Univox u-1511

[galtjunk]

I picked up a head that is blowing fuses.
It has 4 6550's supposedly putting out 150 watts.
It is marked as a 1101 with another sticker above it stating u-1511.
I can find the schematic for the 1101 but no luck with the 1511.
The board in it says 1101 and the controls and preamp tubes are the same on it so the schematics should be close.

Would the voltages on the 6550's be the same as the 6L6 model?

Is there a schematic available for the 1511?

The panel by the fuse holder is not marked and it contains a blown 3 amp slo-blo.

The transformers on this thing are massive!

The chassis is marked "Replace with 6550 only.".

[Phil_S]

Can't help directly. Massive transformers should be expected for a quad of 6550. The 4 tubes need about 600mA just for the plates alone -- exact requirement depends on voltage, etc. The power tube filaments alone need about 6.4A or so, as I recall. So, we are probably looking at a 600mA HT secondary and maybe 6.3v @ ~8A, plus a 5V rectifier winding. I'll bet the PT weighs in at 10-12 pounds. OT couldn't be far behind. This isn't just idle commentary. Thinking aloud here, if your secondary requirements are 600mA @ 500v + 8A @ 6.3V + 3A @ 5V, that's 365W (power requirement, not output). If you take a short cut and divide by 120V line supply, 360W/120V=3A. I'm pretty sure that's not the right way to do it, but it suggests the 3A fuse might be marginal. I think I'd start by trying to find out the proper fuse rating.

[cbass]

I'd start buy hooking it up to bulb limiter.Probaly with a 150 watt bulb
.A three amp fuse should at least hold up at idle.

[galtjunk]

I pulled the tubes and tested them.
One was shorted.


The circuit board was floating on the wires from the pots and jacks so I replaced all of the stand offs and re mounted it.

I reinstalled all of the preamp tubes and two of the 6550's and no blown fuse.

The 6550's were all mixed brands, 2 Mesa, 1 GE and 1 RCA(dead) so I'll order a new quad.

I don't want to pay 400 bucks for a quad.

Who makes a good replacement?

[sliberty]

Glad there was nothing too seriously wrong with the amp.

I haven't tried them, but the Tung Sol's are not priced too badly:

http://thetubestore.com/tungsol6550.html

$150 for a quad.