09-12-2023, 05:30 AM
Greetings:
This summer I visited the SCARS meet in Burbank, CA.
(Southern California Antique Radio Society.)
I donated a Yamaha RX-V2600 7.1 channel receiver that I had some problems with due to it being Yamaha's first with HDMI switching. Also, that was my first foray into the vintage radio sceen. Being an avid follower of numerous youtube radio restoration channels, I was looking to advance my test equipment collection beyond my TEK 454 o'scope & Simpson 260 VOM. Someone had two Philco Model 088 signal generators for sale at $5 each, so I bought one. I forgot to mention that I had bought an old Heathkit model V-7A VTVM that seems to have had a rough life, and was amidst a complete verification of its non-working status and conversion to BNC input. And elimination of the battery requirement for the ohms function.
Okay. Now I can talk about the model 088. I have the two post model with the added Modulation On/Off switch). The original 088 had the modulation ON always and no switch.
My 088 does not have the carrying strap, so I guess it was part of the early set tester combo that shared a common case.
I have never powered the unit up as it was battery powered only and I only recently cobbled together three switch mode power supplies to create the needed 67.5 vdc HT supply and 2 volt filament supply.
The 3 binding post schematic shows a 250 ohm attenuator pot while my unit has a 5K ohm pot wired as a rheostat. Obviously the 1K/100 ohm voltage divider to create the MED output is missing. I was surprised to find that one end of the attenuator was not connected to item 15. Instead item 15 was connected directly to the wiper of item 16.
I am still working on item 08, the 250K ohm resistor which is mounted in the range switch between wafers B & C. I suspect that the schematic should have that resistor drawn to the left of the connection between the tube plate and band switch wafer "C", but I am old with poor eyesight and hand muscles so weak squeezing alligator clips open is a major task. My 40 year old son is helping me with repairs as he learns to solder.
I have removed the skinny bakelite block adjacent to the ugly modulation coil to replace the .05 uf cap and add a replacement for the .02 wax cap with a 400v .018 uf mounted internally (it is nice that modern caps are much smaller).
I am replacing all components more than 10% out off value. I hope the tube still works, but any heptode should work. The paralleling of the coils through wafers C & D looks like somebody had fun with math.
I expect to make frequent use of my VTVM as I explore the model 088's circuits.
Wish me luck, and I will report any definitive progress I earn.
Dr.Chiron
This summer I visited the SCARS meet in Burbank, CA.
(Southern California Antique Radio Society.)
I donated a Yamaha RX-V2600 7.1 channel receiver that I had some problems with due to it being Yamaha's first with HDMI switching. Also, that was my first foray into the vintage radio sceen. Being an avid follower of numerous youtube radio restoration channels, I was looking to advance my test equipment collection beyond my TEK 454 o'scope & Simpson 260 VOM. Someone had two Philco Model 088 signal generators for sale at $5 each, so I bought one. I forgot to mention that I had bought an old Heathkit model V-7A VTVM that seems to have had a rough life, and was amidst a complete verification of its non-working status and conversion to BNC input. And elimination of the battery requirement for the ohms function.
Okay. Now I can talk about the model 088. I have the two post model with the added Modulation On/Off switch). The original 088 had the modulation ON always and no switch.
My 088 does not have the carrying strap, so I guess it was part of the early set tester combo that shared a common case.
I have never powered the unit up as it was battery powered only and I only recently cobbled together three switch mode power supplies to create the needed 67.5 vdc HT supply and 2 volt filament supply.
The 3 binding post schematic shows a 250 ohm attenuator pot while my unit has a 5K ohm pot wired as a rheostat. Obviously the 1K/100 ohm voltage divider to create the MED output is missing. I was surprised to find that one end of the attenuator was not connected to item 15. Instead item 15 was connected directly to the wiper of item 16.
I am still working on item 08, the 250K ohm resistor which is mounted in the range switch between wafers B & C. I suspect that the schematic should have that resistor drawn to the left of the connection between the tube plate and band switch wafer "C", but I am old with poor eyesight and hand muscles so weak squeezing alligator clips open is a major task. My 40 year old son is helping me with repairs as he learns to solder.
I have removed the skinny bakelite block adjacent to the ugly modulation coil to replace the .05 uf cap and add a replacement for the .02 wax cap with a 400v .018 uf mounted internally (it is nice that modern caps are much smaller).
I am replacing all components more than 10% out off value. I hope the tube still works, but any heptode should work. The paralleling of the coils through wafers C & D looks like somebody had fun with math.
I expect to make frequent use of my VTVM as I explore the model 088's circuits.
Wish me luck, and I will report any definitive progress I earn.
Dr.Chiron
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