The ultimate DIY? A Stax SRM-T2!

[Craig Sawyers]

Yea, his website is the first place i looked. Can't remember if I saw one there.

Justin has taken most (or all) of the parts off his site, and only lists finished products. That does not mean that he does not have them, and that they are available for purchase if asked. Either PM him, or contact him via his site. I've bought several DACTs off him after he took them off his site.

[Craig Sawyers]

Some of us already had a group buy for the now obsolete parts (2SA1968 and 2SC3675) so count me out. I have enough to last me a long, long time.

Darn. Wish I'd spotted that opportunity - I'd definintely have joined in.

[spritzer]

It was just me, KG and Justin so it was never posted.

[justin]

Justin has taken most (or all) of the parts off his site, and only lists finished products. That does not mean that he does not have them, and that they are available for purchase if asked. Either PM him, or contact him via his site. I've bought several DACTs off him after he took them off his site.

i still have the parts, but yes i took them off the site because I almost got more emails from annoyed vendors regarding my too-competitive pricing than I did sales, which were almost 0.

[n_maher]

Al,

Kerry should have the parts soon. PM incoming...

Kerry,

You should have the parts soon. I've got a 40lb or so box with your name on it and and email that will be sent shortly.

N

[Craig Sawyers]

It was just me, KG and Justin so it was never posted.

Ah - OK.

I nailed 41 (all the stock) 2SC3675 from a UK vendor at a very good 85p each. They will either all be good, or a waste of money. Let's see if I can get them before Christmas, so I can resurrect the T2 as a personal pressie. None of them are going into the beast until they have been screened for hFE.

[spritzer]

If it is was Dalbani then they should be genuine. Some of the others I'm not so sure about...

[Craig Sawyers]

If it is was Dalbani then they should be genuine. Some of the others I'm not so sure about...

Nope - the duff ones came from Dalbani. As did the good ones, but the orders were separated by some months.

[Kerry]

Al,

Kerry should have the parts soon. PM incoming...

Kerry,

You should have the parts soon. I've got a 40lb or so box with your name on it and and email that will be sent shortly.

N

Looking forward to it. I'm really excited to get this going.

[deepak]

edit: we are sorted out. Order placed

Edited December 20, 2010 by deepak

[Kerry]

EDIT: Just saw deepak's post. Nevermind.

And just to add to eveyone's 2SC3675 paranoia, Sanyo are disconintuing the part:

SANYO Transistor: 2SC3675

Only 1200 left in Sanyo's inventory. After that - nothing.

Anyone in the US up for a group buy of 200 or more (200 is the MOQ) at 86c each? You could certainly count me in for a T2's worth of them (34) plus a bunch of spares.

[Craig Sawyers]

Having just found a wiring error in my Tek 577 curve tracer (which was there since the instrument was built - orange and brown wires were transposed at one point. So Tek could not possibly have calibrated the thing), I can now at last give much more definitive measurements for my transistors.

The good 2SC3675 measure a DC beta of between 74 and 90 at 750V and 5mA. Which is why the battery should work with good parts. This matches quite well with KG's base current measurement of 50uA on his prototype battery.

The duff 2SC3675 measure a DC beta of between 9 and 11, but you cannot get close to 750V. The curves turn upwards on a fast power law over 550V. I have no idea what crap piece of random silicon is in the packages, but the correct one it isn't. Which is why they die, catestrophically in the T2, with serious collateral damage.

The 2SC4686A measure between 30 and 34 at 750V and 5mA, and are probably too low to work properly in the T2 batteries without some mods. According to the spec sheet these transistors can have a beta of up to 60 at 3mA and 5V, but none of my batch do this (and neither did Inu's).

[blubliss]

OK, transformers wired, PS voltages tested correct, voltages correct at amp, all leds lit, batteries on one side quickly adjusted to 750v with RV2.

But, on the other side, both batteries are stuck at 530v and no change when moving RV2 all the way in either direction. We tested the 10k pot before putting it in and had it centered. The leds on these batteries are much dimmer, more so on one than the other.

Ideas?

[Craig Sawyers]

Ideas?

What are the voltages at each end of the batteries with respect to ground?

[Craig Sawyers]

But, on the other side, both batteries are stuck at 530v and no change when moving RV2 all the way in either direction. We tested the 10k pot before putting it in and had it centered. The leds on these batteries are much dimmer, more so on one than the other.

Ideas?

Gate-drain short in Q22? One or all of the 2SA1486's the wrong way round? Wrong values for R33 and R34?

[kevin gilmore]

This is why i have been so drop dead exhausted for the last 3 weeks. Almost done now.

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

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

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

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

Seems that we have risen to the top of the food chain, at least

in the USA (poor MIT)

Should be getting back into audio design in a big way soon.

[chinsettawong]

What machines are those?

Wachara C.

[blubliss]

Thanks, Craig.

Some more testing. Battery test points on the problem side test around 18v on the positive side and -540 on the negative side (in relation to ground).

We now noticed two leds are out, D10 & D11. D8 & D9 are very dim. The leds work because they flash on at start up.

Seems like something must be wrong in common to both batteries.

[luvdunhill]

Any idea what Idss grade the JFETs are?

[Craig Sawyers]

Thanks, Craig.

Some more testing. Battery test points on the problem side test around 18v on the positive side and -540 on the negative side (in relation to ground).

We now noticed two leds are out, D10 & D11. D8 & D9 are very dim. The leds work because they flash on at start up. Seems like something must be wrong in common to both batteries

Ah. Maybe not. Test D10 and D11. If they are kaput, check the 100V zeners and the K216's on that side.

[Dreadhead]

This is why i have been so drop dead exhausted for the last 3 weeks. Almost done now.

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

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

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

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

Seems that we have risen to the top of the food chain, at least

in the USA (poor MIT)

Should be getting back into audio design in a big way soon.

? What do these do that some other x-ray crystallography system can't do?

[wink]

? What do these do that some other x-ray crystallography system can't do?

.

Grow tomatoes...?

[kevin gilmore]

? What do these do that some other x-ray crystallography system can't do?

Well its the amount of flux, and the size of the beam that is of the most importance.

So for all these new drugs we are working on, where you can only grow pure crystals

that are 50 microns in diameter, these new sources generate much more accurate

data, and a bunch quicker.

I grow tomatoes at home, very nice tomatoes. With special fertilizer that i mix

up from the good stuff.

I'm trying to figure out if blubliss has a problem in one channel, or a balance issue.

If its a balance issue, the circuit ping-pongs till both batteries in a channel are close

enough. Pretty much the same way with the BHSE.

Edited December 21, 2010 by kevin gilmore

[Dusty Chalk]

? What do these do that some other x-ray crystallography system can't do?

Throw the circuit breaker if all turned on at once?

[luvdunhill]

It would be interesting to compare trimmer values I suppose of the various working channels. I was assuming that one channel wasn't working, but after rereading I see the confusion.