combination thereof. PL
::::
::::
:::::Hello folks,
:::::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
:::::
:::::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
:::::
:::::
Bill
Update: Checked voltage on that 99k resistor: it holds fine on the power supply side (staying at 200 some volts) but on the side it shares with that coupling cap is where the voltage is falling off. All connections look fine-I redid them anyway in the event of cold solder joints with no change-I guess that coupling cap is leaky...
:
::There's nothing wrong with the power transformer primary reading 5 ohms. Wade you got the wrong resistor value for R36 or a big glob of soder or additional resistance between field coil and plate. The field coil at 1300 ohms resistance (that's not impedance)wouldn't make that much difference in plate voltage.
::Bill
::
::: Wade, if the voltages are at or close tyo those called for the resistance of the field coil and transformer not critical. Your field coil is only 160 ohms over the schematic value. Primary is puzzling, schematic calls for 5 Ohms? Again, are voltages correct? PL
:::
:::
::::I checked the arrangement of those components and they are all as they should be. I'll check and see if maybe the cap I put in to replace c34 was just a bad sub. I just noticed: both the field coil and audio transformer are replacements. Both have impedances higher than on the schematic: field coil at 1300 ohms and transformer primary at 500 ohms. Shouldn't be a problem, shouldn't it?
::::
::::: Wade, the only component between the B+ and plate of 6K5 is the 99K resistor. The .015 mfd cap (C34)if leaky or shorted would pull that voltage down. If resistor correct value and cap and tube OK, something is mis-wired. One side of 99K (R36) to tube socket pin 3 and the other side to + on 8 mfd (C11 A)or downstream terminal of field coil or terminal stripe (block) that white wire to speaker goes to or any combination thereof. PL
:::::
:::::
::::::Hello folks,
::::::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
::::::
::::::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
::::::
::::::
Oh, I don't have my notes right with me, but the voltage on pin 5 of 6f6 was a little higher than per the schematic, but only by about ten volts. The voltage at that pin also stays steady as 6k5 loses plate voltage.
:Wade, you can check cap 34, or just replace it, but for information, what's the voltage reading on pin 5 of the 6F6. And what's the color code on your 99k resistor.
:Bill
:
:Update: Checked voltage on that 99k resistor: it holds fine on the power supply side (staying at 200 some volts) but on the side it shares with that coupling cap is where the voltage is falling off. All connections look fine-I redid them anyway in the event of cold solder joints with no change-I guess that coupling cap is leaky...
::
:::There's nothing wrong with the power transformer primary reading 5 ohms. Wade you got the wrong resistor value for R36 or a big glob of soder or additional resistance between field coil and plate. The field coil at 1300 ohms resistance (that's not impedance)wouldn't make that much difference in plate voltage.
:::Bill
:::
:::: Wade, if the voltages are at or close tyo those called for the resistance of the field coil and transformer not critical. Your field coil is only 160 ohms over the schematic value. Primary is puzzling, schematic calls for 5 Ohms? Again, are voltages correct? PL
::::
::::
:::::I checked the arrangement of those components and they are all as they should be. I'll check and see if maybe the cap I put in to replace c34 was just a bad sub. I just noticed: both the field coil and audio transformer are replacements. Both have impedances higher than on the schematic: field coil at 1300 ohms and transformer primary at 500 ohms. Shouldn't be a problem, shouldn't it?
:::::
:::::: Wade, the only component between the B+ and plate of 6K5 is the 99K resistor. The .015 mfd cap (C34)if leaky or shorted would pull that voltage down. If resistor correct value and cap and tube OK, something is mis-wired. One side of 99K (R36) to tube socket pin 3 and the other side to + on 8 mfd (C11 A)or downstream terminal of field coil or terminal stripe (block) that white wire to speaker goes to or any combination thereof. PL
::::::
::::::
:::::::Hello folks,
:::::::I just finished up a restoration on my Philco Radiobar cabinet and I have the radio working as well. But as you can tell by the title, my plate voltage is still low.
:::::::
:::::::This is a philco 38-7 chassis, I have replaced every paper and electrolytic capacitor as well as some of the resistors that were reading off target. However, when powered up, the radio receives poorly and plays quietly. Checking voltages, I have found every one of them consistent with the schematic save for one-the plate voltage on the 6k5 tube is reading too low- at about seventy volts. I replaced the 99k resistor by that pin and voltage climbed to 90 volts. But this is still about half of what it should be. Any other components seem suspect to anyone?
