Can anyone recommend which universal output transformer from antique Electronics would be correct for an American Bosch 28? Primary goes to push-pull 71A"s while secondary connects to output jacks for external speaker.
Use the least expensive. P-T291 seems to be lowest cost in the 2008 catalog. Universal Output transformers have multiple taps for matching different output tubes.
These output transformers are made to match low impedance speakers. A few early radios had output transformers to match high impedance speakers. If your radio has high impedance output 2 transformers, back to back, will be needed.
Norm
:Hello All,
:
: Can anyone recommend which universal output transformer from antique Electronics would be correct for an American Bosch 28? Primary goes to push-pull 71A"s while secondary connects to output jacks for external speaker.
So to use the original speaker, I'm pretty sure its 2000 ohms, what would I have to do? The original output transformer is open.
Hi Bill
:
: Use the least expensive. P-T291 seems to be lowest cost in the 2008 catalog. Universal Output transformers have multiple taps for matching different output tubes.
:
: These output transformers are made to match low impedance speakers. A few early radios had output transformers to match high impedance speakers. If your radio has high impedance output 2 transformers, back to back, will be needed.
:
:Norm
:
::Hello All,
::
:: Can anyone recommend which universal output transformer from antique Electronics would be correct for an American Bosch 28? Primary goes to push-pull 71A"s while secondary connects to output jacks for external speaker.
Your radios uses push-pull for audio output. You need a transformer to connect from tubes to speaker.
http://www.nostalgiaair.org/PagesByModel/767/M0040767.pdf
A transformer will give a low impedance output. To be right a second output transformer should be connected in reverse to the first one. This will bring impedance back up.
Here is another way to do it. Connect a 1 mf cap from each output tube plate to you high impedance speaker. This way you won't be using output of the transformer. The primary side is already high impedance and caps from tube plates will isolate DC voltage from the speaker.
Don't really need a cap from each tube plate but it's a good idea in case a wire touches chassis.
Norm
:Hi Norm,
:
: So to use the original speaker, I'm pretty sure its 2000 ohms, what would I have to do? The original output transformer is open.
:
:
:
:Hi Bill
::
:: Use the least expensive. P-T291 seems to be lowest cost in the 2008 catalog. Universal Output transformers have multiple taps for matching different output tubes.
::
:: These output transformers are made to match low impedance speakers. A few early radios had output transformers to match high impedance speakers. If your radio has high impedance output 2 transformers, back to back, will be needed.
::
::Norm
::
:::Hello All,
:::
::: Can anyone recommend which universal output transformer from antique Electronics would be correct for an American Bosch 28? Primary goes to push-pull 71A"s while secondary connects to output jacks for external speaker.
Yhanks for the advice so far. No if I understand correctly, the 2 PT291's will create the proper impedance. With the primary going to the plates, the secondaries (multiple taps) must be connected with the reversed primary of #2 transformer going to the speaker jacks. As there are multiple taps on the Pt291, which are connected for proper function?
In the second case of using 1 MF caps from plate to speaker jacks, how would I run the B+? The primary of the original output transformer is open.
Would I just run the B= from the center tap to the plates?
Really appreciate your input ands suggestions.
:Hi Bill
:
: Your radios uses push-pull for audio output. You need a transformer to connect from tubes to speaker.
:
:http://www.nostalgiaair.org/PagesByModel/767/M0040767.pdf
:
: A transformer will give a low impedance output. To be right a second output transformer should be connected in reverse to the first one. This will bring impedance back up.
:
: Here is another way to do it. Connect a 1 mf cap from each output tube plate to you high impedance speaker. This way you won't be using output of the transformer. The primary side is already high impedance and caps from tube plates will isolate DC voltage from the speaker.
:
: Don't really need a cap from each tube plate but it's a good idea in case a wire touches chassis.
:
:Norm
:
::Hi Norm,
::
:: So to use the original speaker, I'm pretty sure its 2000 ohms, what would I have to do? The original output transformer is open.
::
::
::
::Hi Bill
:::
::: Use the least expensive. P-T291 seems to be lowest cost in the 2008 catalog. Universal Output transformers have multiple taps for matching different output tubes.
:::
::: These output transformers are made to match low impedance speakers. A few early radios had output transformers to match high impedance speakers. If your radio has high impedance output 2 transformers, back to back, will be needed.
