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Another One Bites The Dust: SDS-DOA


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thanks Mike.

Very sweet that it is working again. Would like to know which parts he swapped

out, so that you can stock up for next time.

And i did not have to touch it. The best part of all.

The ES1's are repairable too, just a fuckload of work.

Either Steve can post or I will get the info and do it. It was small stuff -- resistor, maybe that diode, and a bad solder joint -- and nothing in the amp. He bought another one of the transformer that looked cooked and the new looked exactly the same! :P thanks again Kevin.

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Thats only if it dies 7 times and is resold to 6 more different people.

And i do expect that it was just a few parts that were the cause of the problem.

Cold solder joints, probably all over the place... Wasn't worth the shipping charges

both ways...

And i did not expect that there was going to be anything wrong in the amp

chassis except for a few bad solder joints and shit sockets.

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That is just awesome news Al. Any word on how Neil is faring?

Steve has agreed to pick my amp when he drops yours off in the next few days. The awesomeness that is Ironbut cannot be stated enough.

Hopefully some sort of secondary deal with the devil can be had... electrostatic style...

Neil

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I was kidding. I realize how much work some of these things are.

I thought it was going to be an easy fix. Boy was i wrong.

Then again the ES1 repair thing went thru 3 rev's to get it perfect.

And each rev was more work.

Nate only got half of the singlepower experience.

Years later he will be left wanting more...

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Hey you guys. I haven't visited the boards lately so here's the lowdown on the repair.

The problem(s) with Al's amp were pretty pedestrian. I kinda figured it would be seeing that it rocked and rolled 400 miles and then suddenly died.

The filament transformer is on isolation mounts so it's free to move a tiny bit. The thousands of tiny movements loosened a couple of wires that crossed it which in turn moved some others. A ground from the high voltage board was totally loose and the wire from the regulator selector to the first regulator tube was just hanging on by a thread (it may have even been just the insulation since it broke 1/4" away from the solder joint). A 50 ohm wirewound was fried and during the testing I managed to cook the MosFet and diode twice! (I did try and find the MosFet that Kevin suggested but didn't find any in stock right off hand). There were a few other iffy connections/cold solder joints that I fixed both in the PS and the amp section. I can't really remember which ones I actually "touched" with the soldering iron since that was during the first round 2 weeks ago.

Overall, nothing very exciting but man, hooking those sockets back into the lid with just 2 inches of clearance without dropping a single nut back into the chassis was a challenge (just another good reason to find a girlfriend with tiny hands!).

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I just listened to the SDS-XLR for the first time since the blowup, and it sings again! I didn't have any extra tubes with me because I forgot they were in Mayberry, so I had to use one of the 6SN7s that looks fried to me (ironbut had told me he thought at least one of them was shot). I am pretty sure that I need to check/replace everything to be really sure about the amp, but it does make music and I am hopeful that it will be in good form when I have proper tubes.

For those in the know, with the PS using two OA3s for 75 volts, it sounds fine without stressing the volume too much. I then tried with four OA3s and after a minute there was crackles in the left channel and it cut in and out. I turned everything off and let it sit. I then tried again with two OA3s, and the music was back and sounding good again although the left channel wasn't really stable and dropped off occasionally. I think that the bad driver can explain these things -- can't handle higher voltage, cuts on/off, etc -- but tell me if I am nuts.

All of this is consistent with Steve's experience, so it wasn't unexpected. I will get another pair of gain tubes asap so that I can try it out again, but I will probably put in all new/tested tubes so that I am sure none of them is compromised.

Nothing is easy, but I am hopefully making progress.

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