Hey all in radio land, Still working on a Coronado 908.
And will be until I get it fix this is my training radio. On the plates the schematic calls for 235vdc I have 315 is the 235 a average a minimum or the max? Other plated call for 85v and I have 115 B+ calls for 290 I have 313. is this a problem or can I move on the other problem with this unit?
Thanks,
KY

Do all of the voltages measure excessively high?

Tubes weak? Excessively high line voltage? Non-original power transformer? Open circuit somewhere? Drifted resistors especially in the output section?

If all tubes and components test normally, then you should suspect a non-original power transformer, speaker field (or possibly a shorted field coil), or excessive line voltage.

T.

:Do all of the voltages measure excessively high?
:
:Tubes weak? Excessively high line voltage? Non-original power transformer? Open circuit somewhere? Drifted resistors especially in the output section?
:
:If all tubes and components test normally, then you should suspect a non-original power transformer, speaker field (or possibly a shorted field coil), or excessive line voltage.
:
:T.
:All V check a little high so do I go by the schematic or if the schematic said 85V is 111V way to much?
KY

It's a bit excessive. Do the voltages at the power transformer measure high, too? Have you checked all resistance values, including the speaker field coil?

Have you checked the emissions of all of the tubes?

T.

:It's a bit excessive. Do the voltages at the power transformer measure high, too? Have you checked all resistance values, including the speaker field coil?
:
:Have you checked the emissions of all of the tubes?
:
:T.
:The B+ should be 290 I have 313, other transformer v are normal. I did change out the field coil with a 1k 20 watt resistor. This is my first recap and I fill like I have a cap or resistor in the wrong place.

Hi

A couple more things. Does your radio have a 5W4 rectifier tube? If someone used 5Z4 or 5V4 voltage will be high.

http://www.nostalgiaair.org/PagesByModel/174/M0007174.pdf

Schematic shows 117 volt line. A 125 volt line will give higher voltages. What filament voltage do you measure? Normal voltage is 6.3 volts AC.

Norm

:Hey all in radio land, Still working on a Coronado 908.
:And will be until I get it fix this is my training radio. On the plates the schematic calls for 235vdc I have 315 is the 235 a average a minimum or the max? Other plated call for 85v and I have 115 B+ calls for 290 I have 313. is this a problem or can I move on the other problem with this unit?
:Thanks,
:KY
:

:Hi
:Hi, the schematic calls for 5w4GT there is a 5v4 in the radio. and I have 6.8 on the fil. I also have the unit pluged into a Variac set at 120 not at 117 this could be my over voltage?
KY
: A couple more things. Does your radio have a 5W4 rectifier tube? If someone used 5Z4 or 5V4 voltage will be high.
:
: http://www.nostalgiaair.org/PagesByModel/174/M0007174.pdf
:
: Schematic shows 117 volt line. A 125 volt line will give higher voltages. What filament voltage do you measure? Normal voltage is 6.3 volts AC.
:
:Norm
:
:
::Hey all in radio land, Still working on a Coronado 908.
::And will be until I get it fix this is my training radio. On the plates the schematic calls for 235vdc I have 315 is the 235 a average a minimum or the max? Other plated call for 85v and I have 115 B+ calls for 290 I have 313. is this a problem or can I move on the other problem with this unit?
::Thanks,
::KY
::
:

Hi

You found the main reasons for higher voltage. A 5W4 has an internal voltage drop around 45. A 5V4 has a drop around 23 volts. This alone gives a DC output of 22 more volts. Having line voltage a little high also increases voltage.

Since tubes probably have a lot of use emission will be lower. This also causes higher voltages as can be seen on the plates where schematic calls out 235.

Higher voltage isn't a problem unless it beyond component ratings. Use 450 volt rated electrolytic caps and there shouldn't be a problem.