:::
:::Norm
:::
::::Hello All,
::::
:::: Can anyone recommend which universal output transformer from antique Electronics would be correct for an American Bosch 28? Primary goes to push-pull 71A"s while secondary connects to output jacks for external speaker.
You can use any taps when having universal output transformers back to back. Just as long as they are the same ones on each transformer. If you use taps #1 and #6 on one transformer use the same taps on the other.
When driving the speaker through caps you still need 1 output transformer with a good primary. You just don't need the second transformer.
Norm
:Hi Norm,
:
: Yhanks for the advice so far. No if I understand correctly, the 2 PT291's will create the proper impedance. With the primary going to the plates, the secondaries (multiple taps) must be connected with the reversed primary of #2 transformer going to the speaker jacks. As there are multiple taps on the Pt291, which are connected for proper function?
:
:
: In the second case of using 1 MF caps from plate to speaker jacks, how would I run the B+? The primary of the original output transformer is open.
:Would I just run the B= from the center tap to the plates?
:
:
: Really appreciate your input ands suggestions.
:
:
:
:
::Hi Bill
::
:: Your radios uses push-pull for audio output. You need a transformer to connect from tubes to speaker.
::
::http://www.nostalgiaair.org/PagesByModel/767/M0040767.pdf
::
:: A transformer will give a low impedance output. To be right a second output transformer should be connected in reverse to the first one. This will bring impedance back up.
::
:: Here is another way to do it. Connect a 1 mf cap from each output tube plate to you high impedance speaker. This way you won't be using output of the transformer. The primary side is already high impedance and caps from tube plates will isolate DC voltage from the speaker.
::
:: Don't really need a cap from each tube plate but it's a good idea in case a wire touches chassis.
::
::Norm
::
:::Hi Norm,
:::
::: So to use the original speaker, I'm pretty sure its 2000 ohms, what would I have to do? The original output transformer is open.
:::
:::
:::
:::Hi Bill
::::
:::: Use the least expensive. P-T291 seems to be lowest cost in the 2008 catalog. Universal Output transformers have multiple taps for matching different output tubes.
::::
:::: These output transformers are made to match low impedance speakers. A few early radios had output transformers to match high impedance speakers. If your radio has high impedance output 2 transformers, back to back, will be needed.
::::
::::Norm
::::
:::::Hello All,
:::::
::::: Can anyone recommend which universal output transformer from antique Electronics would be correct for an American Bosch 28? Primary goes to push-pull 71A"s while secondary connects to output jacks for external speaker.
So if I understand correctly, I should use the primary of the PT291 as a filter choke to supply the plates and then run the caps from the plates to the output jacks. Space is at a premium since the power unit and amplifier are together and separate from the radio section. I dont believe I could use 2 PT291's unless a lot of modification. Thanks for the advice and help so far..
Hi Bill
:
: You can use any taps when having universal output transformers back to back. Just as long as they are the same ones on each transformer. If you use taps #1 and #6 on one transformer use the same taps on the other.
:
: When driving the speaker through caps you still need 1 output transformer with a good primary. You just don't need the second transformer.
:
:Norm
:
::Hi Norm,
::
:: Yhanks for the advice so far. No if I understand correctly, the 2 PT291's will create the proper impedance. With the primary going to the plates, the secondaries (multiple taps) must be connected with the reversed primary of #2 transformer going to the speaker jacks. As there are multiple taps on the Pt291, which are connected for proper function?
::
::
:: In the second case of using 1 MF caps from plate to speaker jacks, how would I run the B+? The primary of the original output transformer is open.
::Would I just run the B= from the center tap to the plates?
::
::
:: Really appreciate your input ands suggestions.
::
::
::
::
:::Hi Bill
:::
::: Your radios uses push-pull for audio output. You need a transformer to connect from tubes to speaker.
:::
:::http://www.nostalgiaair.org/PagesByModel/767/M0040767.pdf
:::
::: A transformer will give a low impedance output. To be right a second output transformer should be connected in reverse to the first one. This will bring impedance back up.
:::
::: Here is another way to do it. Connect a 1 mf cap from each output tube plate to you high impedance speaker. This way you won't be using output of the transformer. The primary side is already high impedance and caps from tube plates will isolate DC voltage from the speaker.
