Philco 38-690 electronics restoration.

Philco 38-690 electronics restoration. - Printable Version

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RE: Philco 38-690 electronics restoration. - morzh - 04-30-2017

Ken

These caps a fairly inductive and so can possibly pick up interference from currents around, possibly from oscillator coil(s) if any are in the vicinity etc. The shield will prevent it from happening or at least attenuate the pickup. I have not analyzed what the possible offenders are and if there are any, but these three being shielded I suspect there was some sort of unwanted interactions going there.

RE: Philco 38-690 electronics restoration. - morzh - 04-30-2017

The Power / Audio Amp chassis is on the bench now.

Same deal, whoever owned it at some point painted it with aluminum paint using a brush.
Plus the caps are not original, obviously, with one seem to be missing (will find out when the sch comes from Chuck). And some substitutes are axial under-chassis jobs/

Some Candohm; at least one I checked, the shorter one, seems OK; will know with the sch.

I also extracted the sole aluminum can cap from the main chassis.

Here's something I don't get from the label; maybe someone knows why:

The label says "Replacing mfd: 8 - 8", which is understood, replacing a dual 8uF cap. But then it says "Actual Mfd - 1.75- 1.75" which tells me it is a dual 1.75uF cap. (BTW still measure 3-3uF).
What does that mean?

RE: Philco 38-690 electronics restoration. - morzh - 05-01-2017

And I saved myself from a blunder by being a bit slow: when disconnecting the chassis it looked like it is soldered to the tweeters. I was about to start cutting and labeling the wires when upon close examination I realized they are, after all, connectorized, each being an individual single-pin connector. So I pulled them out, labeling with a P-touch as I went.

What prompted me to look closer was the notion that 38-690 is way too expensive and upscale a radio to not have a connector for the speakers, and it especially made no sense if the big one is connectorized and the small ones are not.

Although in Philco 16B, which is supposed to be a high end radio, the speaker was soldered without a connector. While a cheaper 20, or 70, did have a plug.

RE: Philco 38-690 electronics restoration. - morzh - 05-06-2017

Wll post some photos tomorrow.
I did the nastiest caps in the Power/Amp chassis.

First I restuffed the two backelite blocks. As in the 37-116, they had eyelets flooded with solder - no easy restuffing. I mean, I did not spend an hour but the process was messy. In the second cap what I did, I unsoldered and unwrapped the lead wires and then after one or two suctions from the eyelets I heated them 'till the tar bubbled and filled the eyelet, then I quickly pulled the wire ip while wiggling it just a little, and so it centered with the tar around and the rest of the solder displaced.
Still too much trouble.
I do realize Philco did not have restuffing in mind but still can't see why they started flooding the eyelets.

Then came what I thought would be the worst: the tubular metall shell 1uF cap for the tweeters.
I used cutters to start unrolling the edge, proceeding with needle nose pliers, then pulled the metal cover and used a corkscrew to extract the tarred roll. It came out very easy with no heat.
After that I put a polyester audio cap I happened to have around, which also fitted the size ideally, inside, potted the top, put the cover back and replaced it in the chassis. Whew.

Here I put a paper circular piece to keep the molten plastic from hurting the cap.

Now just the conventional paper tubulars and can lytics remain; tomorrow I'll tackle those.

RE: Philco 38-690 electronics restoration. - Ron Ramirez - 05-07-2017

Mike

Before you go much further on your 38-690, you might want to read this:

http://www.philcoradio.com/phorum/showthread.php?tid=14968

I would replace that 1 uF tweeter cap with a 4.7 uF polyester cap. Also check the tweeter wiring as indicated in the link above. You will thank me later. Icon_smile

Regarding the 1.75 - 1.75 uF cap: I'm afraid I have no clue on that. I might hazard a guess and say that perhaps this was a World War II replacement when parts were scarce and repairmen were limited on what they could use for replacements? Again, that is just a guess.

RE: Philco 38-690 electronics restoration. - morzh - 05-07-2017

Ron

Thanks, yes I read your article long time ago and do remember you having discovered in 38-690 the tweeters are wired in counterphase, and I will correct that.
As to the value of the cap, I put in 1.5uF (the article says 2.2uF is needed) at this point and I will listen to it first; I do have a suitable 4.7uF cap if they will lack the response.

About the electrolytic: I would support that theory but the Aerovox put it on the label which is weird, at least. It almost looks like "our microfarads are better than other people's microfarads and so our replacement ratio is 1:5 as our farads simply perform better".
Icon_lol

PS. Are you saying that 1uF was an electrolytic cap? It cannot be, as it is supplied with AC input, that would kill it. Was it really?

RE: Philco 38-690 electronics restoration. - morzh - 05-07-2017

More pics:

Potted

Cover's in

Closed (well, I lack proper tool so it is not exactly beautiful)

In citu

RE: Philco 38-690 electronics restoration. - Ron Ramirez - 05-07-2017

Mike

I will have to look at the parts list again to see whether Philco specified an electrolytic for part (151). I assumed that if it is electrolytic, then it must be a nonpolarized electrolytic. The nonpolarized electrolytics were widely used for speaker crossovers, as you know, until fairly recently when polypropylene and metalized foil replacements became affordable. Nonpolarized electrolytics are still being sold, but I think the foil and poly units are edging electrolytics out for speaker crossovers.

RE: Philco 38-690 electronics restoration. - morzh - 05-07-2017

Ron

Yes it can be a NP lytic, sure.
I just don't know if they existed at the time.

RE: Philco 38-690 electronics restoration. - jcassity - 05-08-2017

very nice,, wishi i had delayed my resto to integrate thsi method you are doing.

maybe on my next radio i get i will do all this fun purist work

RE: Philco 38-690 electronics restoration. - morzh - 05-08-2017

As I said before, this is not necessary and is a personal choice. Any valid reliable and knowledgeably performed restoration is a good thing.

Dans ses écrits, un sage Italien
Dit que le mieux est l'ennemi du bien Icon_smile

RE: Philco 38-690 electronics restoration. - Ron Ramirez - 05-08-2017

Just looked at the parts list. It merely states "Condenser (1 mfd.)". From your photo, it appears to be paper. Is it? Probably low voltage.

RE: Philco 38-690 electronics restoration. - morzh - 05-08-2017

Well, that is what I think. It is merely a paper cap. What also makes me think it is a non-electrolytic, is that it was fully dry upon extraction BUT when measured before it did show about 5uF (old paper caps tend to increase in value) so my thought is, yes, it is a metal-cased paper cap. Which, yes, can be replaced by a NP electrolytic, or (choice that sounds better to me) by a polyester cap.

PS> Someone on the Ukrainian forum suggested using a reloading press for gun cartridges to roll the edges. Could possibly work if the diameter fits.

RE: Philco 38-690 electronics restoration. - morzh - 05-09-2017

Yesterday finished the tubular caps.
Remaining: the electrolytic caps, one on the main chassis and a bunch on the Power/Audio chassis. One is missing, so is the clamp. I might have a clamp, though not sure it can be properly riveted to the chassis.

RE: Philco 38-690 electronics restoration. - Kenneth F. Besso Jr. - 05-09-2017

I though that ,,,it was a condenser,,,from a chevy point distributor,,,lol