Assuming the 2SK117 that's in there now is the component "limiting" the voltage to 340V, I would find it's Idss less than (approximately) 2.5mA?
So I should find one 2.8mA or better? (by your formula)
Gary
3mA in circuit should go full tilt 400V. They give bit less IDSS than free with a battery when in circuit due to less VDS there, so a 3mA free should suffice.
Salas,
BTW - I did not yet substitute a 1 ohm for the 10ohm sampling resistor, I do not have a 1% MF.
I found a strong 2SK117 with an Idss of 5.6mA (using the 9V battery test)
However, it did not make so much of a difference.
I can now readily get the output to 350V, at 80mA. However, that's with a minimum of 420V in. If I drop below that, the output falls pretty fast. I think that's a maintainable number (420V) for Vin, since it's coming off of my plate supply, but why would I need 70V overhead to maintain a Vo of 350V??
Very odd, the other board id not behave like that at all!
Last edited:
OK, I found the problem. Time for a break while I fix my head...
Ok, all better now. I had 2 resistors in series for the load, a 5K and a 820 ohm. I had my meter clipped across just the 5K.
Next time I'll look a bit closer
before I send an SOS.Sorry to bother you Salas, and thanks for your help.
Gary
The multiplier will ruin the flat low Z. Rather not. If you meant putting the mult before, rather yes. But use output cap on the mult to avoid it will ring with CCS.
I ask because as you know I use an AZ1 so PSU can have more than 60uF, could you link me to a schematic or thread where I can get the information?
Salas....I changed the shape of the heat sink and now I am fitting two SSHV2 boards in my PSU box....
I will set each board to about 30mA giving about 8-9mA to each VT25A tube.
If I connect 2 x SSHV2 boards to the PSU instead of one SSHV2, do I need to change the bleeder value or other parts of the PSU??
R5 (10 OHM TP resistor) catching fire means strong current. Because its the passing bridge from CCS part to shunt part. I don't see more than 2W on CCS Q1 sink if drawing 30mA over a 66V drop, so it should have been something in the grounding or handling that took out one or two CCS semis. (How did you try ground the voltage doubler? Diodes must be 2xPIV. Transformer can supply half its normal current). We rather recently discussed using 100mA 500V ceramic fuse in series to SSHV2 when you experiment...
It will have impact only on series drop resistors or coils internal resistance. If you had calculated Vo for strong bleeders, recalculate DCin including two CCS and bleeders total for drop on series elements mentioned.
I explaint you:
-I tried the voltage doubler because I have a Bartolucci 125VAC 100W that I don't use, your 6V6 tube lineamp uses 340VDC, others lineamp I'm experimentig uses 250VAC, 280VAC & 300VAC that's the reason I tried.
-I used the voltage doubler without the chokes: R/C/R/C 600R/40uF/600R/40uF with the Bartolucci tx and worked OK.
-Before to connect the new R/C/L/C/L/C I verified with a dummy load 15K to adjust the voltage & current working fine without burning nothing, only burned with the real load.
-I tested the wires between the reg & the real load & all wires are OK.
-Sorry my ignorance, what's 2xPIV? something relationated with power & voltage?
-Yes you told me the ceramic fuse but can't get in the local shop, I wil include in the next online order to RS or Farnell.
Last edited:
On having dismantled the regulator I have realized that the screw that holds Q3 was sluggish(weak), can it be the reason of that is situated burnt R5?
You can use 300V and 7.5K instead of 5K plate resistor and 340V in my 6V6 pre.
Is the real load referencing to ground, and where is the doubler being grounded? What happens if you don't ground the chain from doubler to reg to 6V6?
You can use two diodes in series where there is one shown, that doubles the peak inverse voltage spec.
Voltage doubler is not connect to chassis gnd, not connect to AC mains earth. Have I to connect to mains earth or to chassis gnd?
Yes, real load is grounded to chassis gnd, also SSHV2 is grounded to chassis gnd.
Thinking about the changes that I have introduced, now I use 2 chassis instead of only one and between both chassis there is no connection of AC earth, can be the issue?
Yes, real load is grounded to chassis gnd, also SSHV2 is grounded to chassis gnd.
Thinking about the changes that I have introduced, now I use 2 chassis instead of only one and between both chassis there is no connection of AC earth, can be the issue?
Last edited: