Univox U-45B

[benjamo]

Hello - thanks for super helpful info.

My situation: a friend donated a 45b to me, knowing the output transformer was blown. I replaced it, and got some sound going, but the tremolo, while working, also gave a 60 cycle hum of epic proportions. This sounded like a bad cap, so I began replacing them. Replaced some of them, and turned it on. The sound was gone, and the tremolo pot began smoking! What happened? Pretty sure I used correct value caps, no shorts anywhere. Is this because I replaced one of the blown caps that has now begun to pass correct voltage further down the line to another bad cap? Or something else?
Thanks.

[loudthud]

Did you get the polarity right on the replacement cap?

[benjamo]

Polarity is good. Just went ahead and replaced all caps, and problem solved. One of them must've been shorted out. The amp is now working! My first restoration, replaced power cord, input jack, volume pot, 12AX7 socket, all the caps. Cost under $100.

[The Dude]

Did you clip out the death cap?

[benjamo]

Do you mean C16 in the attached schematic? Otherwise, I don't believe that there is one on the 45B

[The Dude]

Yes, that's the one. If it's not there, all the easier to remove it.

[Axtman]

I just picked up a Univox Meteor U-45B amp off Craigslist yesterday. It was $150 and the guy delivered it to my house. How could I resist? The amp still had the old 2 prong power cord. I did not even turn the amp on. It went right to my bench and got a new 3 prong power cord installed. (I had a recent bad experience with an ungrounded amp that I will write about later.) After spending the entire day yesterday cleaning it up it looks great. (I should have taken before and after pictures.) Now I plan to replace all the electrolytic caps and possibly get new output tubes since one tested weak. I don't play harmonica, but this would be a great harp amp!