URGENT - Repair assistance needed - MATRIX 5000 failures

[BillP]

I have posted before on this issue, but it has become urgent.

I need to speak with ANYONE that can assist with diagnosing the failures we are having on both APC MX5000xx units.

One unit has a charger failure, the other flops between MAIN and BYPASS RLY FAULT.

I would be happy to pay someone for their time to assist us.

[BillP]

Hi,

Try CoastTec.com They repair single phase APC UPS. 

[BillP]

Yea, I already called them and I'm hoping they can help.
So far they say they don't anymore, but the sales guy said he would try to connect me with someone.

HOWEVER, if there is ANYONE out there that feels confident they can assist me with determining where on the board I can look for diagnosing this issue, please chime in.

[BillP]

Hello, 

From what I read in your previous topic, you already disassembled and reassembled them, so I assume you have some electronics skills to do component level repairs. The following things that I am going to write come from my personal experience with APC units in general, and info that was read on the net. Although I have a disfunctional matrix unit, I did not yet have time to disassemble and repair it. Relay issue: I'd go and check electrolytic capacitors on the control board where the relays are located. They are bound to fail after decades of operation, especially smaller capacitance ones. If DC power supply becomes unreliable, it might cause this issue even if the relays themselves are OK. 

Battery charger failure: what is the exact symptom? Error message on LCD, and no charging voltage measured at battery pack? In smaller apc units, battery charging is done using UC2843 IC, I'd start debugging around it. 

[BillP]

Thanks for the advice.

Regarding the battery charger, yes - the LCD said that the charger had faulted.

I can reassemble it and check the voltage to the batteries, but unless you feel it's likely a false alert, then I'm willing to trust it.
I'll get started on the testing process and get back to you, but would you be available to discuss this as I proceed through the boards?

Also, for the community, I'll post the progress and findings here as they happen.

[BillP]

I'm going to share some images in this thread for everyone to get on the same page as we progress.

I cannot locate the IC you refer to (UC2843) though.

[BillP]

As I try to fix the bypass/main relay fault, where is this relay located?

Is it the large SCR? (Remove in my previous images for testing, which I have 3 of these components and they all test identical, so I assume they are good.

[BillP · Accepted solution]

It seems that matrix has 3843 instead of 2843. It is the one marked CS3843 sightly offset left of the small signal transformer. The reason I'd check for battery charge voltage is so that we don't try to fix something that is not broken & get more specific about the issue. The voltage measurement at the battery pack could help to determine the nature of charger failure, eg. too high/too low/nonexistent charge voltage or false alarm. 

I don't have any schematics for the unit, so I cannot tell which relay is the one. As per my previous post, I'd simply replace all the electrolytic caps on the board (with same uF rating, slightly higher voltage rating of the original capacitor), maybe also check the semiconductors in the vicinity of the relays, then try and see if the problem is gone.