The ultimate DIY? A Stax SRM-T2!

[Pixiy]

Definitely Dale M60. Better than Xicon IMO.

 

Thanks, but Dale rn60 would have some noise problem like prp's?

[spritzer]

Never use Holco in any high voltage circuit and I'd stick with the Xicon's.  Mouser has free international shipping if you order for 100$ or more....

[pedefede]

Hi All

 

 

Thanks, but Dale rn60 would have some noise problem like prp's?

My experience:

 

I had a LOT of trouble with noise, and replace a lot of parts. Changing my Shinkohs to Xicons helped a bit, but the trouble/noise came back. This made me think, that Xicons were better because of the 50ppm, but that 50ppm is still way too high. So i re-replaced some of the resistors with only small benifit.

 

Finally the one thing that did the job was replacing the 10K pots in the four battery-sections, with a super-low ppm resistor:

5ppm (!!) in the series ptf56 from vishay,

that had the same value as what i adjusted the 10K-pot to (6K in my case). Then i could do all the final tuning with the 2K pot.

http://dk.mouser.com/ProductDetail/Vishay-Dale/PTF566K0400BZEK/?qs=V4kc8PiwqSBAoWKdj%2fYdnMPewyQYMP1WCgstHSwEDSg%3d

 

 

THIS thing made the amp TOTALLY stable, and dead silent.

So for 6 month i have enjoy'd the fantastic sound from this beast of an amp  

 

 

Happy new year to you all!!

 

Peter

Edited December 31, 2012 by pedefede

[JoaMat]

Interesting, thanks for sharing your findings.

[justin]

Has anyone seen 2SA1486 that look like this?  ive had green ones, black ones...the package is the right size but ive never seen the labeling look like this

 

[spritzer]

Never seen them like that. Screams fake to me...

[justin]

when was this part introduced?  if someone had a 25 year old stock of them...i could see them maybe looking like that.  

[Inu]

2SA1486 is on the “1985 NEC New Product Info”

Picture is not 2SA1486 but the one from my old collections (30+ years old).

NEC changed their logo in 1992 but they never used simple character logo on their products.

 

https://picasaweb.google.com/inuponken/T2#5829408747652314498

Edited January 4, 2013 by Inu

[justin]

the first 200 pieces are on the way for me to evaluate.  this should be good.

[Milosz]

I recently bought a  B&K 501A curve tracer, was incredibly cheap on eBay.  Seems to work fine.  Anybody have any experience with these?  

 

I've also got one of those little Chinese transistor tester gizmos too, that gives you breakdown voltage and a few other parameters. That seems sufficient to screen out fakes, but now with a curve tracer I should be able to match devices decently when that's needed.

 

Still haven't freed up enough workshop space to build my T2.  I might be deaf by the time I finally get around to it......

 

Also got one of those Tektronix differential HV probe gizmos, too.  Girding up.....

[justin]

ok, testing the fake looking 2SA1486 i just got.  they came packaged in tubes.  

 

The back of the parts look just like the real ones

The front is very clean but doesnt use the NEC font

 

The part feels lighter than the real ones.  The leads are much thinner, and are brightly tinned on the 'fake' ones.

 

Now for the testing....

Voltage - 685 to 715.  just like the real ones

HFe - 70 to 80.  real ones - 110 to 115.  both are labeled "K" grade which is good for 60 to 120 HFe.

 

so very confused right now

Edited January 16, 2013 by justin

[justin]

the ones i got dont look exactly like the ones in the image though...the text is brown, more legible, and more centered on the part.

[Victor Chew]

Question is whether its worth the risk putting it to real work and what is the worse case scenario.

[johnwmclean]

what is the worse case scenario.

 

An angry HeadAmp customer out for blood.

[nattonrice]

John beat me to it!

 

I really feel for Justin and others that need to source these oft faked parts in small commercial quantities.

The whole situation blows.

[justin]

John beat me to it!

 

I really feel for Justin and others that need to source these oft faked parts in small commercial quantities.

The whole situation blows.

 

i can order a couple thousand of legit ones from Arrow -- Renesas branded, which should be identical to the NEc part.  though they tried and tried, they were unable to ever tell me the HFe grade of the part.  

 

this is just less $$.  they test good for 700V, they have HFe in the proper range, so, i have no reason to believe these are fake.  my concern would be that the picture they send me doesnt look exactly like the 200 that they shipped to me.  

 

Could someone fake a transistor and still have 700V and proper HFe?  i guess its possible.  i'll see if KG can do some further testing

[eggil]

Milosz just bought a B&K 501A curve tracer which I guess could help sort this out?

[kevin gilmore]

I think that a curve tracer or a specifically designed test circuit

is the way to go. What i am really looking for is a 500 series tektronix

curve tracer, i will ask around in a few hours. If the curves are close

and the BC capacitance is right, then even if they are fakes, they are

usable. But the ROHM parts should be an exact substitute except they are

surface mount only.

The problem with the cheap curve tracers is that they don't go up to

the high voltages.

I put in a bid on a tek 577 thats local to me, so everyone stay away

and we will all benefit.

Edited January 16, 2013 by kevin gilmore

[kevin gilmore]

the joys of 35 year old gear with dirty switches...

Finally got the higher voltage range working, but did

not take pictures. Never did get the trace blanking working.

50 volts per division horizontal, .5ma per division vertical

20 ua base current per step. Horizontal and vertical flipped

so it looks like a npn.

The first 3 are known real

http://gilmore.chem.northwestern.edu/dsc_0316.jpg

http://gilmore.chem.northwestern.edu/dsc_0317.jpg

http://gilmore.chem.northwestern.edu/dsc_0318.jpg

the next 3 are

http://gilmore.chem.northwestern.edu/dsc_0319.jpg

http://gilmore.chem.northwestern.edu/dsc_0320.jpg

http://gilmore.chem.northwestern.edu/dsc_0321.jpg

So other than beta being lower, sure look to be the real thing.

High voltage tests, all of them break down between 650 and 700v

will measure capacitance later.

Edited January 24, 2013 by kevin gilmore

[justin]

and the beta is still in the middle of the 60-120 range for the K grade

[Milosz]

The old B&K 501A  only goes up to 100v on the collector / drain  so not of use in sorting these out.

 

The little DY294 tester goes up to 1500v for it's breakdown test, so with that unit you can see if the breakdown voltage is where it should be; this is at least a good start for the DIY user, but for someone like Justin, or Kevin, it doesn't go far enough.

 

 

DY294

Edited February 4, 2013 by Milosz

[eggil]

Justin, any news on the 1486s?

Edited February 21, 2013 by eggil

[justin]

Justin, any news on the 1486s?

 

yeah, i got 5,000 of them.  they test good for about 700V, or at least most of them do.  a few percent do not.  the quality of the leads is poor.  They also test full of lead, thanks to Kevin Gilmore's testing.  not that i would care, but the box says Pb-Free which makes the whole thing suspect.

[kevin gilmore]

the nitric acid blank (i used the cheap stuff)

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

the nitric acid blank over the sample

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

the expanded sample alone actually saturated the detector

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

Its so nice to have an ICPMS laying around

Edited February 21, 2013 by kevin gilmore

[c12mech]

Can anyone tell me if the Phillips 2sc3675 is the same as the Sanyo.  I found some of the Phillips version for a reasonable price but don't want to buy them if they will not work in this application.