Maybe you guys can point me in the right direction..... I etched a board for the maida reg posted a page or 2 back. So, I built it up using the parts specc'd here. On the bench with my HV PSU, I put 320V into it, and I get an adjustment range of 288-316V (under no load). However, when I put this into an aikido preamp, which is pulling 33mA at 300V, I get just a few volts of adjustment, maybe 5 or so.
Something must be preventing the 317 adjusting, or acting as a current choke or something?
Fran
Something must be preventing the 317 adjusting, or acting as a current choke or something?
Fran
Yep, ~5v or so.... just being clear:
Connected preamp & measured current draw with no maida - supply voltage is 300, current draw by the aikido (4 x 6sn7) is 33mA). Inserted maida, I still have 300V from the PSU, but the output of the maida is adjustable from say, ~292-297V or so when loaded.
So input V with 33mA is 300V, output adjustable from ~292-297/98.
Is that too much current draw for a maida?
Fran
Connected preamp & measured current draw with no maida - supply voltage is 300, current draw by the aikido (4 x 6sn7) is 33mA). Inserted maida, I still have 300V from the PSU, but the output of the maida is adjustable from say, ~292-297V or so when loaded.
So input V with 33mA is 300V, output adjustable from ~292-297/98.
Is that too much current draw for a maida?
Fran
Max current draw for the reg is dependent on the pass transistor. I used one of those boards for an Aikido I built for a friend of mine, similar current draw, and used a TIP50. No problems, reg works perfectly after three years in the field. So... really, you're not regulating at all, which points to a more fundamental problem.
Did you drop the value of the set resistor to get things centered at the nominal voltage (which ought to be at least 25V below the input voltage)?
Did you drop the value of the set resistor to get things centered at the nominal voltage (which ought to be at least 25V below the input voltage)?
You could certainly drop that value; 47k would be more appropriate if you're shooting for 260-270V nominal. But first, doublecheck the wiring- you're not getting any regulation at all, which makes me suspect the hookup. And make sure that you haven't inadvertently escorted the pass transistor through the Pearly Gates- with a multimeter, it should show no shorts from base to emitter nor collector to emitter.
Nope, no joy yet. I replaced the 317 and the tip50, and reduced the set resistor to 40k and still get no regulation. Ran out of time tonight, need to go back and check everything again. All the resistors measure ok though, and if I check the zener on a dmm I get 0.667v drop across it. Must be something else arseways.
Sy, if you get a chance check out James Vincent mcmorrow who is in Austin at the moment.....
Sy, if you get a chance check out James Vincent mcmorrow who is in Austin at the moment.....
Well it is easy alright! Something I had a red face over before was to etch a board mirror to the way it should have been....... so everything fitted and looked ok, but of course didn't work! Not ruling that out here!
The dead bug style maidas in my rld amp have been faultless for a few years now so it's obviously something I've done!
James Vincent is up next on my playlist after some john martyn tonight. He will be playing at a place called the big red sun I see from his facebook.
Fran
The dead bug style maidas in my rld amp have been faultless for a few years now so it's obviously something I've done!
James Vincent is up next on my playlist after some john martyn tonight. He will be playing at a place called the big red sun I see from his facebook.
Fran
You can use a separate regulator for each screen- it's not like a Maida costs much...
I understand the idea of doing individual regulators. I'm wondering if it is possible to have the screen regulators track the balance and adjust for zero offset. Alternatively, how much drift in set point happens in an EL-34 or EL-84 or KT-77? I looked at the TENA, I cant figure out what goes where or how it works. It is so badly drawn and laid out. I also don't think it needs to be that complicated to do the job.