Hi All,

I am restoring a 1949 Bendix 75P6 AM/FM table model radio (I've done two or three over the past couple of years). In this case the tubes were tested/replaced as needed, as were all capacitors (both electrolytic and non-electrolytic) and out-of-tolerance resistors too.

I've already downloaded the schematics and service manual pages from the Nostalgiair website.

The AM band works just fine, and the problem is that there is no functionality on FM. No audio or reception just a faint hum. I have used a signal generator to input 90 mHz signals into the radio through the external antenna wire, which can be tuned in/heard. Just no reception (white noise or stations).

I've cleaned the AM/FM band change switch, and tried to adjust the IF cans.

If anyone can give me a clue/hint as to what could possibly be amiss I would be grateful. I'd love to get this old set (the bakelite case is in wonderful cosmetic condition) working on both bands.

Cheers and thanks in advance for the help...

Skyliner

:Hi All,
:
:I am restoring a 1949 Bendix 75P6 AM/FM table model radio (I've done two or three over the past couple of years). In this case the tubes were tested/replaced as needed, as were all capacitors (both electrolytic and non-electrolytic) and out-of-tolerance resistors too.
:
:I've already downloaded the schematics and service manual pages from the Nostalgiair website.
:
:The AM band works just fine, and the problem is that there is no functionality on FM. No audio or reception just a faint hum. I have used a signal generator to input 90 mHz signals into the radio through the external antenna wire, which can be tuned in/heard. Just no reception (white noise or stations).
:
:I've cleaned the AM/FM band change switch, and tried to adjust the IF cans.
:
:If anyone can give me a clue/hint as to what could possibly be amiss I would be grateful. I'd love to get this old set (the bakelite case is in wonderful cosmetic condition) working on both bands.
:
:Cheers and thanks in advance for the help...
:
:Skyliner
:
Check your FM oscillator and FM RF coils. Change the 12AT7 if the coils are OK.
Johnnysan-

:Check your FM oscillator and FM RF coils. Change the 12AT7 if the coils are OK.
:Johnnysan-

Hi Johnnysan,

Thanks for that. Sorry for another question, but how can I test the FM oscillator and RF coils? Would I use a continuity tester or ohm meter and if so what would I be looking for?

Changing the 12AT7 has done some good, and I can receive stations. Even with a good FM antenna, though, they are quite faint (unlike those on FM); I have to put the volume up full to hear them.

Cheers.

:
::Check your FM oscillator and FM RF coils. Change the 12AT7 if the coils are OK.
::Johnnysan-
:
:Hi Johnnysan,
:
:Thanks for that. Sorry for another question, but how can I test the FM oscillator and RF coils? Would I use a continuity tester or ohm meter and if so what would I be looking for?
:
:Changing the 12AT7 has done some good, and I can receive stations. Even with a good FM antenna, though, they are quite faint (unlike those on FM); I have to put the volume up full to hear them.
:
:Cheers.
:
You would use an ohmmeter to check the coils, which are labelled 108 and 110 in the Sams; not sure what is in NostalgiaAir files. These are low resistance coils and will read about 0 ohms (sometimes they listed 0 ohms when the resistance was below .2).
You said you adjusted some IF transformers (?); you may have misadjusted the FM section. I consider it essential that alignment of any type be left to the last step; most radios that have been sitting for decades will only be slightly out of alignment. Replace all the bad parts, and the radio will usually work fine, even without an alignment.
Do you know how to align a radio and have an FM generator? I can email the Sams to you if you need it.
Johnnysan-

:You would use an ohmmeter to check the coils, which are labelled 108 and 110 in the Sams; not sure what is in NostalgiaAir files. These are low resistance coils and will read about 0 ohms (sometimes they listed 0 ohms when the resistance was below .2).
:You said you adjusted some IF transformers (?); you may have misadjusted the FM section. I consider it essential that alignment of any type be left to the last step; most radios that have been sitting for decades will only be slightly out of alignment. Replace all the bad parts, and the radio will usually work fine, even without an alignment.
:Do you know how to align a radio and have an FM generator? I can email the Sams to you if you need it.
:Johnnysan-

Hi Johnnyson,

Many thanks for that. I have my trusty EICO FM signal generator and follow the instructions in Sams for the AM & FM alignment.

I'll continue to tinker, though the FM oscillator coil (if I got the right one under the chassis based on my reading of the schematic) has an R of 0.4 Ohms.

Cheers,

Hello Again Johnnysan,

If you could let me have the SAMS on the 75P6 by email (skyliner@storm.ca) that would be really great. I'm using a copy of the Ryder's from this site, but the SAMs would also help.

Cheers and many thanks.

:Hello Again Johnnysan,
:
:If you could let me have the SAMS on the 75P6 by email (skyliner@storm.ca) that would be really great. I'm using a copy of the Ryder's from this site, but the SAMs would also help.
:
:Cheers and many thanks.
:
:
You should have the Sams now.
Johnnysan-