Afternoon all,
I have here an old and heavy PSU unit, apparently made by ITT and is model MP10B V
It seems to be a standard 723 design - well almost, however before I wreck my brain & eyes on tracing the pcb out. does any one have any info on it?
I've spent several hours google-ing for details but none to be found (either as text or images).
I've put photos of the unit here:
AGGGH
It was not supposed to post that - Let's try again
Many thanks in advance
Regards
Avpx
I assume it's not working. So you could start replacing the parts, I'd remove the 723 and put a socket in to start with.
These units IIRC were made by ITT/STC Harlow around 1966. They have essentially the same linear analogue circuitry as the Advance PSUs of the same period. From memory( a bit shaky these days) , the regulators were 3055? transistors. The circuit was a transformer, bridge rectifier, large reservoir capacitor, Zener reference diode, buffer amplifier and series regulator. With load and over current sensing. Can't remember any more details, but the circuitry was common to a number of manufacturers.
Oh ta! This one has a 723 and associated circuit - so a bit posher than just a zener :-) (and it's been hacked by someone)
It has given me a few more search terms to try out ...
I may be some time
Avpx
I would split the problem into two parts. Firstly all the power transistor effectively forming one dirty great emitter follower. So put a modest load on the output - a filament light bulb say and drive the base of the mega emitter follower with a pot connected to the input DC supply. you should be able to vary the output voltage with the pot. If any of the pass transistors are short circuit the lamp will be at max output all the time. Assuming voltage out changes then somewhere each transistor should have a small emitter resistor to facilitate current sharing. Measure the voltages across all these and confirm they are around equal. if some are different then the relevant transistors are not sharing and maybe open circuit say.
Part 2, With a current limited bench supply, you should be able to fire up the control board with reference to a 723 data sheet and close the loop around that in isolation and prove that will regulate small loads just using its diver transistors. Obviously you will have to re-do the solder joints on those pins to get any sense out of it. Take a logical approach, keep notes on what you are doing and you should have a good chance of sorting it out. 723 regulators are not rocket science but there are lots of opportunities to prang it especially with lots of charged up uFds if you are not careful.
I'm sure there are lots of 723 datasheets/application notes online but if you are really stuck I could scan one for you.
Watch out if they implemented foldback current limiting. It can lead to some strange effects ie errors lead to the regulator not starting up etc.
Have fun
Not trivial to take apart but I have the feeling it 'works'. Must find a
24V light bulb!(lux)
As I say I get a nice stable 24V (variable from about 21V - 25V with the pre-set I've V on the pcb)
Got one ta! and a couple of circuits as well.
I suspect that may be why it has been 'bodged'
Many thanks
Avpx
(lux) Yes I know 2x12V is series!
Meccano brackets??
Now you mention it - yes I think you may be right, so ...
Not the original PCB?
or ...
?Oh well onward
Many thanks
Avpx
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