[ftovar72]

Hi all,

I started the restoration of my "new" philco 46-350 code 125 first of all I noticed that it had cut the power cord so I was not sure if was safe to turn it on, I opened it and remove the internals to review it I got a surprise that the radio was already modified with new electrolitic caps and some ceramic caps were also replaced, so i decided to turn it on. The philco came to live again with a very loud "hum" so I turned it off and started to look for answers, lot of responses and some of them where very helpful I found the schematics and philco troubleshooting document for this model. I also found that some electrolitic caps were replaced with wrong values so I rebuild the candhom with electrlitic caps and with proper values (30mf/150v,30mf/150v,10mf/150v,30mf/25v) after replaced the wrong ones and test the radio... "hum" disapeared but now there is no radio signal, I cannot get any radio station across all the spectrum. I used my mobile phone with a frecuency generator android app and tested the sound in volume control I got sound but still not sure if I can test all other test points without blowing up my mobile. Also after replacing the caps I got the following voltages: in R100 I get 117 | after R100A : 105 v | After R100B : 60 v | After R100C : 12.5 volts and in all tubes in the filaments I get the following values:

        terminal  |  voltage
1U5 :    1 - 7    |    1.7 v
              2      |    22 v
              3      |    15.4 v

3LF4 :   1 - 7    |    1.4 v
           1 - 8    |    2.8 v
              2      |    83 v
              3      |    86 v

1T4 :     1 - 7    |    1.38 v
              2      |    86 v
              6      |    3.3 v

1R5 :     1 - 7    |    1.78 v
              2      |    86 v
              4      |    0 v

1T4 :     1 - 7    |    1.6 v
              2      |    86 v
              6      |    0 v

Any idea on what is wrong ?

I am interested to have this radio fully working, your comments and advices are really welcome.

[sam]

welcome  frank
i started your own thread






sam

[Radioroslyn]

Hi Frank and welcome,
With a quick look at your notes you are missing voltage on pin 3 of the 1R5, and you don't have any screen grid voltage on the If amp tube should see abt 50vdc. Check R-2.

GL

[ftovar72]

Hi Terry,

I verified voltages again and I got the following measures:

** Values in parenthesis are the expected according to wiring diagram http://www.nostalgiaair.org/PagesByModel...013633.pdf

3LF4 1 - 7 : 1.49 v
1 - 8 : 2.74 v
7 - 8 : 1.25 v
7 : 120 v AC (77 v AC)
2 : 84 v (72v )
3 : 87 v (74v)
6 : 1.6 v (~9v)

1U5 1 - 7 : 1.71 v
2 : 25 v (9v)
3 : 14.9 v (16v)
4 : 1.6 v
6 : 1.1 v

1T4 1 - 7 : 1.42 v
IF Amp 2 : 87 v (76v)
3 : 65 v (45v)
6 : 3.4 v

1R5 1 - 7 : 1.74 v
Converter 2 : 86.7 v (76v)
3 : 65.1 v (45v)
4 : 0 v (0.5 - 2.5v)
6 : 0.76 v

1T4 1 - 7 : 1.66 v
RF Amp 2 : 86.6 v (76v)
3 : 65.1 v (45v)
5 : 3.4 v
6 : 0.2 v

I am following the 48-360 wiring diagram since this radio uses the 3LF4 amplifier and after checking the wiring it fits that wiring.

Regards!

[Radioroslyn]

That schematic give me a headache!!
I did find one for a 46-350 121 that's clean but doesn't use that locktol output tube. Any way I think there is a misprint on your schematic as I can see why if there is 74v on the plate there's 72v on the cathode (filament). that's on the 3lf4.
Methinks your 680 ohm (R-207) resistor is a problem. Shouldn't be see any ac voltages around those directly heated tubes.

[Raleigh]

The Philco service info lists a LOT of production changes for this radio. The 3LF4 was added in Code 125. The note says "voltages are the same" as the 3Q5. It shows 8.5 volts DC on cathode/filament pin 7, and 7.0 volts DC on the filament center tap pin 8, if that helps. 67 volts on the plate pin 3.

[ftovar72]

Thanks John for the info, where I can get all the related info for this code 125 ? When I bought this radio from ebay I thought it was code 121

Regards!

[Raleigh]

Frank,

I bought the service package I have from http://www.philcorepairbench.com/schematics/

Chuck Schwark runs that site. He made sure that the package included production changes from two different sources. Most of the information printed in the package is for Code 121, so you have to look at the production changes to make sure it is up date for Codes 122 and 125. You might want to mark up your schematic from the list of changes, because they aren't there to begin with.

