I'm surprised you found a 30 Volt DC power supply at Radio Shack. What current capacity/power rating does it have?
:
:I'm surprised you found a 30 Volt DC power supply at Radio Shack. What current capacity/power rating does it have?
13.5/30V, 1000MA is what it says on the top, I get stations, but the volume is quite low.
Sir David :
Have you actually monitored the voltage as being 30 VDC under load with the radio running ? If so you can place 2 "D" cells in series to bring up to 33 VDC for testing as they are good for up to 4 amp bursts, so that you can test and see if that is really the fault, I don't suspicion it, at such a relatively minute overall / proportional voltage difference.
73's de Edd
:::I just completed restoration of a console that runs on 32 Volt DC, the closest power supply I could find was one for 30Volts DC at Radio Shack, the radio works, but volume is LOW, any ideas on where to find a 32 VDC supply or how to boost my 30 ? Thanks, DaveF
::
::I'm surprised you found a 30 Volt DC power supply at Radio Shack. What current capacity/power rating does it have?
:13.5/30V, 1000MA is what it says on the top, I get stations, but the volume is quite low.
Lewis
:
:
:
:Sir David :
:
:
:
:Have you actually monitored the voltage as being 30 VDC under load with the radio running ? If so you can place 2 "D" cells in series to bring up to 33 VDC for testing as they are good for up to 4 amp bursts, so that you can test and see if that is really the fault, I don't suspicion it, at such a relatively minute overall / proportional voltage difference.
:
:
:73's de Edd
:
:
:
:
:
:
:
::::I just completed restoration of a console that runs on 32 Volt DC, the closest power supply I could find was one for 30Volts DC at Radio Shack, the radio works, but volume is LOW, any ideas on where to find a 32 VDC supply or how to boost my 30 ? Thanks, DaveF
:::
:::I'm surprised you found a 30 Volt DC power supply at Radio Shack. What current capacity/power rating does it have?
::13.5/30V, 1000MA is what it says on the top, I get stations, but the volume is quite low.
T.
1) Tube Lineup. This will tell you if the tubes run at the same amperage, and if they will add up to 120V if you are trying to convert to 120V.
2) Does the set use a vibrator or are the plates run at 32V? If it uses a Vibrator, you need to disconnect it and get a power transformer with a 120V winding that converts it to the proper B Voltage to a 120V conversion.
3) Are any dedicated "Low Voltage" type tubes used (for example, 12AF6, 28D7, etc)? If so, connecting to 120V will probably damage them. If these are used, you need to change them or go the 32V power supply route.
4) Is the Audio Section Single Ended, Push-Pull, or Push-Pull Parallel? If it is Push-Pull or Push Pull Parallel, you may need to change the Bias and Transformer impeadence, as well as this may make the radio too loud at low volume settings. In fact, often the reason for this output was to drive a speaker with a 32V B+.
5) If the set does not contain a rectifier you will need to add one if converting to 120V.
6) Sometimes converting to higher voltage can offset the biasing of some of the tubes, too.
:Since many of those radios use conventional tubes, if the tubes all have the same filament current rating, you can string them in series and convert the set to an AC/DC set. All you need then is a resistor for the string, and a solid state full wave rectifier for the B supply, along with some 250 WVDC 47 MFD 'lytics, and an appropriate filter resistor (you will probably want about 100 to 120 volts at the output tube, and 90 volts to the rest of the tubes...this extra-filtered voltage is necessary so that hum isn't amplified through all of the stages). Should be an easy conversion. If you have a difficult time with stringing the tubes in series (amperages aren't all the same), you can also leave them as-is and just run them with a 32 volt AC transformer (so long as all tubes can have their filaments run on AC...supplying us with a model number will determine this). Since the set is a consol, it shouldn't be too hard to build a separate box with the necessary parts, if you don't want to put them inside of the chassis. Mount the box inside the radio, and carry wires up to the radio chassis. Use the radio's on/off switch to control the power of the power supply (line cord).
:
:T.
:
:1) Tube Lineup. This will tell you if the tubes run at the same amperage, and if they will add up to 120V if you are trying to convert to 120V.
:
:2) Does the set use a vibrator or are the plates run at 32V? If it uses a Vibrator, you need to disconnect it and get a power transformer with a 120V winding that converts it to the proper B Voltage to a 120V conversion.
:
:3) Are any dedicated "Low Voltage" type tubes used (for example, 12AF6, 28D7, etc)? If so, connecting to 120V will probably damage them. If these are used, you need to change them or go the 32V power supply route.
:
:4) Is the Audio Section Single Ended, Push-Pull, or Push-Pull Parallel? If it is Push-Pull or Push Pull Parallel, you may need to change the Bias and Transformer impeadence, as well as this may make the radio too loud at low volume settings. In fact, often the reason for this output was to drive a speaker with a 32V B+.
:
:5) If the set does not contain a rectifier you will need to add one if converting to 120V.
:
:6) Sometimes converting to higher voltage can offset the biasing of some of the tubes, too.
