[victor3d]

I have been restoring the electronics and cabinet of this unit for some time now as a heartfelt gift of time and resources for my neighbor and friend. the radio belonged to her grandfather. So far I have refinished the cabinet, reconed a badly damaged speaker (through my club njarc), replaced missing knobs, replaced the electrolytics and all paper caps and replaced a number of resistors that have floated in value. I have alligned the BC, FM and SW and alligned the pushbuttons. The radio does not have a working record player.....looks like someone attempted to fit in a replacement that would play newer record types other than 78s. It was never connected and is in bad condition and not worth the trouble.
Here is my problem....the radio still does not sound right..I know and believe that it should sound much better. I have heard demos of this radio on youtube and it sounded much much better than this one.
Here is what I belive to be the culprit at this point. The transformer and speaker all test out ok. I followed the testing procedures in the manual that I obtained and the voltages were high for Section One and manual indicates that it could be (among other things) a faulty T200 - Transformer Output Part 32-8274. The Schematic indicates 240 Ohms and I am reading 750 ohms. Now I tested the resistance while still attached but do not believe that this should matter.
My question for the Phorum is does this sound like I am on the correct track or am I off track. I still consider myself to be a novice and much of this is still abover my head but this has proven to be a great learning experience. If it is a bad output transformer, can I find a replacement somewhere...where....thanks much for any and all help or suggestions.

[jerryhawthorne]

A link to the schematic below. It is a little unclear if the resistance of the full primary of the output transformer is 280 ohms (Plate to Plate on the output tubes) or if that reading is for one leg to the center tap.
Jerry

http://www.nostalgiaair.org/PagesByModel...013606.pdf

[victor3d]

yes....I was wondering the same thing........but even if You double the value you then get 560 and my reading is 750 ohms...still seems too high.....?????

[victor3d]

one more question.....does not the center tap divide the voltage readings but I am uncertain at to whether the resistance or ohms reading is halved as well......

[Joeztech]

Victor;

Is the transformer an original equipment type? In my 40-201, it had been replaced by an after-market substitution. I believe all the Philco transformers had their actual part number stamped into the metal or somehow written on it to identify it. The replacement in my radio had significant ohm differences from CT to either end, yet it seems to work OK after recapping and phase splitter resistor replacements. Someone pointed out that the main issue is that the two halves of the primary windings have the same inductance value, whether or not the actual DC resistance is the same. That said, I think the plate voltages going to the two push-pull output tubes should be pretty nearly equal. So should the screen grid voltages. One thing that might make the voltages different to some extent would be if one or the other tube had a leaky coupling capacitor going to its grid.

The schematic referenced above shows that one side of the transformer should measure about 280 ohms from the CT and the other should read about 310 ohms from CT or about 590 ohms plate to plate of the two 6V6GT output tubes. The cathodes of both output tubes are tied to ground and the screen grids and the plate circuits to the two tubes both are tied to the same B+ source. If one of the tubes had shorted its plate to the suppressor grid/cathode circuit it could have burned 1/2 of the winding in the transformer. Do some checking with a volt meter and let us know the voltages you see on cathodes, grids, screen grids and plates of the two tubes. Make sure that there is -16VDC at the grids of both output tubes.

Joe

[victor3d]

ok........after some more checking....I see that the tone/on off control reads 12 M Ohms and specs say 4.....I sprayed the heck out of it but still reads 12 M Ohms....sound is scratchy and cuts out as I rotate the tone control to bass position....could it be this simple......I say simple but would have to come up with another tone control......opinions and advice please and thanks

[jerryhawthorne]

Victor, I do believe your on the right track. I don't think the problem is in the OP transformer. I'm certain you can find a proper pot at Mouser or Mark Oppat.
Regards, Jerry

[victor3d]

thanks you everyone....I will check with mark as I have dealt with him in hte past and will come back to report my progress (I hope)

[victor3d]

OK...still need help.....one thing I can say is that far from knowing exactly what I am doing.....I think that I am getting to know my way around.......So I have ruled out the tone control even though I could probably use a new one....but I took it out of the circuit and still have the same distortion etc. I put a signal trace on AF and sound is clear at the volume control......so trying to trace it back I find myself looking for a bunch of caps 100 mmf and a few 250 mmf that I can not seem to locate. I see three type of doohickeys under the chasis.....one is square with dots which I was loathe to mess with since my experience tells me that the dots discolor forcing me to go to the schematic which I should be doing anyway but might make a mistake....I know that these rarely go bad (or do they)...at least the mica ones rarely go bad....but are these mica or paper ???????

so first question.....are these my 100 MMF caps.

