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Check out posts with pictures in other threads - no one else seems to have any issues with pic quality. Give it a go - you have nothing to lose and, potentially, a lot to gain.
well as i mentioned in my first post,i dont know if the schematic i posted is actualy is to my actual psu,its just one someone suggested to me,it seems any schemaics to my psu dont seem to be documented,the resistor has been cooked that you mention,im waiting for the new diodes to arrive,i will then test after fitting them and go from there,i am recovering from a foot operation at the mo so cant walk so everything takes 10x longer as even getting too my workbench is a major task.
The schematic doesn't match the circuit board for one......
The basic principle is simple - the standard series regulating circuit (built around a load of heatsinked power transistors) is fed from a DC supply whose output itself is determined by the range in use. As the output (selected) voltage rises the comparators switch secondaries of the transformer to the relevant bridge rectifiers to derive a DC source to be regulated - this is done by relays to prevent having a large voltage difference between input and output (when you have a low voltage set at the output) to reduce power dissipation in the bypass transistors.
Accordingly they use relays to select the transformer taps and the diode bridges develop the DC to feed to the smoothing capacitors.
The board you show seems to have TWO sets of bridge rectifiers and relays so perhaps your PSU has two channels? If not then they may be paralleled - either way there is little to go wrong on the board itself but given the power levels it would be foolish to change individual parts of 'sets' i.e. one diode in the bridge. Such diodes (or, as an alternative, a POTTED rectifier block as shown in the post above) are cheap enough to fit new all round. It's 'criminal' to not do this!
Relay chatter may be as a result of damaged contacts - an overload/fault 'somewhere' has blown the diodes and the high current fault cndition probably took out the relay contacts too so when it tries to develop a voltage for the regulator circuitry it's failing to deliver it and dropping to the next level before trying to switch back again - repeatedly, hence the chatter.
As with the diodes and the high current situation, the relays are cheap enough to replace ALL of them - compared to the cost and usefulness of a working supply it's another 'criminal' act to NOT change them!
So, new diodes, new relays to start with. Test the board to ensure it delivers a DC voltage by activating the realys manually (shorting wire to power them up) then move on.
Check the series regulating transistors (big jobbies on the heatsinks on the rear of the kit) - I'm convinced one or more are shorted. You can run the power supply from 'any' transformer and just ONE working bypass transistor to prove its operation before working towards getting the full current capability.
If the schematic/component designations match the board then we can move forward else we'll have to take this step-by-step as above.
The basic principle is simple - the standard series regulating circuit (built around a load of heatsinked power transistors) is fed from a DC supply whose output itself is determined by the range in use. As the output (selected) voltage rises the comparators switch secondaries of the transformer to the relevant bridge rectifiers to derive a DC source to be regulated - this is done by relays to prevent having a large voltage difference between input and output (when you have a low voltage set at the output) to reduce power dissipation in the bypass transistors.
Accordingly they use relays to select the transformer taps and the diode bridges develop the DC to feed to the smoothing capacitors.
The board you show seems to have TWO sets of bridge rectifiers and relays so perhaps your PSU has two channels? If not then they may be paralleled - either way there is little to go wrong on the board itself but given the power levels it would be foolish to change individual parts of 'sets' i.e. one diode in the bridge. Such diodes (or, as an alternative, a POTTED rectifier block as shown in the post above) are cheap enough to fit new all round. It's 'criminal' to not do this!
Relay chatter may be as a result of damaged contacts - an overload/fault 'somewhere' has blown the diodes and the high current fault cndition probably took out the relay contacts too so when it tries to develop a voltage for the regulator circuitry it's failing to deliver it and dropping to the next level before trying to switch back again - repeatedly, hence the chatter.
As with the diodes and the high current situation, the relays are cheap enough to replace ALL of them - compared to the cost and usefulness of a working supply it's another 'criminal' act to NOT change them!
So, new diodes, new relays to start with. Test the board to ensure it delivers a DC voltage by activating the realys manually (shorting wire to power them up) then move on.
Check the series regulating transistors (big jobbies on the heatsinks on the rear of the kit) - I'm convinced one or more are shorted. You can run the power supply from 'any' transformer and just ONE working bypass transistor to prove its operation before working towards getting the full current capability.
If the schematic/component designations match the board then we can move forward else we'll have to take this step-by-step as above.
Show a pic of the bottom side of the board too please!
im bedbound at the moment after a operation on my foot,im waiting on the replacement diodes,i wonder if the shorted diode was supplying a sort of charge pump for a negative rail for the opamps,hence the 3volts ish minimum output and the vmin trimmer having no effect,as the hyland psu used to get the -ve rail for the opamps?.
some more pics
and another pic
and the final pic
yup had my big toe joint removed and heel bone cut and refitted with screws,so stuffed for another 8 weeks,been crawling on my knees but now they are raw and sore,happy days lol.luckily my bench is only about 12 feet from my bed but still a big effort to get there.get well soon martin,73 m3vuv.Me too, I somehow broke my ankle. But I am a couch potato with TV films now!
Martin
Yours sounds serious, mine is stupid!!
I had a gout attack and didn’t realise I’d broken it!.
You too get well soon.
Martin
Lots of paralleling on that board. You can see how the relays are used to switch between taps on the secondary and the diode 'packs' along with the smoothing capacitors are connected in parallel. It should be very straight forward to apply 'any' AC voltage to that board to trace the resultant DC output and switch the relays manually.
The board could even be reverse engineered to get the full schematic quite easily too but it's not really necessary in this case.
If you don't want to go to the expense of the proper replacement diodes (although you should) then even fitting some basic 1N4001's would suffice to 'prove' its operation.
Unless I've put my foot in it.........
The board could even be reverse engineered to get the full schematic quite easily too but it's not really necessary in this case.
If you don't want to go to the expense of the proper replacement diodes (although you should) then even fitting some basic 1N4001's would suffice to 'prove' its operation.
Unless I've put my foot in it.........