:
:
::Since many of those radios use conventional tubes, if the tubes all have the same filament current rating, you can string them in series and convert the set to an AC/DC set. All you need then is a resistor for the string, and a solid state full wave rectifier for the B supply, along with some 250 WVDC 47 MFD 'lytics, and an appropriate filter resistor (you will probably want about 100 to 120 volts at the output tube, and 90 volts to the rest of the tubes...this extra-filtered voltage is necessary so that hum isn't amplified through all of the stages). Should be an easy conversion. If you have a difficult time with stringing the tubes in series (amperages aren't all the same), you can also leave them as-is and just run them with a 32 volt AC transformer (so long as all tubes can have their filaments run on AC...supplying us with a model number will determine this). Since the set is a consol, it shouldn't be too hard to build a separate box with the necessary parts, if you don't want to put them inside of the chassis. Mount the box inside the radio, and carry wires up to the radio chassis. Use the radio's on/off switch to control the power of the power supply (line cord).
::
::T.
::
::1) Tube Lineup. This will tell you if the tubes run at the same amperage, and if they will add up to 120V if you are trying to convert to 120V.
::
::2) Does the set use a vibrator or are the plates run at 32V? If it uses a Vibrator, you need to disconnect it and get a power transformer with a 120V winding that converts it to the proper B Voltage to a 120V conversion.
::
::3) Are any dedicated "Low Voltage" type tubes used (for example, 12AF6, 28D7, etc)? If so, connecting to 120V will probably damage them. If these are used, you need to change them or go the 32V power supply route.
::
::4) Is the Audio Section Single Ended, Push-Pull, or Push-Pull Parallel? If it is Push-Pull or Push Pull Parallel, you may need to change the Bias and Transformer impeadence, as well as this may make the radio too loud at low volume settings. In fact, often the reason for this output was to drive a speaker with a 32V B+.
::
::5) If the set does not contain a rectifier you will need to add one if converting to 120V.
::
::6) Sometimes converting to higher voltage can offset the biasing of some of the tubes, too.
::
::
:::Since many of those radios use conventional tubes, if the tubes all have the same filament current rating, you can string them in series and convert the set to an AC/DC set. All you need then is a resistor for the string, and a solid state full wave rectifier for the B supply, along with some 250 WVDC 47 MFD 'lytics, and an appropriate filter resistor (you will probably want about 100 to 120 volts at the output tube, and 90 volts to the rest of the tubes...this extra-filtered voltage is necessary so that hum isn't amplified through all of the stages). Should be an easy conversion. If you have a difficult time with stringing the tubes in series (amperages aren't all the same), you can also leave them as-is and just run them with a 32 volt AC transformer (so long as all tubes can have their filaments run on AC...supplying us with a model number will determine this). Since the set is a consol, it shouldn't be too hard to build a separate box with the necessary parts, if you don't want to put them inside of the chassis. Mount the box inside the radio, and carry wires up to the radio chassis. Use the radio's on/off switch to control the power of the power supply (line cord).
:::
:::T.
Looking at the schematic, I would say that the radio should be run only on 32 Volts. This is a real departure from what I am familiar with, the audio driver tube filament is the cathode load for the output stage, for example. This thing has 32 Volt Plates, somewhat like car radios had 12 Volt plates 25 years later. I think his one Amp supply might be able to run this radio, as it has no vibrator supply, and might just work with the 32 Watts he has on hand. I have suggested that he check the pilot lamp, as it is in series with the speaker field, and is very necessary for proper operation.
Lewis
:
:1) Tube Lineup. This will tell you if the tubes run at the same amperage, and if they will add up to 120V if you are trying to convert to 120V.
:
:2) Does the set use a vibrator or are the plates run at 32V? If it uses a Vibrator, you need to disconnect it and get a power transformer with a 120V winding that converts it to the proper B Voltage to a 120V conversion.
:
:3) Are any dedicated "Low Voltage" type tubes used (for example, 12AF6, 28D7, etc)? If so, connecting to 120V will probably damage them. If these are used, you need to change them or go the 32V power supply route.
:
:4) Is the Audio Section Single Ended, Push-Pull, or Push-Pull Parallel? If it is Push-Pull or Push Pull Parallel, you may need to change the Bias and Transformer impeadence, as well as this may make the radio too loud at low volume settings. In fact, often the reason for this output was to drive a speaker with a 32V B+.
:
:5) If the set does not contain a rectifier you will need to add one if converting to 120V.
:
:6) Sometimes converting to higher voltage can offset the biasing of some of the tubes, too.
:
:
::Since many of those radios use conventional tubes, if the tubes all have the same filament current rating, you can string them in series and convert the set to an AC/DC set. All you need then is a resistor for the string, and a solid state full wave rectifier for the B supply, along with some 250 WVDC 47 MFD 'lytics, and an appropriate filter resistor (you will probably want about 100 to 120 volts at the output tube, and 90 volts to the rest of the tubes...this extra-filtered voltage is necessary so that hum isn't amplified through all of the stages). Should be an easy conversion. If you have a difficult time with stringing the tubes in series (amperages aren't all the same), you can also leave them as-is and just run them with a 32 volt AC transformer (so long as all tubes can have their filaments run on AC...supplying us with a model number will determine this). Since the set is a consol, it shouldn't be too hard to build a separate box with the necessary parts, if you don't want to put them inside of the chassis. Mount the box inside the radio, and carry wires up to the radio chassis. Use the radio's on/off switch to control the power of the power supply (line cord).
