An Introduction and a Philco 90 issue. - Printable Version
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+--- Thread: An Introduction and a Philco 90 issue. (/showthread.php?tid=23024)
RE: An Introduction and a Philco 90 issue. - cknob - 11-24-2021
Here are a few more pics of the "work" I've done. All are from the orientation of the short length of the chassis at the base of the picture.
RE: An Introduction and a Philco 90 issue. - Phlogiston - 11-24-2021
What Morza is pointing out is important. An 80 rectifier is rated for a first filter of 10 uf (MFD). B+ is also usually higher using larger filter caps, which is already a problem because of the higher line voltages of today. Another problem with these old radios is - tube warm-up time. The voltage in the first filter can go way up waiting for the rest of the tubes to begin conducting. This is also a good reason not to test with the speaker's field coil unplugged.
P.S. when you pull out the old caps, don't throw them out. Several of the forum members would appreciate having them.
RE: An Introduction and a Philco 90 issue. - cknob - 11-24-2021
Excellent...I have a bunch of 10 and 22 uf electrolytics at 200V floating around in my supplies. I will use them...save the Nichicons. Plenty of waxy saves...haven't thrown anything out in fact, I drilled one out and stuffed it with an axial of the same value and filled it with hot glue.
RE: An Introduction and a Philco 90 issue. - cknob - 11-24-2021
For the H**l of it, I put a 10uf 450V electrolytic between the 80 tube and the first terminal post on the voltage resistor and in 20 seconds it vented.
RE: An Introduction and a Philco 90 issue. - Bob Andersen - 11-24-2021
The original caps were only 6 mFd. You really don't need much since there is both a dedicated filter choke and the speaker field coil.
Might you have connected the cap that just vented between one of the 80 plates and the resistor ?
Also check the resistance between that first terminal and the chassis.
Looks like you used all 1/2 watt resistors for replacements. Four of them should be 1 watt.
Check out this "before" photo of mine for reference. They are the big red ones on the left and one green/brown one on the right. (You can click on it for a bigger version).
[Image: https://live.staticflickr.com/65535/9118096859_f820800d8a_z.jpg]
RE: An Introduction and a Philco 90 issue. - morzh - 11-24-2021
cknob
What are you planning to do with 10uF and 20uF 200V caps?
May I suggest something? It seems to me you are just do trial and error and "maybe it will work" approach.
It rarely works.
Maybe it is a good time to stop and try to understand what you are trying to do and why.
Develop a plan. And go by it. The photo of the chassis you put here looks horrible. I sincerely hope this is what you are trying to fix, and not what you think you have fixed.
Find out what parts to use, what not to use, check the wiring. Do not just turn it on: I've been fixing these for over 10 years AND I am an EE, AND I will never ever turn a radio on UNTIL I fully checked everything.
RE: An Introduction and a Philco 90 issue. - RodB - 11-24-2021
Hi Chris - To measure continuity you want to measure zero or low ohms from one point to another. In this case measure from Tab 1 of the resistor to terminal 4 of the power transformer. Same with terminal 12. If you don't get zero, then why not?
RE: An Introduction and a Philco 90 issue. - cknob - 11-24-2021
Thank you Bob and Morzh. Bob, I ordered the resistors according to the original parts list but I'll go back and double check. The electrolytic that vented is connected between that first tab on the resistor and, when you look at the 80 socket from the bottom with the radio in the position I've been referencing, it's connected to the upper right tube socket tab. Is that correct?
Morzh...I certainly qualify as a novice and I'm trying to learn! The radio was working fine for a while and I might have misrepresented it as virginal when I got it because someone put in a 1/8th inch external jack to plug in an aux input at some point. My trouble started when I began to replace the darn resistors!
RE: An Introduction and a Philco 90 issue. - radiorich - 11-24-2021
Ckbob ,
Anyway as morzh pointed out to double check your work !
I agree with you mozh "You really don't need much since there is both a dedicated filter choke and the speaker field coil". I have been buying Some Nichicon Capacitors rated at 500 volts for sets just like this .
Sincerely Richard
RE: An Introduction and a Philco 90 issue. - Steve Davis - 11-24-2021
Was the rectifier tube removed at some point? If so, it could have been reinserted with the wrong orientation. Sometimes the socket holes become wallowed enough a tube can be inserted more than one way. By turning the tube one quarter turn, the tube filament will connect the B+ line to the HV winding of the transformer.
Steve
RE: An Introduction and a Philco 90 issue. - cknob - 11-24-2021
I'll check Steve...thank you
RE: An Introduction and a Philco 90 issue. - cknob - 11-24-2021
Tube 80 is inserted fine but continuity is not. Zero ohms on terminal 4, 200 ohms on terminal 1.
RE: An Introduction and a Philco 90 issue. - Steve Davis - 11-24-2021
Something connected to terminal 4 is shorted. Trace the wiring connected to that terminal. Unplug the speaker and remeasure terminal 4.
Steve
RE: An Introduction and a Philco 90 issue. - cknob - 11-24-2021
Hi Steve...I'm going back over this again and I'm not sure I understood what RodB asked me to do. He said. "Hi Chris - To measure continuity you want to measure zero or low ohms from one point to another. In this case measure from Tab 1 of the resistor to terminal 4 of the power transformer. Same with terminal 12. If you don't get zero, then why not?"
Tab 1 of the resistor to terminal 4 of the power transformer? Does he mean the center tap line 4 and not terminal 4? He uses the same nomenclature referring to terminal 12. Line 12 is another center tap from the transformer and both taps 4 and 12 are normally connected to terminal one of the voltage resistor. I'm confused!
RE: An Introduction and a Philco 90 issue. - Steve Davis - 11-24-2021
Chris, maybe it's me that is confused. I thought you were reading 0 ohms from the far right terminal of the large resistor to the chassis.
Steve