Electronics > Repair
Xantrex/Sorensen XHR 40-25 schematic?
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ifonlyeverything:
Pulled every electrolytic capacitor on the main PCB and they all tested fine on ESR meter: C22, C28, C35, C37, C39, C41, C77, C90, C100, C108, C289. Pulled Q11 and tested it on my transistor tester, looked fine.

I think my next step is to pull every diode, resistor, and non-electrolytic in this UC3842 circuit block and test for dead shorts. If nothing is bad then I'll pull just replace UC3842 and hope that works, because I have no clue what else it could be other than the transformer being bad (unlikely) or something pulling down the +18P rail (a ton of shit.)

Or maybe I could just unplug it from mains and inject +18VDC from my bench power supply at CR17 and see what kind of current draw I'm getting.
ifonlyeverything:
Pulled CR17 and F1, swapped R14 with a 10K resistor temporarily, and powered the downstream size of F1 with +30VDC with a 1A CC limit from my bench power supply. All voltages are looking nice and stable. Plugged in the secondary control board and the front panel, voltages were fluctuating and the front panel was visibly flickering. Unplugged front panel from secondary control board and voltages were still fluctuating. Looks like the problem is isolated to the secondary control board.  :)
coppercone2:
ohhh I see its a totally different form factor then mine. i thought it was the single unit high pizza box

the schematics look very similar. but mine had 0 capability for isolation unless you want to cut traces. All I could do is unplug the GPIB card. I did not think of that trouble shooting technique


I forgot to mention, do you have crappy sockets in there for op amps? Because one of mine had a bad socket for a op amp. they are not machine pin, it had some really dodgy ass leaf socket

pic1 confirms you do have the shitty sockets.




Just thinking about it, flickering is sometimes caused by bad contacts. On those cable harness too. But I can't think of how it would cause the vref voltage to drop down to 20%

if you fix it you might wanna replace them all for 10$ before you put it back together, so you don't explode something later on.



I had the linear one in that form factor, the only thing I renember about it before I threw it out
1) it had something like 5 transistors working together on the output stage for the big power transistor, that is a bunch of 'passives' (do hardly any work with current). One of them broke. I replaced all of them and it started to work. I over tightened a chassis screw and caused a bolt to fry one of them again because a spacer was missing or not engineered in. it fried something again. Then traces started coming off during rework and i threw it out. if the power transistor breaks the ones around it break too
2) one of the wires on the IDC cable (insulation displacement cable) broke and came out of the harness. Clever method to weld the wire to the connector but I don't like it. you can't really poke it back in there, whole cable needs to be replaced or a solder fix has to be made with a external jumper wire. the crimp tool causes it to cold weld to the pin fork. once that breaks it done. its like wire wrap, not a crimp. the crimp tool is expensive
ifonlyeverything:
Fed the secondary control board with my bench power supply, the 5V and 9V sections were fine. 18V and -18V had shorts, replaced the linear regulators U238 and U252 and the short went away.

Found out that main A3 board and the secondary A2 can have connection issues because the box headers aren't properly sized, meaning the pins will shift over 1 row... when this happens it will trip the auxiliary supply like before. Not sure if this caused the U238/U252 regulators to blow for the previous owner, but they did not blow for me.

I reassembled A2, A3, and the front panel and made sure A2-A3 connectors mated properly. Fired up the auxiliary power supply with +18VDC from my bench supply and it worked perfectly. All of the buttons on the front panel worked as expected, holding in V/I to set up a commanded V/I worked fine -- no drift in the numbers.

Re-soldered CR17, put F1 back in, swapped R14 for the 68K resistor. Reassembled everything. It fires up, front panel lights up, fans run, and there is an output voltage... but it's not working right.

I click in STANDBY and hold in V/I to set the V and I and the numbers will drift. They did not drift when I was powering it off +18VDC bench supply. I click out STANDBY to enable the output and I can hear a buzzing sound. Not sure if this is expected. Voltage refuses to go over 20V and it jumps around. Current limit is also acting strangely. It looks like the CC and CV limits are being obeyed but it just drifts around and won't stabilize. I'm using resistive loads.

Rear panel SW1 is in default configuration and I have J2 SNS- wired to the negative bus bar and SNS+ wired to the positive bus bar.

So... back to troubleshooting!  |O Will be sure to double check ALL of the sockets.
coppercone2:
ok but if the regulators were shorted it might mean that there was a shorted load connected to them and that is why they maybe over heated and died after a while. like one of the op amps. or a cap shorted out and went open.

idk how to check the sockets though, replace. I had this bullshit where I pressed it in and it would work. then after i reassembly chassis it stop working. I open it up and push on chip it works again.

its like playing peek a boo with a troll

if you think you fixed anything by messing with the socket just replace the damn thing, its not reliable, i think you can get 30V randomly if the wrong socket goes up. meaning bye bye load (and a reason to fuse your prototypes even if your on a lab suply). i bought like 20 fuse holders and a whole set of fuses so I don't have to worry about malfunctioning opamps burning things

but thankfully when my op amp socket acted up, it dropped down to 3V max. idk how it decide on which set point to fall down to. maybe its built so it goes down to a low level if it fails, but I can't verify this... also it did once go to 17V when set to 15V I think, which caused a fan to burn out (otherwise tolerance circuit)



if your setpoint is acting up, that is either a reference drifting (it all based on reference), resistor divider or op amp malfunctioning.

or it might be nooise from a broken capacitor causing circuits not to settle (filter went haywire)


intermittant connector might cause things to dance around too. 14x+ magnification and a healthy dose of paranoia help find this problem


I think that really bad connector develop sensitivity to current load (resistance changes with load) and probobly temperature, which causes very minor motion due to expansion, makes it ACT up. *


*could it be a bad pin on a op amp making a very high impedance that ends up effecting the setpoint of a voltage circuit?


when your done fixing it, hook it up to a high current load (i.e. big ass resistor) and leave it on for a while to make sure it won't malfunction after 2 minutes and make danger



I have a feeling these power supplies probobly have distributed damage (lots of minor wear and tear) and that replacing stuff generally helps them. i think they basically get generally clapped out


when you screw in the pCB it gets flexed and stretched a little bit. might work when its out then stop working when you put it in. this is mechanical damage



the other thing you can do, recommended, is to reheat every solder joint on it, but it needs to be well fluxed. this means you need to do a big ass clean up after wards. I would do it for a 1kW supply though. but renember it needs to be well fluxed, and that means big cleanup. if you just do it dry to make it easy to clean it might not help things. like probobly a few hours of scrubbing to get it really nice, and you possibly loose some text and component indicators if your not careful. if you carefully apply flux, on both sides, and clean as you go, its not much worse then other penal labor >:( . And heat can reveal problems, so you need to grid the board and test in between doing squares if you want the most benefit and highest success rate from this method to say.. maybe identify a bad bond wire or something from heat. where it goes from intermitant to broken. if you do it all at once you can get a fix, but you won't know where.
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