NAD: Univox U-1061

Hi guys, I just picked a U-1061 that's been bouncing around craigslist locally. The first I saw it was a few months ago in non-working condition paired with a 212. Eventually it was "taken to a reputable tech" though when I showed up it had a noticeable amount of noise in the EQ section. Word is that he replaced some diodes. I'll find out soon enough. In the end I scooped it up with the cab for $300. Maybe a little high for an amp that needs work but just look at that iron!

I'm going to try replacing the 600/.01 cap before volume 1, 600/.02 before volume 2, and the 600/.02 cap before the treble control and go from there as far as the noise issue. (See post 2.) Filter caps, a bias check, and a 3 prong power cable are also on the short list.

Tangent topic: Does anyone have a schematic to a U1511 or U1561 amp? According to a few forum posts, the main (only?) difference between the 10xx and the 15xx was that the latter came from the factory with 6550s. Here's a link to a U1561 using the same layout, chassis, and transformers. It has a sticker where the chassis is stamped for the 1061. I think you know where I'm going with this...



Those transformers make my 20 oz powerade look tiny!

 

So as it turns out the amp is actually quiet and functional (except for it's pull high boost on channel 2) when fired up at my home.

Not ruling out anything yet but I may have been using a bad instrument cable at dude's place. The first guitar I plugged in made no sound. The second worked but still made noise I would have associated with the preamp caps or possible a bad cable. Maybe he wasn't feeding me a line when he swore his buddy played it for hours the other day trouble free.

 

The noise didn't sound like a tube issue that I've experienced (mirophonic or dying). I've got some good Telefunken 12AX7 I pulled from a Bogen MX30A I'll try in there though.

I'll definitely recap the power supply. I want this thing to kick harder than it ever did when I'm done with it.

It sounded pretty good and plenty loud through the 212 with the stock(?) '72 CTS AlNiCo speakers.

 

Mine did too. Double score! Nice amp btw.

No doubt. That was part of why I was interested in it. For $300 I feel like I did pretty good.

Admittedly, the sockets on my amp are pretty crap. I guess that might make the list too.

 

Foot in mouth here, turns out V1 & V2 were on their last leg. I just hadn't played it for a long enough time period for the problem to show up again. Supposedly the mystery tech tested all the tubes. Not sure about any of dude's story at this point. Either way, it's sounding a lot better.

Edit: The midrange and top end are really quite nice and airy now. For fun I dimed everything but bass, jumped the channels, and plugged in a Rick 4003. Now we're getting somewhere! I was overdriving the normal channel and had a totally clean high boost on top of it with the bright channel. It sounds really effin' good. Reminds me of a Sound City 120 I once had tonewise.

 

Thanks!

Nice! I've never heard a Walkabout in person but I've heard lots of good things. Hang onto those tubes! Mine were toast. The tube swap was night and day on the 1061.

Cool, how'd it treat you? I swapped the speakers in the 2x12 the instant I got it because I knew I was going to turn the amp all the way up.

 

Guys, has ANYONE got a 1501, 1511, or 1561 Univox schematic? I really want to see what their factory setup was with 6550's.

Best I have is a gut shot of a 1561 from another forum... Thankfully they appear to be the same as the 1061 with the power tubes and a sticker on the back being the only difference.

 

I was on my way there when all of a sudden, I found the amp that photo was of. Right here on Talkbass! http://www.talkbass.com/threads/fs-univox-u-1561-150-all-tube-watts.703321/

I think I'm good now...

 

The transformers and topology look to be identical other than the power tubes employed. You can even see where the U1561 sticker was slapped over the U1061 and serial number stamped into the chassis. This is also the case of the guitar amps (U1011 and U1511) that share this particular chassis and transformer setup.



Proof from inside a 1561. See the model number?

 

Thanks. We had a Sam Goody here until sometime into the '00's I think.

Dang! I've only paid $1 per watt once for a tuber, a Fender PA100 that I should be recapping later today.