:::::::
:::::::
I next hooked up the cap, tube plate still disconnected. 190VDC held. I removed the old wire leading to the tube plate and replaced it. Voltage held up until I hooked it back up to the plate. Then it dropped down to 90vdc.
So would a worn out tube be cause for this low B+? I tested it and it rated highly. Hmmm.....
Looking at the involved plate circuitry of the 6K5 1st audio, and then consulting the markup supplied, how's about these confirmations?
The first consideration that can be cleared would be the probability that you are using a high-Z metering
for measurements and not loading down the 6K5 plate circuitry whilst taking the plate voltage reading,
albeit the fact that this application is using a quite low 99k plate load vice the common 1/2 meg or so + , being found in other situations.
The markups associative routings are:
[RED] for the sub B+ buss feeding just the particular circuitry area of interest.
[GREEN] for the negative 1st grid biasing of the AF output stage.
[BLUE-GREEN] for the 1st grid biasing of the 1st audio tube.
I would consider these aspects as a possibility for that plate voltage not being up to the voltage that you have found being stated as being the proper level.
Just on that plate circuitry, there is merely the possibility if the 99,000 res upping in value (appreciably !)
which, I think that you have probably already cleared . Next would be voltage leakage off through cap #34,
lift its right connection from the circuitry and see if the 6K5 plate voltage goes up.
To further confirm that #C34 capacitor, lift the right side of the cap from circuitry and clip on the DC metering of a DVM . . ( inherently Hi Z.). .and power up the set to then get B+ up and see if there is + voltage reading on the meter.
To speed up the inconvenience of the initial onset charge effect, short out the metering junction to chassis ground and see if anything greater than ~50 mvDC then builds back up as a reading. If so, look for a better capacitor to replace C34 with.
The next aspect of analysis would be to confirm that the low B+ on the plate is merely due to that tube conducting more and thus pulling down that plate voltage by virtue of the 1st grid circuitry not having a high enough negative voltage biasing; which is being supplied up from the [Blue -green ] buss from its derivation via the technique of the floating of the HV centertap of the up from ground through the tri-series 35-8-202 ohm resistances of #43.
That will result in the highest negative level being derived for the [Green] buss feeding the AF output and then the next level, (unhighted). . . . due to it not being of interest, as being a negative counterpoise for the AVC of the system in order to get a wider overall dynamic AVC swing.
Then finally, your node of the 35-8 ohm resistors of #43 will be the sourcing of the negative voltage going up the [Blue-green] buss and initially into a 1 meg dropping resistor #33 and then a bit of decoupling via the .1 ufd cap #30, just past that resistor and then the coupling into a second 1 meg resistor #R31, then, just above that is the point of the DC isolated introduction of the sets AC audio info thru .015 ufd cap #28.
Probably already confirmed but error of either of those resistors values could cause decreased - biasing to the
6K5 and increased plate current consumption / the dropping of the plate voltage.
Then one needs to give like consideration of the assurance of no leakage on those # C28-C30, such as was just afforded to the testing of # C34.
Considering that C34 and R36 passed specs, a quick test for a grid biasing error or grid emission fault on the 6K5 tube could be effected by the following test:
Power up the set and DC monitor the 6K5 plate via DVM and then take a clip lead and short the 6K5's 1st grid cap to chassis ground. The 6K5 plate voltage should go up to almost what one DC meters at the B+ supply side of R36.
Lastly, are we considering that the three sections of the PWR resistor # R43 are within tolerance ?
Standing by:
Markup Schematic Referencing:
73's de Edd
After all that, I tried shorting the 6k5 grid clip to chassis ground while observing B+. There was no change. As I wasn't too sure on what to do, this test was done with the grid clip removed from the tube and while still attached to the tube. Neither configuration changed anything.
I did go back and check the rest of the pin voltages given by the schematic, and none were affected by my work. Luckily, they are per the schematic, so that is a good thing. So, anywhere else we can go with this one?
:
:
:
:
:
:
:
:Looking at the involved plate circuitry of the 6K5 1st audio, and then consulting the markup supplied, how's about these confirmations?
:
:The first consideration that can be cleared would be the probability that you are using a high-Z metering
:for measurements and not loading down the 6K5 plate circuitry whilst taking the plate voltage reading,
:albeit the fact that this application is using a quite low 99k plate load vice the common 1/2 meg or so + , being found in other situations.
