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The ultimate DIY? A Stax SRM-T2!


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Finished...   Back plates before I mounted them...

I finally got the last plate machined.  I had to replace the spindle on my CNC and also made a mistake on the CAD so had to redo this plate, but it's looking great now.  

So here's a progress update on my T2 mini build. I started off with the a golden reference version of the T2 supply.  Had a couple of issues.  There was some 60Hz noise I was hearing (I'm guessin

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With the PEEK screws the question is whether you need to use loktite. I think Inu did. If this is the case this presents a another issue other than the fact that you will get decreased device life from improper torque. I dont see it an obvious choice.

Justin may have a point given his situation. Others not sure.

 

I had understood that there would be less expansion/contraction with the PEEK screws over the metal ones - but maybe that isn't the case.

 

Also, not sure if anyone has compared the real life heat transfer between using PEEK with less torque versus using metal. I can't say this is indicative of sufficient or proper heat transfer, but the heatsinks on my T2 get stink'n hot, even the PSU. In any case, I am sure the life span will be affected regardless of whether it is PEEK or stainless, the question is to what degree, if any, are there any measurable differences. I used a mixture of stainless and PEEK, using stainless where I could use the larger Aavid shoulder washers and PEEK where I could not (I recall Craig or Kerry actually drilled/reamed the transistors so the shoulder washers would fit and used steel bolts throughout).

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the pricing for the PEEK would be about 30 cents for the phillips and 40 cents for the socket head. this is probably less than you'll find anywhere else online. thats for M3 - 8mm length, which is enough for any heatsink or flange that is threaded, but if you're trying to go thru a 1/4" thick flange and put a nut on the other side it wont work. i dont know what quantities i would have to order in different lengths, i only had that one size quoted for 5,000pcs

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another possibility could be to use M2.5 stainless screws, which are 0.098" diameter compared to #4 which are 0.112" and M3 which are 0.118" diameter. This could allow selection of a shoulder washer that is a little smaller in both inner and outer diameters to fit all the transistors without trouble, and less capacitance since the screw has more distance to the tab hole.  you just wont be able to use any pre-threaded PCB mount heatsinks, since all the ones ive seen for sale are #4-40 or #6-32. overseas im sure they're metric but probably M3 or M4

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2sa1486 has exposed collector on the back side. and extra capacitance from metal screw on t2 definitely an issue

in all of the current sources where they are used. also capacitance is an very important issue for the 2sc3675 in the battery.

(Douchy HF voice)

What did the original T2 use? I prefer to follow the original designers intent for maximum plankton retrieval capability.

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Having a live metal tab to contend with is a complete pita.

On the t2 I used nylon cap screws on nylon shoulder washers where I'd get them to tension and then glue them at the nut (have to cut them off now)

This worked on average about 60% of the time whereas the other 40% would get close to the tension I was happy with and then the bolt would strip out.

 

It was heaps easier in the 300b build because the CREE diodes are to247 (packed with plastic around the bolt hole).

Used a pps washer, ss cap screw, and a Al oxide tablet.

It's yet to blow through to the case despite the 850VDC pre-reg bonanza that's riding on the live underside of the diodes.

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the pricing for the PEEK would be about 30 cents for the phillips and 40 cents for the socket head. this is probably less than you'll find anywhere else online. thats for M3 - 8mm length, which is enough for any heatsink or flange that is threaded, but if you're trying to go thru a 1/4" thick flange and put a nut on the other side it wont work. i dont know what quantities i would have to order in different lengths, i only had that one size quoted for 5,000pcs

 

M3 is great for me Justin if this gets off the ground, if thats cool. dont need heaps, is 50 socket-head OK, or would you prefer 100? want me to shoot you an email to follow up?

Edited by qusp
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the pricing for the PEEK would be about 30 cents for the phillips and 40 cents for the socket head. this is probably less than you'll find anywhere else online. thats for M3 - 8mm length, which is enough for any heatsink or flange that is threaded, but if you're trying to go thru a 1/4" thick flange and put a nut on the other side it wont work. i dont know what quantities i would have to order in different lengths, i only had that one size quoted for 5,000pcs

 

Good price, but if people are intending to use them for the T2 i think they need to be 15mm.

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The L brackets in the T2 are not tapped and 4mm thick. Add the nut, ceramic washer, 3mm board thickness and the sand itself, something 15mm would be appropriate here.

I would be still in for 100pcs of 8mm ones anyway.

Edited by Lil Knight
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any previews of your case renderings while we struggle to contain the excite? i am probably late in my aesthetic input but those useless rings on metal that frame the heatsink fin edges would be nice. i keep scratching myself when i pick these amplifiers up off the ground, etc.

pretty sure i wont be eating for a while, between this and the megatron

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If you look back some pages, you could see me own cases. These would basically look like that, with some minor/major changes... The top plates will have lots of punched venting holes. The front panels, not sure yet.. how many jacks you guys want? I am thinking of one jack on the right, volume knob in the middle, and 5mm LED on left. Power switch on the PSU's front or just blank? If yes, which type? I do know place in China that sells latching switch, rated 5A. These switches are made of anodized aluminum, not cheap plastic ones on fleabay or PC-related sites.

 

These are the volume knobs, spikes (optional, either stainless steel or anodized aluminum) and decorative tube rings that I am going to use.

 

9609180336_57f7904dd5_c.jpg

 

9609193694_09fea32a82_o.jpg

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I am ordering from satodenki soon, so anyone needs anything from there, just let me know via PM. I will finalize things on Thursday.

 

To make it easier, here are the required parts for the T2 that are available from them:

 

34  2sa1486  8  2sk216  4  2sk246gr  4  2sj79  Edited by Lil Knight
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I am ordering from satodenki soon, so anyone needs anything from there, just let me know via PM. I will finalize things on Thursday.

 

To make it easier, here are the required parts for the T2 that are available from them:

 

34  2sa1486  8  2sk216  4  2sk246gr  4  2sj79 

 

If you guys can stock up on 2sa1968 I would do that, our Sato batch was genuine :) Doesn't the Megatron use it in the CCS?

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