Another One Bites The Dust: SDS-DOA

[Torpedo]

Very bad news indeed, Al I hope you find someone close who can fix it, though considering how Mikhail built those amps, maybe rebuilding it were a more correct term.

Do you have the circuit schematics and other info that the technician might need?

Good luck

[foo_me]

Sorry to hear Al...yes, I used Nick Gowan from Truesound as he came recommended to me. Have had good experience with him so far if you decide to try him.

[Smeggy]

Bummer dude, that sucks big time.

If there's anything I can do to make it worse, lemme know. I have the soldering iron at the ready..

[morphsci]

Wow, I've been gone a few days and it looks like all the shit has hit the fan. Sorry to hear that about the SDS. At least yours appeared to be wired much better than a lot of the SP exercises in chaos theory. I'm sure there are a few good techs out there that can work on these. Oh, and bourbon is the preferred drink down here (currently in SC) when it is 95+ for both the temperature and relative humidity.

[matt fury]

Al, my boy, look at the bright side...maybe your amp will come out of this better than it was going in!

[Voltron]

Sorry to hear Al...yes, I used Nick Gowan from Truesound as he came recommended to me. Have had good experience with him so far if you decide to try him.

I left Nick a message this morning. Thanks.

If there's anything I can do to make it worse, lemme know. I have the soldering iron at the ready..

RUN AWAY! RUN AWAY!

[Edwood]

Ah, fucking shit, Al. That sucks. Hopefully someone can figure out how to fix it.

-Ed

[MASantos]

Just read this and it really sucks!

I remember listening to and SDS at headfest 07 (I don't remember who's it was) with a pair of HD650's and it sounded absolutely beautiful.

Good luck with getting it fixed!

[blessingx]

Man that sucks. Sorry to hear Al. Was there anything electrical that survived VanJam?

[kevin gilmore]

From information just supplied from voltron, (no pictures yet)

A knob on front selects 1,2 or 3 gas tubes per channel.

But the gas tubes can only run at about 10ma.

So there has to be some kind of pass element. And knowing

mikhail its a big FET. What has happened is that the FET

is shorted putting full supply current into the gas tubes thus

making them go pop.

Inside pictures will definitely confirm.

Partial likely schematic tomorrow.

[kevin gilmore]

tomorrow came quick

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

2 of these in the box. Has to be. Or something extremely close probably

with more capacitors in a RCRCRC type thing....

[n_maher]

Kevin,

Could the power supply be fixed easily without the amp section present?

[luvdunhill]

I'd guess it would be as simple as replacing the pass element. The diagnosis makes sense to me. Hopefully, nothing in the amp section went along with it.

[Iron_Dreamer]

KG to the rescue!

[kelvinz]

ouch that's a expensive toy to have go wrong, hopefully it's something small/cheap!

[Voltron]

These pics aren't going to help much but here is what I could do with an iPhone and a partially opened PSU. One end piece was removed because the top has 4 capacitors strapped to it and all the tube socket wiring and I couldn't get much of an angle. The insides contain the following, although I have not seen any FETs or any chips of any type that I can recognize:

1. small transformer at the IEC input. Hammond 266N12

2. two larger transformers. Hammond 278X

3. one small PCB labeled "ES1HTRSPLY Rev. A Aug 2006" on the bottom left rear

4. one larger PCB on the right side wall labeled "PMOD Rev. A 2006" and I cannot get much of any shots of it

[kevin gilmore]

1. small transformer at the IEC input. Hammond 266N12

2. two larger transformers. Hammond 278X

3. one small PCB labeled "ES1HTRSPLY Rev. A Aug 2006" on the bottom left rear

4. one larger PCB on the right side wall labeled "PMOD Rev. A 2006" and I cannot get much of any shots of it

Item 1 is the filament transformer for the amplifier, used with item 3. Which

is a diode bridge, 2 large capacitors and a resistor. Exactly the same as shown

in the ES1 schematics i published. Runs the 6 tubes at about 2.5 amps total.

The amp has a warmup/run switch which is why this extra transformer is necessary???

Otherwise the other filament windings in items 2 would suffice.

Items 2 are the power transformers as shown in my schematic above. One for

each channel. 800 volts center taped plus a 5 volt winding for the 5u4.

Plus an extra 6.3 volt winding that is likely unused.

Item 4 is where all the action is going to be. Too many parts on there and some

are probably hidden (the fets).

Another poorly made, impossible to repair mikhail hunk of crap. Its no wonder he

never published pictures of any of his power supplies.

It would be easy to just have the power supply fixed without having the amp

chassis.

The gas tubes have a starting current of 75ma, but a max of 30ma run current, no way

that can drive a pair of WCF's. So unless mikhail is driving the crap out of the tubes

(certainly possible) there has to be some kind of pass element.

I did come up with a circuit to guarantee that the tubes light, but adding it to that

fucking mess could be quite a bit of trouble.

Edited June 23, 2009 by kevin gilmore

[kevin gilmore]

schematic updated

[spritzer]

Is there any way to remove the bottom of the chassis, Al? That would mean a much better view of the whole PSU.

[Voltron]

First of all, thanks Kevin for diving into this and trying to help figure it out. More than two of the regulators regularly failed to fire without assistance (from a flash camera usually), and there was no way to get six to ignite without a major halogen light source. Mikhail always said he could build a separate PS just to fire all six. Also, he said he "forgot" to put in a drain (or similar term) so the light on the plates switch would stay on after shutdown for 30 minutes or more.

I would be happy to try the bottom plate, but was not sure on the method. The transformers and other stuff are all bolted to it and I cannot tell how much play there is in the wires. I'd be happy for some advice on how to do this because I could not see much of the PMOD board on the side wall.

Not sure what to do from here, but maybe tonight I will have a camera and will try the bottom plate.

[nikongod]

I think from previous descriptions that this PS is more of a simple shunt regulator without any SS followers. Perhaps something was lost in translation, but time will tell as this box gets cracked.

something like this:

The thing could totally run a WCF depending how the resistor is sized, but I have read that getting a tube-based shunt regulator to "light" can be quite the trick, and I cant imagine it being any easier considering that different combinations of audio tubes will draw different amounts of current in the amp.

The first time I read about the photo-flash trick, I thought that someone had wired the electronics from a photo-flash (or something like it) into the PS to bitch-slap the tubes into operation. LOL

[Edwood]

Man, what a mess. But, that looks to be typical Mikhail wiring work.

[swt61]

Just now seeing this thread. It's like a domino effect.

Sorry to hear about the amp Al. Hopefully you'll be able to get it fixed correctly.

[kevin gilmore]

I think from previous descriptions that this PS is more of a simple shunt regulator without any SS followers. Perhaps something was lost in translation, but time will tell as this box gets cracked.

This is mikhail, and anything is possible. But note the big power diodes on the

side board. Wonder what they are for since the diode bridge is already mounted

to the ES1heater board.

I still think that 40ma to run 2 x WCF is pretty minimal, and in any case with the

0d3's is already over spec.

Also the fact that the one channel is consistently popping tubes as soon as you

put them in, points to much more current than normal.

What i was thinking of for the auto-ignite is my stacked high voltage multiplier

used to make the bias voltage for electrostatics. The doubled voltage would

end up about 800 volts, and is perfect for starting 3 tubes in series.

You add a large value resistor in series with a .1uf cap and a diode and it will

definitely popstart the gas tubes.

[n_maher]

Any chance that Al has a bad tube in the amp section that is causing super high start up currents and causing the power supply to act up? I know in the Menace if you hot start it it'll go arcy-sparky in the rectifiers (overdraw).