The ultimate DIY? A Stax SRM-T2!

[UFN]

I always tap by hand. Having had to fix a couple of broken taps (and discard a couple of heatsinks that couldn't be fixed) I've decided once and for all that those extra minutes to do it by hand is a good investment...
 

//UFN

[JoaMat]

/

Edited November 11, 2015 by JoaMat

[kevin gilmore]

the name of the game is to keep the tap completely perpendicular to the surface

i got a super old tapping jig that does just that, so simple to use, and the 10 inch or so handle makes it easy to figure out how much torque to apply

[spritzer]

I do it much the same way.  By hand with a power drill with good speed control and a low torque setting.  I do snap one every now and then but then again... I do a lot of this.   

[kevin gilmore]

this is a reasonably cheap version, probably a very good idea if you are doing T2's

http://www.micromark.com/microlux-tapping-fixture,8363.html

 

[nopants]

does the original t2 use any plug-in cards a la 727? seems like another way to save some depth / width for stuff like the batteries or anything that doesn't require the sink

[spritzer]

It didn't have plug in cards but there were PCB's on all four walls of the chassis plus the batteries were located in tall heatsinked modules that stood off from the main PCB. 

[Craig Sawyers]

I get a tap started by putting it in the pillar drill chuck to get it perpendicular.  I turn the chuck by hand while applying a bit of pressure with the drill lever.  Once started, I take the tap (and workpiece) out of the chuck to the workbench and finish tapping using a hand wrench.

Only works if you can get the workpiece into the throat of the pillar drill of course.

this is a reasonably cheap version, probably a very good idea if you are doing T2's

http://www.micromark.com/microlux-tapping-fixture,8363.html

 

That I like, Kevin.  Want one, want one rignt now.

Edited September 13, 2015 by Craig Sawyers

[nopants]

Anyone here use spacers to lift the resistors off the board? Wondering if an appropriate part exists that meets all the clearances over the board.

[b0bb]

Anyone here use spacers to lift the resistors off the board? Wondering if an appropriate part exists that meets all the clearances over the board.

Have been thinking along the same lines, these are ceramic spaces, stack them to adjust height

Allied sells these, or for larger quantities Ebay.

http://www.alliedelec.com/essentra-components-cer-1/70208725/

Another option is a wire forming plier from Excelta or Xuron with adjustable lead bend radius, it puts a U-shaped bend in the wire that holds up the resistor.

http://www.pemro.com/productDetails.cfm?itemCode=EXL-1944

http://xuron.com/index.php/main/industrial_products/13/56

 

Excelta is very nice but expensive around 6-10x the cost of Xuron depending on the model.

Heat shrink might also be useful but I think the T2 runs far too hot for that.

[spritzer]

I just use teflon tubing that I cut to length using my automatic wire stripper.  I only do it for power resistors though. 

[insanity]

For the power resistors I used these on my amps: http://www.mouser.ch/ProductDetail/BIVAR/939-375/?qs=%2fha2pyFaduhil5LnpddCPNfcxCoAyB34XTcpULg7ziRXscMXtfXbDw%3d%3d

 

[nopants]

thanks for suggestions

is there a standard way of attaching terminals for the single spots, like the vcc spots, etc? wondering if there's an alternative to directly soldering wires to the board

[luvdunhill]

No, you need to start a revolution for wire to board connectors. Kerry and I are the grassroots movement

[nopants]

you guys and your crimping are too corporate for me, fight the power

[s_r]

So I've gotten to the point in my build where I can fire up the amp itself. Unfortunately some LEDs are unlit and the batteries don't want to change their voltage (+250V/-559V) with the trimpots. Specifically D1, D6/D7, D10/D11 and D24 are unlit. Aside from those the LEDs outside of the batteries are dim. The PSU voltages measure dead on. Any obvious culprits I should check?

[JoaMat]

/

 

Edited November 11, 2015 by JoaMat

[GeorgeP]

Use the 10k trimpot to set the 6.55v.

[shipsupt]

I told George I wasn't going to get to open the package he sent me until later in the week, but Sunday morning was quiet in the house so i could not resist.  His chassis parts came out amazing, photos are not showing off how clean a job this is. 

Thanks George!! 

 

[chinsettawong]

Wow!

[Kerry]

^ Yes!

[Pars]

Those look very nice. Now wrap them back up so you can open them later in the week to duplicate the Christmas-like atmosphere...

[purk]

I told George I wasn't going to get to open the package he sent me until later in the week, but Sunday morning was quiet in the house so i could not resist.  His chassis parts came out amazing, photos are not showing off how clean a job this is. 

Thanks George!! 

 

I'm jealous of the laser engraving....

[Kerry]

I wanted to mention that a few folks have been having issues with the power supply not supplying enough current on the -500V rail.  Seems like setting the 30 ohm resistors to 20 ohms helps.  The behavior is that if just one channel (either side) is connected then everything works perfectly, but if you connect both sides, then the rail sags and it's impossible to adjust the batteries correctly. 

If you're not having the issue, there is no reason to do this.

I'm not sure if the amp is drawing a bit more or the current sources are providing a bit less than needed.

In other news, I just got my PS together.  I need to mount transistors to heatsinks, which I'll be working on today.  I did test the relay driver and found a small issue for the LED output, but it was easily solved.

I've got it mounted in a jig so I can easily solder the remaining transistors from the bottom.

Here's some shots

 

EDIT:  I just wanted to add that I love working with the SMD parts and heat gun.  I'd say I can move about four times faster when stuffing components.

Edited September 20, 2015 by Kerry

[b0bb]

I told George I wasn't going to get to open the package he sent me until later in the week, but Sunday morning was quiet in the house so i could not resist.  His chassis parts came out amazing, photos are not showing off how clean a job this is. 

Thanks George!! 

 

Got my set from GeorgeP as well, the quality of the work and finishing is superb, many thanks GeorgeP

Edited September 20, 2015 by b0bb