:
:
:
:The markups associative routings are:
:
:
:[RED] for the sub B+ buss feeding just the particular circuitry area of interest.
:
:[GREEN] for the negative 1st grid biasing of the AF output stage.
:
:[BLUE-GREEN] for the 1st grid biasing of the 1st audio tube.
:
:
:
:
:I would consider these aspects as a possibility for that plate voltage not being up to the voltage that you have found being stated as being the proper level.
:
:Just on that plate circuitry, there is merely the possibility if the 99,000 res upping in value (appreciably !)
:which, I think that you have probably already cleared . Next would be voltage leakage off through cap #34,
:lift its right connection from the circuitry and see if the 6K5 plate voltage goes up.
:
:
:To further confirm that #C34 capacitor, lift the right side of the cap from circuitry and clip on the DC metering of a DVM . . ( inherently Hi Z.). .and power up the set to then get B+ up and see if there is + voltage reading on the meter.
:
:To speed up the inconvenience of the initial onset charge effect, short out the metering junction to chassis ground and see if anything greater than ~50 mvDC then builds back up as a reading. If so, look for a better capacitor to replace C34 with.
:
:
:The next aspect of analysis would be to confirm that the low B+ on the plate is merely due to that tube conducting more and thus pulling down that plate voltage by virtue of the 1st grid circuitry not having a high enough negative voltage biasing; which is being supplied up from the [Blue -green ] buss from its derivation via the technique of the floating of the HV centertap of the up from ground through the tri-series 35-8-202 ohm resistances of #43.
:
:That will result in the highest negative level being derived for the [Green] buss feeding the AF output and then the next level, (unhighted). . . . due to it not being of interest, as being a negative counterpoise for the AVC of the system in order to get a wider overall dynamic AVC swing.
:
:Then finally, your node of the 35-8 ohm resistors of #43 will be the sourcing of the negative voltage going up the [Blue-green] buss and initially into a 1 meg dropping resistor #33 and then a bit of decoupling via the .1 ufd cap #30, just past that resistor and then the coupling into a second 1 meg resistor #R31, then, just above that is the point of the DC isolated introduction of the sets AC audio info thru .015 ufd cap #28.
:
:Probably already confirmed but error of either of those resistors values could cause decreased - biasing to the
:6K5 and increased plate current consumption / the dropping of the plate voltage.
:
:Then one needs to give like consideration of the assurance of no leakage on those # C28-C30, such as was just afforded to the testing of # C34.
:
:
:Considering that C34 and R36 passed specs, a quick test for a grid biasing error or grid emission fault on the 6K5 tube could be effected by the following test:
:
:Power up the set and DC monitor the 6K5 plate via DVM and then take a clip lead and short the 6K5's 1st grid cap to chassis ground. The 6K5 plate voltage should go up to almost what one DC meters at the B+ supply side of R36.
:
:
:Lastly, are we considering that the three sections of the PWR resistor # R43 are within tolerance ?
:
:
:
:Standing by:
:
:
:
:Markup Schematic Referencing:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
Bill
Well Edd gave me plenty to do, but in short, there has been no change from last time. I did replace R31, R33, 15 and 27, along with the R43 202/8/35 ohm strip, but the voltage still dropped down to 90 VDC after about 45 seconds of warmup.
:
:After all that, I tried shorting the 6k5 grid clip to chassis ground while observing B+. There was no change. As I wasn't too sure on what to do, this test was done with the grid clip removed from the tube and while still attached to the tube. Neither configuration changed anything.
:
:I did go back and check the rest of the pin voltages given by the schematic, and none were affected by my work. Luckily, they are per the schematic, so that is a good thing. So, anywhere else we can go with this one?
:
::
::
::
::
::
::
::
::Looking at the involved plate circuitry of the 6K5 1st audio, and then consulting the markup supplied, how's about these confirmations?
::
::The first consideration that can be cleared would be the probability that you are using a high-Z metering
::for measurements and not loading down the 6K5 plate circuitry whilst taking the plate voltage reading,
::albeit the fact that this application is using a quite low 99k plate load vice the common 1/2 meg or so + , being found in other situations.
::
::
::
::The markups associative routings are:
::
::
::[RED] for the sub B+ buss feeding just the particular circuitry area of interest.
::
::[GREEN] for the negative 1st grid biasing of the AF output stage.
::
::[BLUE-GREEN] for the 1st grid biasing of the 1st audio tube.
