[BrendaAnnD]

Thank you Chuck. That will be very helpful.

[morzh]

So the divider can be say 93/7 Ohm (or 930/70) since taps are rarely 7%.

[Chuck Schwark]

Brenda,

If the feedback tap is "too much"on a univ. repl. transformer for the circuit (not in this original case), one can always use a simple two-resistor voltage divider between the tap and the circuit to cut it down.

Chuck

[BrendaAnnD]

I may have found a transformer that will do the trick in my stash (didn't even remember having it.) It's a universal that seems to work pretty well, with the divider network on the feedback tap. Good sound, good power output. Still hope to find an original to put in there, though. Started changing the crumbly rubber wire on the surface (mainly to the lamp sockets.)

Now I need to find a bunch of the lamp sockets for the station indicators. I have posted this need in the WTB thread.

[BrendaAnnD]

Next problem...

I've discovered that the two 'lytics that are used in the remote section are both completely DOA. Any idea where I can find a 16uf/150V non-polarized (#95 on the schematic) (this one is a mid-production change from a 16uf/200VDC) and a 30uf/30V (#88 on the schematic) Not sure about the package on this one, whether DC or non-pol)

Got any suggestions, Ron?

I only discovered these because I got the Mystery Control powered up tonight and it works, but the stepper does not work properly, although the mechanicals of it seem to be in good shape and it steps properly if I work the ratchets manually. I'm figuring at this point that #95 will make a huge difference on how strong the main solenoid will pull in, and so it should work the stepper properly once that's replaced. The other cap is in the on/off/vol. control motor circuit.

I need to find replacements for these, and not really used to looking for these type caps.

TIA

[morzh]

I bought 100uF some hi volts NP cap from Parts express a gear ago when fixing my HP oscillator.

http://www.parts-express.com/cat/non-pol...itors/1385

They are 100V max but can be serialized.

[klondike98]

Russ pointed me to these when I was working on an AK 55C.

[morzh]

Bob

$8.50 for one 250V 15uF Solen cap.

$1.96 ($0.98 for one) for two 100V 33uF NP caps.


Unless huge ripple rating is needed (somehow I think not, NP caps are not customarily used for it)

[Ron Ramirez]

Brenda

The one (and only) time I ever worked on a 39-116, I remember finding some non-polarized electrolytics at a motor shop.

If I had to do it now on a set I was going to keep, I think I would use metalized film caps. Those are expensive, but should last the rest of your life.

15 uF, 400V from Parts Express:
http://www.parts-express.com/audyn-cap-q...r--027-119

If you want 16 uF, they have them, but almost double the cost:
http://www.parts-express.com/solen-16uf-...r--027-578

30 uF, 250V:
http://www.parts-express.com/dayton-audi...r--027-440

Edit: (95) is polarized, but I don't see why a non-polarized film cap wouldn't work. I now remember replacing a similar cap in the 41-616 I used to own with a conventional polarized electrolytic. If I had it to do over again, I would try the film cap. I do not remember what I used as the motor run cap in the 41-616; Joe (w4rtc) could tell you as he now owns the radio and he did some fine-tuning and finishing to my not quite 100% completed job on that chassis.

[Eliot Ness]

Brenda, A.E.S. sells Metalized Polypropylene caps too, you might want to check voltages, values, and shipping to see who is the cheapest:

https://www.tubesandmore.com/products/ca...ypropylene

[BrendaAnnD]

Ron,

Thanks for the l links.

95 was originally a polarized 'lytic, but Philco superseded that in later runs with a 16uf/150V NP (original was 16uf/200VDC).

I'm presuming that they had problems with cap failure in that circuit for whatever reason.

[codefox1]

You can always put a couple of polarized caps back to back to make a NP. Two 33 mf back to back would make about 16. Can't remember whether it makes a difference whether the +'s or -'s are joined in the middle.

[BrendaAnnD]

I found a starter cap (16uf) that will fit very nicely inside the original can for the stepper cap.

[BrendaAnnD]

The volume control finally gave up the ghost last night. I was testing a homebrew cap in the motor circuit (yes, the motor did run better, faster.. it had been annoyingly slow) and turned the set off with the front panel control.. never came on again. The shaft just spins in the control without moving the innards. Apparently, this control has a sort of slip clutch mechanism inside to allow the shaft to spin once the control has reached either limit, so as not to damage the control if the motor is run for too long in either direction. It's not "clutching" well enough anymore, so it won't toggle the power switch. Oh well, the control was all sorts of flakey anyway, with lots of dead spots.

I've written Mark Oppat to see what he can come up with.. but I may just have to find a donor part. I've temporarily subbed in a 500K pot/switch and the volume goes up and down smoothly with no crackle. Unfortunately, the thing's got no loudness tap and is too low a value to allow the tone control to do anything.

[morzh]

Codefox


Yes you could put electrolytics back to back, does not matter what is in the middle, but then you have to bias it so if say plusses are in the middle, they are always above the minuses.
This usually is accomplished through a resistor connecting the middle to the respective porential, like B+, if the plusses are together, and the minusses should be pulled down to the GND potential.