::
::T.
Thomas
Yes you are right. It does work sometimes. Where it is most likely to work:
1) Tubes in question can handle 120V plate voltage (no low voltage tubes used)
2) Tubes have similar amperage to allow series operation
3) Tube biasing can handle the higher voltage
4) Models that use a power transformer that steps up to a B+ Voltage that is a common voltage output in which the transofmer can be replaced with a 120V version
Where it doesnt work well:
1) Where Low Voltage tubes are used
2) Where DC Type Fillament tubes are used
3) Where the tubes all have different amperage ratings
4) Where a low impedance push-pull or push-pull parallel is used to drive a spekaer from 32V B+
:Hi. I didn't say that it would work every time. I just said that it may be possible. One way or another, a simple circuit can be made that would allow easy conversion to 120 volts. You can balk at it all you want. I've already done it. It works great, and now I have a loud, reliable radio.
:
:Thomas
The B supply can be AC/DC for simplicity. A power transformer isolates better, but costs more. If the original power supply was of the vibrator kind, then you probably don't need a boost in the B section. In that case it is probably best to just stick with a 32 volt DC supply for the whole radio. If the radio originally ran directly from 32 volts, with no boosting supply, then the 120 volt AC/DC B supply would be most beneficial. Many tubes designed specifically for 32 volt power can handle a bit more voltage, perhaps as high as 67.5 or 90 volts (very much likely). Consult a tube manual to be sure. If conventional tubes are used, they certainly can handle up to 100 volts. If 32 volt tubes are used, check to be sure. I know that I have used 12 volt space charge tubes quite successfully in AC/DC radios. I had the equivilants for a 12BE6 and a 12BA6, and they worked well. They weren't output tubes, though, which handle more current.
If you don't like how quiet your radio currently sounds, consider converting it for AC use.
Thomas
If you string the tubes in series, and make the set a completely AC/DC set (using #43 tubes in the output), you may obtain power for the pilot lamp either via a small dropping resistor in the filament string to which the pilot lamp is wired across, or two 6.8 volt Zener diodes wired back to back, in series with the filament string. They must be able to handle full current, should the pilot lamp burn out. If they cannot, parallel them with more. The two zeners are wired back to back (positive to positive or negative to negative), so make sure that any paralleling zeners are also wired facing the same direction.
The B supply should be isolated from the A supply (remember that it was originally connected to the 32 volt supply, which was also the A supply). Any other AC or AC/DC radio with a similar tube layout can be used as an example for this. Get a full wave bridge rectifier from Radio Shack (their 1 or 2 ampere 400 volt model works great, and costs little). Place a 50 ohm resistor in series with its positive output. Place a 30 MFD 200 WVDC electrolytic after the resistor, and connect the negative side of the 'lytic to the negative side of the rectifier. Connect the 120 ohm field coil between the positive of the 1st 'lytic and the positive of a second 'lytic. From here connect the center tap of the output transformer, and the screens of the output tubes. After this use a resistor around 3000 ohms to feed the B+ to the rest of the radio. Place another electrolytic from it to B- (negative side of rectifier). The voltage after the 3000 ohm resistor should be between 67.5 and 90 volts. If not, adjust the resistor accordingly. The voltage ACROSS the field coil should be around 26 volts. If it is higher, parallel the field coil with an appropriate resistor (doesn't have to be more than 1 or 2 watts capacity). If you cannot get enough voltage drop across the field coil, omit it from the circuit and connect the items that were originally connected after it directly to the 50 ohm resistor (omit one of the electrolytics if you wish). If it is necessary to omit the field coil from the B circuit, rectify the 25 volt A supply with another Radio Shack full wave rectifier (it doesn't have to handle more than 100 volts at perhaps 1 ampere). Filter with a 100 MFD 50 WVDC electrolytic. If you didn't originally use a 25 volt transformer, obtain one, and wire it to power the speaker field as I just suggested.
Be sure to also connect B- of the power supply to B- of the radio.
For the output tube cathodes (#43 tubes), connect them to B- via an 80 ohm resistor for the pair (if you used the original #48 tubes, they require a similar bias, so they will also work well with this set-up.....if you use #42 tubes, you may need to adjust for best power and least distortion). The wattage for the resistor should be about 2 watts, though more is better. Bypassing the resistor isn't really necessary, since the tubes are in push-pull. You can bypass it with a 30 MFD 50 WVDC electrolytic, but it probably won't make much difference.
Let me know how the radio performs. This should be a fairly simple conversion (it is more complicated on paper than it really is), and it should perform very well. It will have great tone, since the output is push-pull. Very little modification to the radio will be necessary, so a purist may always convert it back.
Thomas
One hint - I had similiar problems with an old set and eventually narrowed it down to an open antenna coil. When I fixed the coil, volume was more than adequate.
