41-285 troubleshooting help - Printable Version
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+--- Thread: 41-285 troubleshooting help (/showthread.php?tid=3226)
41-285 troubleshooting help - jstaf40 - 05-03-2011
I'm trying this radio to make some music i have replaced the caps and a number of resisters
i have a good signal from the generator at grid & plate on 2ND I.F 7b7..... on FIRST I.F on pin 2 it gets very distorted and stops,,, could it be the #34 or 33 cans I'm not sure how they work but they have continuity but I'm a newbie I'm reading every thing i can but i am lost, hope you can help and the main transformer is on the warm side
Re: 41-285 troubleshooting help - Radioroslyn - 05-03-2011
Are you taking about the 1st IF amp tube? Try turning the generator output down. You maybe overloading it.
Terry
Re: 41-285 troubleshooting help - jstaf40 - 05-04-2011
thanks terry for the reply
i turned down the signal gen and had no signal in 1st IF 7B7 pin 2 but on high a vary distorted signal,, on the 2nd IF 7B7 on pin 2 loud and clear but on pin 6 it starts to get a little distorted but still loud, i ck the tubes and they test OK I'm rechecking my wiring and components placement, i am at a lose what is real strange is i had a one time a good signal at the antenna so what happened after that I'm at a lose, I'll keep looking. but i thank you for your help
Re: 41-285 troubleshooting help - Chuck Schwark - 05-04-2011
You didn't mention in your original post if you had checked all coils for continuity.
Philco impregnating wax was(is) notorious for corroding the copper windings, due to the high sulpher content of the wax.
Over time moisture in the air combines with the sulpher compounds and forms weak sulphuric acid that eventually attacks the exposed copper at solder lugs and in the windings themselves. Tiny green-ish spots to look for.
Chuck
Re: 41-285 troubleshooting help - Radioroslyn - 05-04-2011
If you inject a signal at the IF frequency at pin 6 of the 1st IF amp do you get any sound from the speaker?
Terry
Re: 41-285 troubleshooting help - jstaf40 - 05-06-2011
when i inject a signal to the 2nd IF pin 2 clear signal at pin 6 it starts to distorted a little when i get to 1st IF pin 2 its vary distorted and the signal stops there, i have ck wiring and so far i haven't found a mistake, it had a lot of rubber wire i replaced it all, i could have hooked it up one wrong i am still checking it out.. all the radios i have restored have been in working condition so it was easy to do, this one was broke when i got it so its still a mystery
thank you again all the members have been generous with there time.. thanks again
john
Re: 41-285 troubleshooting help - Radioroslyn - 05-06-2011
So if you apply a 455kc signal at pin 6 of the 1st IF amp you get no response from the speaker? If so check the voltages at pins 2,3,and 7 from chassis ground and report back.
Terry
Re: 41-285 troubleshooting help - jstaf40 - 05-07-2011
terry
the volts are 1st IF pin 2=154 v pin 3=0 v pin 7=0 v
on 2nd IF pin 2=155 v pin 3=0 v pin 7=18.5 v
some of the other voltage are down by 20 v like # both 41 tubes are 150v instead of 175v
i ran the ohms on the transformer and they seem OK but I'm missing something i just don't no what....i have d/l the 41-255 step by step guide it's a great look at a pro at work hope i can glean something from it..{.I just retested 2nd IF and the signal gen works only on pin2 and will NOT pass to pin7
thanks
john
Re: 41-285 troubleshooting help - Radioroslyn - 05-07-2011
Ok so here is the problem. You have no screen grid voltage on your IF amp tubes and I'll bet you don't have any plate voltage on the oscillator. Check #28 18K resistor (open) and #27 8ufd cap. (shorted). Should have about 75 to 120vdc on pin 3.
Terry
btw if #27is in backwards it will act like a short. +side goes
to the resistor. - side goes to the chassis
Re: 41-285 troubleshooting help - jstaf40 - 05-09-2011
thanks for your help terry this is what i found some one has worked on this unit the 18k is 15k the e caps are turned the right way one thing i did was replace the # 61 resistor group
with 2 watts 150 ohms 39 & 20 ohms i followed the 41-255 step by step he made up the unit i just followed it it looks like some one replaced some wiring and I'm not sure if they put them in the right place,,,using a schematic if very hard for me i do much better with a pictorial diagram like the one i just finished 46-1226 I'll ck with chuck he mite help me with it
it' something simple i know my last redo it was 1 cap in the wrong place i moved it 1 pin over and music ,,,,,, Sorry for being wordy I'm tired
john
Re: 41-285 troubleshooting help - Radioroslyn - 05-09-2011
No problem. You could poke around with your volt meter and see where your volt drop is. 18K or 15K isn't going to make much difference. Don't think that's your problem.
Terry