Well, the boards are in, but I don't like the results -- all of the work is done by the 1K resistor -- and if the B+ on the input rises to, say, 400V the current limiter formed by the LM317/120R resistor seems to fail at its job and we start to get white smoke. Kind of like the old joke -- looks good feels bad (1). Even without the filter caps, and extensive zener filtering the output looks very clean indeed, but it just doesn't regulate. I also had a design error which was my fault -- this was easy enough to correct. A couple folks sent $ to my PayPal account which I have returned. I don't want to disappoint.
(1) This joke is not to be repeated in "pleasant company" and I repeat it not here for fear of the sin bin.
(1) This joke is not to be repeated in "pleasant company" and I repeat it not here for fear of the sin bin.
Yes I'm one of those....
Hello Jack,
the mistake was in the layout or in the circuit?
Since I've bought (besides the PCBs that were refunded for) also the BJTs to build this regulator, I'm still willing to use it, even if only on veroboard.
Please advice.
Andrea
Hello Jack,
the mistake was in the layout or in the circuit?
Since I've bought (besides the PCBs that were refunded for) also the BJTs to build this regulator, I'm still willing to use it, even if only on veroboard.
Please advice.
Andrea
I rewired with BU208A instead of the MJE3439 -- once the devices get cooking (I see about 25 ma out of the power supply -- 12 ma for the zeners and 13 ma for the load resistor) the voltage creeps up from 284 to 308. I am using 5 watt zeners so they aren't getting fried.
There was a small error on the board -- not difficult to fix but it p*sses me off that I made a stupid mistake -- too much hubris. I wanted to move the zener string to a location where it would get some ventilation -- certainly not a problem if you are using a TO-3 pass transistor.
I have your address and will send a pair of boards -- let me know how you do.
There was a small error on the board -- not difficult to fix but it p*sses me off that I made a stupid mistake -- too much hubris. I wanted to move the zener string to a location where it would get some ventilation -- certainly not a problem if you are using a TO-3 pass transistor.
I have your address and will send a pair of boards -- let me know how you do.
An externally hosted image should be here but it was not working when we last tested it.
i had used some EBC transistors, the MJE3439 should fit OK (as Rich points out - MJE3439 is ECB). Will change the picture as soon as I regain access to Adobe Photoshop -- but I fried my main computer last week.
Here's a graph of V(in) X-Axis) vs V(out) -- and Zener Current (Left Y-axis) -- etc., etc.:
An externally hosted image should be here but it was not working when we last tested it.
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