Norm

::Hi
::Hi, the schematic calls for 5w4GT there is a 5v4 in the radio. and I have 6.8 on the fil. I also have the unit pluged into a Variac set at 120 not at 117 this could be my over voltage?
:KY
:: A couple more things. Does your radio have a 5W4 rectifier tube? If someone used 5Z4 or 5V4 voltage will be high.
::
:: http://www.nostalgiaair.org/PagesByModel/174/M0007174.pdf
::
:: Schematic shows 117 volt line. A 125 volt line will give higher voltages. What filament voltage do you measure? Normal voltage is 6.3 volts AC.
::
::Norm
::
::
:::Hey all in radio land, Still working on a Coronado 908.
:::And will be until I get it fix this is my training radio. On the plates the schematic calls for 235vdc I have 315 is the 235 a average a minimum or the max? Other plated call for 85v and I have 115 B+ calls for 290 I have 313. is this a problem or can I move on the other problem with this unit?
:::Thanks,
:::KY
:::
::
:

What was the resistance of the original field coil? Was it 1K?

T.

:What was the resistance of the original field coil? Was it 1K?
:
:T.
:Yes it was 1k.
KY

:What was the resistance of the original field coil? Was it 1K?
:
:T.
:
terry

::What was the resistance of the original field coil? Was it 1K?
::
::T.
::
:
:Ok, call me a grumpy old coot, but I still believe that a resistor is a very poor substitute for a field coil. In addition to the electrical difference between a resistor and an inductor, the coil was an integral part of the filtering system of the B+ supply. Ok, coils are harder to come by than a resistor, but a good substitute is the primary of a door bell transformer. I don't mean to step on any toes, and it's obvious that I have a high regard for each of you, and your knowledge. I'm just sayin' my 2 cents, that's all.
:terry
:Terry, 2cents worth could fix it. This is my first restore, I have recapped and replaced all out of tolerance resistors. I replaced the 2 @ a time and tested to unit. All seem to go well until I took the speaker out to refinish the cabinet. Then the speaker got a tear in the cone and the project went south from there. So any opinion is better than no opinion. Thanks,
KY

:::What was the resistance of the original field coil? Was it 1K?
:::
:::T.
:::
::
::Ok, call me a grumpy old coot, but I still believe that a resistor is a very poor substitute for a field coil. In addition to the electrical difference between a resistor and an inductor, the coil was an integral part of the filtering system of the B+ supply. Ok, coils are harder to come by than a resistor, but a good substitute is the primary of a door bell transformer. I don't mean to step on any toes, and it's obvious that I have a high regard for each of you, and your knowledge. I'm just sayin' my 2 cents, that's all.
::terry
::Terry, 2cents worth could fix it. This is my first restore, I have recapped and replaced all out of tolerance resistors. I replaced the 2 @ a time and tested to unit. All seem to go well until I took the speaker out to refinish the cabinet. Then the speaker got a tear in the cone and the project went south from there. So any opinion is better than no opinion. Thanks,
:KY
:
Terry

Regarding resistors, they can work well. Once I built an amplifier from the schematic I found inside of an old 1930s Magnavox phonograph (shame, 'cause it was a nice phonograph--speaker even had an aluminum voice coil for high fidelity). I used a resistor for the field coil, and hum was almost non-existant. A choke is better, though, and I can attest to the superb performance of the field coil and hum bucking coil in the speaker of my Philco 60. There is NO hum!! ....My Crosley 1117 is a different story, however, but I may have some other issues, including that the 1st audio could use shielding. Holding my hand near the front of the cabinet is enough to aggrevate the situation.

Regarding speaker repair, I prefer Elmer's only because it is long lasting. It can be applied in very thin amounts, allowing it to be flexible. Rubber cement is far more flexible, but has a tendency to go bad after a few years. Give it a try, though. You won't harm anything. It certainly is light and flexible, and has an extremely low frequency of resonance, so it won't add any unpleasant characteristics to your speaker. Peter also uses sewing glue, which is like Elmer's, but is more flexible. There may be other good suggestions, too. I cannot agree with the use of silicon caulk because it has a tendency to tear and let loose with time. Others might have more success with it than me. Perhaps it would bond more strongly if there were a way to thin it and allow it to penetrate the paper more thoroughly.

T.

