Model 80 Jr Restoration question - Printable Version
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Model 80 Jr Restoration question - RadioBoy - 08-20-2024
A freind asked me to take a look at an PHilco Model 80 Jr with the idea of getting the electronics to work. He's the woodworker in group and did a great job restoring the cathederal cabinet, But I an going crazy with the electronics..It appears there has been to previous attempt at restoration or repair.
When I powered it up using the variable transformer to ease it into operation. I saw all the tubes and pilot light light up. Tried measuring the voltages on the tubes..First thing I noticed that even though voltages were the right magnitude my meter showed them as minus. Also, there is no B+ on the plates of the 42 and the 36 of the detector Oscillator. There is Voltage on the Screen grids. Sooo. Any clues about the polarity issue? I tried using the chassis as a ground and the cathode of tube I was measuring as ground.
Any help would be appreciated?
Brian Cieslak K9WIS
RE: Model 80 Jr Restoration question - morzh - 08-20-2024
I suggest using many, many articles here on how to start restoring a radio.
I will repeat myself, but:
1. Powering on a radio without a recap (weeding out old tubular paper caps and electrolytic caps) - big no-no-no.
2. Check the tubes.
3. Then proceed with power-up.
(you have more or less checked the power transformer, though this should be done differently).
PS. 80 jr is not the best radio to learn restoration. It is a superhet-regen, and as such will be finicky to align.
PPS. If your meter shows the wrong poilarity...well, make sure yer red wire goes to V input and yer black one to "Common".
RE: Model 80 Jr Restoration question - jrblasde - 08-20-2024
Good afternoon! You mentioned that it looks as though someone has attempted repairs before. You may want to compare the existing circuitry against the schematics provided here at the PhilcoRadio.com link. Navigate to Library, and then go to Service Info. These are the best reference to use for a baseline. I also like to refer to the Rider's manuals for many of these older Philco radios, because Rider often added diagrams showing the physical location of each component on the chassis. I've found these before on Antique Electronic Supply's website, and find that they are incredibly faithful to the Philco schematics. One more thing--you mentioned the potential for reversed polarity on your voltmeter. The Philco service manual will tell you if you need to invert the probes of your voltmeter. I have seen this in writing before, while aligning my 49-906.
As morzh mentioned, I would also recommend a recap. It will behoove you to test for any out-of-tolerance resistors as well. Wildly out-of-tolerance resistors will change your plate voltages.
RE: Model 80 Jr Restoration question - Radioroslyn - 08-20-2024
Hi Brian and welcome,
Here's the service bulletin for the 80 Philco Service Bulletin 140.pdf (philcoradio.com) Would replace 34 & 35 w/10mfd @ 450v. Check the notes @ the bottom as some of the parts have moved or been deleted. Measure the resistances from the 80 filament pin to pin 3 of the 42 (field coil) and from pin 3 to pin 2 on the 42 (opt). That should get you started.
Wouldn't hurt to post a couple of pics of the chassis top and bottom.
de N3GTE
RE: Model 80 Jr Restoration question - RodB - 08-20-2024
Hi and welcome to the Phorum. One more thing to check out before powering on is to verify that the tube numbers are correct and plugged into the correct location. Been there...
RE: Model 80 Jr Restoration question - GarySP - 08-20-2024
Welcome to the Phorum, Brian! +1 what has been said already. This Phorum is full of some of the most knowlegable pholks you can ask for help. I would also look over all the wiring for fraying and brittle insulation and replace as needed. Take care and BE HEALTHY! Gary