JoaMat

Wow, a Kopparberg. Skål!

Happy Birthday Jose!

Happy Birthday Birgir!

Happy Birthday Kerry!

I believe ver 2.0 is taken – Kerry’s shrinked smd…

My T2 PSU differs some from the original DIY T2 PSU as I have a -560V section which is as capable as the -500V. So with this modification the only work the -500v is doing is to set the 6CA7 G1 potential. LTspice simulation I’ve done indicates that -500V at G1 might be desirable. But I don't trust myself doing this kind of work in LTspice. Below schematic: removed Q24,Q25,Q28,Q29,LED, R48,R49. Added jumpers between drain k216 and cathode 6CA7.

I had to open up the KGST for adjustment since I lowered the rail voltages. Four plain old good trimmers. My right foot for size comparison.

Thanks a lot George, but I actually have a small stock of j79/k216 myself. Living in the middle of nowhere you need to be prepared. Have been socializing with the faulty channel today and we are now both happy again. Maybe it’s more of a Grounded Grid with dual tube input and active batteries than a T2. Picture below shows the modded T2. No j79/a1486 at the output stage. Upper right the middle a1486 is missing – replaced with resistor so upper tube grid voltage is set by a voltage divider. If you have a well defined supply voltage you don’t need to send 2.5mA through a 27K resistor – I think.

Happy Birthday!

If running short of 2sj79 one could rebuild the T2 to something similar to a Grounded Grid. I removed j79s, 750R resistors, a1486s and corresponding LED. Works/ed like charm. Unfortunately right channel started to obstruct after a while. Perhaps this kind of modification isn’t appropriate. For the time being I run left channel to both sides.........

MINIWATT tubes - Nice!

Draft of dual 6922 input (similar to T2 input), with current tunnel (as Carbon etc.) Voltage cross 2sa1486 580V and 700mW of heat.

Kerry, do you hear any bump or whistle in the headphone when power off with the servo?

Make your pick. Then Whitigir build the other.

I suggest a Sandwich.

Suddenly left channel went down – turned out that one mosfet 2sj79 had transformed itself to a PNP.

Nice. Like the 08N100D up there. IC1 is?

Reduced voltage on my “modified” T2. DHT by night.

@@bui501, I’ve no idea if the PBHVs will do or not – someone should try. But how about KSA1156? Max voltage cross pnp in battery is around 370V. As for space it might be a little tight though. The squirrels sit on them.

Here is a link to a post. In that post there is a link to a BOM. In that BOM you find LTL-4213. I’ve two different BOMs on my computer from the same topic, both with LTL-4213.

The first electrostatic amplifier I built was the first version of KGSSHV with onboard heat sinks and I used LTL-4213 LED forward voltage 2.1V. At that time the suggested LED was LTL-4213 which also was used in the DIY T2. I’m aware of that some builders stick to LED with lower voltage. My experience is that you very well can use the “higher voltage” LED without changing resistors.

Voltage cross the resistor is LED voltage minus base-emitter voltage - roughly 1.9V – 0.6V = 1.3V. So approximately current through R33/Q17 2.5 mA (RV2 centered) and R50/Q20 4mA. Those values will depend on the individual components.

Very nice indeed! Like them Blue (Hawaii) lights.

1A at 450V – yeh, that’s a pretty decent load

Wow, that’s wonderful! U1 - op amp in sot23-5 package, any suggestion?