Tube complement on the amp is a variety of mix-n-match options:

Gain tubes include 6sn7, 2c51, 5965, E88CC/01, 6922

Output tubes include 6sn7, 6bl7GT, 5687, 12az7, 12av7, 5670

I used all 6sn7s sometimes, 6sn7s with 6bl7s, and most often or all 2c51s with 6bl7s.

And now we know why the filament transformer looks a bit crispy.

Some of those tube combo's especially 6bl7's as the output tubes

gets the filament current in the 6.6 to 7.5 ampere range.

Mikhail thought the 6BL7s were the best output tubes for this amp. I rarely used others, so there you go.

So the FET is actually that thing screwed into the bottom plate?! It is 4 wires to my recollection, but I will see if that is correct tonight. There are some other similar components screwed to the chassis near the heater supply and over by the other pcb (I think). You want the numbers if I can read them later?

Here is a pic of the amp section and I will see if there are others. If Asr reads this and has more pics, I would appreciate them being posted.

i really hope you get it up and running again, Al, because that amp with the HD800s is probably the best dynamic phones setup i've heard.

That's the bitch of it, ain't it?

It looks like the amp and psu were done by completely different people. The PSU looks like a mess, the amp section actually looks fairly well organized. It's very perplexing

One thing Al (and all of those that own SP amps) check the umbilical cables on the inside. I just did and one wire was loose with plenty of them dangerously close to shorting out. Ohh, and it's built VD style with a rubber hose and some loose wires inside. One of them didn't even have anything to secure the techflex...

To open them up you just screw the back part of the plug. You need a bit of force but once you are inside the black clamp can be opened up with some pliers and it just pops off the cable.

I will take a look Birgir, because the original problem with the former incarnation was that the umbilicals had a problem and the amp would power up once and then not the next time.

Here is a pic of the amp section and I will see if there are others. If Asr reads this and has more pics, I would appreciate them being posted.

sdsat_1.jpg

That's the only internal pic I've got, sorry. Hopefully there are enough pics to work from though, for the people able to help out with your amp.

Ouch, sorry to hear about your amp Al =(

Mikhail's "planned obsolescence" (due to incompetence) strikes again.

Spark inside the rectifier could mean a bad tube.

I had a similar incident with my AMR CD player.One of the 5687 tubes sparked during warm up (when the HT had just come on) and it took out the LH output board

That is a different kind of thing as the board in the cd player is dc coupled.

But i'm now thinking that a quick (quick??) replacement of the FET and the diode

that feeds it might get you running again pretty quick, and once you take it apart

enough to figure out what the part number of the fet is, someone local could probably

fix it pretty fast.

I will take a look Birgir, because the original problem with the former incarnation was that the umbilicals had a problem and the amp would power up once and then not the next time.

Here is the full glory of the SP umbilicals. At least there is some teflon insulation on these wires or probably tefzel. The amps are all wired with PVC...

What's going on with Mikhail now? Is he still around?

Spark inside the rectifier could mean a bad tube.

I had a similar incident with my AMR CD player.One of the 5687 tubes sparked during warm up (when the HT had just come on) and it took out the LH output board

Thanks for the thought, Rob, but the spark happened in a different set of rectifiers than the ones in the PS when the gas tube popped. I have used those rectifiers before, and would find it hard to believe that I had one problem in the PS and then had an unrelated bad tube exhibit that behavior.

That is a different kind of thing as the board in the cd player is dc coupled.

But i'm now thinking that a quick (quick??) replacement of the FET and the diode

that feeds it might get you running again pretty quick, and once you take it apart

enough to figure out what the part number of the fet is, someone local could probably

fix it pretty fast.

I was not in Mayberry last night so I did not have a chance to do further investigation or take any more pics. So, you think there is a FET on the back of the larger PCB on the side wall and the one screwed into the bottom is the diode? I can get numbers, etc, tonight I hope. Thanks.

What's going on with Mikhail now? Is he still around?

He was trying to push some half baked ES-1 (aren't they all) earlier this month. Claiming that the normal input was a preout or some other such nonsense.

I was not in Mayberry last night so I did not have a chance to do further investigation or take any more pics. So, you think there is a FET on the back of the larger PCB on the side wall and the one screwed into the bottom is the diode? I can get numbers, etc, tonight I hope. Thanks.

I want really good pictures of the insides of the amp.

Reason is i want to see how the high voltage is wired. Need

to know how it is split.

Absolutely there is A FET on the back of the large PCB. You are going to

need to flip out that side of the chassis. And take some straight on pictures

of that board, and underneith it.

Please get a better camera

Like a Nikon D3X...

Better yet, the new mamiya with the 32mp back...

What's going on with Mikhail now? Is he still around?

Yes, I emailed him about a capacitor value on my MPX3 and he replied immediately - but didn't answer my question - and disappeared. He's selling tubes on Ebay, but I forgot his shop's name - USA Tubes or something like that.

Well, there was a fet hiding on the side wall

International Rectifier IRFP460 HEXFET MOSFET. The pictures will be posted soon. From a better camera, no less.

I simply could not upload the originals of these or other shots taken tonight, but at least there is some info to be had.

One of these on the back of the large PCB, and the data sheet is in the post above:

Two of these under/next to the ES1HTRSPLY:

Diode bridge:

Four wires on the diode bridge:

Lousy shot of the big pcb:

Amp pics later.

Lets start with the pass fet. It is under rated for at least 50 volts. Likely

it and the diode feeding it are toast. There is only one fet right??

here is a much better part that i have not been able to kill yet with extreme abuse.

http://ixdev.ixys.com/DataSheet/DS99843B(IXFH-T20N100P).pdf

Direct replacement.

I'm worried about the diode bridge attached to the center of the chassis

also not being rated for voltage. Hard to figure out the part number with

the chassis nut in the middle, but will try and find it.

Back shot of the circuit board would be VERY HELPFUL.

Was that fet even bolted to the chassis, and was there any thermal grease??

Because at the power that was running at...

If you have trouble uploading the pictures email them to me and i will

put them where everyone can see them.

Edited June 26, 200917 yr by kevin gilmore

the diode bridge sure looks like gbu6m (fairchild)

and is rated for 1000 volts... Trouble is it is running at 1100 volts...

current best guess

http://gilmore.chem.northwestern.edu/sdsgasps.jpg

getting pretty close...

there have to be a few hidden diodes... for the ignition circuit to work.

Back of the circuit board is difficult because the wires do not allow enough give (after much effort in this direction) to get a full back-shot. I took a couple pics of parts so we will see if I can upload them or email them.

The FET is screwed into the side wall with a thin membrane of rubbery material in between. In the back shot of the FET, you can see that the membrane was sticking to the device and left a layer of material behind when I took it off.

At some point, I can try to find any more diodes in there, although I have tried to look before. ironbut is going to pick up the amp today and take a look and see what he can see. I will be out of town for 10 days so this way maybe progress is still possible.

Thanks again.

the diode bridge sure looks like gbu6m (fairchild)

and is rated for 1000 volts... Trouble is it is running at 1100 volts...

It's actually a GBU8M.