I'm restoring a Philco 84 that made no sound when I got it (but all the tubes lit). The tubes check out OK, as does the 4/8 mfd cap. I found a bad 240K resistor which, when replaced, brought sound and very weak station reception out of the speaker. The volume control was shot, so I replaced it with a 25K ohm pot. The new volume control has no effect on the sound coming out of the speaker (still very weak and distorted). I tested the filament, plate and grid voltages and found that the 1st Det (77) had low volatage on the grid (55.8 VDC). The 2nd Det (also a 77) has high volatage on both the plate (176 VDC) and grid (37 VDC). The rest of the voltages are in line with specs. Any ideas or advice on what might be the problem between the two detectors would be greatly appreciated.

Hi,
There are three resistors you should check. First, check the value of the plate resistor on the 77, this should be 6000 ohms. The next two will trace to the 3rd grid of the 77, the one that goes to ground should be 15,000 ohms, and the other goes to the B+ buss, and that should be 16,000 ohms.

If these have changed greatly, they will impair performance.

If these check out okay, look for a bad solder joint. Then align the radio.

They do need some antenna length, and that in and of itself can keep performance way down.

:I'm restoring a Philco 84 that made no sound when I got it (but all the tubes lit). The tubes check out OK, as does the 4/8 mfd cap. I found a bad 240K resistor which, when replaced, brought sound and very weak station reception out of the speaker. The volume control was shot, so I replaced it with a 25K ohm pot. The new volume control has no effect on the sound coming out of the speaker (still very weak and distorted). I tested the filament, plate and grid voltages and found that the 1st Det (77) had low volatage on the grid (55.8 VDC). The 2nd Det (also a 77) has high volatage on both the plate (176 VDC) and grid (37 VDC). The rest of the voltages are in line with specs. Any ideas or advice on what might be the problem between the two detectors would be greatly appreciated.

Thanks for the insight. The resistors turned out to be OK, but it turns out the set was badly out of alignment. Another question (this time for refinishing advice): The cabinet on this unit is in good shape, but there's a light dusting of paint spray on the top of the cabinet(like the unit was in a room where the ceiling was being painted, and a light mist of paint landed on it). I'd like to get the unwanted paint off without damaging the original finish, then use a clear laquer to protect the original finish. Any ideas on how to get the overspray off without having destroying the original finish? Again, your assistance is greatly appreciated!

Jeff

Hi,
:There are three resistors you should check. First, check the value of the plate resistor on the 77, this should be 6000 ohms. The next two will trace to the 3rd grid of the 77, the one that goes to ground should be 15,000 ohms, and the other goes to the B+ buss, and that should be 16,000 ohms.
:
:If these have changed greatly, they will impair performance.
:
:If these check out okay, look for a bad solder joint. Then align the radio.
:
:They do need some antenna length, and that in and of itself can keep performance way down.
:
:
::I'm restoring a Philco 84 that made no sound when I got it (but all the tubes lit). The tubes check out OK, as does the 4/8 mfd cap. I found a bad 240K resistor which, when replaced, brought sound and very weak station reception out of the speaker. The volume control was shot, so I replaced it with a 25K ohm pot. The new volume control has no effect on the sound coming out of the speaker (still very weak and distorted). I tested the filament, plate and grid voltages and found that the 1st Det (77) had low volatage on the grid (55.8 VDC). The 2nd Det (also a 77) has high volatage on both the plate (176 VDC) and grid (37 VDC). The rest of the voltages are in line with specs. Any ideas or advice on what might be the problem between the two detectors would be greatly appreciated.

Hi,
If the paint spatter is not large drips, but small overspray drops, these can be removed with Mcguires "Medium Cut Cleaner", and then followed with "Light Cut Cleaner". These are automotive finish products, and will not usually cause a problem with a finish applied over their residue if it is not completely wiped clean. If the radio does need a shot of lacquer over the original, use the Macguires over the whole radio- excepting bare wood if possible (the oils may darken the wood a bit)- This would be to make sure that you remove any residue of polution etc. If there is a chance it had been exposed to Silicone overspray, or a silcone wax/polish, you would want to get a product like Ditzler DX-33 (wax and grease remover), and "Fisheye preventer". Silicone residue will "Fisheye" everything but shellac that gets applied over it.

The other use for the remaining rubbing compound is rubbing out finishes that have been wet sanded. Be it other radios, furniture, cars, etc. Just be sure to grade down to 1000 grit before rubbing compound is used, otherwise the tiny scratches will turn white once a wax has been applied.

:Thanks for the insight. The resistors turned out to be OK, but it turns out the set was badly out of alignment. Another question (this time for refinishing advice): The cabinet on this unit is in good shape, but there's a light dusting of paint spray on the top of the cabinet(like the unit was in a room where the ceiling was being painted, and a light mist of paint landed on it). I'd like to get the unwanted paint off without damaging the original finish, then use a clear laquer to protect the original finish. Any ideas on how to get the overspray off without having destroying the original finish? Again, your assistance is greatly appreciated!
:
:Jeff
:
:Hi,
::There are three resistors you should check. First, check the value of the plate resistor on the 77, this should be 6000 ohms. The next two will trace to the 3rd grid of the 77, the one that goes to ground should be 15,000 ohms, and the other goes to the B+ buss, and that should be 16,000 ohms.
::
::If these have changed greatly, they will impair performance.
::
::If these check out okay, look for a bad solder joint. Then align the radio.
::
::They do need some antenna length, and that in and of itself can keep performance way down.
::
::
:::I'm restoring a Philco 84 that made no sound when I got it (but all the tubes lit). The tubes check out OK, as does the 4/8 mfd cap. I found a bad 240K resistor which, when replaced, brought sound and very weak station reception out of the speaker. The volume control was shot, so I replaced it with a 25K ohm pot. The new volume control has no effect on the sound coming out of the speaker (still very weak and distorted). I tested the filament, plate and grid voltages and found that the 1st Det (77) had low volatage on the grid (55.8 VDC). The 2nd Det (also a 77) has high volatage on both the plate (176 VDC) and grid (37 VDC). The rest of the voltages are in line with specs. Any ideas or advice on what might be the problem between the two detectors would be greatly appreciated.