::
::
::
::
::I would consider these aspects as a possibility for that plate voltage not being up to the voltage that you have found being stated as being the proper level.
::
::Just on that plate circuitry, there is merely the possibility if the 99,000 res upping in value (appreciably !)
::which, I think that you have probably already cleared . Next would be voltage leakage off through cap #34,
::lift its right connection from the circuitry and see if the 6K5 plate voltage goes up.
::
::
::To further confirm that #C34 capacitor, lift the right side of the cap from circuitry and clip on the DC metering of a DVM . . ( inherently Hi Z.). .and power up the set to then get B+ up and see if there is + voltage reading on the meter.
::
::To speed up the inconvenience of the initial onset charge effect, short out the metering junction to chassis ground and see if anything greater than ~50 mvDC then builds back up as a reading. If so, look for a better capacitor to replace C34 with.
::
::
::The next aspect of analysis would be to confirm that the low B+ on the plate is merely due to that tube conducting more and thus pulling down that plate voltage by virtue of the 1st grid circuitry not having a high enough negative voltage biasing; which is being supplied up from the [Blue -green ] buss from its derivation via the technique of the floating of the HV centertap of the up from ground through the tri-series 35-8-202 ohm resistances of #43.
::
::That will result in the highest negative level being derived for the [Green] buss feeding the AF output and then the next level, (unhighted). . . . due to it not being of interest, as being a negative counterpoise for the AVC of the system in order to get a wider overall dynamic AVC swing.
::
::Then finally, your node of the 35-8 ohm resistors of #43 will be the sourcing of the negative voltage going up the [Blue-green] buss and initially into a 1 meg dropping resistor #33 and then a bit of decoupling via the .1 ufd cap #30, just past that resistor and then the coupling into a second 1 meg resistor #R31, then, just above that is the point of the DC isolated introduction of the sets AC audio info thru .015 ufd cap #28.
::
::Probably already confirmed but error of either of those resistors values could cause decreased - biasing to the
::6K5 and increased plate current consumption / the dropping of the plate voltage.
::
::Then one needs to give like consideration of the assurance of no leakage on those # C28-C30, such as was just afforded to the testing of # C34.
::
::
::Considering that C34 and R36 passed specs, a quick test for a grid biasing error or grid emission fault on the 6K5 tube could be effected by the following test:
::
::Power up the set and DC monitor the 6K5 plate via DVM and then take a clip lead and short the 6K5's 1st grid cap to chassis ground. The 6K5 plate voltage should go up to almost what one DC meters at the B+ supply side of R36.
::
::
::Lastly, are we considering that the three sections of the PWR resistor # R43 are within tolerance ?
::
::
::
::Standing by:
::
::
::
::Markup Schematic Referencing:
::
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
Best,
Carl
:Wade pin 5 of the 6F6 should have negative voltage. What do you measure? I don't see where the schematic indicates it.
:Bill
:
:Well Edd gave me plenty to do, but in short, there has been no change from last time. I did replace R31, R33, 15 and 27, along with the R43 202/8/35 ohm strip, but the voltage still dropped down to 90 VDC after about 45 seconds of warmup.
::
::After all that, I tried shorting the 6k5 grid clip to chassis ground while observing B+. There was no change. As I wasn't too sure on what to do, this test was done with the grid clip removed from the tube and while still attached to the tube. Neither configuration changed anything.
::
::I did go back and check the rest of the pin voltages given by the schematic, and none were affected by my work. Luckily, they are per the schematic, so that is a good thing. So, anywhere else we can go with this one?
::
:::
:::
:::
:::
:::
:::
:::
:::Looking at the involved plate circuitry of the 6K5 1st audio, and then consulting the markup supplied, how's about these confirmations?
:::
:::The first consideration that can be cleared would be the probability that you are using a high-Z metering
:::for measurements and not loading down the 6K5 plate circuitry whilst taking the plate voltage reading,
:::albeit the fact that this application is using a quite low 99k plate load vice the common 1/2 meg or so + , being found in other situations.
:::
:::
:::
:::The markups associative routings are:
:::
:::
:::[RED] for the sub B+ buss feeding just the particular circuitry area of interest.
:::
:::[GREEN] for the negative 1st grid biasing of the AF output stage.
:::
:::[BLUE-GREEN] for the 1st grid biasing of the 1st audio tube.
:::
:::
:::
:::
:::I would consider these aspects as a possibility for that plate voltage not being up to the voltage that you have found being stated as being the proper level.
