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Thread: Univox U-1220 w/ 1221 pickyback amp & 1005 2x12 cab

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    Univox U-1220 w/ 1221 pickyback amp & 1005 2x12 cab

    I put the Astro Amp aside for a while after a major setback and started looking at my latest acquisition. It's a tube amp with a schematic! That's what I like!

    I picked this up for $240 a few weeks ago. It seemed like a small price for a tube amp with a speaker cabinet. I know Univox doesn't have the demand or appeal of a fender amp, but I'm always curious to compare the tonal differences and build quality of these lesser known amps to the fender. This amp was used by a pro musician for many years so I'm told. Upon inspection, there were no hums or buzzes, just a nice clean tone. Volume was weak for 50 watts, and reverb and tremolo not working. I was told the chassis was all original but the speakers likely not.

    I brought it home and let my son try it out. He plays jazz and really likes the tone. Now it's time to get it back into good working order. Here's a pic. Sorry it's not a closeup. I forgot to get a shot before I took it apart. If you zoom in, it's on the back wall between the keyboard and drums.

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    According to vintageunivox.com the 1005 cab originally came with two 12" Eminence special design speakers. The cabinet has a rating of 16 ohms, but the speakers combined measure 8 ohms. When I pulled the cabinet apart, I found two Kustom 12" speakers. I didn't find any info from the markings on the speaker, so I know nothing about them other than they seem to sound good.

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    Supporting Member TomCarlos's Avatar
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    Someone swapped the speakers and hooked up as 8 ohms to use with a different head? That is always a possibility. So right now, you have two speakers in parallel measuring 8 ohms or do you have two 4 ohm speakers in series?

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    The Univox chassis in on the bench. I didn't expect such a solidly made chassis. Seems on par with a fender. There's a cover on the bottom which keeps it totally enclosed. Remove the cover to reveal the components inside. This one is clean inside and does look all original. It has a pcb. When you remove two covers from the top side it reveals the bottom of the pcb. That should make servicing easy!

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    Supporting Member TomCarlos's Avatar
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    The amp looks very clean. I found a pic on the web and the schematic.

    Here is a page with info on the Univox amps - http://www.vintageunivox.com/amps/uniamp.html

    Looks like you picked up a nice amp!!
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    Last edited by TomCarlos; 03-21-2019 at 04:10 PM.

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    Quote Originally Posted by TomCarlos View Post
    Someone swapped the speakers and hooked up as 8 ohms to use with a different head? That is always a possibility. So right now, you have two speakers in parallel measuring 8 ohms or do you have two 4 ohm speakers in series?
    I'm pretty sure it's two 16 ohms speakers in parallel. The amp and cabinet remained together. It appears there is a 16 and 8 ohm tap on the OT. I'll have to checked to see if that was changed to 8 ohm as well. I prefer an 8 ohm cabinet for versatility.

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    I replaced all the electrolitic capacitors. There were a lot. They didnt look bad and I wasn't getting any hum, but I didn't want to diagnose the amp with 40 plus years old caps. I was concerned that my work might introduce more problems. My concerns seemed realized when after replacing all the caps, I powered the amp and I got no output. With a little more time I found a bad solder connection and repaired. I also found a fried power filter resistor and replaced, added 3 prong power cord and switched to the 8 ohm tap on the OT. To my relief the amp now seems in good working order. Tremelo and reverb are now working too! Here are pics with new caps.

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    Last edited by tigerzilly; 04-01-2019 at 04:29 PM.

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    Still some issues

    Close, but not there yet. I still have some issues I need to work through. With the amp reassembled I did some testing, and I'm hearing a faint 60 cycle hum. I need to lift the ground that I installed and see if it goes away. There was no hum before the cap replacement.

    I'm still sorting out the footswitches for the reverb and tremolo. I picked up a dual footswitch, but when I went to switch out the two RCA connectors with 1/4", I discovered only one conductor going to one of the plugs. That's not working here.

    Lastly I'm getting a pop when I switch off the power. I don't recall that before either, put I'm thinking arcing in the switch.

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