:
:One hint - I had similiar problems with an old set and eventually narrowed it down to an open antenna coil. When I fixed the coil, volume was more than adequate.
The model is 1935 from ironically 1935 and specifically states on the label, 32 Volts DC only. It has a pair of 48 outputs also. I just wanted to know if the voltage being lower than specs would cause low volume, or perhaps it is the antenna coil or tube issue, although all tubes tested fine and I believe all caps were replaced, I did them many years ago, going to pull the chassis today and check again. The only battery eliminator I can find is $50.00, which I really dont want to spend for the same results. Dave F
::
::One hint - I had similiar problems with an old set and eventually narrowed it down to an open antenna coil. When I fixed the coil, volume was more than adequate.
:
:The model is 1935 from ironically 1935 and specifically states on the label, 32 Volts DC only. It has a pair of 48 outputs also. I just wanted to know if the voltage being lower than specs would cause low volume, or perhaps it is the antenna coil or tube issue, although all tubes tested fine and I believe all caps were replaced, I did them many years ago, going to pull the chassis today and check again. The only battery eliminator I can find is $50.00, which I really dont want to spend for the same results. Dave F
Here is an idea....this crazy radio (schemaitc below)
http://www.nostalgiaair.org/PagesByModel/836/M0016836.pdf
has the pilot lamp in series with the speaker field coil. If the pilot lamp is burned out, the residual magnetism is the speaier field will give you very low volume. Is the pilot burning??? Also, what Voltage does you 1000 mA. supply produce when the radio is operating? After seeing the schematic, one Amp may be plenty, after all.
Lewis
Have a 32V Airline of similar design that performs well down to 28 volts. Uses the 32V for plate voltage same as your Silvertone.
http://www.nostalgiaair.org/Resources/view.asp?FN=\M0011954.pdf
Richard
:
:Have a 32V Airline of similar design that performs well down to 28 volts. Uses the 32V for plate voltage same as your Silvertone.
:
:http://www.nostalgiaair.org/Resources/view.asp?FN=\M0011954.pdf
:
:Richard
The pilot lamp is burning fine,I am going to test the 48 outputs on the tester again, perhaps they are weaker than I thought. DaveF
:The pilot lamp is burning fine,I am going to test the 48 outputs on the tester again, perhaps they are weaker than I thought. DaveF
If the pilot light is burning fine, I must assume that the power supply is able to handle the current this radio needs.
Hummm...... back to the thinking hat.....
Lewis
Be careful with your 48 tubes. They operate directly off of 30 volts and will be destroyed it someone plugs the radio into 120 volts.
For testing you can use 43's in place of 48's. Output will be less but they don't cost so much.
30 volts should be enough for the radio. Be sure it holds voltage under load. Some power supplies have an adjustment for voltage where it can be brought up. Some 24 volt supplies can be adjusted to 32 volts. If a supply has a crow bar circuit it can be disabled. A crow bar circuit shorts the supply when voltage is exceeded.
You could wire a supply in series to increase voltage for testing.
Norm
:I just completed restoration of a console that runs on 32 Volt DC, the closest power supply I could find was one for 30Volts DC at Radio Shack, the radio works, but volume is LOW, any ideas on where to find a 32 VDC supply or how to boost my 30 ? Thanks, DaveF
After seeing the tandem series stringing up of the filaments as shown along with the additional power consumption of the field coil being the main current
hogs,
that 1 amp figure does seem to be quite accomodating with only a paltry amount of additional power being consumed by virtue of running the plates
at low B+ potential.
Now, upon having the schematic available for viewing , relevant to the pilot lamp-field coil loop and looking at the parameters given.... seems like it would like
to see ~ 215 ma across it at 6.3VDC.
With possibilities of three sets of lamps, according to the socketing requirements. A #46 or #44 would pass adequate
current thru the loop for the
field coil, as would a #50 or #51 with a longer lifespan expectancy. However, a #40 - 47 - 1847 being used in that slot would have a very short lifespan..
That mentioning of the pilot lamp being open sounded like a very plausible reason for the low volume....but, its not open.
With a referencing of the volume that you would normally listen to a radio, would you say that your present situation is giving possibly only half of that volume or a quarter of that amount ?
Or, possibly the volume level is just being adequate, but you are wondering why it has no power reserve. Also, just for info purposes would you check to see what number of pilot lamp that unit is using, and also twist / screw it out of the circuit to actually find out how much it additionally drops the volume level without the speakers field coil activation (~3-4 W )
73's de Edd
:Dave
:
: Be careful with your 48 tubes. They operate directly off of 30 volts and will be destroyed it someone plugs the radio into 120 volts.
:
: For testing you can use 43's in place of 48's. Output will be less but they don't cost so much.
:
: 30 volts should be enough for the radio. Be sure it holds voltage under load. Some power supplies have an adjustment for voltage where it can be brought up. Some 24 volt supplies can be adjusted to 32 volts. If a supply has a crow bar circuit it can be disabled. A crow bar circuit shorts the supply when voltage is exceeded.
:
: You could wire a supply in series to increase voltage for testing.