Well T,
As noted many times before, I use Elmers Craft Bond Paper and Fabric glue. It dries clear in blobs, with the consistency much like RTV, is water soluable, can be diluted and brushed on like paint (cones),is washable, ie waterproof, and much easier to apply than RTV, rubber glue or many others. Haven't tried coating old wiring, but should work well there too.

marv

:Regarding resistors, they can work well. Once I built an amplifier from the schematic I found inside of an old 1930s Magnavox phonograph (shame, 'cause it was a nice phonograph--speaker even had an aluminum voice coil for high fidelity). I used a resistor for the field coil, and hum was almost non-existant. A choke is better, though, and I can attest to the superb performance of the field coil and hum bucking coil in the speaker of my Philco 60. There is NO hum!! ....My Crosley 1117 is a different story, however, but I may have some other issues, including that the 1st audio could use shielding. Holding my hand near the front of the cabinet is enough to aggrevate the situation.
:
:Regarding speaker repair, I prefer Elmer's only because it is long lasting. It can be applied in very thin amounts, allowing it to be flexible. Rubber cement is far more flexible, but has a tendency to go bad after a few years. Give it a try, though. You won't harm anything. It certainly is light and flexible, and has an extremely low frequency of resonance, so it won't add any unpleasant characteristics to your speaker. Peter also uses sewing glue, which is like Elmer's, but is more flexible. There may be other good suggestions, too. I cannot agree with the use of silicon caulk because it has a tendency to tear and let loose with time. Others might have more success with it than me. Perhaps it would bond more strongly if there were a way to thin it and allow it to penetrate the paper more thoroughly.
:
:T.
:

::::What was the resistance of the original field coil? Was it 1K?
::::
::::T.
::::
:::
:::Ok, call me a grumpy old coot, but I still believe that a resistor is a very poor substitute for a field coil. In addition to the electrical difference between a resistor and an inductor, the coil was an integral part of the filtering system of the B+ supply. Ok, coils are harder to come by than a resistor, but a good substitute is the primary of a door bell transformer. I don't mean to step on any toes, and it's obvious that I have a high regard for each of you, and your knowledge. I'm just sayin' my 2 cents, that's all.
:::terry
:::Terry, 2cents worth could fix it. This is my first restore, I have recapped and replaced all out of tolerance resistors. I replaced the 2 @ a time and tested to unit. All seem to go well until I took the speaker out to refinish the cabinet. Then the speaker got a tear in the cone and the project went south from there. So any opinion is better than no opinion. Thanks,
::KY
::
:
:Ky- note to self- The VERY first thing to do when removing a radio from the case is to put a piece of cardboard over the speaker. I can't believe how many experienced people don't remember this simple rule. I've even forgot to REMOVE the cardboard, and had to take the radio out again. Hint- a speaker cone CAN be repaired, as long as the whole thing isn't powder. I use rubber glue, not plastic cement, and a small piece of thick, single ply toilet paper. Yep, toilet paper. It's never gonna look good, but it is flexible and it's about the same thickness. Any time I've replaced a speaker with a field coil, I've used some kind of coil. Ok, I've only done about three. AES has some chokes, and I read in an old radio repair manual that the primary of a transformer can be used. Like I said, there's a reason it's a coil and not a resistor. That said, lots of people use resistors with no problem. Keep me posted, I'd like to know how it turns out.
:Terry
:Well Terry got to live and learn, the speaker was fine and the radio worked before I started. I have 3 other radios to do after this and you can believe some cardboard will be installed. I installed the transformer from the old speaker onto the new speaker.
Thanks, for any help and guidance KY

If voltage values are still a concern..
AS a test ...you could put the old FC speaker back .. forgetting about tears .. and just measure voltages .. try a 5w4 as well...
This way you can determine what degree of change a resistor substitute makes for the FC.

:If voltage values are still a concern..
:AS a test ...you could put the old FC speaker back .. forgetting about tears .. and just measure voltages .. try a 5w4 as well...
:This way you can determine what degree of change a resistor substitute makes for the FC.
:Peter, I wish I had been smart enough to keep the old speaker. I will order and install a 5w4 and see what the voltage is then.
Thanks, KY
:

:If voltage values are still a concern..
:AS a test ...you could put the old FC speaker back .. forgetting about tears .. and just measure voltages .. try a 5w4 as well...
:This way you can determine what degree of change a resistor substitute makes for the FC.
:
:
I have had great success with a elmers glue stick and then applying little by little darker color lint from the dryer. Take a wad of lint and lightly dab over the glue till it sticks no more. The flex of the lint holds up nicely.

Very interesting idea.

Regarding field coil speakers, try to use the original speaker whenever possible. Cones are available for most speakers.

T.