The ultimate DIY? A Stax SRM-T2!

[shipsupt]

I'm down for a chassis LK...

[Lil Knight]

I'm down for a chassis LK...

I put a link in my sig, feel free to put your interest there.

Edited July 23, 2013 by Lil Knight

[johnwmclean]

I’m down for chassis parts.

Depending on final cost though... 

 

...and thank you Lil Knight for all your hard work!

Edited July 23, 2013 by johnwmclean

[wink]

YAY...! about time, John.

[johnwmclean]

You're up early, couldn't you sleep?

[chiguy]

I'm really tempted but the cost of parts for a T2 is big pill to swallow.

[Lil Knight]

I'm really tempted but the cost of parts for a T2 is big pill to swallow.

Save it up slowly then

I need to sit down and double check with the machinist but guesstimate would be around $1k-1.2k, depending on options.

Powder coating might be the only option for surface treatment. I still haven't found an anodizing shop yet.

 

I am able to get all the sands from Satodenki and teflon tube sockets locally. Also got a whole pile of genuine 2sc3675 (not enough for 15 sets though) that I kept for future use.

[nattonrice]

I think facing Mecca (or equivalent) helped the most.

 

Nice to see that my spray-n-pray method was your biggest take away from the thread 

 

The build looks great!

[eggil]

mmmh.... tempting indeed....

I understand the T2 can be finicky due to its complexity. How many working units out there?

Expensive fireworks if it blows on first start. Heck, the adrenaline rush makes it worth it, whether it works or not 

 

EDIT

2SC3675.... 13...... 7.12 at BD

2SK216 ........4........5.69

2SJ79........2......8.82

1486........17......?

2SC3381BL...6.....17.75

Crazy BDent prices

I may have counted then wrong.

LilKnight, I assume you also have boards?

Edited July 28, 2013 by eggil

[nattonrice]

There are some general themes established throughout the thread (in no particular order) which if followed seem to lead to success more often than not.

 

-> You can use (correctly rated) wanky resistors anywhere except the 700v batteries: these must be the specified Xicon part and should be raised off the board surface (for memory they are slightly inductive which adds a stabilising factor and stops a particularly annoying type of noise on the output).

 

-> As a (possibly unique to me) extension of this: the dividers at the output of the regulators should be Xicon and raised (in my case the PRP units were leaking and causing the voltage to swing all over the place which is bad).

 

-> At the minimum adjust all pots to the middle of their resistance/travel: Inu suggested middle for the 10k, max resistance for the 2k (this worked for me).

 

-> Don't risk using possibly shitty nos 6922's: try for matched triodes as well as matched pairs (as an example, everything I've had from tubedepot has been good).

 

-> Check your transformer voltages (at load if possible) before connecting them to any terminal blocks: never trust that things are as the spec sheet says.

 

-> Fire up the psu BEFORE connecting it to the amp and check the voltages: load test if you can.

 

-> Check all LEDs discarding ones that either don't work or have odd Vf: saves un-needed hassle and annoyance.

 

-> Don't use fake parts: they are shit and cause various failure modes, none of which are good.

 

-> If you have some form of tester then test all the sand: past basic sanity checks on the bjt's I didn't, this was a bit reckless and ymmv. 

 

-> Use teflon sheafed test points (digikey for example) on the batteries and only ever use one hand when moving probes (preferably you right one): this is basic practice, don't fuck it up.

 

 

Apart from that there really is nothing else except to take a lot of care that you put the correct things in the right places.

The great thing about the t2 is all of the leds in almost every major circuit component.

Any time a bunch of them come on but others don't it really triangulates the fault.

If you get the batteries into the right ranges then every led should be lit to some extent, if any are completely dark then that's your first place to start hunting for problems.

Edited July 28, 2013 by nattonrice

[Lil Knight]

I could arrange a shipment from satodenki for genuine and much cheaper sands for the T2. Boards are no problem at all. PM me and I could point you to places that have reasonable parts.

I made a big mistake not getting my hands on KG's chassis and I do know lots of people feel the same way.

[GeorgeP]

Nice to see that my spray-n-pray method was your biggest take away from the thread 

 

The build looks great!

 

Thanks! And I think that the theme here is that there is no precise scientific way to getting this thing to run the first time - that was certainly the biggest take away.

[GeorgeP]

There are some general themes established throughout the thread (in no particular order) which if followed seem to lead to success more often than not.

 

-> You can use (correctly rated) wanky resistors anywhere except the 700v batteries: these must be the specified Xicon part and should be raised off the board surface (for memory they are slightly inductive which adds a stabilising factor and stops a particularly annoying type of noise on the output).

 

-> As a (possibly unique to me) extension of this: the dividers at the output of the regulators should be Xicon and raised (in my case the PRP units were leaking and causing the voltage to swing all over the place which is bad).

