I commented on the “B+ Power Supply Options, Upcoming Project Release, And More!” video, and said:
I built a small 300V power supply while I had a K2-W op amp on order.
Do-oh! It needed two supplies (+300, -300).
So, screw it. I couldn’t find any new or used DUAL HV power supplies in my budget, and often I’d need B+ and a screen voltage, etc. So, I put THREE HV power supplies in a box with a filament transformer to boot. Made my life quite easier. I imagine I have a little over $100 (US) in it.
The circuit uses 1:1 isolation transformers, voltage doubler, LR8, some fat caps and an FET, with a transistor to drop the gate voltage if the current goes over 10 ma. There is a switch to disable the current limit for AFTER the initial debugging is done if more current is desired. Also, voltage and current display on all three channels.
The transformers, capacitors, V/A readouts and 0.8Ω shunt resistor were purchased – all other parts were on hand.
And then, Ovi4 suggested:
Hmm, it sounds interesting. To show-case your PSU (IMHO) the best way to do it is on MCL’s website removed link
So, here it is.
Notes:
I didn’t want to spend time building three, isolated 5V supplies for the V/A meters, so I broke open and soldered onto the main board 3, $1, 5V USB bricks.
The unlabeled switch on the “Front” image turns on/off the filament supply.
The single-sided circuit board was CNC isolation milled on the foil side and toner-transferred on the silkscreen side.
The individual on/off switches don’t actually turn on the volts unless the “Enable” switch is on. In that way, I can turn on all three (or two or one) supply(ies) simultaneously.
The Hi/Lo switch switches in a 39Ω shunt resistor to make the transistor drop the FET gate if the current goes over 10mA. (Google said that wouldn’t kill me). Otherwise, the current shunt is 3.9Ω and it will bite a lot harder! The voltage will sag if you ask for too much. This supply is not for testing power amplifiers or output stages. It’s for all the fun stuff up front, and does it somewhat safely. Of course, If you let the magic smoke out of the FET, you get unregulated, capacitor-backed, 370 volts, killing current, so if anyone knows a better way to shut this thing down if you cook the FET, let me know.
A very nice feature, is that with the Enable switch off (or a channel switch off), you don’t have to wait for the bleeder resistors to drain the caps. They are on the other side of the switch! Only if the cover is off of the unit is voltage presented with the switches off.
The V/A meters are $6 jobbies from Amazon but read to 10A. I removed the 8Ω shunt resistor and replaced it with a 0.8Ω. These are SMD parts. Fairly tedious (that’s why I haven’t fixed the third channel amps display – the magic smoke got out of it and I lazy’d out). The decimal place is wrong, but the price is right.
The case is an old set-top box from the 1980’s I got as surplus (NABU Adapter).
And yes, If you series the outputs, you can get a KV out of it at 25mA or so.
Documentation at: removed link
Removed Link was http (no s) colon slash slash www dot visioncomm dot net slash HVPS
(Paul, please fix this!)
Hi, I see that your post has finally showed up (minus) the link. Well,….on this website apparently the admin has very strict rules that filters out certain types of links that are suspected to promote spam etc. I do not know the full extent of the let’s say “algorithm” but if you’re having trouble with posting the links to your picture hosting service provider is easier then, to switch to the tried and trusted/approved picture hosting provider such as IMGUR. It just so happened the MCL has “freshly” posted a picture based “how to” showing the “step by step” procedure with a simple free account for Imgur. here is the post:
https://mrcarlsonslab.com/community/general-chat/uploading-pictures-to-this-forum/#post-1611
Alternatively, there are some other picture hosting services that worked for me in the past. One is Google and another is called postimages.org where I didn’t even needed an account . it worked straight “out of the box” :). and by choosing the option Direct link the picture will be directly shown in your post (instead of just a link to it) Here is an example:
