Help with Water Pump

[salty joe]

IDK if it's under warranty. Shipping would probably cost as much as a new one.

My computer is getting pretty bad. I did manage to get the image on the computer, when I try to download it the dropdown menu jumps back real fast. That's a new one. Since it still works to read stuff and purchase things and email, I keep it. No doubt, it's days are numbered. We have an iPad bouncing around, I'll try to post a pic with it later.

I have the PS opened up and can't find any burn marks or anything. I did notice they did not wash the flux from the back of the board.

 

[alec_t]

Shipping would probably cost as much as a new one.

That's the problem these days.

I have the PS opened up and can't find any burn marks or anything.

Well that's a positive. Even if something has failed at least it didn't cook everything else. On the other hand non-visible faults can be trickier to find. Once we can see the layout we'll be better placed to suggest where to get cracking with your DMM. Do take care though. High voltage can persist even after the mains is turned off if the PS is the SMPS type.

 

[salty joe]

Thanks for the high voltage warning. I connected a pump to the unplugged PS to drain it. The pump did not even twitch. IDK if that helped or not.

Since I'll need a third PS for high powered LEDs for an algae filter and supplimental lighting on the display tank, I have another on the way. So worst case we'll only have to wait for the new PS for a full blown test run of this epic system. And I do mean epic.
Should be fun to see if this limping PS can be brought back to a healthy state.

 

[alec_t]

Should be fun

Let's hope so. After the various set-backs you've had you deserve abit of fun .
I'm taking the liberty of posting your pics of the PS here, in case others can suggest suitable test points:

I'm reading the pics as showing the mains input, rectification and smoothing along the bottom third or so of the pics.
Cap C6 (first pic bottom right) and its neighbour are likely to store a lethal charge for a while after power off, so BEWARE if poking around in that vicinity. BTW, what is that hairy thing running north west from C6?

Edit: One possible suspect is the mains bridge rectifier (that black thing just above the words "against fire" in the first pic). If only half of it is working the PS might show the volts sag you get under load.
After a decent time from power-off, use your DMM diode test function to check it by probing between two of its pins at a time with both probe polarities (assuming you can get to the back of the pcb). You should be able to get four sensible similar diode readings ~700 (they will probably drift because of C6 etc).

 

[salty joe]

There must have been a piece of grass on C6. I went outside to get decent light and set it in the yard for a minute.

I had no idea there could be a lethal charge in this thing. Is there no way to safely discharge?

Thanks for posting the pics.


Edit; How long is long enough to be safe to start checking this thing out?

 

[alec_t]

Odd that you could email the pics but not post them directly to this site. Could your mouse be playing up? Mine does sometimes. I think I've clicked on one thing but some unwanted action occurs because the cursor jumped elsewhere.

Is there no way to safely discharge?

Any well-designed SMPS would have a bleed resistor of 1meg or so connected across the cap to discharge it in a few seconds. Best to allow an hour or two. Time to put the kettle on!

 

[KeepItSimpleStupid]

Remember to click one of the UPLOAD buttons on the page.

 

[KeepItSimpleStupid]

Check for conformal coatings. an insulator on the board. Measure cap voltage when on and about 5 min after turn off. Use the 1 hand in pocket rule or a probe in each hand.

The voltage rating of the caps is a good indication of the max 400 VDC. Mains rectfied.

The bridge shoule be labeled ~ and ~ and I expect line voltage there.

Look at - to and + to each ~. Expect ~ +- 0.6 V. ~ to ~ line votage and - to + ballpark 400 VDC. Also look at AC voltage at the 400 V point.

 

[salty joe]

On the mains bridge rectifier I got 477and 475. With probes reversed, both were 1.

The only thing I could find labeled at the bridge is BD1.
Does not seem to be any conformal coating.
Do you want me to check C6 or its unlabeled twin? I'm gonna call it C7. The negative terminal of C6 is connected to the positive terminal of C7.

It looks like I can post pics again. I absolutely don't get this computer. It is inconsistent. Oh well, it's working I'll go with it.

 

[KeepItSimpleStupid]

The bridge rectifier has 4 leads, and it probably has a pin out like: https://www.electro-tech-online.com/custompdfs/2013/08/ds21225.pdf

Note the chopped off corner and the AC applied to the middle pins. Here is a schematic: https://powersupply88.com/rectifier-circuit.html/bridge-rectifier-symbol

So, there are 8 readings you should get.