 

-> At the minimum adjust all pots to the middle of their resistance/travel: Inu suggested middle for the 10k, max resistance for the 2k (this worked for me).

 

-> Don't risk using possibly shitty nos 6922's: try for matched triodes as well as matched pairs (as an example, everything I've had from tubedepot has been good).

 

-> Check your transformer voltages (at load if possible) before connecting them to any terminal blocks: never trust that things are as the spec sheet says.

 

-> Fire up the psu BEFORE connecting it to the amp and check the voltages: load test if you can.

 

-> Check all LEDs discarding ones that either don't work or have odd Vf: saves un-needed hassle and annoyance.

 

-> Don't use fake parts: they are shit and cause various failure modes, none of which are good.

 

-> If you have some form of tester then test all the sand: past basic sanity checks on the bjt's I didn't, this was a bit reckless and ymmv. 

 

-> Use teflon sheafed test points (digikey for example) on the batteries and only ever use one hand when moving probes (preferably you right one): this is basic practice, don't fuck it up.

 

 

Apart from that there really is nothing else except to take a lot of care that you put the correct things in the right places.

The great thing about the t2 is all of the leds in almost every major circuit component.

Any time a bunch of them come on but others don't it really triangulates the fault.

If you get the batteries into the right ranges then every led should be lit to some extent, if any are completely dark then that's your first place to start hunting for problems.

 

This certainly is an excellent summary of all the key points found throughout this thread. And when you consider them, they are really quite simple to follow and will save you a pile of heart-ache later on. A couple other points that I followed were to avoid low hfe 2sc3675s (preferably somewhere in the 50s to the 70s) in the batteries and avoid high hfe 2sk246s (that is, avoid the BL grade for this one) as well - these were educated observations made by Inu and Craig Sawyers (and perhaps others as well). I certainly did test every single part that went into my T2 (even matched resistors and transistors), and you take a huge risk where you don't test everything, including the transformers. I originally thought to fire up each side separately, but this didn't seem to make a difference (except and unless something were to blow up) and in fact both sides needed to be on to properly adjust the pots and get all the LEDs to light up in my case. Certainly worth it in the end.

[eggil]

I could arrange a shipment from satodenki for genuine and much cheaper sands for the T2. Boards are no problem at all. PM me and I could point you to places that have reasonable parts.

I made a big mistake not getting my hands on KG's chassis and I do know lots of people feel the same way.

This certainly makes it palatable.

When would you expect the chassis to be ready?

[Lil Knight]

We need to reach 15 people first, then I will talk with the machinist and get the ETA. Probably a month or so.

[eggil]

The other big question is the Megatron. If it is as good as the T2 as somebody mentioned before.

[spritzer]

It isn't. 

[GeorgeP]

There really isn't anything quite like it - though am limited to Stax amps, KGSS and KGSSHV.

 

Plus it doubles as a space heater.

[luvdunhill]

At the minimum adjust all pots to the middle of their resistance/travel: Inu suggested middle for the 10k, max resistance for the 2k

Just curious, how do you (and Inu) define max resistance for the 2K trimmer? The wiper shorted to the leg of R32 or R33? I am not sure "max" makes sense here.

[luvdunhill]

R32. I should have searched

[Inu]

Buzzing noise when adjust VR1(2K) toward the R33 side.

So I set VR1 wiper to R32 side to avoid buzz noise at the beginning.

 

Both VR1 and VR2 affects voltage of Active battery but VR1 affects much less.

I have no benefit from adjusting VR1 so I replaced VR1 (2K) to fixed 2K ohm register and center(Q17 Base) connected to the R32 side.

And changed VR2(10K) to 9.1K fixed resistor with 2K pot. After replaced these, no more intermittent static noise when amp is heats up   

 

https://picasaweb.google.com/inuponken/T2#5566996623938911634

[nattonrice]

R32. I should have searched

 

Yup, sorry I should have been more specific there.

[Lil Knight]

We are reaching 15 people on the list I'd like to ask, how many of you guys already have the boards?

 

After a long search, I've found a factory that could offer 400mm or 404mm long heatsinks. Problem is, the amp board is 407mm long. So if I go with either of these 'sinks, the board needed to be trimmed down some final mm. This would consequently affect those who already got the boards.

 

Another option is sticking 2 pieces of 'sinks together which is easy.

[Milosz]

Hey nattonrice,  thanks for the COMPENDIUM OF BUILDERS' TIPS....  I am still mired down in other projects but when I finish building my T2  these will come in SUPER handy!!!!!

 

 

OH,  and congratulations  to GeorgeP on completing his DIY T2

[shipsupt]

Already have boards here.