Mike McLane
Active member
Ah, replace the 220K w/ a 250K trimmer!?!? Good idea! Sometimes I'm slow on the uptake. Unfortunately I don't think there's enough real estate on the HV board to insert the Trimmit.
High Voltage Power Supply
- Thread starter Mike McLane
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vigilante398
Authorized Vendor
That's a fair point, I was aiming for small footprint, so it's fairly tightly packed.
Mike McLane
Active member
Got the parts in to modify the trimmer for the HV board. It appears that the "top" side of the 220K (next to the word DAUGHTER) connects to the 5K trimmer. Correct?
vigilante398
Authorized Vendor
Yup, that's correct.
Mike McLane
Active member
THX! MERRY CHRISTMAS!!!!!
Mike McLane
Active member
Replacing the 220K with a 4K7+220K "Teepee" and the 5K trimmer with a 1K makes things MUCH easier to dial in.
Mike McLane
Active member
Will this unit power two 12AX7's?
BTW, don't forget the cad file for the PA drill template. Thx.
BTW, don't forget the cad file for the PA drill template. Thx.
vigilante398
Authorized Vendor
Yup, absolutely. I've used it to power as many as 3 without problem.
And sorry about the cad file, I'll get that over to you now.
vigilante398
Authorized Vendor
The input for the L7806 comes from the 9-12V input, not from the HV output. It could potentially get warm depending on how many tubes you're using it for as each tube will present a load of close to 300mA, but L7806 is rated for a 1.5A output.I got this HV PSU from musikding. Maybe a dumb question but doesn't the 7806 need a heatsink? doesn't it heat up considerably especially at 350v? Just checking
Cheers
Sono
The amount of heat generated can be approximated by (Vin - Vout) * Iout. So on a 9V input powering a single tube's heater we have (9-6) * 300 = 900mW. If you're really abusing it running 4 tubes on a 12V input (not recommended) you're looking at (12-6) * 1200 = 7.2W, and that will get very hot.
I'll use max 2 tubes really so it'll be fine. I could always screw it to the enclosure
)))Thanks Nathan
Cheers
Sono
Mike McLane
Active member
Slept a few times since we went thru this. . .in order to make the 250v voltage easier to dial in we sub'd a 4k7 in series with the 220k for R3, but I can't recall if the captioned comment meant that I REPLACED the 5k trim with a 1k . . . I think so. Pls confirm.
Mike McLane
Active member
Reread. . . yeah, that's what we did. For the Emily Latella fans in the audience. . . . NEVERMIND
matmonster58
Active member
Do you think this power supply would work in some of rob Robinettes micro amps. I think they make a few watts.
I know you're power amp pedal is similar to a firefly amp which I believe is pretty similar to rob's stuff
I know you're power amp pedal is similar to a firefly amp which I believe is pretty similar to rob's stuff
vigilante398
Authorized Vendor
Depends on the amp, but potentially. I have one running a 3W amp right now and it's doing great.
Tassieviking
Member
I would love to see the schematic on that 3 watt amp, I would love to build me a small tiny amp and run it from your HV power supply.
I think I mentioned it in a PM I sent you that I would love a tube amp pedal for home practice that I can run from the Bassdude or Nobelium, 1 watt would be great but 3 watts would really rock.
The Hammond 125A TX should easily easily fit inside a 1590BB2 box.
I am really falling for your pedal designs, I have to watch it so I don't become a pain in the ars..... eh ...ear.
Mike McLane
Active member
Just finished an experimental build on a breadboard with the high voltage SMPS mounted on a side panel. Last time I used it got 250vdc on the nose, but now I can't coax more than 167VDC out of it. Any thoughts?
vigilante398
Authorized Vendor
How many of what type of tube are you running? How are the tubes biased? In short, what does the circuit look like?
Mike McLane
Active member
It's the power amp stage only of the Robinette RR763 Micro. . . a 12AT7 & 12AU7. I'll "push" it with the Particle Accelerator. I'm trying the SMPS in place of conventional PSU/rectifier/power tranny, etc. I'm testing the output directly off of the + lead of the SMPS.
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Mike McLane
Active member
Hmmmm? . . . got up this morning and took the tubes out. I get 370v out of the PSU. The 12AU7 gets much warmer than the 12AT7. If I read the data sheets correctly it also pulls tons more current (20mA?) than the rest of the 12A*7 family (5-10mA?). If 30mA is near the ceiling for this unit (as Vig398 guestimates) then that probably tells the tale. I read a post re: use of SMPS's for powering Class D amps and they cautioned against marginally sized units as the less expensive units experience significant voltage drop when they get anywhere near their max current capacitites. I want to recall that their example showed a 24v-3A SMPS powering a TPA3116 (which needs around 3A) and the output voltage dropped to 17v.
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