:
:Norm
:
:
::I just completed restoration of a console that runs on 32 Volt DC, the closest power supply I could find was one for 30Volts DC at Radio Shack, the radio works, but volume is LOW, any ideas on where to find a 32 VDC supply or how to boost my 30 ? Thanks, DaveF
I finally found in a post here that the pilot lamp was working ok. Is the lamp the proper one? Does the cone of the speaker move freely? Can the strength of the center pole piece of the speaker be tested with a screwdriver/nutdriver for magnetic strength?
Radiodoc
************
:
:
:
:
:
:After seeing the tandem series stringing up of the filaments as shown along with the additional power consumption of the field coil being the main current
:
:hogs,
: that 1 amp figure does seem to be quite accomodating with only a paltry amount of additional power being consumed by virtue of running the plates
:
:at low B+ potential.
:
:Now, upon having the schematic available for viewing , relevant to the pilot lamp-field coil loop and looking at the parameters given.... seems like it would like
:to see ~ 215 ma across it at 6.3VDC.
:With possibilities of three sets of lamps, according to the socketing requirements. A #46 or #44 would pass adequate
:current thru the loop for the
:field coil, as would a #50 or #51 with a longer lifespan expectancy. However, a #40 - 47 - 1847 being used in that slot would have a very short lifespan..
:That mentioning of the pilot lamp being open sounded like a very plausible reason for the low volume....but, its not open.
:
:With a referencing of the volume that you would normally listen to a radio, would you say that your present situation is giving possibly only half of that volume or a quarter of that amount ?
:Or, possibly the volume level is just being adequate, but you are wondering why it has no power reserve. Also, just for info purposes would you check to see what number of pilot lamp that unit is using, and also twist / screw it out of the circuit to actually find out how much it additionally drops the volume level without the speakers field coil activation (~3-4 W )
:
:
:73's de Edd
:
:
:
:
:
:
:
::Dave
::
:: Be careful with your 48 tubes. They operate directly off of 30 volts and will be destroyed it someone plugs the radio into 120 volts.
::
:: For testing you can use 43's in place of 48's. Output will be less but they don't cost so much.
::
:: 30 volts should be enough for the radio. Be sure it holds voltage under load. Some power supplies have an adjustment for voltage where it can be brought up. Some 24 volt supplies can be adjusted to 32 volts. If a supply has a crow bar circuit it can be disabled. A crow bar circuit shorts the supply when voltage is exceeded.
::
:: You could wire a supply in series to increase voltage for testing.
::
::Norm
::
::
:::I just completed restoration of a console that runs on 32 Volt DC, the closest power supply I could find was one for 30Volts DC at Radio Shack, the radio works, but volume is LOW, any ideas on where to find a 32 VDC supply or how to boost my 30 ? Thanks, DaveF
Gentlemen: I checked all the tubes and realized the 76 was replaced long ago with a 37 and the 48's with 2 43's, I am going to check the pilot lamp next. As for the volume level, if I put a ground wire to the metal radiator, the volume is at best 20% of what I would consider normal volume and that is with the control to the max, although the antenna that I am using is only a 3 foot copper wire. DaveF
:
:I finally found in a post here that the pilot lamp was working ok. Is the lamp the proper one? Does the cone of the speaker move freely? Can the strength of the center pole piece of the speaker be tested with a screwdriver/nutdriver for magnetic strength?
:
:Radiodoc
:************
:
::
::
::
::
::
::After seeing the tandem series stringing up of the filaments as shown along with the additional power consumption of the field coil being the main current
::
::hogs,
:: that 1 amp figure does seem to be quite accomodating with only a paltry amount of additional power being consumed by virtue of running the plates
::
::at low B+ potential.
::
::Now, upon having the schematic available for viewing , relevant to the pilot lamp-field coil loop and looking at the parameters given.... seems like it would like
::to see ~ 215 ma across it at 6.3VDC.
::With possibilities of three sets of lamps, according to the socketing requirements. A #46 or #44 would pass adequate
::current thru the loop for the
::field coil, as would a #50 or #51 with a longer lifespan expectancy. However, a #40 - 47 - 1847 being used in that slot would have a very short lifespan..
::That mentioning of the pilot lamp being open sounded like a very plausible reason for the low volume....but, its not open.
::
::With a referencing of the volume that you would normally listen to a radio, would you say that your present situation is giving possibly only half of that volume or a quarter of that amount ?
::Or, possibly the volume level is just being adequate, but you are wondering why it has no power reserve. Also, just for info purposes would you check to see what number of pilot lamp that unit is using, and also twist / screw it out of the circuit to actually find out how much it additionally drops the volume level without the speakers field coil activation (~3-4 W )
::
::
::73's de Edd
::
::
::
::
::
::
::
:::Dave
:::
::: Be careful with your 48 tubes. They operate directly off of 30 volts and will be destroyed it someone plugs the radio into 120 volts.
:::
::: For testing you can use 43's in place of 48's. Output will be less but they don't cost so much.
:::
::: 30 volts should be enough for the radio. Be sure it holds voltage under load. Some power supplies have an adjustment for voltage where it can be brought up. Some 24 volt supplies can be adjusted to 32 volts. If a supply has a crow bar circuit it can be disabled. A crow bar circuit shorts the supply when voltage is exceeded.
