6V6 line preamp

[stajo]

Ok. I load them with usual dummies and put 20 V on input and measure ovet TP?


Dude my LCR tells me I have 1000 uF over the 0,33 cap
On the the other board it says 0,42.

 

[Salas]

And still some resistance short on input. Ok, maybe the IRF

If with resistance short don't start even with low voltage. Find the shorted part/path first.

 

[merlin el mago]

Yes first the CCS alone and check and set in the TP.

 

[Salas]

Ok. I load them with usual dummies and put 20 V on input and measure ovet TP?


Dude my LCR tells me I have 1000 uF over the 0,33 cap
On the the other board it says 0,42.

There is no need for dummies for CCS only test in low voltage. The shunt part won't get enough to reference up. Just return a crock cable to the voltage source from where the CCS tail ends and be sure you measure no resistance shorts. That one checking virtual capacitance I have no guide for.

 

[stajo]

Seems like it was the IRF. They show similar values now. I'll replace the filter resistor to and give it a go.

Here the lightning struck

 

[stajo]

Replacement of IRF840 didnt help, I got like 5 V out of it so I replaced the SK117, took some 430 ish value, and both KSA. Now the diode lits up nicely and it flows about the same voltage out as what I load it with, 315 V. Turning the VR doesnt seem to affect anything. Ideas?

 

[Salas]

Here the lightning struck

That is why proper CAT IV probes are either shrouded near to tip or twist isolating from CAT III to IV. So you can't arc with near items when probing HV.

 

[Salas]

Replacement of IRF840 didnt help, I got like 5 V out of it so I replaced the SK117, took some 430 ish value, and both KSA. Now the diode lits up nicely and it flows about the same voltage out as what I load it with, 315 V. Turning the VR doesnt seem to affect anything. Ideas?

You mean the voltage trimmer? It can be easily dead too. There is not much contact material in there to sustain lightning or over-current.

 

[flatheadmurre]

Since you got one working unit start by measuring the static values that will give you a hint.

If you run out of parts i have several sets of sand and resistors for it but you´ll have make a trip out in the bush then

 

[Salas]

There are not many things left to check, the two trimmers and the lower DN2540.

 

[stajo]

All those voltages made my stummach cry so I ran over to my local greek

Should I take Souvlaki Paidaka or Edessa?

 

[Salas]

Kokoretsi!

 

[stajo]

Since you got one working unit start by measuring the static values that will give you a hint.

If you run out of parts i have several sets of sand and resistors for it but you´ll have make a trip out in the bush then

I measured different values both over trimmer and the KSA next to it. And I have lots of sand but a trip to the bush is always nice. I love that area and I would love to come over and bench some stuff or so when I have the opportunity.

 

[stajo]

Kokoretsi!

They didnt have, so that will have to be next time in Athens. Paidaka it was

 

[flatheadmurre]

I measured different values both over trimmer and the KSA next to it. And I have lots of sand but a trip to the bush is always nice. I love that area and I would love to come over and bench some stuff or so when I have the opportunity.

You´re very welcome just let me know a bit in advance so i can clean a path into the workroom .

 

[stajo]

Metaxa

 

[Salas]

Metaxa

Metaxa and HV don't blend well. Allow many hours after a few shots, else you will probe to Zeus caliber arcing.

 

[stajo]

Only one small for the stummach To late, already have the pot and that KSA loose again. Pot seems to work, replacing it anyway, and the KSA once again

 

[stajo]

No, it doesnt want today. I can max current to 243 on the TP and voltage doesnst move. 310 on and out and 13,5 k load. Maybe the poor guy need sa break

 

[stajo]

D1 felt a little bullied to so it was replaced. Now its set happily to 260 Vout and 40 mA. I thank Metaxa for that one and wave to Zeus