:::
:::Just on that plate circuitry, there is merely the possibility if the 99,000 res upping in value (appreciably !)
:::which, I think that you have probably already cleared . Next would be voltage leakage off through cap #34,
:::lift its right connection from the circuitry and see if the 6K5 plate voltage goes up.
:::
:::
:::To further confirm that #C34 capacitor, lift the right side of the cap from circuitry and clip on the DC metering of a DVM . . ( inherently Hi Z.). .and power up the set to then get B+ up and see if there is + voltage reading on the meter.
:::
:::To speed up the inconvenience of the initial onset charge effect, short out the metering junction to chassis ground and see if anything greater than ~50 mvDC then builds back up as a reading. If so, look for a better capacitor to replace C34 with.
:::
:::
:::The next aspect of analysis would be to confirm that the low B+ on the plate is merely due to that tube conducting more and thus pulling down that plate voltage by virtue of the 1st grid circuitry not having a high enough negative voltage biasing; which is being supplied up from the [Blue -green ] buss from its derivation via the technique of the floating of the HV centertap of the up from ground through the tri-series 35-8-202 ohm resistances of #43.
:::
:::That will result in the highest negative level being derived for the [Green] buss feeding the AF output and then the next level, (unhighted). . . . due to it not being of interest, as being a negative counterpoise for the AVC of the system in order to get a wider overall dynamic AVC swing.
:::
:::Then finally, your node of the 35-8 ohm resistors of #43 will be the sourcing of the negative voltage going up the [Blue-green] buss and initially into a 1 meg dropping resistor #33 and then a bit of decoupling via the .1 ufd cap #30, just past that resistor and then the coupling into a second 1 meg resistor #R31, then, just above that is the point of the DC isolated introduction of the sets AC audio info thru .015 ufd cap #28.
:::
:::Probably already confirmed but error of either of those resistors values could cause decreased - biasing to the
:::6K5 and increased plate current consumption / the dropping of the plate voltage.
:::
:::Then one needs to give like consideration of the assurance of no leakage on those # C28-C30, such as was just afforded to the testing of # C34.
:::
:::
:::Considering that C34 and R36 passed specs, a quick test for a grid biasing error or grid emission fault on the 6K5 tube could be effected by the following test:
:::
:::Power up the set and DC monitor the 6K5 plate via DVM and then take a clip lead and short the 6K5's 1st grid cap to chassis ground. The 6K5 plate voltage should go up to almost what one DC meters at the B+ supply side of R36.
:::
:::
:::Lastly, are we considering that the three sections of the PWR resistor # R43 are within tolerance ?
:::
:::
:::
:::Standing by:
:::
:::
:::
:::Markup Schematic Referencing:
:::
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
:Swap out the tube. Anyone want to make a bet?
:
:Best,
:Carl
:
:
::Wade pin 5 of the 6F6 should have negative voltage. What do you measure? I don't see where the schematic indicates it.
::Bill
::
::Well Edd gave me plenty to do, but in short, there has been no change from last time. I did replace R31, R33, 15 and 27, along with the R43 202/8/35 ohm strip, but the voltage still dropped down to 90 VDC after about 45 seconds of warmup.
:::
:::After all that, I tried shorting the 6k5 grid clip to chassis ground while observing B+. There was no change. As I wasn't too sure on what to do, this test was done with the grid clip removed from the tube and while still attached to the tube. Neither configuration changed anything.
:::
:::I did go back and check the rest of the pin voltages given by the schematic, and none were affected by my work. Luckily, they are per the schematic, so that is a good thing. So, anywhere else we can go with this one?
:::
::::
::::
::::
::::
::::
::::
::::
::::Looking at the involved plate circuitry of the 6K5 1st audio, and then consulting the markup supplied, how's about these confirmations?
::::
::::The first consideration that can be cleared would be the probability that you are using a high-Z metering
::::for measurements and not loading down the 6K5 plate circuitry whilst taking the plate voltage reading,
::::albeit the fact that this application is using a quite low 99k plate load vice the common 1/2 meg or so + , being found in other situations.
::::
::::
::::
::::The markups associative routings are:
::::
::::
::::[RED] for the sub B+ buss feeding just the particular circuitry area of interest.
::::
::::[GREEN] for the negative 1st grid biasing of the AF output stage.
::::
::::[BLUE-GREEN] for the 1st grid biasing of the 1st audio tube.