:::
::: Don't really need a cap from each tube plate but it's a good idea in case a wire touches chassis.
:::
:::Norm
:::
::::Hi Norm,
::::
:::: So to use the original speaker, I'm pretty sure its 2000 ohms, what would I have to do? The original output transformer is open.
::::
::::
::::
::::Hi Bill
:::::
::::: Use the least expensive. P-T291 seems to be lowest cost in the 2008 catalog. Universal Output transformers have multiple taps for matching different output tubes.
:::::
::::: These output transformers are made to match low impedance speakers. A few early radios had output transformers to match high impedance speakers. If your radio has high impedance output 2 transformers, back to back, will be needed.
:::::
:::::Norm
:::::
::::::Hello All,
::::::
:::::: Can anyone recommend which universal output transformer from antique Electronics would be correct for an American Bosch 28? Primary goes to push-pull 71A"s while secondary connects to output jacks for external speaker.
When using the caps, the primary of the output transformer would act as a choke, stopping the audio, and the caps would conduct the audio to the speakers.
Lewis
Thanks Lewis and Norm for the help and advice.
Will give it a shot.
::Hi Norm,
::
:: So if I understand correctly, I should use the primary of the PT291 as a filter choke to supply the plates and then run the caps from the plates to the output jacks. Space is at a premium since the power unit and amplifier are together and separate from the radio section. I dont believe I could use 2 PT291's unless a lot of modification. Thanks for the advice and help so far..
::
::
::
::
::
::
::
::
::
::Hi Bill
:::
::: You can use any taps when having universal output transformers back to back. Just as long as they are the same ones on each transformer. If you use taps #1 and #6 on one transformer use the same taps on the other.
:::
::: When driving the speaker through caps you still need 1 output transformer with a good primary. You just don't need the second transformer.
:::
:::Norm
:::
::::Hi Norm,
::::
:::: Yhanks for the advice so far. No if I understand correctly, the 2 PT291's will create the proper impedance. With the primary going to the plates, the secondaries (multiple taps) must be connected with the reversed primary of #2 transformer going to the speaker jacks. As there are multiple taps on the Pt291, which are connected for proper function?
::::
::::
:::: In the second case of using 1 MF caps from plate to speaker jacks, how would I run the B+? The primary of the original output transformer is open.
::::Would I just run the B= from the center tap to the plates?
::::
::::
:::: Really appreciate your input ands suggestions.
::::
::::
::::
::::
:::::Hi Bill
:::::
::::: Your radios uses push-pull for audio output. You need a transformer to connect from tubes to speaker.
:::::
:::::http://www.nostalgiaair.org/PagesByModel/767/M0040767.pdf
:::::
::::: A transformer will give a low impedance output. To be right a second output transformer should be connected in reverse to the first one. This will bring impedance back up.
:::::
::::: Here is another way to do it. Connect a 1 mf cap from each output tube plate to you high impedance speaker. This way you won't be using output of the transformer. The primary side is already high impedance and caps from tube plates will isolate DC voltage from the speaker.
:::::
::::: Don't really need a cap from each tube plate but it's a good idea in case a wire touches chassis.
:::::
:::::Norm
:::::
::::::Hi Norm,
::::::
:::::: So to use the original speaker, I'm pretty sure its 2000 ohms, what would I have to do? The original output transformer is open.
::::::
::::::
::::::
::::::Hi Bill
:::::::
::::::: Use the least expensive. P-T291 seems to be lowest cost in the 2008 catalog. Universal Output transformers have multiple taps for matching different output tubes.
:::::::
::::::: These output transformers are made to match low impedance speakers. A few early radios had output transformers to match high impedance speakers. If your radio has high impedance output 2 transformers, back to back, will be needed.
:::::::
:::::::Norm
:::::::
::::::::Hello All,
::::::::
:::::::: Can anyone recommend which universal output transformer from antique Electronics would be correct for an American Bosch 28? Primary goes to push-pull 71A"s while secondary connects to output jacks for external speaker.
:
:
:
:
:When using the caps, the primary of the output transformer would act as a choke, stopping the audio, and the caps would conduct the audio to the speakers.
:Lewis