Using a Hammond 270FX Transformer and realized my B+ is way to high...
550VCT, so 275VAC to Aikido board. Want to use 6922/6NP1 and see the B+ is about 100 Volts too high (currently at around 360VDC)...
So I am trying to use a 100V 5W Zener on HV windings to drop B+ (I have done this on HV for another amp tranny with CT and worked perfectly), but I do not have CT on this setup...so I put in two 1N4007 across winding with the zener (to "make" a CT)
Still get 360VDC for B+...I am thinking I dont have enough current to make this work? I figure 8x5ma = 40ma total thru tubes and flowing thru Zener arrangement.
The Zener is 5W at 100v so 50ma limit on the Zener, so I know am pushing it, but its not dropping B+...and I waited enough for the tubes to start... what am I missing?
550VCT, so 275VAC to Aikido board. Want to use 6922/6NP1 and see the B+ is about 100 Volts too high (currently at around 360VDC)...
So I am trying to use a 100V 5W Zener on HV windings to drop B+ (I have done this on HV for another amp tranny with CT and worked perfectly), but I do not have CT on this setup...so I put in two 1N4007 across winding with the zener (to "make" a CT)
Still get 360VDC for B+...I am thinking I dont have enough current to make this work? I figure 8x5ma = 40ma total thru tubes and flowing thru Zener arrangement.
The Zener is 5W at 100v so 50ma limit on the Zener, so I know am pushing it, but its not dropping B+...and I waited enough for the tubes to start... what am I missing?
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Remember, a zener gets installed backwards. Flip the polarity and check it again 😀
I'd put it on the B+ rail though.
I'd use a string instead of a single. Say 3x36V 5W... Also leave the leads long - they improve power handling.
FWIW running the Akikdo at 360V won't kill it. You just need to tweak some of the values of resistors etc.
I'd put it on the B+ rail though.
I'd use a string instead of a single. Say 3x36V 5W... Also leave the leads long - they improve power handling.
FWIW running the Akikdo at 360V won't kill it. You just need to tweak some of the values of resistors etc.
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I have 400v coupling caps was my worry...I actually saw that I hooked the primary to 115V instead of the the 125V tap, once corrected, that reduced the B+ a bit...and per your advice, I just left alone and modified the R12 resistors to get the plate voltages on 6922 down to about 180vdc...
Thanks!
Even you set 115v, the outlet is 120v in US, then you add up another 5v.
Try this, work fine with mine, no choke needs. Adjust R12 to get the voltage needs.
Mine is tube rectifier, I put the resistor there instead of choke, then adjust R12
Try this, work fine with mine, no choke needs. Adjust R12 to get the voltage needs.
Mine is tube rectifier, I put the resistor there instead of choke, then adjust R12
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I would just use dropping resistors. Put a cap after, say 10uf450V or 22uf/450V and you have nice ripple reduction. You could use one string per channel. I am not a big fan of zeners.