Cap input
Just wondering if I can drop in to this thread and ask : ( Thomas ? )
I'm wondering about cap-input issues when using dampers like 6CJ3 .
Designing a power supply that will deliver about 300mA at 460V .
Hybrid bridge using diodes and 2-off 6CJ3 from a non-c.t. winding .
I'm getting close to the limit of the 6CJ3's as PSUD suggests they will be running about 335mA rms . May have to go to 4 smaller diodes or perhaps 2-off EY500A .
Question is - how will they cope with cap-input, as this circuit requires ( for reasons too long to explain ) about 20uF input cap ?
Just wondering if I can drop in to this thread and ask : ( Thomas ? )
I'm wondering about cap-input issues when using dampers like 6CJ3 .
Designing a power supply that will deliver about 300mA at 460V .
Hybrid bridge using diodes and 2-off 6CJ3 from a non-c.t. winding .
I'm getting close to the limit of the 6CJ3's as PSUD suggests they will be running about 335mA rms . May have to go to 4 smaller diodes or perhaps 2-off EY500A .
Question is - how will they cope with cap-input, as this circuit requires ( for reasons too long to explain ) about 20uF input cap ?
For what it is worth, I have a pair of 2a3 amity amps that use a pair of 6cj3 dampers in a hybrid bridge that I have used for several years with a 75uf input cap. They are being fed by a lundahl mains transformer that has two 250 volt windings in parallel, which results in a low dcr source. I have had no problems whatsoever with them facing a relatively large turn on surge.
Thanks Jim - very relevant info .
Interestingly I used pairs of 6CJ3's on a c.t full-wave supply to power 'Aurora' monoblocks a few years ago. Those were running VV32's , so the demand was high-ish , but only 1uF input cap .
Anyway, I guess it's the peak current that is affected by the cap input size ? - and they can run 2A approx .
Actually 6CM3 is better for rms current , just been checking .
Interestingly I used pairs of 6CJ3's on a c.t full-wave supply to power 'Aurora' monoblocks a few years ago. Those were running VV32's , so the demand was high-ish , but only 1uF input cap .
Anyway, I guess it's the peak current that is affected by the cap input size ? - and they can run 2A approx .
Actually 6CM3 is better for rms current , just been checking .
Yeah, I remember reading about your build back when I was building mine. These originally began life as 300Bs, but I could never get them quiet enough, and I thought the difficulty in driving them always resulted in what I would term an "icy" sound, which I attributed to section mismatch in ecc99s I was using as drivers. 2a3s amps are silent, and I use a 5695 as a driver, which have really good section balance. I use a separate rectifier for the driver, a 5ar4 into a choke input with a gas regulator tube. Sounds really good, but I rarely use it, as I have become more of a SE listener.
Hi!
These are tough tubes with high peak current capability. They should be able to cope with this easily
Thomas
These are tough tubes with high peak current capability. They should be able to cope with this easily
Thomas
That means that you can have the heater supply grounded, and the cathode can have up to +900VDC on it. Which is what you normally see up to in half wave rectifier circuits. TV damper diodes were designed to have high cathode to heater voltages. Higher than regular tubes.
Right. Plate current is 250 mA. Guess I saw the voltage drop: 25V @ 350 mA. It will do the job anyway since I don't push the 211.
Hi!
I just wrote a small article about the 6CJ3 in my Tube of the Month series. If you are interested:
VinylSavor: Tube of the Month : The 6CJ3
Best regards
Thomas
I just wrote a small article about the 6CJ3 in my Tube of the Month series. If you are interested:
VinylSavor: Tube of the Month : The 6CJ3
Best regards
Thomas
Not Thomas, but the answer is certainly! Check the 6CJ3 data sheet out. Notice that the PIV rating is 5500. Play safe: use a separate 6.3 VAC filament trafo for the damper diode pair and connect each cathode to an end of each heater.
Hi!
The PIV rating is given for TV Damper service. It needs to be considerably derated for rectifier service. I would derate at least by 50%.
In your case you will have PIV of over 2500V, depending on the filter after the rectifier. Which means you are close to the limits.
I wouldn't recommend it. For such voltages I prefer full wave bridge rectification with 4 diodes and a single 1000V secondary. PIV is half in the bridge arrangement. But it would require 3 separate heater windings.
Best regards
Thomas
The PIV rating is given for TV Damper service. It needs to be considerably derated for rectifier service. I would derate at least by 50%.
In your case you will have PIV of over 2500V, depending on the filter after the rectifier. Which means you are close to the limits.
I wouldn't recommend it. For such voltages I prefer full wave bridge rectification with 4 diodes and a single 1000V secondary. PIV is half in the bridge arrangement. But it would require 3 separate heater windings.
Best regards
Thomas
Hi again,
an alternative to the bridge with 4 TV dampers would be a hybrid bridge. Then only a single heater winding is needed which should be connected to the cathodes of the dampers at one end. But you need to ensure that the heater winding has proper isolation rating for the voltage.
Best regards
Thomas
an alternative to the bridge with 4 TV dampers would be a hybrid bridge. Then only a single heater winding is needed which should be connected to the cathodes of the dampers at one end. But you need to ensure that the heater winding has proper isolation rating for the voltage.
Best regards
Thomas
Thomas,
The "OP" stated that the power trafo is 1000-0-1000. So, a 4 diode bridge is out. Regarding your PIV concerns, headroom can be gained by installing a 2 part stack of UF5408 SS diodes in series with the plate of each 6CJ3.
FWIW, I'm with you in preferring bridge rectification at these dangerous voltage levels.
The "OP" stated that the power trafo is 1000-0-1000. So, a 4 diode bridge is out. Regarding your PIV concerns, headroom can be gained by installing a 2 part stack of UF5408 SS diodes in series with the plate of each 6CJ3.
FWIW, I'm with you in preferring bridge rectification at these dangerous voltage levels.
Hi Eli,
Yes you are right, but maybe he does not have the transformer yet.
Also your suggestion of enhancing PIV is valid of course.
The 6BY5 is the only TV damper tube which also has specs for rectifier service. Rectifier PIV is derated about half. Hence my suggestion to derate at least 50% in this case too.
And from experience I know that the rectifier PIV rating of the 6BY5 is not conservative. It will break down if operated beyond that.
Best regards
Thomas
Yes you are right, but maybe he does not have the transformer yet.
Also your suggestion of enhancing PIV is valid of course.
The 6BY5 is the only TV damper tube which also has specs for rectifier service. Rectifier PIV is derated about half. Hence my suggestion to derate at least 50% in this case too.
And from experience I know that the rectifier PIV rating of the 6BY5 is not conservative. It will break down if operated beyond that.
Best regards
Thomas
Last edited:
At home I have three huge transformers available (military) FREED 1000-0-1000V (500mA) with a 115V primary. On the transformers is also spelled "INTERMITTENT DUTY" (?) Do not know what it means, electronically speaking.
I also have available a transformer with 0-600-700-800-900-1000V (1A).
My idea is to build a SEP that GM70 with work possibly under 1000V.
Perhaps the second transformer would give me less trouble taking advantage of the 600 or 700V outlet.
I would understand (Thomas I can answer this question) what is the limit of safety work in a power supply with a pair of 6CJ3?
I also have available a transformer with 0-600-700-800-900-1000V (1A).
My idea is to build a SEP that GM70 with work possibly under 1000V.
Perhaps the second transformer would give me less trouble taking advantage of the 600 or 700V outlet.
I would understand (Thomas I can answer this question) what is the limit of safety work in a power supply with a pair of 6CJ3?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.