The ultimate DIY? A Stax SRM-T2!

[kevin gilmore]

i did not even know Phillips made a 2sc3675

[spritzer]

Ditto but that might explain the very strange 3675's I have here that test like the real thing... 

[c12mech]

I've spent most of the morning looking for a data sheet or any other documentation from Philips and have found nothing.  The only thing I can find is that they say high voltage transistor.  I'm considering ordering a few but I have no way to test them. 

 

Would one of the test sets like mentioned a couple of posts prior work for this?  I'd buy one if I knew that it would mean that I could at least have a chance of seeing if the parts were good or not.

[GeorgeP]

It could be that Philips does not manufacture the 3675, but rather supplies it as a part for part replacement purposes for its own products. They are probably made by Sanyo but distributed to the parts resellers by Philips as OEM parts. But if I am mistaken, and they are viable and reasonably priced, sure would be better than current high priced sources for the 3675. In any case, would you be willng to share your source (once you have secured your allotment)?

 

As an aside, does anyone know a reputable source for the 2sc3381 and 2sk246gr - have been searching for some time with no success. Have found some that seem too cheap and/or too suspicious.

[Lil Knight]

2sc3381 can be sourced here. Works fine for me.

http://www.diyaudio.com/forums/swap-meet/143997-fs-toshiba-2sk389-gr-2sa1349-gr-2sc3381-gr.html

Edited March 2, 2013 by Lil Knight

[GeorgeP]

Cool - thanks Tran.

[GeorgeP]

Not sure if this is an appropriate price ($2.16), but Sears Parts Direct carries the 2sk246gr in case anyone was looking. Shipping in US only, though.

 

http://www.searspartsdirect.com/partsdirect/part-number/2SK246GR/0057/528?pathTaken=directMatch&filterPart=&pop=flush&prst=0&shdPart=2SK246GR

[Voltron]

Ugh. I moved my DIY T2 from Mayberry back to SF without incident but was listening tonight and there is a persistent static crackle in the left channel. Same on two headphones and same after switching both sets of tubes from left to right in sequence. Any suggestions?

[livewire]

Sorry to hear this Al. Maybe give Kerry a call?

Before doing any heavy duty troubleshooting with a multimeter, I would check the following:

 

1) inspect all external connections (audio cables and umbilicals) for looseness, dirt, damage and bridging across pins.

 

2) Try a different source and signal cables.

 

3) open it up and check the pcb mounted screw type terminal block wire connections for looseness,

    especially for those wires coming off of the transformer.

   (I remember you posting that it did have shipping damage to the trafo in the past.)

 

4) while the covers are off do a visual inspection for anything that may look funky on the pcb boards.

    If you do open it up, make sure that all power is removed and that any high voltage capacitors are drained down first.

 

5) A ground loop or other external source of interference could be present.

    Try moving the setup to a different part of the house and plugging into a different receptacle.

     Do not stack the metal cases while testing.

 

6) When you said "both sets of tubes" does that mean you have eight of the EL34s? and eight of the input tubes as well?

    If you are only testing with the tube set that came with the amp, try switching the tubes front to back and back to front as well.

 

7) if none of the above helps, re-biasing the affected channel may do the trick.

    Sometimes the pots can get "noisy" with age and tweaking them to a slightly different position does the job.

Edited March 20, 2013 by livewire

[Voltron]

Wow, thanks for the great response and all the information.  Of course, I sat down the headphones for awhile with everything on and now I do not hear the sound.  By both sets of tubes I meant the input and EL34 and I just switched them from left to right.  Does this amp self-bias?  Maybe switching them did something.  I don't know jack.

[livewire]

Glad to hear it is working good now!

 

I believe it does self-bias the tubes, am not really sure - I have not built my T2 yet.

There is a bias type adjustment for the 740 volt batteries, the pots are marked RV1 and RV2.

Not something you want to mess with though.

[spritzer]

It's most likely the servo for the output stage was off.   Basically the "batteries" need to be adjusted to 740V and then the servo can kick in and null the output.  If it isn't at 740V then you can hear noises like that.  

[luvdunhill]

Another suggestion would be related to the parts in the servo becoming noisy, such as one of the pots. I think replacing one of the two pots in each battery with a fixed resistor is a good idea, once it is dialed in.

[Kerry]

Hi Al,

 

Just seeing this now.  Glad that the crackle is out for now.  It could be any number of things, but I agree that the batteries could be a source of the problem. 

