ICT 12012-12BC repair

[CapLeaker]

I am starting this thread for a ICT 12012-12BC repair on my bench.
It's a nice little 13.8V, 12A PSU with a built in battery backup / charger. Those are quite rare, so I like to keep them going. Besides the repair, it gets a full recap, since it is a unit from 2004, running 24/7/365.
Finding a schematic on the net is equal to none for the one with the battery charger. However the tech guys at ICT are awesome, dusted off some old files and sent me the schematic! Again, many thanks to ICT's tech department!

Complaint: Light on the switch is on, unit does not turn on properly and the output power is sitting at 2.8V. The display isn't working and the unit didn't switch over to the battery backup.

The repair:
Open the PSU up and I don't see anything at all visual. Since the PSU is working somewhat sitting at 2.8V, the problem has to be with the feedback circuit or a vref circuit. If there would be a bad PWM, there would be nothing at all. Put the hot air gun on an the voltage would increase to like 6V as soon as I went over the opto isolator. Bad opto? Wrong! So I decided to socket the two LM324 IC's and quickly figured out by leaving certain pins out (pin 5vref or pin 7output to the opto) of U6, that the PSU turns on! Well sorta... I don't have any regulation and it would sit there at 15.6V on the output. After that, I needed a schematic to figure this out. Well, a glance at the schematic, there was a little 78L05 (REG1) regulator in the vref1 circuit I have trouble with, with only 1V coming out. Put a new regulator in, and a new 2N2222 transistor (Q7) I found to be bad.
Q7 isn't at all in the schematic for some reason, but it is between the output filter capacitor and the big relay.

Result is, that I have a working PSU with a battery backup that goes back in service after a full recap!

Pictures and schematic to follow.

[CapLeaker]

Re: ICT 12012-12BC repair

Here are some pictures and a couple of schematics for the ICT 12012-12BC power supplies.

[sam_sam_sam]

Re: ICT 12012-12BC repair

Very nice repair

Very interesting how you troubleshooting and the way you figured out what was wrong with it

Very interesting way that this battery charger is setup in that it uses a micro controller and type of components that it has in it

What I find interesting is that it so many chokes in it I am wondering why

Good work

[sam_sam_sam]

Re: ICT 12012-12BC repair

Finding a schematic on the net is equal to none for the one with the battery charger. However the tech guys at ICT are awesome, dusted off some old files and sent me the schematic! Again, many thanks to ICT's tech department!

I have to agree with you hole hardly about this fact

It is very hard to find a tech support person willing to go out of their way to help you and give you schemes for the item that you are working on or they are willing to walk you through how and what to check to figure out what wrong with the device

I also appreciate the tech department for ICT they also in my book

[CapLeaker]

Re: ICT 12012-12BC repair

Sorry, been occupied with old Motorola Micor repeater squelch cards and a few other things. These were an interesting repair too. Anyway... switch mode power supplies can fail in a weird way. These failures are hardly documented if something failed like this one. It’s more to encourage to stay with it and try to solve the problem a different, more logical way.
This power supply is for comms duty and ICT wants to keep RF out of the PSU as much as possible. These are over engineered for this purpose and for commercial use, if you compare it to other PSU’s. But they do work like a charm, rare failure rate.
ICT literally dug around and dusted off some files for me and that was all I needed. It’s nice to see a company these days to stay behind their products like that.