Flame On!: Tragic loss of magic smoke

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I was.. testing a modified B&K Pro-5 Preamp..and then..after all 'safe' tests were done, via a power metered Sansui receiver..I hooked it up to one of my main amps to see how it actually sounded.

I flipped switches, checked for noise etc.

Suddenly..the right channel of my Counterpoint SA-220 decided to let out all it's magic smoke!:bigeyes:

So there I was, desperately pulling wires, hitting switches, pulling power cords..all in a desperate effort to get as much of the magic smoke out as possible. I was standing right over the power amp when it let go, so why not, I figured.

Perhaps, if I inhaled feverishly, like a teenager fighting with a roach that was all paper.. I could store all the smoke in my lungs for a minute, until I could find a bag to put it in. Then I could find some transitors and put the Counterpoint brand magic smoke into them. Seemed reasonable to me.

In over 20 years of fiddling with the innards of gear, that is the very first time I've ever seen flame come out of an amplifier, or ever had anything blow up. Oddly, not one bit of DC was passed to the speakers. Hmmmm..... fuses survived fine, I'll get to use them again. Saved a few bucks there. It was probably ultrasonic osc., combined with a nice square wave output fro the pre-amp, I figure.

I was looking to get the 'Octal tube/BJT output' updated board set from Mike Elliot soon. It looks like I'll be moving my timetable up a bit!

I knew the Counterpoints had a reputation for doing something like this, but well.. I've never had it happen before.. so...

What sort of rating do I get, with possibly all 8 outputs fried, do I get a medal of some sort? :D

How's your Sunday afternoon been going? Mine's over. I don't care to repeat.
 

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The Original Belles Hot-rod

It's likely to be all superficial. ("Very superfical....smoke got out them all...." you can sing along too...!)

As for the pots, I dunno. I never bought the tech manual. Looks like I might have to, now!

I can buy another blown Counterpoint, or buy the new boards for $1500. Hmm....

I've heard/owned the newer Counterpoint NPS amps and knew that they were much better sounding than the SA-220-100 series, right on the first note heard. That obvious. The new boards are a better and revised design on the NPS series, so..

I'm choking on the price, I've NEVER paid that much for any piece of audio gear. Ever. $1500 bucks for the assembled and tested baords. Musically, it's a bargoon. But it still hurts. By the time it gets to Canada...it hurts to the tune of about $2k CDN, total. Ouch.

Here's the back-up champ! A Belles 450, Modded. This is likely the amplifier that helped push Dave Belles over the edge into making the "Hot-Rodded" versions. I bugged him for years, and years, and years.. to just make the bloody things. People WILL buy them, I told him. "Look at mine!", I said. I kept telling him everything I did to them, and how it improved the sound. (I've owned three)

A completely Stoopid 300,000+uf's of capacitance.

It takes 3 seconds to fully charge..and it takes over 30 seconds to shut off. All the traces have been built up. All the heatsinks have been damped, as well as the boards. The Rectifier was upgraded. Etc. Lots of metal film caps, etc.

It's had a blown diode junction in it for about 8 years running now. It has a DC offset in the one channel of 0.8 volts, but I can't be bothered to find the blown diode. These Belles 450's are an incredible pain to strip down. Really ugly.

But, I think, after the kind of abuse the basic design has taken..and STILL runs after all that time (it has a steel bar for a fuse, I use the circuit breaker in the basement as the mains fuse!). This is likely to be what helped Dave finally go the modified Amplifier route, and show people what his amps can -really- do... after I told him how much fun I've been having with Belles 450's for over the past 10 years... :D

By the way, the amp is 100% DC capable..and has fried many a driver without even blinking in the slightest. It just takes the driver..punches it with about 90 Volts DC..and just holds it there, until something dies, explodes, burns to a crisp.....somewhere. Whatever. It doesn't care. Like the perfect zipperhead Soldier.

Not to be left on when leaving the house, not to be used by audio wimps. It's too much like walking around with the audio equivalent of a loaded, hair triggered ,12 Gage with 3" magnums.

But, it's the only way to fly! The failures, 'issues/dangers vs great sound'..to me..the advantages of running so darned dangerously have -always- outweighed the disadvantages of the sound of fuses and the like.

Every now and then.. something explodes. Like the Counterpoint did, today. The fun part will be turing on the Belles 450, after it has been sitting for half a year. That's always scary. I literally DO stand back when hitting the power swith for the first time after a long time sitting, with this unit. I even hang on to the power cord, to yank it from the wall, if need be. Once it's up, then it's fine after that. It's when the caps are fully drained, then it's an issue.

Like right now.

Fire in the Hole!
 

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Hi KBK,
Sorry to see that. Standard SA-220 blow up. It may not have had anything to do with the preamp at all.

Your SA-220 is not worth repair. I fixed one and used up a hell of a lot of matched Mosfets to get one set of super matched transistors. An entire day just for matching. That was earlier this year. I didn't charge near enough.

NPS amps sound worse than the original SA series in some ways. At least they didn't explode as often. The bias circuit is actually a constant temperature regulator for the heatsink. Really silly. There are much better ways to spend your money.

Don't bother with the manual. It is expensive to buy. This thing is roughly the same as an SA-100. Either buy another SA-220 or another amp entirely.

-Chris
 
I stuck them in there. My favorite thing to do, a bit of the local reserve energy, one might say. A lower impedance, via local capacitance. I've been doing that to just about every amp I've ever owned, back to my early 20's. I don't think it was the cause here, but it sure helped it have the grunt when it was needed!

