Univox U-1061 restoration

[fossilshark]

Drove 5 hours today and picked up this super cool half stack from facebook market. Super excited to get it restored.

I know it need new filter caps, tubes, and a 3 prong plug.

I am currently a very long ways away from the shop all week and im jonesing to see if it works.

How dangerous would it be for me to power it up as is with the 2 prong plug and ancient filter caps?

Is it OK to run with only 2 output tubes? I read it should be fine as long as the speaker cabinet is double the impedance than the amp is set for (so set it to 4 ohms to play this 8 ohm cab)

Owner said it hasn't been turned on since 1983 but it worked perfectly then.

Anyone have any info on these old univox amps? Someone carved their SSN into the faceplate and the previous owner thinks this was bought on base in Vietnam and shipped back to the states. I cannot find a single date code in this amp but I am leaning towards late 70s so, probably not a true story.

[fossilshark]

More pics

[astronomicum]

I have restored a few of the 100-150W Univoxs. Not the 1061 specifically, but its big brother the 1561, essentially a 1061 with 6550s, and also the 1011, 1501, and 1086. Message me and I will try to help.

[Platefire]

I haven't had any experiance with Univox amps but had a Superfuzz and a Tape Ehco in the 70's. Looks good and un-tampered with! Didn't see where you had a schematic posted for it. Here is what I found on Doug's Miscl schematics===a good start!
https://el34world.com/charts/Schematics/files/Univox/Univox1061.pdf

And the wind cries "MASTER VOLUME PLEASE"

[fossilshark]

Thanks for posting the schematic!

It definitely had a meltdown at some point. Going to do a full recap, replace the plate resistors (one is cracked), replace all resistors in power/bias section with metal oxide, all new tube sockets and AC rewiring.

Here is a drive with alot more pics. Very excited!

https://drive.google.com/drive/folders/1OPMvzFUbhCTWYzoFqHgfu6p1MQOfvDZg

[Platefire]

Yelp, I see the melt down on photo #44 and looks like continued on photo #707 choke? Got your work
cut out for ya:>)

[elams1894]

Very cool monster amp. Referring to the schematic, I think that missing resistor value in the phase inverter might be 100k (as seen in the U1226).

[Platefire]

On the schematic I'm trying to figure out the speaker hookup. Looks like 4 output jacks. So is each speaker hooked up separately to each jack?

[astronomicum]

I think that missing resistor value in the phase inverter might be 100k (as seen in the U1226).

Yes. It is. Good pick-up.

[astronomicum]

On the schematic I'm trying to figure out the speaker hookup. Looks like 4 output jacks. So is each speaker hooked up separately to each jack?

Four axillary speakers all in parallel. The schematic shows a shorting jack for speaker 1. They did not use one however. All jacks are non-shorting.

[Platefire]

OK, Thanks!

[fossilshark]

Good catch on the phase inverter, I will make sure im able to fix that.

So should I just order a replacement choke right off the bat? I really do suspect that its blown but I cant be sure until next week when I have my tools.

Very glad I didn't fire this up and inspected closer lol