 

[salty joe]

Thanks KISS.
Let's call negative pin 1, AC pins 2 and 3 and positive pin 4.
pins
1-2, 470 & 1
1-3, 484 & 1
1-4, 1023 & 1
2-3, 1 & 1
2-4, 501 & 1
3-4, 467 & 1

Well darn, that's 12 readings, hopefully 8 of them are useful.

OK, now I see the label on the bridge.

 

[KeepItSimpleStupid]

Looks OK.

 

[alec_t]

Agreed. Well that's one suspect eliminated from our enquiries. Without a schematic of the PS it's difficult to know where to check next. ESR measurements for the caps are out of the question without suitable test gear, so a shot in the dark would be to use the DMM to check all diodes (anything labelled 'D...' . or having a single coloured bar at one end) on the board.

 

[salty joe]

OK thanks, I'll check the diodes. If they're good, I'll throw in the towel. It's pretty cool to even take a stab at fixing something like this. I'm pretty sure the damage occurred when the wire from the - battery slipped and touched the + battery terminal that still had the wire hooked to it. I think I'd have noticed the power indicator LED on the PS flickering. In any event, thanks for the redundancy of 2 PSs.
If one PS got unplugged or failed completely, would the battery run that pump while the other pump continued to run on house current?

Meanwhile, the other PS should arrive this week. Then a full system test run will be in order.
Thanks guys.

 

[alec_t]

If they're good, I'll throw in the towel.

Hey, we're not done yet. Something else to do is re-flow the solder joints on anything which looks as though it might be carrying heavy current, e.g. output terminals, big power transistors, inductors, 3-legged regulators. There could be a dry joint which is limiting current flow.

If one PS got unplugged or failed completely, would the battery run that pump while the other pump continued to run on house current?

Yes, providing the battery is charged.

 

[salty joe]

Hey, we're not done yet. .

All right then. (; Some diode readings look maybe not so good. IDK.
D3 & D4 595/1470 (located at bottom of row of parts by C6)
D5 & D6 585/1440 (located near top of row of parts by C6)
ZD1 & ZD2 496/573 (beside C7)
All other diodes were 5-8 hundred/1.
All readings with DMM in diode mode, negative probe on cathode/ negative probe on anode. Values are give or take a few-they were all very close.

Yes, providing the battery is charged.

That’s awesome!, it really is. Could there be a situation where only one PS failed and a pump is running off the battery while the battery is being charged?
If those diode numbers look good, I’ll put the fat tip on the soldering iron and re-flow a bunch of parts.
Hoping for bad numbers- this is a first.
Thanks.

 

[alec_t]

Could there be a situation where only one PS failed and a pump is running off the battery while the battery is being charged?

Yes. The live PS would be running one pump and charging the battery at ~0.5A, while the pump running off battery would be drawing ~1.1A from the battery; so overall the battery would be discharging at ~0.6A.

If those diode numbers look good

The diodes clearly aren't open circuit or short circuit, which is good. I'd assume they're ok. More suspects eliminated.

 

[salty joe]

I re-flowed all the solder joints except for the little ones and there's no change. I did notice the fan always runs if the PS is plugged in, but it's supposed to only come on at a certain temp. Time to administer last rites?
It's a cute little fan. It's being driven by 12.9V. No idea how many amps, no label. Could a little fan like this be connected to the same leads as the green LED charging indicator to blow on the LM317?

Could a second red LED be added to the first 'battery in use' red LED? I think having one in the fish room as well as the circuit board would be good. The circuit board will live in the basement, directly below the fish room.

Tonight, I can use the smiley faces, last night I could not It's crazy.

 

[alec_t]

Time to administer last rites?

Probably, unless others can suggest what else to test with just a DMM and no schematic .

Could a little fan like this be connected to the same leads as the green LED charging indicator to blow on the LM317?

Can't connect it there (it draws more current than the LM324 can provide). But you could connect up another '317 (seeing as you have a box-full ), powered from the +Vext point, to give another 12V output dedicated to the fan only. The fan could then cool both '317s ! If you want to do that I'll draw up a schematic.

Could a second red LED be added to the first 'battery in use' red LED?

. Yup. Here you go:-

This schematic (FPPB-Mk3) incorporates changes to date and adds the second 'on backup' LED. Note new values of resistors R5,R6 and added 'SetLEDs' trimmer. The trimmer enables LED contrast between 'on' and 'off' to be maximised.

 

[KeepItSimpleStupid]

@Joe
What is the IC part #?
What is the p/n for Q1/Q2?

Check R10, R11 and R12 and the similar grey resistors near Q1/Q2 and near C29.
and basically all the resistors near Q1/Q2.

Check D13.