[brjernej]

Does Vpump need cooling? Precisely, IRF740. It will run a single 12ax7 (both triodes) . Is a small 27K/W heatsink enough? Or is it better to screw it to the chassis (yes, I know it must be isolated) (It is much easier to plan "the guts" of a unit if you don't have to put all the things to the chassis.) Is it easy enough to calculate it myself? The maximum rated output is 220V x 15mA => 3,3W. The minimum stated rating for the input voltage is 4VA. Roughly that is 4W. So this is 0,7W difference to dissipate. If the IRF dissipates all that heat, it has junction to ambient rating of 62°C/W. So at the full operating specs the temperature will rise for 43°C, that is around 65 alltogether. This is pretty safe even without any heatsinking - if my calculations are correct. Please, verify ...

Also, are the holes of pcb plated through? Because I will probably mount the IRF from the bottom side to lay it on the bottom of the chassis. What is the frequency of the device at 2mA 220V output? And what is the portion of noise? Should I use a HV linear regulator after it to get really clean DC?
What about the capacitors? Both C1 and C4 look incredibly small in comparison with values in ordinary tube circuits - one would use min. 1000uF for C1 and 22uF for C4 ... Thanks for the answers!

[Dirk]

Hallo,

if you use the VPump within its spec than you DON'T need any modifications of course.
Also the heatsink that comes with the VPump is large enough.

Best regards, Dirk

[brjernej]

Thank you!
I soldered it together and it made a 270V output - all good so far.
I assembled it in the unit and it was all good. At least it looked like.
Then I managed to short B+ to the signal path (my sloppy design) - and I get a nice "motor" sound from the amp from now on. And a nasty smell. From the said Vpump.
I disassembled it from the amp, hoping that it would then behave normaly and I would be able to go on with troubleshooting (to my knowing there are no such components in the system to be damaged by such short, what do you think - practicallly all caps are rated to 630V and resistors can also take such "abuse" - what about the tube? - the B+ wire touched signal wire before the grid resistor ... Any ideas, what I could fry by this accident?).
Then (full of hope) I connected VPump to the external regulated 12V PSU. (Just) 16V otput, IRF740 heats up enormously (I noticed smoke and quickly turned the PSU off). My "chinese tester" recognises both transistors, so they are probably not fried ... Which component(s) are faulty, what do you think? (if you have any ideas, before I unsolder individual components and test them). My thinking: 1)timer IC 2)diodes 3)inductor 4)still transistors ... (there is no chance to test the timer IC, so it would be nice to know, if it is critical in this type of fault).

My design:
a) (switchable) banana boooster (with kick switch)->
b) alembic preamp (single stage) (I need Vpump for this stage) ->
c) Kemo 40W integrated amp module -> speaker
(attached is schematic for the alembic)
http://moosapotamus.net/images/AlembicF2B_SCH.gif

[brjernej]

Looks like it was the choke ... Shorted (not discontinued)  - which is at given parameters hard to measure, because multimeter kit probes themselves have some resistance ... I almost gave up, changing every active component (thanks god they have them all in our local electronics store), and still nothing, my 740 hot as fire and cca.30V output. I measured the resistors and checked also the caps. It is still possible that it was a cold solder joint or discontinued trace to the choke. Anyway, it works now. I hope it would also work in the amp ... When it will be finished, I will show it.