:::
::: You could wire a supply in series to increase voltage for testing.
:::
:::Norm
:::
:::
::::I just completed restoration of a console that runs on 32 Volt DC, the closest power supply I could find was one for 30Volts DC at Radio Shack, the radio works, but volume is LOW, any ideas on where to find a 32 VDC supply or how to boost my 30 ? Thanks, DaveF
You lost some volume by having a 37 in place of 76 tube. Gain of 9 vs. 13. Although 43's will work in place of 48's they have reduced output. In one case you are better off with 43's. They draw 300 ma filament current while 48's draw 400 ma. Total radio load with 43's will be around 1 amp.
If the radio is aligned and components are corrent you may want to put it aside until you get the proper tubes? Be sure supply voltage doesn't drop off with your radio load. No problem getting a 76. The 48's will cost more and aren't as common.
Norm
::Gentlemen,
:Gentlemen: I checked all the tubes and realized the 76 was replaced long ago with a 37 and the 48's with 2 43's, I am going to check the pilot lamp next. As for the volume level, if I put a ground wire to the metal radiator, the volume is at best 20% of what I would consider normal volume and that is with the control to the max, although the antenna that I am using is only a 3 foot copper wire. DaveF
::
::I finally found in a post here that the pilot lamp was working ok. Is the lamp the proper one? Does the cone of the speaker move freely? Can the strength of the center pole piece of the speaker be tested with a screwdriver/nutdriver for magnetic strength?
::
::Radiodoc
::************
::
:::
:::
:::
:::
:::
:::After seeing the tandem series stringing up of the filaments as shown along with the additional power consumption of the field coil being the main current
:::
:::hogs,
::: that 1 amp figure does seem to be quite accomodating with only a paltry amount of additional power being consumed by virtue of running the plates
:::
:::at low B+ potential.
:::
:::Now, upon having the schematic available for viewing , relevant to the pilot lamp-field coil loop and looking at the parameters given.... seems like it would like
:::to see ~ 215 ma across it at 6.3VDC.
:::With possibilities of three sets of lamps, according to the socketing requirements. A #46 or #44 would pass adequate
:::current thru the loop for the
:::field coil, as would a #50 or #51 with a longer lifespan expectancy. However, a #40 - 47 - 1847 being used in that slot would have a very short lifespan..
:::That mentioning of the pilot lamp being open sounded like a very plausible reason for the low volume....but, its not open.
:::
:::With a referencing of the volume that you would normally listen to a radio, would you say that your present situation is giving possibly only half of that volume or a quarter of that amount ?
:::Or, possibly the volume level is just being adequate, but you are wondering why it has no power reserve. Also, just for info purposes would you check to see what number of pilot lamp that unit is using, and also twist / screw it out of the circuit to actually find out how much it additionally drops the volume level without the speakers field coil activation (~3-4 W )
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
:::
:::
::::Dave
::::
:::: Be careful with your 48 tubes. They operate directly off of 30 volts and will be destroyed it someone plugs the radio into 120 volts.
::::
:::: For testing you can use 43's in place of 48's. Output will be less but they don't cost so much.
::::
:::: 30 volts should be enough for the radio. Be sure it holds voltage under load. Some power supplies have an adjustment for voltage where it can be brought up. Some 24 volt supplies can be adjusted to 32 volts. If a supply has a crow bar circuit it can be disabled. A crow bar circuit shorts the supply when voltage is exceeded.
::::
:::: You could wire a supply in series to increase voltage for testing.
::::
::::Norm
::::
::::
:::::I just completed restoration of a console that runs on 32 Volt DC, the closest power supply I could find was one for 30Volts DC at Radio Shack, the radio works, but volume is LOW, any ideas on where to find a 32 VDC supply or how to boost my 30 ? Thanks, DaveF
I ran some numbers and it indicates that 30 volts at 1 amp won't make it. Here is how it goes.
According to the schematic the low side of the 48s' heaters have 2 volts. This 2 volts is across a 2.5 ohm resistor, R14. Using ohms law, that gives us 0.8 amps just to power those heaters. On the series filament string we have another resistor to adjust heater voltage, R13. On one end of it it has the 32 volts, on the other it has 24. Again using ohms law the current is 32v-24v/26 ohms, which is a little more than 0.3 amps. We have overextended the power supply already and we haven't gotten to the speaker field. I estimate total current draw to be 1.5 ampere.
I saw on a posting that perhaps 43s' are in place of the 48s'. If these are taking less filament current, then the bias on the 76 will be effected, taking the 76 toward saturation, degrading its efficiency.
Bottom line, the power short fall in current is enough to explain the weak perfromance. Tube changes in the power output (the 48s) will cause biasing changes in the AF section which would also degrade performance.
Best Regards,
Bill Grimm
:Hi All,
: I ran some numbers and it indicates that 30 volts at 1 amp won't make it. Here is how it goes.
