SU2200XLNET won't run on batteries

[Anonymous user]

I have a SU2200XLNET with what I'm 90% sure are good batteries that won't run off the batteries.  It sat unused for about 6 weeks due to dead batteries.  Replacements came in but sat for a couple of weeks before being installed.  It sat with no load for 12 hours to allow the batteries to charge.  Unplugging from power shuts it down immediately.  If unplugged, trying to power up from batteries brings all lights on for less than a second before shutting off.

I've got a meter and basic/intermediate electronic/DIY skill but I don't wanna go poking around those huge transformers without knowing where to look for the problem.  I don't have anything connected to the serial port but could probably do that if it provides useful diagnostic info.

All worthwhile advice appreciated.

[BillP]

The inverter circuit has most likely failed. I am currently debugging a SU2200INET unit with the same symptoms. Components of interest: R38, R43 (which may be crusty and drifted out of tolerance due to being undersized wattage), all of the 22uf 16v electrolytic capacitors, especially the ones around the heatsinks. If C34, C35 capacitors failed, transistors Q29, Q30, Q32, Q33 are likely bad, and the MOSFETs associated with them are usually bad as well. In this case, IC16 and IC17 might have died and so they are to be replaced. 

This info is based on my own experience and info found on the net, please attempt the repair only at your own risk. 

[Anonymous user]

I haven't cracked the case yet and not sure if I'll get the time for resistor/capacitor level repairs for a while.  Is there a "board replacement" level option?  If so, price & source?

Thanks! 

[BillP · Accepted solution]

In my country, it is possible to ask for a 'mainboard replacement' in the service center. Since the whole thing consists of one circuit board with 2 main transformers, it is usually just similarly expensive to replacing the whole unit altogether. Therefore I'd recommend to do the repairs by yourself if you have the skills and the time (DIY orientation). It is a lot less money but of course larger risk not working if not being done properly. It requires patience, precision, attention and diagnostic skills but if you succeed it feels quite rewarding for saving a quality product not manufactured any longer.