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Warning About The Singlepower Extreme - Owners Please Read - Page 21

post #301 of 407
Thread Starter 
I have no clue what Mikhail was trying to do with this amp, but it's clear that he failed miserably. The parallel/series resistor group was certainly an effort to better dissipate heat, which failed, and the stacked caps was likely a result of needing a high voltage rating but I can't be sure there.

Honestly I don't know where to tell you to start when it comes to fixing this particular amp. It's in bad shape, that's for sure and you're probably lucky that something very bad has not happened as a result.
post #302 of 407
Quote:
Originally Posted by n_maher View Post
I have no clue what Mikhail was trying to do with this amp, but it's clear that he failed miserably. The parallel/series resistor group was certainly an effort to better dissipate heat, which failed, and the stacked caps was likely a result of needing a high voltage rating but I can't be sure there.

Honestly I don't know where to tell you to start when it comes to fixing this particular amp. It's in bad shape, that's for sure and you're probably lucky that something very bad has not happened as a result.
Thanks for the info. And I should find an experienced tech to help me fix it. If any idea come through about how to fix it, please let me know. And I appreciate any inputs.
post #303 of 407
Your amp is in fairly poor shape with all the overheated parts.

The high voltage circuit should be removed. It does not improve the sound when running the output tubes at high voltage. If anything, it degrades the performance. The switch is rated 25 volts. It is likely to fail at any time. The switch should be used to change sources, not in high voltage circuits.

If you are familiar with procedures of working on high voltage tube amps, the next step would be to measure the filament voltage. With all tubes in, a load (headphones) plugged in and power turned on. VERY carefully measure across pins 7 and 8 of the output tubes.

DO NOT DO THIS if this is the first piece of tube gear you have looked at. You CAN hurt yourself and the amp very badly if a probe slips and touches the wrong point!

If the voltage measured is below 6 volts, I would suspect that the transformer does not supply enough current for the tubes being used.

If the filament voltage is low, you are looking at a transformer replacement, replacement of the overheated diodes in both HV and filament circuits. Removal of the higher voltage circuit, replacement of the voltage dropping resistors, installation of bleeder resistors across the power supply caps and probably one or two other surprises.

The circuit board can be rather difficult to remove and re-install. Most of the screws used are secured with Loctite and have to be heated to very high temps to loosen the grip of the chemical adhesive.
post #304 of 407
If available, I'll bring a meter for the Columbus meet and have a looksee.

Jun, good luck finding a tube amp tech. Let me know if you find one and I will do the same. I've found a retired Navy guy in Dayton who's a radio professional/ham hobbyist. If he pans out, I'll let you know.
post #305 of 407
Quote:
Originally Posted by Happy Camper View Post
If available, I'll bring a meter for the Columbus meet and have a looksee.

Jun, good luck finding a tube amp tech. Let me know if you find one and I will do the same. I've found a retired Navy guy in Dayton who's a radio professional/ham hobbyist. If he pans out, I'll let you know.
Thanks, and hope someone in the meet can help me check and figure out how to fix my amp.
BTW, I think it's running out of time to conform the meet place and determine the gear list. Do you find someone also in the OSU willing to take the job with me or not? I am a newer here, so I don't think I can take everything by myself.
post #306 of 407
Here are some shots of the latest Extreme to visit me.

First is the standard overheated transformer.



In this amp's case, it led to failure of the capacitor in the filament circuit.



In other words, the cap puked it guts out.

Here is the bottom of the case with more cap puke.



As an added bonus, it certainly looks like the large film cap in the HV power supply was never soldered in place.

post #307 of 407
here is the latest surprise.
http://gilmore.chem.northwestern.edu/mmax1.jpg

all the cable ties are broken. Which happens a lot. But mikhail superglued
the cable ties to the capacitors. So when i removed the superglued parts
some of the plastic protector on the capacitors came off.

Warning to all that have the black gate output caps. when the plastic
breaks off, and exposes the can, the can is electrically hot, and tied to
the minus terminal of the cap.

http://gilmore.chem.northwestern.edu/mmax3.jpg

And if you have stacked caps, and they are wired to different output
channels you have to insulate them from each other.

I'm not going to discuss the 3 major ground loops inside this thing.
post #308 of 407

Rebuilt Extreme

Here is a nice, fuzzy shot of a completely rebuilt Extreme.



This unit was pretty much stripped to the chassis. The RCA input connectors, AC inlet, AC switch, volume control, LED and headphone connector are just about the only things left from the stock unit.

The transformer was replaced with a Electra-Print. The filament circuit is an all new design. Everything is point to point wired. The circuit boards were built from scratch using turrets for wire connections. The tube sockets were replaced. The input wiring are shielded, twisted pairs.

There were some Black Gate caps used in the power supply. They were re-used as output coupling caps. I kept one of the Black Gates in the HV supply. New caps are Panasonic. All electrolytic caps are bypassed with film caps mounted on the underside of the boards.

The amps has just been running for about 24 hours and is breaking in nicely. Great dynamics and very good extension into my HD-600s. The back of the case where the filament bridge is now mounted and the transformer are warm to the touch, but in no way hot.
post #309 of 407
GJ Bolder
post #310 of 407
so the only thing salvageable was the chassis. good grief.
post #311 of 407
That's the case with most SP amps. Attenuators (as long as they weren't built by SP), input and output jacks and perhaps some of the electrolytic caps are the only things you can save, the rest is just trash.
post #312 of 407
So if you rebuild a Singlepower with new components and change certain aspects of the design, is it still a Singlepower?
post #313 of 407
No and that is a good thing. My ES-1 is much truer to the original design then that hack job Mikhail shipped out.
post #314 of 407

duh data

It sure would be nice if true measurements could be taken on what a SinglePower Extreme scopes out 'before' and 'after'. What a concept, let data do the talking.
post #315 of 407
Quote:
Originally Posted by spritzer View Post
That's the case with most SP amps. Attenuators (as long as they weren't built by SP), input and output jacks and perhaps some of the electrolytic caps are the only things you can save, the rest is just trash.
I'm not sure that is really accurate. My SP Extreme needed a new trafo, and a pair of new resisters. That is all. Sounds better than it did before, and is perfectly safe.

Singlepower was a train wreck of company, and their amps all have to be checked out to be safe, but I think it does a disservice to say that they all have to be completely gutted - many can likely be saved with a less costly approach. I think it's important for current SP owners to understand that.
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