:
: According to the schematic the low side of the 48s' heaters have 2 volts. This 2 volts is across a 2.5 ohm resistor, R14. Using ohms law, that gives us 0.8 amps just to power those heaters. On the series filament string we have another resistor to adjust heater voltage, R13. On one end of it it has the 32 volts, on the other it has 24. Again using ohms law the current is 32v-24v/26 ohms, which is a little more than 0.3 amps. We have overextended the power supply already and we haven't gotten to the speaker field. I estimate total current draw to be 1.5 ampere.
: I saw on a posting that perhaps 43s' are in place of the 48s'. If these are taking less filament current, then the bias on the 76 will be effected, taking the 76 toward saturation, degrading its efficiency.
: Bottom line, the power short fall in current is enough to explain the weak perfromance. Tube changes in the power output (the 48s) will cause biasing changes in the AF section which would also degrade performance.
:
:Best Regards,
:
:Bill Grimm
:
::Hi All,
:: I ran some numbers and it indicates that 30 volts at 1 amp won't make it. Here is how it goes.
::
:: According to the schematic the low side of the 48s' heaters have 2 volts. This 2 volts is across a 2.5 ohm resistor, R14. Using ohms law, that gives us 0.8 amps just to power those heaters. On the series filament string we have another resistor to adjust heater voltage, R13. On one end of it it has the 32 volts, on the other it has 24. Again using ohms law the current is 32v-24v/26 ohms, which is a little more than 0.3 amps. We have overextended the power supply already and we haven't gotten to the speaker field. I estimate total current draw to be 1.5 ampere.
:: I saw on a posting that perhaps 43s' are in place of the 48s'. If these are taking less filament current, then the bias on the 76 will be effected, taking the 76 toward saturation, degrading its efficiency.
:: Bottom line, the power short fall in current is enough to explain the weak perfromance. Tube changes in the power output (the 48s) will cause biasing changes in the AF section which would also degrade performance.
::
::Best Regards,
::
::Bill Grimm
Gentlemen:
I thank you for all your advice, I am going to look for a 76 tube, and then see if volume improves. If not, I will look for a 32 volt supply or the 48's to improve performance. Best regards to all.
DaveF
::
:::Hi All,
::: I ran some numbers and it indicates that 30 volts at 1 amp won't make it. Here is how it goes.
:::
::: According to the schematic the low side of the 48s' heaters have 2 volts. This 2 volts is across a 2.5 ohm resistor, R14. Using ohms law, that gives us 0.8 amps just to power those heaters. On the series filament string we have another resistor to adjust heater voltage, R13. On one end of it it has the 32 volts, on the other it has 24. Again using ohms law the current is 32v-24v/26 ohms, which is a little more than 0.3 amps. We have overextended the power supply already and we haven't gotten to the speaker field. I estimate total current draw to be 1.5 ampere.
::: I saw on a posting that perhaps 43s' are in place of the 48s'. If these are taking less filament current, then the bias on the 76 will be effected, taking the 76 toward saturation, degrading its efficiency.
::: Bottom line, the power short fall in current is enough to explain the weak perfromance. Tube changes in the power output (the 48s) will cause biasing changes in the AF section which would also degrade performance.
:::
:::Best Regards,
:::
:::Bill Grimm
:
:Gentlemen:
:I thank you for all your advice, I am going to look for a 76 tube, and then see if volume improves. If not, I will look for a 32 volt supply or the 48's to improve performance. Best regards to all.
: DaveF
:::
::::Hi All,
:::: I ran some numbers and it indicates that 30 volts at 1 amp won't make it. Here is how it goes.
::::
:::: According to the schematic the low side of the 48s' heaters have 2 volts. This 2 volts is across a 2.5 ohm resistor, R14. Using ohms law, that gives us 0.8 amps just to power those heaters. On the series filament string we have another resistor to adjust heater voltage, R13. On one end of it it has the 32 volts, on the other it has 24. Again using ohms law the current is 32v-24v/26 ohms, which is a little more than 0.3 amps. We have overextended the power supply already and we haven't gotten to the speaker field. I estimate total current draw to be 1.5 ampere.
:::: I saw on a posting that perhaps 43s' are in place of the 48s'. If these are taking less filament current, then the bias on the 76 will be effected, taking the 76 toward saturation, degrading its efficiency.
:::: Bottom line, the power short fall in current is enough to explain the weak perfromance. Tube changes in the power output (the 48s) will cause biasing changes in the AF section which would also degrade performance.
::::
::::Best Regards,
::::
::::Bill Grimm
::
::Gentlemen:
::I thank you for all your advice, I am going to look for a 76 tube, and then see if volume improves. If not, I will look for a 32 volt supply or the 48's to improve performance. Best regards to all.
:: DaveFHello!
Sorry for the blank post...unfamiliar with how this type of forum operates. Use multiple transformers...2 12.6V and a 6.3V wired in series give 31.5V. You should be able to find transformers rated at 3-4 amps surplus inexpensively. Just be sure to check your connections with a voltmeter to be sure the windings are all running in series, and use transformers with the same current rating.
