New ??? for the experts, especially Philco lovers. The audio interstage xformer for the pickup to amplifier has an RCA jack connected to the primary, and looked like a good spot to input a turntable, and it works, but with a low hum/oscillation as volume is advanced beyond the lower end. Problem #2. I've searched all schems forward and backward from the 42-1008, with all showing a single 0.0015uf cap across the plates of the PP output 41's. My set came with each plate having a 0.003uf to ground, and judging from the old spagetti on the leads, it looks orig factory install. Any info on this change?

marv

Problem #2. I've searched all schems forward and backward from the 42-1008, with all showing a single 0.0015uf cap across the plates of the PP output 41's. My set came with each plate having a 0.003uf to ground, and judging from the old spagetti on the leads, it looks orig factory install. Any info on this change?
:
:marv

Nothing about these output cap changes in the Production Change notes for the 42-1008. Could be a very old repair or likely an undocumented factory change (known to happen occasionally). If it sounds fine then freshen the existing caps or go with the original (schematic) and be sure to use 630 volt replacements to accommodate the AC audio peaks tied to the P-P plates.

Chuck

Chuck,
Thanks for the tip. The 0.003uf in there now are rated at 1600V. ALL caps and out of tolerance resistors (>10%) have been replaced, but not totally satisfied with the audio quality in the phono mode, and thats when I started research on the plate caps. I'm using a relatively new stereo turntable and some 50's/60's LP's with the channels bridged as a source. Problem #1 seems to be some sort of a ground loop, and only occurs when the turntable is plugged in, and rotating the power plug of the radio doesn't help. I haven't scoped it yet, so source of distortion or oscillations are still unknown.

marv

:Problem #2. I've searched all schems forward and backward from the 42-1008, with all showing a single 0.0015uf cap across the plates of the PP output 41's. My set came with each plate having a 0.003uf to ground, and judging from the old spagetti on the leads, it looks orig factory install. Any info on this change?
::
::marv
:
:Nothing about these output cap changes in the Production Change notes for the 42-1008. Could be a very old repair or likely an undocumented factory change (known to happen occasionally). If it sounds fine then freshen the existing caps or go with the original (schematic) and be sure to use 630 volt replacements to accommodate the AC audio peaks tied to the P-P plates.
:
:Chuck

Just wondering, have you added the proper equalization network for the phono mode? A phono to line pre-amp may be a good choice.

MRO

:Chuck,
:Thanks for the tip. The 0.003uf in there now are rated at 1600V. ALL caps and out of tolerance resistors (>10%) have been replaced, but not totally satisfied with the audio quality in the phono mode, and thats when I started research on the plate caps. I'm using a relatively new stereo turntable and some 50's/60's LP's with the channels bridged as a source. Problem #1 seems to be some sort of a ground loop, and only occurs when the turntable is plugged in, and rotating the power plug of the radio doesn't help. I haven't scoped it yet, so source of distortion or oscillations are still unknown.
:
:marv
:
::Problem #2. I've searched all schems forward and backward from the 42-1008, with all showing a single 0.0015uf cap across the plates of the PP output 41's. My set came with each plate having a 0.003uf to ground, and judging from the old spagetti on the leads, it looks orig factory install. Any info on this change?
:::
:::marv
::
::Nothing about these output cap changes in the Production Change notes for the 42-1008. Could be a very old repair or likely an undocumented factory change (known to happen occasionally). If it sounds fine then freshen the existing caps or go with the original (schematic) and be sure to use 630 volt replacements to accommodate the AC audio peaks tied to the P-P plates.
::
::Chuck

Mark,
No, this was just a quick test to verify a modern player would produce the level required for the amp, and verify the RCA jack was intended for that purpose. Must admit not familar with the old/new RIAA equalization curves or differences between 78's & LP's. The orig player, which I don't have was 78's only Philco "Beam of Light" I'm searching for a substitute, but with no success.

marv

:Just wondering, have you added the proper equalization network for the phono mode? A phono to line pre-amp may be a good choice.
:
:MRO
:
:
::Chuck,
::Thanks for the tip. The 0.003uf in there now are rated at 1600V. ALL caps and out of tolerance resistors (>10%) have been replaced, but not totally satisfied with the audio quality in the phono mode, and thats when I started research on the plate caps. I'm using a relatively new stereo turntable and some 50's/60's LP's with the channels bridged as a source. Problem #1 seems to be some sort of a ground loop, and only occurs when the turntable is plugged in, and rotating the power plug of the radio doesn't help. I haven't scoped it yet, so source of distortion or oscillations are still unknown.
::
::marv
::
:::Problem #2. I've searched all schems forward and backward from the 42-1008, with all showing a single 0.0015uf cap across the plates of the PP output 41's. My set came with each plate having a 0.003uf to ground, and judging from the old spagetti on the leads, it looks orig factory install. Any info on this change?
::::
::::marv
:::
:::Nothing about these output cap changes in the Production Change notes for the 42-1008. Could be a very old repair or likely an undocumented factory change (known to happen occasionally). If it sounds fine then freshen the existing caps or go with the original (schematic) and be sure to use 630 volt replacements to accommodate the AC audio peaks tied to the P-P plates.
:::
:::Chuck