Oh yes...Approp--bleeder ressy....I forgot to add...the bit to watch out is the timing....as direct htr o/p tubes warm up that bit of B+ that appeared on power up will gradually drop until ze relay jumps in. (you know what I mean). That will probably imply a lower ohmage + higher power ressy than might think......500 ohms for a start ? eh... perhaps 10W rating upwards..... 
A serious point to bear in mind is the fire risk if ze relay doesn't close and the resistor toasts away 
............I thought I'd mention this.....
richj
A serious point to bear in mind is the fire risk if ze relay doesn't close and the resistor toasts away ............I thought I'd mention this.....richj
Hi there,
I have managed to get the heater supply up to 5.2V ( a little high now). I used an unused 2V heater secondary in series with the existing 4.45V. I ran this through a 0.47R + 0.22R resistor which drops things down to the 5.2V. If I can find a high power 0.33R resistor I will sub that and I should be spot on with 5V. This seems to eliminate any residual flashover, so the power supply is just about cracked now. The time delay circuit puts my mind to rest about stressing those valuable 5R4WGB's.
Thanks all.
Shoog
I have managed to get the heater supply up to 5.2V ( a little high now). I used an unused 2V heater secondary in series with the existing 4.45V. I ran this through a 0.47R + 0.22R resistor which drops things down to the 5.2V. If I can find a high power 0.33R resistor I will sub that and I should be spot on with 5V. This seems to eliminate any residual flashover, so the power supply is just about cracked now. The time delay circuit puts my mind to rest about stressing those valuable 5R4WGB's.
Thanks all.
Shoog
Getting back to this thread, as my problem is related (Mikael's KT88 amp, and Sherman's PSU (CLC, 38uF [47uF+220uF], 8H, 220uF):
I have noticed today, basically, the 2nd time i have the amp running for more than a few minutes, and i noticed the my RCA 5U4G (italian made, perhaps in the 60s) flashing on top of one of the filaments, the one connected to B+.
I hadn't noticed it before.
I would be ok if it was a sporadic event, but it goes on like this say, every 2~3 minutes. And it's easily seen on daylight.
Only change to Miakel's schematic was the susbtitution of the 6N1P by an E88CC, retaining the same component values.
I was sugested to connect 2 1N4007 diodes, one in series with each anode fo the 5U4G.
Thansk for your help
I have noticed today, basically, the 2nd time i have the amp running for more than a few minutes, and i noticed the my RCA 5U4G (italian made, perhaps in the 60s) flashing on top of one of the filaments, the one connected to B+.
I hadn't noticed it before.
I would be ok if it was a sporadic event, but it goes on like this say, every 2~3 minutes. And it's easily seen on daylight.
Only change to Miakel's schematic was the susbtitution of the 6N1P by an E88CC, retaining the same component values.
I was sugested to connect 2 1N4007 diodes, one in series with each anode fo the 5U4G.
Thansk for your help
I've been waiting for the last week for the new speakers to arrive and introduce my amp to it's new home.
For the time it had been powered on, say, half an hour, it had been flashing continuously every couple of minutes. Oh, i live 1km down of a power station
I then decided to take the given advice and do the diode mod to the 5U4G, i.e., a diode conected between the transformer secondaries and each plate of the tube.
No more flashing! I guess the diodes protect it from reverse peak current or something like that.
A bit, o/t, Sherman, have you tryed the E88CC already?
Cheers to all!
For the time it had been powered on, say, half an hour, it had been flashing continuously every couple of minutes. Oh, i live 1km down of a power station
I then decided to take the given advice and do the diode mod to the 5U4G, i.e., a diode conected between the transformer secondaries and each plate of the tube.
No more flashing!
I guess the diodes protect it from reverse peak current or something like that.A bit, o/t, Sherman, have you tryed the E88CC already?
Cheers to all!
Simpleton said:
I haven't tried it yet. I'm in the middle of another project so when that one is complete I'll probably plug in an E88CC for a listen.
I'm glad the diodes worked to clear the flashing problem. When I changed out my Chinese 5U4-Gs for Sovteks the flashing on mine stopped and hasn't happened again.
I have flashing Rgn1064 rectifiers in the following setup:
-350-0-350 AC with 150 ohm from one leg 350 to 0
-LCLC-Filter with 22H/85ohm, 50uF, 40H/800ohm, 100uf.
-e182cc tube running at 12 mA.
If I understand you guys right, I could try:
- Increase the current draw by a bleeder resistor so that the L will be seen by the rectifier from the beginning on
- Make the ground connection of the Mid-tap of tge transformer switchable, so that rectifier can heat up first
- Have a resistor across that switch to allow softstart
I hesitate to put silicon back in there as I could have used than the whole setup without tubes anyhow.
Did I get that right ?
-350-0-350 AC with 150 ohm from one leg 350 to 0
-LCLC-Filter with 22H/85ohm, 50uF, 40H/800ohm, 100uf.
-e182cc tube running at 12 mA.
If I understand you guys right, I could try:
- Increase the current draw by a bleeder resistor so that the L will be seen by the rectifier from the beginning on
- Make the ground connection of the Mid-tap of tge transformer switchable, so that rectifier can heat up first
- Have a resistor across that switch to allow softstart
I hesitate to put silicon back in there as I could have used than the whole setup without tubes anyhow.
Did I get that right ?
Last edited:
Ok, I tried the bleeder resistor: No success, flashes become worse. I tried a rc-network over the main switch: Flashes are still there. Tried to lower the first cap after the choke (choke:22H/85ohm) from 50uf to 30uf: Still flashing. Same with 1k8/0.1uF Snubber at the secondaries.
The only thing sofar which works is to have a 1500ohm resistor in series with the first choke/before the first cap and switch after two seconds bypassing it...still not satisfying as it feels like a workaround, but not a healing of the root cause...
The only thing sofar which works is to have a 1500ohm resistor in series with the first choke/before the first cap and switch after two seconds bypassing it...still not satisfying as it feels like a workaround, but not a healing of the root cause...
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