May I disagree? 31.5 RMS Volts will give a peak of (31.5 X 1.414) or 44.54 Volts, a little high, IMHO. 24 Volts will give a peak of 33.93, or close to 32 under load. I say forget the 6.3 Volt transformer. Funny thing, I fished a power supply out of the trash at work, the regulator board was shot and no parts available, so I have a 24 Volt 50 Ampere, I think, transformer in my basement. Anyone wishing to pay the shipping costs can have it for free.
Lewis
I forgot to mention that if you get a bigger power supply you must not use a switching power supply. Switching power supplies can power the radio just fine, but are notorious for interfereing with AM radio!
John M. described using transformers in series. That will be good. Make sure you have the phasing right if you do that, though.
Best Regards,
Bill Grimm
O.K.....O.K. .. on my part....... I was just overly fixated in on that field coil excitation voltage at that time, and its potential non presence due to a dial lamp malfunction. Now, I had initially accounted for the separate 6V series of tubes current consumption in their string as well as the speakers field coil, plus the minimal drain on the 32V DC B+ supply by the low plate potential utilized on earlier RF and AF stages along with a bit more required in the driver and then progressively more in the P/P power output stage. (With their dissipation actually being a shared condition, as each tube alternatively responds to its + or - portion of the audio, being presented to it by the driver transformer.)
What I had done was to have forgotten to finish the calculation of the output tubes..... as 41's and 42's were as close to that numbering as I had ever personally used or seen in equipment...... and seeing their schema hook up, I SAW the specified voltage across them as well as the bottom end series resistor utilized for setting up above ground and acquiring bias voltage. I still wanted to confirm those tubes filament and current design spec's as well as the also mentioned '43. I found only the basing diagram on this site for those tubes and that Kapps on line tube site didn't even seem to have those two oldies covered.
So now, after retrieving my RCA #RC-29 from storage to consult its "ole" tube section in the rear, I see that the 48's filament is spec'd at 30V @400 ma....in precise accordance with Sir Bill G's numbers....But what I am seeing for the '43 tube is a design spec of 25V @300 ma. Hey..that particular combined filament string load has just now dropped from 800 ma (using 48's) down to 600 ma (using 43's).
But..... and hea-v-yyyy on the BUT...... the most important thing to see in that situation, would be the fact that if one just subbed in those '43's for the 48's in THE circuit shown in the referenced schematic, things would then just not be right.
Initially, with the using of the 48's, the dropping resistor placed at the low end of the filament string would have a dual purpose, with the developing of bias for the driver stage across that 2.5 ohm resistor, and with the resultant balance of the initially applied 32 Vdc being reduced to the correct 30 V level for those 48's filaments.
Should 43's be plugged into the identical circuit, the series voltage division between the tubes and that power dropping resistor will balance out with ~1.8 Vdc developing across the dropping resistor but that is then going to leave 30.2 Vdc going to the 43's. That is 30.2 volts across them instead of the spec'd 25. Mind you, not the typical 6-8 v or 12-14 filament voltage leeway commonly spec'd on car radios and mobile electronics (using those two common 6 and 12V filament voltage ranges), but this is up a full 5 volts from the norm.
What I think that is logical to have happened, is that within the time frame of having using those 43's, and being used at that 32 volt supply level has resulted in the "cooking" away and the fierce depletion of its active cathode coating..... to the extent that emission of the output tubes has dropped drastically over time of use. Gain performance typically just sliding down with more time of use. This also combining the fact that the circuitry is using low plate potential supply, where tube transconductance IS of major importance.
Now, for confirmation, got a mutual transconductance tube tester, or some known good 43's...????
Seems like If you want to stick with using 43's.....in this chassis' design......then along with a their replacement you would want to replace the inital 2.5 ohm dropping resistor with a total 11.5 ohm unit. I say total , because that value alone would upset the derivation of the prescribed 2 Volt level offset above ground voltage, with a healthier ~6.9 Vdc level then being developed across that series dropping resistor. However, if one was to come up from ground and connect in 3 paralleled 10 ohm 2 watt resistors and then take 3 paralleled 25 ohm 2 watt resistors and connect the two clusters in series to then go up to the filament connection. The tap point between the two would then derive the specified 2V source. Those specified resistor values are stock values as well , as compared to the odd fractional resistive values that are otherwise required to get that divisional ratio.
I also remember the Wincharger with its spinning / flying little "airplane" propeller and the multi wet cell bank (some of the salvaged heavy glass jars now serving as planters) which one had to monitor quite closely for its electrolyte level and keep topped off with collected "distilled" water from the rainwater barrel.I was to young at that time to even fathom the electrical aspect of the unit...particularly the charging aspect and any charging /regulation issues. Assuredly the battery bank was the primary reason for the stability of its delivered voltage. With our system ,it was always plenty hot at all times, for the additional items on its line, with nary ever a dim light bulb. An attribute, I guess, to the ever healthy wind levels present on the high plains of Tx.
73's de Edd
:Hi Dave,
: I forgot to mention that if you get a bigger power supply you must not use a switching power supply. Switching power supplies can power the radio just fine, but are notorious for interfereing with AM radio!
: John M. described using transformers in series. That will be good. Make sure you have the phasing right if you do that, though.
:
:Best Regards,
:
:Bill Grimm