TSAU1 SS Speed control questioin

I had rebuilt my Seeburg AY160 about a year and a half ago. I had put -a lot- of work into this jukebox and it's a source of real pride. The last thing I had to do was to service the TSAU1 SS Speed control unit.
I had replaced the resistors which were out of tolerance and replaced all the electrolytic caps and a general clean-up. I even fabricated a new relay cover and repainted the slightly rusty transformers.

I did final operational voltage checks and set the Drive and converter HZ according to the manual. Everything looked good so I installed it in the jukebox.

It played for maybe a half an hour then a loud POP as a capacitor inside the TSAU1 unit exploded.
I was really just put off by it...so I unplugged/bypassed the speed unit to set it aside for another day.

Today was the another day.
I gave it a good inspection. C754 had exploded in the oscillator/converter section:


The parts list shows this to be a 10uf 100v non-polarized cap. I had replaced it with two 22uf 50V connected back to back for a non-polarized configuration.

After checking the transistors for damage (shorts) it all looked good so I bought two 22 100V electrolytics, and again configured them to be non-polarized. You cans see them in the photo below in the top right:


Ok here's my question.
My TASU1 speed unit is operating properly- in that it works to control the motor speed. I don't have a strobe disk but I've set the oscillator to about 44hz. No problem there.
However I've been paying close attention to my newly replaced pair of capacitors and they get warm to the touch. Not hot, just warm. I'm not used to having electrolytics get warm and I don't want to deal with anymore trouble from it. I am getting about 52VAC across these caps and frankly don't understand why they are getting warm.

Do you think replacing them with something like a pair of 22uf 200v caps would be better?
What do you suggest?
Thanks in advance.

Where that cap is located it gets quite a workout -both from the constant AC and the switching transients that probably punched through one cap.

The later LPC versions spec'ed a mylar @200v. The MFD is different because of the native 33 in LPC, but the waveform and spikes will be the same -just different frequency.

Rob

Rob-NYC wrote:Where that cap is located it gets quite a workout -both from the constant AC and the switching transients that probably punched through one cap.
The later LPC versions spec'ed a mylar @200v. The MFD is different because of the native 33 in LPC, but the waveform and spikes will be the same -just different frequency.
Rob

Yep, mylar would be a way better choice for an AC signal like that.
But I'd over-rate it at 400v for more durability.

Thanks for the capacitor tips.
My supply store didn't have anything near a 10uf 400v mylar so I got two metalized polyester film type. Each rated 6uf @ 200v. I put these in parallel for 12uf 400v effective value. I was able to cut my regulator output (drive) down from 24v down to 22v and set my speed control in the half way point to achieve the 44hz output.
Everyone likes pics-the big bright yellow caps on the top right:


I did a final check to see if I was all done.
Not yet.
To my surprise the main electrolytic filter cap I had replaced before was getting warm. It's C751, the one straight off the supply diodes. Dog-gone it!
The parts list it to be 500uf 50v. I had put in a 470uf 50v. I measured -44vdc across the cap when unloaded. Hmm very strange I think that it, too was warming.
Anyway I had a new spare 100uf 500V to replace it. Overkill, yes but it's what I had in the parts bin. It's the big blue cap in the top left of the pic above.
I was still getting 44hz out of the oscillator/converter so I should be good-to-go.
Thanks again!

Steve, FYI paralleling caps does not increase working voltage -only capacitance.

As for the 500@50 the heating might have been due to the proximity of the two power resistors. In any case, moving that cap as far as practical from those resistors via forming the leads is a good idea.

Rob

Steve,
Iz confuzzed ! How does one replace a 500 mfd cap with a 100 mfd cap?? IMHO the 470/50 should be fine ?? --and as Rob stated--there are two "sand block resistors" there, that are designed to get HOT ! Ron Rich