JoaMat

Electrolytics in red…. ….done today - probably on its way to trash can.

Is the jump up to +250 volts not normal behavior? That's what my Carbon does, 500V rails and my multimeter catches +330V before slowly down to 0.

All right, I rather prefer to open you gerbers in Proteus and save them as pdspnl files – works great. Thanks a lot for all work you have done!

I use Proteus v8.5, isn't that the software you are using? I guess you are able to open gerbers you made yourself. Can it be some software setup I've missed?

When I try to open gerbers, probably of newer version, in Proteus I get warning about “Bottom SMT Paste Mask” and file won’t open. After deleting corresponding line in the readme file it opens nicely in Proteus. What might the reason be that it won’t open without delating that particular line in readme file.

Early stage work on a Circlotron (Aug. 2015). The prototype exploded during initial take-off roll.

This is how the small board with trimmer and resistor looks like. I do think the T2 amp board by Kevin is a very good one. Easy to build, just put the right component in right position, solder properly and then you are done. If something goes wrong it’s possible to work on the board. And it's also a terrific board for experiments, tests, modifications…...

Nice, manual control seems to work well.

No, schematically like this: added RV3 and R60. I got it balanced when current was 5.1 respective 5.8 mA. When upper and lower tubes changed place I had to reset back to original setting – the unbalanced like of disappeared.

Finally I did notice…… Four Bugle Boys. Ref. link Nice!

No, trimmer is replaced by a resistor long time ago. The 10m90s current source is connected to ground and set to 1mA. Today I modified the input tubes current sources with a trimmer like T8000. Also changed the servo, using single OP tied direct from output via resistor to one of the lower tube cathode. One channel had more than 200 volts unbalance with no servo and both batteries set to 740 V. With the trimmer I managed to get outputs balanced – have been within +/- a couple of volts for half an hour now (servo disabled)….. to be continued….

Moving the servo to the cathode would that be a good idea?

How to make the servo less complex?

The Drum Major leads the seven LEDs.

Managed to squeeze in the eight diodes under the lf353 op-amp. Batteries resistors killing some 730 volt in series with the LEDs, or in my case lt1021, replaced with 10m90s. Works great in layout software. In real life -

Here is Delay circuit.PDF schematic. R1/C1 determines the delay time and R2/C2 flashing frequency. 12 V is fine, I use this circuit in two T2 power supplies with 12 volts. For time calculations google "R/C time calculation". Values in schematic gives me approximately a 50 seconds delay.

A delay circuit. Similar to Stax. LED flashes during preheat and then steady. Should work with CPC1117N. Will probably cost you more than four bucks.

If dual tube input. One tube as upper device and the other as lower like T2 or one tube each side?

How about a “dual section” tube input similar to the T2?

How about increasing the 6DJ8 plate voltage? Might need additional ksa1156, what else?

I consider this is a fact.

Kevin, function of switch in test position? Resistors in red circles below, have something to do with test?

Happy Birthday!

Thanks for schematic. Guess I'll stick to the t8000DR. The servo is interesting though.

Thanks for clarifications George and Michael. The servo (opto servo) I'm talking about needs both OP27 and 4N25 installed and the jumper next to the 4N25 shortened (do not shorten the other jumper). The trimmer must be set high enough. The opto servo is only capable of lowering the offset set by the trimmer.