I am thinking that the failure might have been due to the fact that the right channel is the one I Didn't remove and re-seat the outputs. On the left channel, I did exactly that. I hadn't even gotten around to siliconing the -03 covers back on. Cleaning and re-seating seemed to be a needed thing, as the unit came from a waterfront CA envirorment. The fuse holders all needed to be scraped clean, just to be able to get a signal through the unit. All new tubes, and all sockets needed to be cleaned and re-stressed. It survived all that, only to pop..finally..at turn-on.

I'm thinking I might call up Elliot and see if he has a set around. Methinks he's well out of them, even ones he's culled from re-builds.

I can recoup some of the cash by by buying and fixing a dead 220 or two, or fixing a few SA-100's and the like. Lots of dead ones around. They seem to pop up on ebay and audiogon every week.

Speaking of that, I just bought and should soon get a Bruce Moore designed Precision fidelity M-8 any day now. It's a hybrid Hitachi (176-56)/12AX7 100W/Ch. unit, with no feedback on the output as well.

Once again, I like the sound of the hybrids. I don't particularly care for pure solid state, or for pure tube. No matter -who- makes either type. price has never played a factor, here, either. At any price, or design, I still don't like either type enough to own them as a singular amplification device.

Drawbacks they may have, but sound good they do.

Pure solid state: shite!!!!!!
Pure tube: euphonic shite!!!!!
hybrid:? maybe.....
 
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Hi KBK,
I don't know why to want to give Mr Elliot more $$$ for improperly designed equipment, but it is your money. Go for it. He wants a fortune for whatever matched sets he has (THEY ARE USED, darn it!!!).

So you are going to continue with the guy that states in the service manual "tighten the screws until just short of breaking the sockets"? Come on, read any app notes from Motorola or IR or anyone with regard to package mounting. All his devices are abused ... period. And you still have an amp that may explode again any second. At least I used brand new, never used parts for my repair. (not trying to solicit, don't want to fix a 220 with mosfets).

There must be more reliable hybrids out there. I am still improving the SA-100 with bipolars. They absolutely blow away an SA-220 for sound quality. I have an idea how to do this with the SA-220, but don't have time yet to develop it. After the SA-100 is done to my satisfaction I'll start on 220's.

-Chris
 
Well, he can get a set of the fets to me. He still has some. I'd do all the matching myself, if I could afford to buy that many..and.. I've no idea if they actualy still come in the -03 package. I don't believe they do. Always ready to be wrong, though. At this time, I simply cannot afford to go into the new amp game. Not this month, at least. Maybe in a few months. So, I have to repair the unit. Do you have a source for matched sets of those particular fets in the $200 US range, delivered? In the -03 case? Right now, it's a blown amp in search of a repair. I plan to fix it. Since I do all my own work, the $200 is the total fee for the whole endeavor.

In the meantime, I use my backup amplifier, and await my Bruce Moore designed Precision Fidelity hybrid, (M-8, 100w/ch, hitachi 176-56 fets) which should be here by the end of the week.

I'm looking for an amp now, not tomorrow, not a year down the road, but now. If you were doing 220 mods to bi-polar now, I might give it a go. But, youse ain't.

Impasse.
 
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Hi KBK,
Do you have any idea how tight those FETs have to be matched?? I do.

I had to make a jig to sort 4 at a time. It's critical to match at the same case temperature. I used a digital thermometer for preheat before the testing. Then match for Vgs and drain current. I went through 40 each. My match was not as tight as I'd like and there are no source resistors to force sharing.

What Counterpoint had to go through to get matched quads was idiotic. If I was the bank, I would have pulled funding hearing this. And believe me, those FETs were matched extremely tightly.

I wish you more luck than I had.

-Chris
 
Counterpoint SA-20 Repair / Exicon MOSFET option

Hello All,
I'm a new member here despite involvement in audio for 20+ years. I have a Counterpoint SA-20 power amp in need of repair, go figure, eh? ;) I would rather not pay Mr. Elliott and crew $1500 for the upgrade to the NPS220...however nice it is. :whazzat:

Instead, I would rather entertain alternate overhaul schemes as Mr. Elliott mentions on his site, like the Exicon MOSFETS:

Exicon MOSFETS

Has anyone here had success with this solution?

Thank you for your assistance,
Tim / Parataxic_Distortion

:xeye:
 
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Hi Tim,
The main problem is getting a tight match on the FET's. After all that pain you still have the problems inherent in that design. I was authorized warranty for Counterpoint products until they closed. That's why I know so much about them. That is also why I have people local to me asking for improved circuit design in these.

-Chris
 
Thanks for your reply and your thoughts on my SA-20 rebuild/overhaul. Assuming I could do this cheaply, I'm still interested in at least considering the "Exicon solution" first over just sending the amp to Mike for a $1500 (plus s/h) cure :bigeyes:

I'll email you backchannel and we can continue this. I don't want to hi-jack KBK's thread :cool:

Best regards,
Tim
 
Little rainbow.... Little pot. etc.

Ok. Just to finsih this off -as a thread- I ended up sending or actually..delivering 9 power amps for Chris (anatech) to look at. If I had not done that, I'd still be having 9 boken amps collecting dust inthe corner. I just can't seem to bother to do such repairs anymore. New gear is more fun. Or designing and/or modifying gear. (re-executing or gear, or second guessing the designers of a given item)

I bought a USED channel from M. Elliot at Altavista audio. Chris did the fun part of cleaning up the smoke abuse and putting it back together, tuning, etc.

I still have not hooked up the SA-220 amp and had a listen. I'm practically frightened of it. It's sitting on top of my other SA-220, which now has... a slight problem........ I had lent it to a friend for over a year. It was MINT. It comes back....not working. Great.

I also still owe Chris for some the work he's done so far. :whazzat: tsk-tsk.

Last blown amp he still has of mine: the Luxman M-05.

Time to hook the amp up, and see what she does.
 
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