[MarkD]

Hi. Im looking for a little help on this. I don't have a real lot of experience with these old radios. I took a break from working on the Cabinet of my 37-116 and tried to start on the capacitors on this RCA. it looks like someone previously changed out some capacitors and put a 15mfd electrolytic capacitor where the schematic says a .5 mfd non electrolytic capacitor should be. Is this possible and is there a reason why this would have been done. I have checked and rechecked the schematic and I don't think Im reading it wrong . Anybody have any thoughts .
Thanks

[morzh]

Mark

It's good to get into the habit of giving an exact model # and a link to the schematic when asking for advice on a radio.

I would like to believe you that "you are not reading it wrong" but then I do not believe anyone who says that. Ever. I have to see for myself.

[MarkD]

The model is an RCA 810k1 and the capacitor is c14 on the schematic coming off the 6h6 tube http://www.nostalgiaair.org/Resources/149/M0015149.htm it is the third electrolytic capacitor I found on the radio the other two being labeled c41 and c42. Any thoughts ??
Thanks, Mark

[jerryhawthorne]

Mark, no that cap should be a .05. The others, c-41 16mfd and c42 25mfd. As far as I can see the last two are the only e-caps.
Jerry

[MarkD]

Thanks Jerry, can you think of any reason that it was replaced with a electrolytic cap? Have you ever seen this before?? The radio worked with this setup. The guy I bought it from had it on when I went to pick it up.
Mark

[jerryhawthorne]

Mark, in the old days it was amazing what people would throw into sets to get them working. Heck, it may have worked with that but certainly would have worked better with the proper cap. Those sets were very forgiving for components.
Regards, Jerry

[Chris Cusick]

Jerry is right - there are only 2 legitimate electrolytics. It looks like C14 comes off the 6K7 tube (IF) and I think it reads 0.5 not 0.05 uF - that's on the big side for a paper / these days mylar type cap but I expect a wide range of sizes would work.

Nice sets when working - love the big 'sunburst' dial !

[MarkD]

Thanks Chris , My schematic shows it coming off the 6h6 tube not the 6k7and it is a .5 and I did use a mylar cap. I replaced all the other caps and put shrink wrap tubing over all the rubber wires but now all I get is a very low loud rumbling hum ..ugh! so now when I get a chance I going to go over everything I have already done and see where I made a mistake. I have checked all the tubes and they all come back good except the tuning eye tube. I have very little experience with these old tube radios and am trying to learn as fast as I can. Its been many years since High school electronics class. I appreciate all the answers I get here . And I do love the dial
Thank you
Mark

[Chris Cusick]

I was looking at the posted schematic so I am puzzled - I don't see this cap, C14, associated with 6H6 (which is 2nd detector), which only has some low value caps associated with it. However in such a case a good test is to carefully touch the centre pin of the volume control (the wiper). If the audio section is OK you should hear a loud buzz. Then you will at least know which half of the radio has the problem. No buzz and the problem is with the audio stage, somewhere after that point (assuming there's only one problem ) .

[MarkD]

Im sorry Chris I should have said the wiring diagram, it clearly shows the c14 coming right off the 6h6 which to someone with not a whole lot of experience is kind of puzzling because the schematic shows it just as you said but in reality it is just as the wiring diagram shows
Thank you again for the tip I will try that tonight.
Mark

[Chris Cusick]

Aha ! I see what you mean. If you look at the wiring diagram, that cap is going to pin 1 of the 6H6, which is just a ground for the metal tube shell. So yes physically it goes there but it is not actually inter-acting with the 6H6 in any way, which explains the difference between the 2 diagrams. That's just a convenient place to use for grounding it. The RCA 810K1 was one of the pioneers for metal tubes which used this arrangement for built in shielding. Not sure that they were really that great but hey it's part of the history of your set.

[MarkD]

Chris thanks for explaining that, it was pretty confusing for me
Mark

[Chris Cusick]

One other thing - the power transformers can get very hot ( they were too small in 1937 and they are too small now !). Strongly suggest a dropping resistor or a bucking transformer on these. I run mine at about 105 V which is the minimum recommended by RCA.

I hope you are making progress otherwise.

Best Regards

Chris

[MarkD]

Thanks so much for the idea Chris, I have never put in a resistor on the transformer before so Ill do a little research . Ive been trying to figure out what to do with another radio that I have a problem with instead. Recently. I took my Philco 37-116 to a professional to have it fixed as its really to much for me at this point of my learning curve but after 2 weeks and $$$ it was to much for him also. He put in the ipod jack ,changed out capacitors and a tube socket etc. but it will only play with the Ipod . He could only get it to work on Broadcast and none of the other bands but only for a few Min. at a time and then it would stop... he finally gave up and gave it back to me... Ugh !! I see your from Fox Lake I used to have my boat up there a few years ago
Mark

[jerryhawthorne]

Mark, sorry about your problems. Sounds like the "professional" only means you paid for his service. Your radio is certainly not the easiest to restore. I did one for a friend and I never wish to work on one again. Perhaps someone can help on here but if you are really new to radios, this is not one to start on fresh. Very nice sounding radio and it appears the amp section is working. That is part of the way there.
Jerry