kevin gilmore

I only have the 5 pin stax jacks at the moment.... http://gilmore.chem.northwestern.edu/t2burnin.jpg its my new home office system... So it turns out that the servo has a wiring error. Which is REAL simple to fix... Remove and cross R81 and R82... The schematic is right, and the board is wrong... Which is why i was hearing some pumping last night. All gone now... Going to add troubleshooting voltages to the schematic in a few minutes. Got to find some decent tubes (well something reasonably priced before i put $600 of real mullards in there) The dynamics of this amplifier really shines.

I listened for no more than 15 minutes, then kind of crashed. then the dogs started making noise... etc... I'm going to do serious listening over the weekend after cleaning up some of the mess. I have a KGSS, Aristaeus, KGBH, KGBHSE prototype and the T2 to listen to. And omega's, omega2's,sr-003, sr-404 headphones and the koss esp950. And some low bias stax phones which at the moment can't be used because i never planned on that. Although its a trivial fix thats on the list.

I can get it to $30k real easy. Its already designed for an additional power supply for dual mono power supplies. And its designed for a quad fully regulated filament supply. In addtion in the same size box i'm pretty sure i can replace the standard power supply board with a shunt regulator board. So 4 chassis seriously maxed out amplifier. Not sure where you would put the black gates, there are no output or coupling caps anywhere, and the 450 volt black gates are way to big for the box unless you cut holes in the top. Will look to see if any of the V-caps would be suitable for power supply use. But you could always use them as brilliant stones and sprinkle them around the listening area.

updated bom with at least the screws and nuts correct http://gilmore.chem.northwestern.edu/t2parts3.xls if you use all stainless steel for the screws, there would be absolutely NO magnetic parts in the amplifier or power supply except for the transformers. It does not look good for me getting any sleep tonight.

Lets just say that if this was a commercial product, and priced at $18k it would be worth it.

And in full glory... ok, i need a 4 inch tripod, that or put the thing on a table (need decent horizontal surface that is not already filled with layers and layers and layers of crap) (LARGE horizontal surface!) http://gilmore.chem.northwestern.edu/t2lites2.jpg So what you all figure?? About 500 hours of burnin The power supply cables are going to take at least 300 hours just to settle down the electrons

So i highly recommend that everyone test their led's. Which i thought i had done. But one either was bad from the start or died infant mortality. It was causing all sorts of dc instability. And yes i know its out of focus, the result of a 3 second hand held exposure. http://gilmore.chem.northwestern.edu/t2lites1.jpg Troubleshooting this thing is real easy as you can do it one channel at a time and the led's point to where the problem is. updated power supply schematic, i decided to change out all 4 diodes for zeners. http://gilmore.chem.northwestern.edu/t2schempower.pdf the last thing to get fixed will be the bom

Change D8 in the power supply from regular diode to 30 volt zener. updated schematic that actually matches the circuit board here. http://gilmore.chem.northwestern.edu/t2schempower.pdf In fact you can also change D2,D5,D11 to the same 30 volt zener. Reason, in testing (and doing stupid things with the bias) i found a way to zotch the -500 volt fet. The zener prevents this.

There is a sizing error on the board for the dact part. Don't know how it could have come out that way, but it did. Since you always had to extend the pins anyway to get it to match the center line of the rk50, a little creativity will get it to fit. the dact has .1 pin spacing, and .580 from first set of pins to second, .800 from second to third and .580 from the third to the fourth somehow i ended up with .15 spacing, .575,.850,.575

By the way as of yesterday i have 9 sets of heatsinks drilled and tapped and 4 sets of fronts/backs fully machined. All of the fronts and backs have been cut to size. Soon i will have tops and bottoms, then 3 sets get shipped for polishing and finishing. More stax jacks and knobs also on the list. You will be able to do your own knob if you want to

Yep, no resoldering of any kind. The leads only get bent an additional .050 inch anyway, and there is more than plenty of room for that. just finished replacing all the ceramics in the amplifier, now wiring the stax jacks. thermal grease all over the place Too bad there is not a .035 inch thick ceramic insulator that is .5 wide.

final power supply picture with the ceramic insulators and the nylon cap head screws (#4-40 x .5) Also used the special double thickness nylon nuts which really hold things tight... Screws came from Mcmaster-Carr, Not sure where the nylon nuts came from. http://gilmore.chem.northwestern.edu/t2power3.jpg Will replace the washers on the amplifier tomorrow or sunday. Going to need longer screws for the 2sa1486's. By the way, the power supply is approximetly 29 lbs finished. Amplifier chassis is about half that.

Drilling out the bracket and circuit board holes to accept #6-32 is certainly something that can be done. I'm not going to do it. I left the power supply run under 50% load overnight, and everything looks great, the nylon screws did not loosen at all. I would sure like to find some glass filled nylon screws, i'm even willing to have a batch made.

The 7721's are just a slight bit too big for the ixys parts. So either drill them out .002 or use the standard plastic washers. I went with the standard plastic washers cause i did not want to drill out the parts while soldered to the circuit board. The ceramic insulators are good for about 4kv. Beryllium oxide is a slight bit better. But its also toxic... Perfect. Still in search of the ultimate in insulating screws. Power supply back under load.

you work area is still way to clean. you are not building enough stuff... 5 projects at the same time in the same space would take care of that problem.

I have some of those for the dynafets i am going to build soon, got them from marc. the ceramics seem like a much better idea, lower capacitance and guaranteed higher breakdown voltage. (i think)

Does anyone have any specs that make sense on the 4171G. Like what the real max voltage is? Errors in the spec sheet have the thinner one being able to stand more voltage. They only need to withstand 600 volts max. I assume that thermal grease is required when using the ceramics... Too bad no one makes berrylium oxide pads.

I like inu's parts, and just ordered a bunch of them. I wonder what the spec on the voltage of the washer is?

yep it was in the power supply... currently the screws are all stainless. Because i have a bunch of them, and they look cool. Got nylon screws coming, but if i can find peek screws that is even better. I use peek tubing for all the LC's... on second thought, at about $7 per screw, and 64 screws needed... maybe spritzer will do it. I know there is no reason not to be excessive, but that is a bit nutty. Need to verify that they are really stronger first.

And after a few hours this is what happened. Due to the current limited power supplies, absolutely NO components burned up. http://gilmore.chem.northwestern.edu/arcscrew.jpg I'm switching to acetate screws once i find some.

The resistors ARE on backorder. But they are not really important as they are the input filter. Too bad i did not wire the stax jacks, I would have something to listen to already ATOMIC BATTERIES TO POWER TURBINES TO SPEED PHASERS ON STUN http://gilmore.chem.northwestern.edu/t2amplifier1.jpg all voltages look good... Filament transformer is a slight bit high... The output tubes are 6.5 vac the input tubes are at 6.7 vac. Don't trust my 30 year old meter, so i'll bring home something recent and calibrated before i re-spec the filament transformer.

http://gilmore.chem.northwestern.edu/t2power3.jpg Got to find better 1/4-20 bolts. 2 of them have cracked off at the screw head.

Patience grasshopper. It will make music soon. Very soon. Have to finish power supply first. Worked on it 3 hours today and 2 hours tomorrow should finish it. Had to go to tristate electronics for the right size spacers. Ordered the rest of the parts including xlr connectors to make cables with which to hook it up to a source, plus the right sized spacers for the amp board. No reason to rush this, it will be done in plenty of time for CJ010. I want it perfect the first time it powers on.

updated amplifier schematic http://gilmore.chem.northwestern.edu/t2schem.pdf

another correction to the bom the spacers (.5 inch and 2 inch) are supposed to be 4-40 not 6-32