Chuck's copies are very good, and usually include an 11 X 17 schematic blow-up for clarity. Unfortunately, he deals only with hard copies delivered by mail, and accepts payment only by check. But in my experience, his copies are so much better than anything else I've found that it is worth the wait.

Another thing you could try is to search for a 1946 "Philco Home Radio Yearbook", which included repair data for all 1946 models, including schematics and production change data. Sometimes these are available on eBay as original documents, and sometimes you find them as scanned copies on CDs.

Another source of good quality service data is http://www.theschematicman.com/index.html. He has downloads for around $5.00 of pdf scans of Sams Photofax for many, many models. His copies are better and cheaper than the ones I've bought directly from Sams.

Sams documentation is pretty good, but it usually lacks the detail of production changes that you probably want for your Code 125. Philco's original service documents are better.

I've restored 2 of these radios, a Code 121 and a Code 122. I found them unusually confusing to work on, and the free schematic from Nostalgia Air was just about unusable because the quality of the copy was so bad. It made a big difference to have the service package from Chuck Schwark.

BTW, I'm not associated with Chuck in any way. I've just liked his products.

[ftovar72]

Thanks John,

I was not sure where to get reliable schemas. I will check the recommended sites.

Do you recommend me to restore it from scratch ? I mean to dissasemble everything and start over again, this radio was already "fixed" by some of the previous owners.

[Image: http://casamadriddev.com/philco/Circuit_46-350.jpeg]

Best Regards!

[Raleigh]

Frank,

I don't think I'd recommend that you take everything apart, unless you just want to for fun. There's too many opportunities to mess up. Of course, it seems like whoever was in there before you did mess up, so you have to find all his mistakes.

I'd recommend a focused troubleshooting approach. The Philco service document and troubleshooting guide is one way to start. It should guide you through some basic procedures. Or, my favorite reference is Marcus and Levy, Elements of Radio Servicing. You can download it in 6 pdf files from here: http://www.antiqueradios.com/archive.shtml Sometimes you can find it on eBay or a used book store.

Probably the first thing to do is to track down the tube pin voltage problems, since you know you have to solve those anyway. Anything that is off by, say, 10% or more, track down the wiring to that pin and make sure it's picking up voltage from the right place and that the components in the path are in spec.

If you have a way to test the tubes, that could possibly save you some steps. Sometimes a bad tube will throw voltages off. I had a Brand Z portable not too different from your 46-350 that worked but sounded bad. Some of the voltages were way off, and I wasted a lot of time trying to track down why. On a whim I replaced the 3Q5 and bingo, it sounded good and the bad voltages were, if not right on, a lot closer.

If you don't get function back after fixing the voltage problems, there are relatively simple tests to go stage-by-stage to isolate the problem area, then you can focus on exactly what is wrong with the problem stage. Start with the output stage, and work backward, using the tests you get from Philco, Marcus and Levy, or you can ask here.

If you have the Philco troubleshooting guide, it divides the schematic into quadrants and includes a simplified component placement and connection diagram for each quadrant. You could use that to make sure Mr. "X" made the right connections with the right value components. This is in the package I got from Chuck Schwark. Be sure to check with the list of production changes, so you can see the changes between the Code 121 that is represented in the diagrams and the Code 125 that you have.

One other thing, you could free up some space and make things more visible in there by restuffing the 4 section electrolytic can and getting those replacement electroytics out of the chassis. Some guys like doing this, some hate it. If it's not your thing, no problem. I like to do it if I can.

And finally, I don't know anything about your frequency generator app, but if you connect anything in the radio to your phone, be sure to isolate it with a .01 uf cap so you don't put any DC high voltage on your smart phone. You might want look into a stand-alone signal generator. There are lots on eBay, some modern, some vintage, for lots different of price points. Some of the recommended stage tests do require that you put an audio frequency or modulated radio frequency onto specific tube pins.

[ftovar72]

Thanks John I have then lot of documents to read and learn before to continue. I am Systems Engineer with a little bit experience with circuits but this is something different and interesting. I will keep posted my progress, still missing to restore cabinet so I would like to make it work first and later on the cabinet.

Regards!

[David]

   
Found this in Beitman from 1948 hope it is useful.David

[ftovar72]

Thanks David for sure it is useful. this will help me to identify the components that are not in a good shape.

Many thanks!

[Raleigh]

Where did you find that schematic, David? I'm always looking for good copies of schematics!

[ftovar72]

Hi,

I also found the link after his post here are some good ones

http://www.americanradiohistory.com/Beitman-Manual.htm

http://www.nucow.com/120,000FREE.htm

these have lot of schematics in PDF format.

Regards!