Trust an old SmartUPS 1400?

[Anonymous user]

Hi,

i've got an old SmartUPS 1400 (a white unit, not the new black ones) for free. Batteries are dead.
I've built a test pack and the UPS turns on and runs fine. Building a replacement Battery Pack should be quite cheap.

My questions is: Would you still trust this old UPS? I would clean it and build a new battery pack for it.
Model Number is: SU1400RMI2U
Serial Number is: AS004321xxxx -> So I guess it was build in 04'th Week 2000?

Not going to run anything mission critical, just a homelab Server, but I would hate it to see this thing burning down my house.

Thanks!
erfus

[Anonymous user]

I would. Older units are better built. I have an old Smart UPS 1500, when the batteries died I found a newer model with USB interface. Cool, I think, I now use the newer model as backup, turned off, under the older model.

Why?  I have also a ham radio, ham radios are very fussy with electro magnetic interference. The older model, emits no noise at any frequencies, when I turn the newer model on it is a hiss at 5/5 on all frequencies that obliterates all but the strongest stations.

[Brad_C]

It's 20 years old now.

My house UPS :

apcaccess | egrep '(^MODEL|^MANDATE|^SERIALNO)'
MODEL : SMART-UPS 2200
MANDATE : 01/17/00
SERIALNO : GS000400XXXX

It's had a bit of a tickle-up. Biggest risks on the older 3rd Gen SU are dried out bootstrap caps in the MOSFET drivers causing shoot-through and smoking the MOSFETS, and the reference divider drifting such that the battery charge voltage creeps up and cooks batteries.

Personally the late 3rd gen units that are still through-hole components are some of my favourites.

[Anonymous user]

Yes, I'm a ham operator as well, but no station at home because of a very bad QTH for HF.

But you're right, my new UPS has a constant inductor hiss, I guess it comes from the battery charger, the old one just has a big transformer and is silent. Thanks for your reply!

[Anonymous user]

Hi Brad,

thanks for your reply.

Changing out the caps is one thing I thought of. I didn't disassemble it completely yet, but it seems that they are just a few. So maybe it would be more safe if I would change all the caps as a maintenance.

Guess I'm going to write a parts list and change the caps. I will monitor the voltage divider via the RS232 interface, hopefully its still fine.

Did you change anything else apart from caps in your tickle-up? Guess theres nothing else in there which could go wrong.

Thanks!

erfus

[Brad_C · Accepted solution]

Just double check your actual battery charge voltage, not whatever the UPS reports over the RS232.

Most of the failures are in the blue 22uf caps. There are really only a couple that probably could do with changing. When I got mine on first power up one of the MOSFET drivers failed and caused a bit of silicon carnage, so I replaced a pile of MOSFETS and rebuilt the drivers.

About 5 years ago I gave it a big birthday and replaced most of the electros, 2 resistors in the MOSFET high side driver, all the relays and all the MOVs. Yours is a 24V model, so no need to do the resistors.

Most of the electros I pulled had a high ESR. The 2 in the high side MOSFET driver were really high (like > 5 ohms), but on the 48V units they sit on part of the board that gets pretty warm. Nothing else was shockingly bad. I did the MOVs because they'd already had 18 odd years of absorbing spikes, so I figured they were due replacement and as I was already ordering relays it was less than $10 to do them also.

I did the relays because I was getting a "AVR relay weld" failure. That turned out to be the input voltage sensing transformer, but by the time I found that I'd already replaced all the relays.

Probably over-capitalised, but I know all the "wear items" are new and I won't have to worry about it for another few years.