::::
::::
::::
::::
::::I would consider these aspects as a possibility for that plate voltage not being up to the voltage that you have found being stated as being the proper level.
::::
::::Just on that plate circuitry, there is merely the possibility if the 99,000 res upping in value (appreciably !)
::::which, I think that you have probably already cleared . Next would be voltage leakage off through cap #34,
::::lift its right connection from the circuitry and see if the 6K5 plate voltage goes up.
::::
::::
::::To further confirm that #C34 capacitor, lift the right side of the cap from circuitry and clip on the DC metering of a DVM . . ( inherently Hi Z.). .and power up the set to then get B+ up and see if there is + voltage reading on the meter.
::::
::::To speed up the inconvenience of the initial onset charge effect, short out the metering junction to chassis ground and see if anything greater than ~50 mvDC then builds back up as a reading. If so, look for a better capacitor to replace C34 with.
::::
::::
::::The next aspect of analysis would be to confirm that the low B+ on the plate is merely due to that tube conducting more and thus pulling down that plate voltage by virtue of the 1st grid circuitry not having a high enough negative voltage biasing; which is being supplied up from the [Blue -green ] buss from its derivation via the technique of the floating of the HV centertap of the up from ground through the tri-series 35-8-202 ohm resistances of #43.
::::
::::That will result in the highest negative level being derived for the [Green] buss feeding the AF output and then the next level, (unhighted). . . . due to it not being of interest, as being a negative counterpoise for the AVC of the system in order to get a wider overall dynamic AVC swing.
::::
::::Then finally, your node of the 35-8 ohm resistors of #43 will be the sourcing of the negative voltage going up the [Blue-green] buss and initially into a 1 meg dropping resistor #33 and then a bit of decoupling via the .1 ufd cap #30, just past that resistor and then the coupling into a second 1 meg resistor #R31, then, just above that is the point of the DC isolated introduction of the sets AC audio info thru .015 ufd cap #28.
::::
::::Probably already confirmed but error of either of those resistors values could cause decreased - biasing to the
::::6K5 and increased plate current consumption / the dropping of the plate voltage.
::::
::::Then one needs to give like consideration of the assurance of no leakage on those # C28-C30, such as was just afforded to the testing of # C34.
::::
::::
::::Considering that C34 and R36 passed specs, a quick test for a grid biasing error or grid emission fault on the 6K5 tube could be effected by the following test:
::::
::::Power up the set and DC monitor the 6K5 plate via DVM and then take a clip lead and short the 6K5's 1st grid cap to chassis ground. The 6K5 plate voltage should go up to almost what one DC meters at the B+ supply side of R36.
::::
::::
::::Lastly, are we considering that the three sections of the PWR resistor # R43 are within tolerance ?
::::
::::
::::
::::Standing by:
::::
::::
::::
::::Markup Schematic Referencing:
::::
::::
::::
::::
::::
::::
::::
::::
::::73's de Edd
::::
::::
::::
::::
::::
If there isn't anything connected to pins #4 and #5 of the 6K5G use a 6Q7G/GT. It's the same tube with diodes added on those pins.
Norm
:Just found an NOS 6k5g for a couple of bucks. Hopefully should arrive this week. Hundreds of tubes in my inventory now, but not that one...sounds like a familiar story.
:
::Swap out the tube. Anyone want to make a bet?
::
::Best,
::Carl
::
::
:::Wade pin 5 of the 6F6 should have negative voltage. What do you measure? I don't see where the schematic indicates it.
:::Bill
:::
:::Well Edd gave me plenty to do, but in short, there has been no change from last time. I did replace R31, R33, 15 and 27, along with the R43 202/8/35 ohm strip, but the voltage still dropped down to 90 VDC after about 45 seconds of warmup.
::::
::::After all that, I tried shorting the 6k5 grid clip to chassis ground while observing B+. There was no change. As I wasn't too sure on what to do, this test was done with the grid clip removed from the tube and while still attached to the tube. Neither configuration changed anything.
::::
::::I did go back and check the rest of the pin voltages given by the schematic, and none were affected by my work. Luckily, they are per the schematic, so that is a good thing. So, anywhere else we can go with this one?
::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::Looking at the involved plate circuitry of the 6K5 1st audio, and then consulting the markup supplied, how's about these confirmations?
