02-07-2018, 01:26 PM
Hello Phorum Members!
I have a Philco Model 37-60 I've been trying to restore for a friend of mine and it's been giving me nothing but fit's to say the least. The problem is: I cant get rid of the "hum".
I have replaced EVERY electrolytic and paper/wax capacitors and several resistors which measured out of tolerance. I did not replace any of the mica capacitors as they very seldom go bad. I also replaced the 6F6 audio output tube and the 6Q7 2nd detector 1st audio tube which were bad. And after all that work the hum is still present.
The schematic shows a 5Y4 for the rectifier tube. But when I got the radio for repair, it had a 5Y3 in it which someone else had previously installed. Checking the tube substitution manual, they are both interchangeable. The only difference is the wiring for filament pins are different.
I realigned the receiver and it receives stations very well except that after it warms up the reception strength weakens and I have the volume control at full volume and the reception is still weak..
So the two problems are: constant hum and weakening signal strength after warm up.
The transformer and the choke winding's checked out good. I ohm'd them an check their output voltages and they are in spec.
My last resort is to re-solder every solder joint. If any of you out there that are more expert on these old Philco's then I am, I would sure appreciate any advise you could render.
Thank you very much!
73's
Bill
KI7ZAD
I have a Philco Model 37-60 I've been trying to restore for a friend of mine and it's been giving me nothing but fit's to say the least. The problem is: I cant get rid of the "hum".
I have replaced EVERY electrolytic and paper/wax capacitors and several resistors which measured out of tolerance. I did not replace any of the mica capacitors as they very seldom go bad. I also replaced the 6F6 audio output tube and the 6Q7 2nd detector 1st audio tube which were bad. And after all that work the hum is still present.
The schematic shows a 5Y4 for the rectifier tube. But when I got the radio for repair, it had a 5Y3 in it which someone else had previously installed. Checking the tube substitution manual, they are both interchangeable. The only difference is the wiring for filament pins are different.
I realigned the receiver and it receives stations very well except that after it warms up the reception strength weakens and I have the volume control at full volume and the reception is still weak..
So the two problems are: constant hum and weakening signal strength after warm up.
The transformer and the choke winding's checked out good. I ohm'd them an check their output voltages and they are in spec.
My last resort is to re-solder every solder joint. If any of you out there that are more expert on these old Philco's then I am, I would sure appreciate any advise you could render.
Thank you very much!
73's
Bill
KI7ZAD
