UPS beeping continuously

[stj]

Re: UPS beeping continuously

put the right resistor in.

i suspect it's a voltage divider so the microcontroller knows if the battery is fucked.

[Dannyx]

Re: UPS beeping continuously

Also someone asked about the caps - no I haven't replaced all of them. Just the small one near the 7812 heatsink so far.

[stj]

Re: UPS beeping continuously

ooo... a life on the ocean waves!
very pretty.

[Behemot]

Re: UPS beeping continuously

Most of those which do not have independent mains power supply usually draw power from the transformer secondary to charge battery and also the comparators and processor, through (usually) linear regulator (as that is cheaper). I think the transistors on the heatsinks act in part as regulators too as the main transformer output must be havily dependent on actual mains voltage etc. That would also be consitent with this The accumulators also smooth the output, that's why the large crap GP Jamicons in this section usually last forever, on the other hand them accumulators are under more stress (also being in plastic chassis with no cooling) and do not survive very long.

[Dannyx]

Re: UPS beeping continuously

Yes it does sense something, no doubt about it. Either the battery level by comparing it to a reference, or simply the presence of the battery, since as we all know these small UPSs don't fire up with JUST mains, though I'm not sure it was "planned" like this, or it's simply because the mains doesn't actually power the circuitry and it's powered by the batteries all throughout.

[Behemot]

Re: UPS beeping continuously

Oh, right, that's kiloohms. So not current…but it measures something, no?

[Dannyx]

Re: UPS beeping continuously

Isn't the value a bit too high to be a shunt ? Also, isn't a shunt resistor a very low value resistor placed between a load and a supply to induce a drop that can be measured ? I need a refresher

[Behemot]

Re: UPS beeping continuously

It's most likely just a current shunt.

Have you replaced the small caps?

[Dannyx]

Re: UPS beeping continuously

Nothing before the resistor - it comes straight off the battery. It forms a resistor divider with another resistor on one pin of the IC...sure hope IT didn't get fried somehow. I know for a fact one of my Arduino ProMinis suffered this: it programmed fine and it worked, but two of its pins died and no longer went "up".

[stj]

Re: UPS beeping continuously

test other parts related to the resistor incase it damaged something up/downstream.

[Dannyx]

Re: UPS beeping continuously

Ok, resistor replaced. I could be on to something here, because now there is some clicking and it tries to stay on (backlight comes on, which it didn't do before) but immediately stops and displays FAULT again...the resistor is not quite the right value. The original was 499Kohms and all I could find were 510Kohms....it could be because of that or because of some other completely unrelated cause. Still, it did change something....not sure if for better or worse

[Dannyx]

Re: UPS beeping continuously

The board looks similar indeed, although the Sweex has a coil on there (GT820) next to the bulgy cap between the heatsinks which my SPS doesn't. I guess it's part of a switching regulator as opposed to a linear 7812.

[Behemot]

Re: UPS beeping continuously

I think it's pretty much the same https://diit.cz/clanek/sweex-pp210-t...e/oprava-pp210

So the output will be

[Dannyx]

Re: UPS beeping continuously

There's a man who got pissed off by UPSs if I ever saw one Yes, they are absolute pieces of rubbish, no doubt about it. Wish I had a scope to help you add this SPS-PRO to your database, provided I can get the damn thing to run again....

[Behemot]

Re: UPS beeping continuously

Must Power (or similar) garbage. Utter crap, it mostly dies with the first battery going bad. I think in next gen they'll weld the plastic with laser so you could not replace the SLA's even if you want. It's so fukin' cheap it barely has any point anyway as it is DESIGNED as single-use, when the battery dies, throw-away-and-get-new-device. Very cheap iron-aluminium transformer, copper's too expensive ya know. Usually has laughably short runtime near rated maximum load. So bad accumulators, lately they use Leoch which ofte leaks acid and eats cables, crack under operation and sprays internals with electrolyte or if nothing else, when you put it to rest after it goes bad, in time they bulge and crack. Good that the electrolyte goes dry by that time. I wonder why people buy such crap, this has absolutelly no use whatsoever unless you overspec it at least three times over average power draw. And even than it is cheap shit with doubtful AVR functionality and only square or modified square-wave output, as you can see in my database (check Sweex for example).

Replace all the caps with 105°C GP ones like Chemi-Con KMG. You can also experiment with long-life like LE series. Beware that it is extremely difficult to solder this piece of shit PCB material - it is indeed some copper-shit alloy. The traces are very thin, easily break away from the board, easily crack and when I pull the caps, no matter how small temperature I use, part of the tab around the capacitor leg always disappears. I don't get this…

If I manage to get some of the new switched regulator replacements like Mornsun K7812-1000 for reasonable price, I'll try replacing the linear 7812CT's, that could bring the wasted power down by 5-10 W in my estimate, not to mention prolonged service life when it won't be baking itself in its own juices.

[stj]

Re: UPS beeping continuously

i have seen resistors go both ways - it only effects carbon-rod resistors afaik.
i dont think a metal-film/oxide resistor can drop in value.

[Dannyx]

Re: UPS beeping continuously

Strange how a resistor LOST some of its impedance...usually when they fail it's the other way around - they open up. I doubt that's the issue - it probably just got damaged by me. Still, it goes between the battery and one of the pins on the IC, so there's something going on there...

[stj]

Re: UPS beeping continuously

right, quad package

[Dannyx]

Re: UPS beeping continuously

Could be. I did find something else though: third picture, R32. It's supposed to be at 499kOhms, but when I accidentally scraped its top with my meter probe, the coating came off and it then read 10 something kilo, so I'll replace it anyway and then continue my searches...

LM324 is just a bunch of op-amps, right ?

[stj]

Re: UPS beeping continuously

i imagine it's centered around that LM324