:::::
:::::The first consideration that can be cleared would be the probability that you are using a high-Z metering
:::::for measurements and not loading down the 6K5 plate circuitry whilst taking the plate voltage reading,
:::::albeit the fact that this application is using a quite low 99k plate load vice the common 1/2 meg or so + , being found in other situations.
:::::
:::::
:::::
:::::The markups associative routings are:
:::::
:::::
:::::[RED] for the sub B+ buss feeding just the particular circuitry area of interest.
:::::
:::::[GREEN] for the negative 1st grid biasing of the AF output stage.
:::::
:::::[BLUE-GREEN] for the 1st grid biasing of the 1st audio tube.
:::::
:::::
:::::
:::::
:::::I would consider these aspects as a possibility for that plate voltage not being up to the voltage that you have found being stated as being the proper level.
:::::
:::::Just on that plate circuitry, there is merely the possibility if the 99,000 res upping in value (appreciably !)
:::::which, I think that you have probably already cleared . Next would be voltage leakage off through cap #34,
:::::lift its right connection from the circuitry and see if the 6K5 plate voltage goes up.
:::::
:::::
:::::To further confirm that #C34 capacitor, lift the right side of the cap from circuitry and clip on the DC metering of a DVM . . ( inherently Hi Z.). .and power up the set to then get B+ up and see if there is + voltage reading on the meter.
:::::
:::::To speed up the inconvenience of the initial onset charge effect, short out the metering junction to chassis ground and see if anything greater than ~50 mvDC then builds back up as a reading. If so, look for a better capacitor to replace C34 with.
:::::
:::::
:::::The next aspect of analysis would be to confirm that the low B+ on the plate is merely due to that tube conducting more and thus pulling down that plate voltage by virtue of the 1st grid circuitry not having a high enough negative voltage biasing; which is being supplied up from the [Blue -green ] buss from its derivation via the technique of the floating of the HV centertap of the up from ground through the tri-series 35-8-202 ohm resistances of #43.
:::::
:::::That will result in the highest negative level being derived for the [Green] buss feeding the AF output and then the next level, (unhighted). . . . due to it not being of interest, as being a negative counterpoise for the AVC of the system in order to get a wider overall dynamic AVC swing.
:::::
:::::Then finally, your node of the 35-8 ohm resistors of #43 will be the sourcing of the negative voltage going up the [Blue-green] buss and initially into a 1 meg dropping resistor #33 and then a bit of decoupling via the .1 ufd cap #30, just past that resistor and then the coupling into a second 1 meg resistor #R31, then, just above that is the point of the DC isolated introduction of the sets AC audio info thru .015 ufd cap #28.
:::::
:::::Probably already confirmed but error of either of those resistors values could cause decreased - biasing to the
:::::6K5 and increased plate current consumption / the dropping of the plate voltage.
:::::
:::::Then one needs to give like consideration of the assurance of no leakage on those # C28-C30, such as was just afforded to the testing of # C34.
:::::
:::::
:::::Considering that C34 and R36 passed specs, a quick test for a grid biasing error or grid emission fault on the 6K5 tube could be effected by the following test:
:::::
:::::Power up the set and DC monitor the 6K5 plate via DVM and then take a clip lead and short the 6K5's 1st grid cap to chassis ground. The 6K5 plate voltage should go up to almost what one DC meters at the B+ supply side of R36.
:::::
:::::
:::::Lastly, are we considering that the three sections of the PWR resistor # R43 are within tolerance ?
:::::
:::::
:::::
:::::Standing by:
:::::
:::::
:::::
:::::Markup Schematic Referencing:
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::73's de Edd
:::::
:::::
:::::
:::::
:::::
Well, we'll know in a few days time...
:Hi Wade
:
: If there isn't anything connected to pins #4 and #5 of the 6K5G use a 6Q7G/GT. It's the same tube with diodes added on those pins.
:
:
:
:Norm
:
::Just found an NOS 6k5g for a couple of bucks. Hopefully should arrive this week. Hundreds of tubes in my inventory now, but not that one...sounds like a familiar story.
::
:::Swap out the tube. Anyone want to make a bet?
:::
:::Best,
:::Carl
:::
:::
::::Wade pin 5 of the 6F6 should have negative voltage. What do you measure? I don't see where the schematic indicates it.
::::Bill
::::
::::Well Edd gave me plenty to do, but in short, there has been no change from last time. I did replace R31, R33, 15 and 27, along with the R43 202/8/35 ohm strip, but the voltage still dropped down to 90 VDC after about 45 seconds of warmup.