Next I see some light brown tubular thingies marked 62-110 but do not see these on the parts list....anyone....what are they...I can't get a measurement ohms or mf because I think that they are below my meter capabilities. So, anybody...what are these caps or resistors

third and last I see some brown tubular thingies with stripes....but with bulges on the ends....caps or resistors...???

thanks

[Mondial]

Its hard to tell without seeing them but the brown tubular "thingies" with stripes are most likely the 100 pF caps.

Are they about 1/4 inch in diameter and less than an inch long? If so, these are early ceramic caps, and like micas they are very reliable and need not be replaced.

They could also be the 250 pF caps, but more likely these would be domino style micas.

Most of these caps will be located in the RF front end and IF sections of the radio.

[jerryhawthorne]

Victor, we need some nice close up pictures to see what your looking at. Nice that the tracer gives a nice tone at the speaker, makes me think you may be looking at the alignment of the radio. Certainly not the OP transformer. Is the distortion present on both the AM and FM bands? I'm not familiar with a signal tracer, never used one. Can you use it to move towards the front of the radio and perhaps inject into the IF section? I use a signal generator and scope when trying to run down these types of things. I need to learn more about the signal tracer. Hook your tracer up to the first IF grid (G1) and see how things sound.
Regards, Jerry

[Marsupial]

Hello Victor.

I have the exact same model radio. When hearing a distorded sound, the first thing you need to do is isolate where that distortion is coming from.

You might not have a record changer, but still have the mono "phono" type plug that was used for input. You can use it to determine if issue is within the radio section, or amplification section.

The phono jack will accept modern-age equipment, such as tape-deck or MP3 player, with a conventionnal RCA-type connector.

The left-most preset button is the phono on/off switch, when pushed in you no longer have radio, but record changer. This completely bypasses the radio section and goes straight in the amp from that input connector.

If you try that and still have distortion, you then know that the issue lies within the amp or after (or perhaps power section?). If you have a clear sound, then you know the issue is before the amp, so likely within the radio section.

Do you have the same issue in AM and FM? do you get Shortwaves? If so, does it too have the same issue?

once you know what section has issue, you'll be halfway trough finding the culprit.

BTW This model is awesome.


Hoping this helps.

[victor3d]

OK.......I thought that I should post my progress on my friends grandfathers phico that I have been working on for feels like a year. Perhaps my progress will encourage someone else and also this post should serve to thank those who reached out and helped. After trying everthing I could think of to remove or find the cause for the distortion in the radio including speaker recone, replacing al of the caps and a lot of resistors, alignment about 5 times, rebuilding the bakelite block, checking out a drifting tone control which is way out of spec but not the problem, spraying and cleaning and of course checking all the tubes, corectly wiring and replacing the three lead cap going to FM section....etc etc. Each time I thought that I had nailed it down. I finally bit the bullet and went wire by wire, connection by connection, capacitor by capacitor, resistor by resistor...i made and interesting and incredible discovery...ha. I began to find first resistors that had drifted..then I began to find resistors that were wrong value by factor of 10 where someone may have read an orange band for a red faded band....then mistakes between the parts list and the schematic values in a few cases where I used deduction to choose what I belive to be the correct values, then wires going where they should not or no wires at all, then about five or siz caps missing and five or six resistors completely missing. End of story, this radio now plays incredibly well, I have learned so much about radios and this model in particular. I consider it a testament to this radio that it even played at all and did not blow up....ha,

Now, two questions....

1. in all of the specs I could find no voltage readings to the tubes etc...only troubleshooting requireing not the measuring of voltages but hooling up complicated equipment to test and not a multi meter...is there such literature or am I missing something.

2. I would like to complete the restoration by installing a record player....I know the original was only 78rpm....is there a replacement that someone can recommend that would fit right in, attaching to all fo the conections without having to rewire the entire radio (which is beyond me)....thanks again to all and it is great to have a site like this....this was my first Philco and I have a new found respect to them.