eliya wrote:benadrian wrote:eliya wrote: I spent a lot of time chasing it and it turned out that one logic IC was put on backwards. I flipped it around and voila!Oh damn, what bullshit!Yep. I'm a little disappointed that the issue wasn't something else, like a faulty part, but I'm comforted that I wasn't the dummy who put that IC in backwards!Always nice to have something remind you to check the stupid stuff first. I'm probably not alone in having the impulse to jump to a complicated conclusion, especially once I've fixed a tough problem with similar symptoms. It's also worth believing you didn't waste any time since inevitably, you learn more about the circuit and design theory just by trying to find the source of a problem. Good work Eliya.

Nate Dort wrote:weezy wrote:^ here is the listing https://reverb.com/item/4554245-sunn-beta-bassLooks like he sold it to a shop near him. Same town. He must have taken a huge hit, because I sold it to him for $730 shipped.You got a steal on that thing. $450 is only slightly more than I had into it.The 1/4 jack for the footswitch was loose upon arrival back when I got this, I just started fiddling with it yesterday and unfortunately I made it short out. I looked inside and found a wire had come loose on the jack, re-soldered it. To get it out of the enclosure was a fair bit of work. Gonna have to fix some of the mounting nuts, one feels stripped, the other's nut/bracket contraption came out and to put it back in correctly would mean disassembling the whole front board from the face plate, fuck that noise. Sheesh, a five minute fix turned into a wrestling match....

weezy wrote:The 1/4" jack for the footswitch was loose upon arrival back when I got this, I just started fiddling with it yesterday and unfortunately I made it short out. I looked inside and found a wire had come loose on the jack, re-soldered it. To get it out of the enclosure was a fair bit of work. Gonna have to fix some of the mounting nuts, one feels stripped, the other's nut/bracket contraption came out and to put it back in correctly would mean disassembling the whole front board from the face plate, fuck that noise. Sheesh, a five minute fix turned into a wrestling match....Sounds like the previous owner had been inside there. Those capture nuts in those things are dumb and I hate them.

Sunn Concert Lead(s) (cont.):I'm pretty sure that the power transformer on the second one of these is bad. Fired it up with a speaker last night for the first time and it was making a horrible static sound. Disconnected the speaker and I could hear what sounded like arcing inside the PT. Disconnected the PT secondaries from the circuit and the arcing sound was still there. A scope on the secondaries showed weird fluctuations, so I'm guessing there's an intermittent short between some of the windings in there.Mercury Magnetics make a replacement PT for this thing, but it would cost more than the entire amp. I can probably get what I need from two or three smaller transformers.

weezy wrote:I meant to take a picture of the punk rocker somebody drew on the top cover before I put it back together....I hope I don't have to open this thing up again. I'll be playing it out later this week so I finally get to put it through it's paces.Oh, I totally forgot about that. I never got a good photo of it either. You can kinda see it here:

Nate Dort wrote:weezy wrote:The 1/4 jack for the footswitch was loose upon arrival back when I got this, I just started fiddling with it yesterday and unfortunately I made it short out. I looked inside and found a wire had come loose on the jack, re-soldered it. To get it out of the enclosure was a fair bit of work. Gonna have to fix some of the mounting nuts, one feels stripped, the other's nut/bracket contraption came out and to put it back in correctly would mean disassembling the whole front board from the face plate, fuck that noise. Sheesh, a five minute fix turned into a wrestling match....Sounds like the previous owner had been inside there. Those capture nuts in those things are dumb and I hate them.I meant to take a picture of the punk rocker somebody drew on the top cover before I put it back together....I hope I don't have to open this thing up again. I'll be playing it out later this week so I finally get to put it through it's paces.

Sunn Concert Lead(s) (cont.):I don't think the transformer was arcing after all. Pulled it out, took off the bell ends, and hooked it up to the variac. No arcing or weirdness. I put the scope on the AC and followed it back from the transformer. Everything after the thermal switch was fluctuating. New thermal switch on the way.

Ampeg SVT-IIP:This guy arrived the other day. It powered up, but had no output. Opened it up, and I could see the tubes light up. Started poking around and wasn't seeing any B+ voltage on the tubes. The power transformer was crooked and separated from the PCB a bit, and when I desoldered it, some of the pins fell right off. Looks like it had taken a fall and the weight of the PT broke its own pins. The 200 V winding was broken at one of the terminals, and a few others were intermittent. Probably going to have to scrap the PT. Mercury Magnetics has a drop-in replacement, but it's $170, which is way more than I want to spend. I may have to rig something else up, but finding something that is small enough to fit in the chassis is going to be tough.

I seem to remember many HT fuses specifying fast blow, with the mains specifying slow blow.Either way, fantastic score.

Nate Dort wrote:benadrian wrote:I seem to remember many HT fuses specifying fast blow, with the mains specifying slow blow.Either way, fantastic score.This one specifically says T 500mA (t = time delay).Here's what I think might have happened: The original output tubes were on their last legs and blew the original T 500 mA fuse. Dude took it to his tech, who put new output tubes in there and a F 500 mA fuse (F = fast-blo). It worked fine for a while, but eventually the F 500 mA fuse blew due to normal inrush current, and his "tech" didn't know the difference between fuse types, so he thought it was fried.Sounds about right. Nate, you won this round, and that dude and his tech lost for sure.