:::::
:::::After all that, I tried shorting the 6k5 grid clip to chassis ground while observing B+. There was no change. As I wasn't too sure on what to do, this test was done with the grid clip removed from the tube and while still attached to the tube. Neither configuration changed anything.
:::::
:::::I did go back and check the rest of the pin voltages given by the schematic, and none were affected by my work. Luckily, they are per the schematic, so that is a good thing. So, anywhere else we can go with this one?
:::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::Looking at the involved plate circuitry of the 6K5 1st audio, and then consulting the markup supplied, how's about these confirmations?
::::::
::::::The first consideration that can be cleared would be the probability that you are using a high-Z metering
::::::for measurements and not loading down the 6K5 plate circuitry whilst taking the plate voltage reading,
::::::albeit the fact that this application is using a quite low 99k plate load vice the common 1/2 meg or so + , being found in other situations.
::::::
::::::
::::::
::::::The markups associative routings are:
::::::
::::::
::::::[RED] for the sub B+ buss feeding just the particular circuitry area of interest.
::::::
::::::[GREEN] for the negative 1st grid biasing of the AF output stage.
::::::
::::::[BLUE-GREEN] for the 1st grid biasing of the 1st audio tube.
::::::
::::::
::::::
::::::
::::::I would consider these aspects as a possibility for that plate voltage not being up to the voltage that you have found being stated as being the proper level.
::::::
::::::Just on that plate circuitry, there is merely the possibility if the 99,000 res upping in value (appreciably !)
::::::which, I think that you have probably already cleared . Next would be voltage leakage off through cap #34,
::::::lift its right connection from the circuitry and see if the 6K5 plate voltage goes up.
::::::
::::::
::::::To further confirm that #C34 capacitor, lift the right side of the cap from circuitry and clip on the DC metering of a DVM . . ( inherently Hi Z.). .and power up the set to then get B+ up and see if there is + voltage reading on the meter.
::::::
::::::To speed up the inconvenience of the initial onset charge effect, short out the metering junction to chassis ground and see if anything greater than ~50 mvDC then builds back up as a reading. If so, look for a better capacitor to replace C34 with.
::::::
::::::
::::::The next aspect of analysis would be to confirm that the low B+ on the plate is merely due to that tube conducting more and thus pulling down that plate voltage by virtue of the 1st grid circuitry not having a high enough negative voltage biasing; which is being supplied up from the [Blue -green ] buss from its derivation via the technique of the floating of the HV centertap of the up from ground through the tri-series 35-8-202 ohm resistances of #43.
::::::
::::::That will result in the highest negative level being derived for the [Green] buss feeding the AF output and then the next level, (unhighted). . . . due to it not being of interest, as being a negative counterpoise for the AVC of the system in order to get a wider overall dynamic AVC swing.
::::::
::::::Then finally, your node of the 35-8 ohm resistors of #43 will be the sourcing of the negative voltage going up the [Blue-green] buss and initially into a 1 meg dropping resistor #33 and then a bit of decoupling via the .1 ufd cap #30, just past that resistor and then the coupling into a second 1 meg resistor #R31, then, just above that is the point of the DC isolated introduction of the sets AC audio info thru .015 ufd cap #28.
::::::
::::::Probably already confirmed but error of either of those resistors values could cause decreased - biasing to the
::::::6K5 and increased plate current consumption / the dropping of the plate voltage.
::::::
::::::Then one needs to give like consideration of the assurance of no leakage on those # C28-C30, such as was just afforded to the testing of # C34.
::::::
::::::
::::::Considering that C34 and R36 passed specs, a quick test for a grid biasing error or grid emission fault on the 6K5 tube could be effected by the following test:
::::::
::::::Power up the set and DC monitor the 6K5 plate via DVM and then take a clip lead and short the 6K5's 1st grid cap to chassis ground. The 6K5 plate voltage should go up to almost what one DC meters at the B+ supply side of R36.
::::::
::::::
::::::Lastly, are we considering that the three sections of the PWR resistor # R43 are within tolerance ?
::::::
::::::
::::::
::::::Standing by:
::::::
::::::
::::::
::::::Markup Schematic Referencing:
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::73's de Edd
::::::
::::::
::::::
::::::
::::::
Looking at the old tube, I see that the grid cap must have fallen off at one point and had been resoldered on. Is it possible that this was causing some thermal intermittent on warm up?