PT-94 no sound - Printable Version
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+--- Thread: PT-94 no sound (/showthread.php?tid=26135)
PT-94 no sound - bridkarl - 12-15-2025
Recapped and rewired this PT-94, but volume/sound not there. It appears the resistors have gone way high on the 7C6.
Order some new ones later this week. Geez this had alot of crumbling wiring.
RE: PT-94 no sound - Joe Rossi - 12-15-2025
Should that blue wire at the bottom of the photo be touching the chassis?
RE: PT-94 no sound - bridkarl - 12-15-2025
No. That’s been detached so I can more easily get at the resistors. These are seriously soldered on.
RE: PT-94 no sound - Arran - 12-16-2025
Karl;
The sockets used in that era of Philco had spade shaped terminals, with no holes to feed wires through, they just wrapped everything around the terminal, and then covered it with a blob of solder. I never did like the way they looked, they always looked untidy, and they are too close together as well, so solder bridges can be an issue. It's particularly annoying when the wire lead for the cap or resistor you need to remove has another lead wrapped around it.
Regards
Arran
RE: PT-94 no sound - bridkarl - 12-16-2025
Exactly my issue. Agreed. It was obviously a cheaper option, but not the best. I'll just keep soldering on with this.
RE: PT-94 no sound - MrFixr55 - 12-21-2025
Hi Bridkarl,
Yes, keep soldering on and soldiering on. Unfortunately, the early 1940s Philco radios including the PT94 were absolute nightmares with the crumbling rubber insulated wire. I know,; I restored one for a friend.
While sometimes controversial, I am a believer in the cut and loop method of replacing caps in some of these sets, as it tends to not disturb the sockets. Cut the leads close to the ends of the original cap, bend loops in the ends, clean the area, loop the leads of the new part through the loops in the leads of the original that was cut off, crimp and solder. However, with this set, it can't be helped, as wiring has to either be replaced, necessitating unsoldering both ends or sleeved, requiring unsoldering one end.
Back when there was a Radio Shack, they made a fairly nice desoldering iron where you squeezed a bulb, touched the tip to the joint and when solder liquified, you released the bulb. These were inexpensive and one of these days, I will hook a vacuum pump to one.
Try to divide and conquer. Inject audio, even if it is merely hum into the center section of the volume control. If a hum or audio is heard, then the problem is south of the control. If no hum, then troubleshoot the amp and power supply.
These sets are also known to have issues with the tube socket contacts, especially in the Loktal tubes.
RE: PT-94 no sound - bridkarl - 12-21-2025
I have a soldapullt for solder removal which I’ve been quite happy with. I’ll keep on with it. Just started a rebuild of a Collins 516F-2 power supply.