 

I would not recommend doing anything unless the crackle comes back.  It could have been the combination/placement of the tubes.  Even though they are matched there are still variances.  The servos could have been operating near or at their max. I adjusted the batteries to what I believed to be the center of the sweet spot. 

 

If the problem reappears I think it would make sense to measure the batteries as a first step.  We can take it from there.

 

Good luck and I'm very happy to help out if needed.

[Voltron]

No worries, Kerry.  I will report back and get in touch directly if there is a need. 

[c12mech]

I ordered some 2sc3675's from Futurelec and the package showed up today with 9 of the 36 I ordered.  Everything indicates that there should be 36 in the package.  Needless to say I was not happy.  I'm waiting for a reply from them about it. 

 

I did a quick hfe check on the ones I got with the crappy meter at work and all were between 65-85.  Is this about right? 

 

Will the DY294 tester be good enough to check all the parts for the T2?  I have no issue buying one if it will do the job.  Is there something better for a reasonable price.  I've looked around and don't really know what to look for.

[GeorgeP]

To these untrained eyes the data sheet seems to suggest only that 30 is a min. But Craig Sawyers' post (and other related posts) should help: Also just typing 2sc3675 in the search bar brings up a bunch of stuff.

 

Others have suggested in this thread that the DY294 is useful to have but can only clear out the obvious fakes - which is better than going in with nothing - but I cannot speak from first hand experience on that.

[livewire]

I tested my latest batch of 2SC3675 Sanyo sand on the DY294.

 

Results were:

11 pieces - hFE measured between 30 to 45

39 pieces - hFE measured between 50 to 68 (will be using these)

 

V(BR) measured >1050 volts on all parts. That's a relief!

 

I don't purport that these measurements are absolute, at least they jive with the datasheet.

The el-cheapo DY294 tester gives me some piece of mind.

 

@c12mech - sorry to hear you got ripped-off. I hope there is a positive outcome.

                     I'm dealing with a similar situation with Dalbani.

                     Long story, still waiting for a refund on T2 sand that was never shipped...

                     Only $50, no biggy. Time for another phone call. <<sighs>>

Edited March 27, 2013 by livewire

[justin]

i recently initiated a chargeback on 5,000pcs of 2SA1486 that I bought.  

 

i now have an order in for 5,000pcs of legitimate Renesas parts, 14 week wait

 

unfortunately, the last time buy for 2SK216 and 2SJ79 was in December.  at that time i already had 1,000 of each so i let it slip.  now that it's gone, i suddenly want more..you can never have enough transistors.

Edited March 27, 2013 by justin

[livewire]

i recently initiated a chargeback on 5,000pcs of 2SA1486 that I bought.  

 

i now have an order in for 5,000pcs of legitimate Renesas parts, 14 week wait

 

unfortunately, the last time buy for 2SK216 and 2SJ79 was in December.  at that time i already had 1,000 of each so i let it slip.  now that it's gone, i suddenly want more..you can never have enough transistors.

 

Renesas, love fresh sand. Hope they test good!

[JoaMat]

/

Edited November 11, 2015 by JoaMat

[c12mech]

^^How does it sound with this mod?

 

I got word back from Futurelec and they are sending another package with the rest of my parts.  I should have it in a week or so.

 

If the DY294 is only good for weeding out the obvious fakes, what would you guys suggest for a good test box.  As long as it is not outrageously expensive I would buy one just for piece of mind.  I've got several projects coming up that I need to make sure all the parts are good for.

[JoaMat]

/

Edited November 11, 2015 by JoaMat

[spritzer]

The DY294 is good for checking basic parameters and for high voltage sand it is ideal as nobody would ever rebrand some nice HV stuff. 

 

Low voltage is more of a problem though as there are so many similar parts out there. 

[Milosz]

How many DIY T2's are in operation now?  Has anyone sold theirs, I wonder...?  Or maybe the estate sold it after the builder stuck his hand inside while the HV was live.....*

 

I am still, slowly, building up my chassis, that's the most complex part for me because I am hoping to make it something special, not a utility box type thing.... not having been part of the original DIY T2 case group buy, I don't have access to one of Kevin's meticulously CNC'd chassis, so I have to build up something on my own. I find that I get the best results when I'm in no hurry to finish.  Going on two years now for this build....

 

*I got "bit" recently by my H-K Citation II, I was tracking down a solder joint that had become intermittent, and I learned that the B+  doesn't really bleed down all that fast after the AC is disconnected.... and that the rubber covering on the handles of  my needlenose pliers has a hole in it....  things like this DO happen.  Ah, well, they say that electroshock is an effective treatment for depression, so maybe some benefit came of it.