Bench PS Problem (Volteq HY3010D)

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Yeah, I meant swapping M2 with M1 lol, otherwise I would have said "replaced" but I can see I got you confused


What are sockets? You mean the potentiometers?


I've got experience soldering/desoldering DIP-SMD-BGA (the latter with no much success soldering since I lack the correct equipment)

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

I'm a bit confused about #33 in which you said you swapped, unless you tried putting the M2 with M1, was that what you meant?

Do you have sockets or did you order these as well? Also, experience with desoldering DIPs from PCBs?

Might be worth scouring your spare parts pile to see if you have any LM741s to steal in the meantime, and hope you don't get fakes from china

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Nah, it's gonna take 2-3 weeks for the delivery, I will replace as soon as I receive them and will update thread, if it's not the IC's, hopefully you will still be sticking around.


My toolbench: 1 oscilloscope (don't know how to use it yet) - 1 hot air rework station (soldering + hot air) - 1 Fluke multimeter - 1 lab power supply (the thing we are fixing now) - 1 wireless digital microscope (on the way)

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

It should be able to adjust to 0V without shorting -- that's what's bothering me!

What do you mean wait...thought you got the replacements already?

I don't know what your toolbench is like to remove/disable these ICs for testing... that's something that needs to be asked to reduce work on your side to help rootcause the failure. Otherwise need to think about other methods to get to the problem.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Well, RP7 wiper is technically 0V read with a multimeter when I short the wiper to GND.


Do you think I should wait and replace all the IC's?

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

The reasoning for removing the LM324 is to both limit the scope of the test so we know what's going on, and also to reduce the amount of damage that can happen.

Well, since you tested without removing it, okay, damage is done if there was any though it should have been okay.

So we're still dealing with multiple failures here since you can't get the center pin of RP7 to 0V no matter what the setting of it and RP6, and shorting the + input of the LM741 to GND does not reduce the output voltage to 0V... hmm...

---

Now that you understand why I want you to remove the LM324/disable the relays, do so, and measure the voltages for each of the pins around the M1 LM741. If they are all below 24V (meaning, no more 38 to 51 volts anywhere), put in a new one and see if shorting the center RP7 wiper pin to GND will reduce the output to 0V.

Another test if you have a known defective or original LM741 in the circuit is to short its pin 6 to its pin 4, and see if the voltage output of the PSU will drop to 0. This can destroy the LM741 if it isn't already dead.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

I think the first thing I did was to swap the "current" potentiometers with the "voltage" ones, I'm about 50% sure about that, maybe I dreamed it up.

The pots are just soldered on a single PCB for the potentiometers.

I have plenty of spare parts (dead motherboards, ATX PSU, etc), my IC list is limited though.

Do I need to remove LM324 before shorting RP7 wiper? I shorted it without removing it and the displayed voltage was 18V, however since it's shorted I'm getting 0V with the multimeter.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Okay, that's very suspicious, reason why I ask to confirm is that you should be able to adjust it to near 0V or at least drop the voltage by around two thirds at the lowest setting. I'd replace that pot but the numbers you gave me either do not match up with the schematic or indicate there's more to it that I don't know. Photograph of the back of the pots? Or is it just plain potentiometers with wire soldered to them?

How hard is it to remove the pot, is it a lone pot or on a PCB?

(Also double check you're testing the voltage pots, not the current pots.)

What is your spare parts kit like... can you fake a pot with hardwire resistors as a test if you don't have another pot to sub?

The next experiment I really would like to see you try is to remove the LM324 (or disable the relays from clicking without removing their contact connections) and simply short that RP7 wiper pin to GND. This theoretically should force the PSU to drop its voltage down. Before putting a fresh new LM741, ensure all the pins are below ~24V with respect to GND so we don't fry another one.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Hello, thanks to you for sticking with me so far.

As I said in post #37, pin 2 (middle) doesn't even go down to 0V, lowest was 51.2V.

EDIT: I meant middle pin.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Okay, I recall a thread we had on badcaps.net about someone else working with the display and we were having all sorts of trouble with it, so thanks for confirming that you're not trusting the readout

So can you adjust the wiper pin of RP7 (coarse) all the way down to 0V when the IC is out of socket, and you can't do it anymore when it is in socket? Doesn't point fingers, but wanted to verify that the resistors can indeed go down to 0V. This is assuming that the voltage on the output of the PSU is that unexpected voltage of >38V with the IC out of socket is still there.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

This is the power supply: http://www.volteq.com/volteq-regulat...new-model.html

RP6 is fine and RP7 is coarse.

Yeah, I'm using a Fluke multimeter to measure the voltage and it's the same as the display on the PSU.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

If you have RP6 tuned all the way down to 0V, if you can't get RP7's wiper (pin 2) to 0V with M1 (or both LM741s) out of circuit, something is wrong with RP7.

I assume RP7 is coarse and RP6 is fine control on the front panel?

Also, just making sure we aren't chasing the wind here: Are you measuring the output with an external (at least somewhat calibrated) meter of some sort, and not reading the display on the PSU itself?

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

I will have to read up on it.

So took out M1 (it's marked as N2 the same for M2) pin 1 (or 3?) and 2 are the same voltages, started out as 51.2V as lowerst, if I moved the knob to maximum it reached 51.8V.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

https://en.wikipedia.org/wiki/Potentiometer for a picture. I would label 1 2 3 as in order, and with these pictures, pin 2 is the middle one, and is connected to the wiper.

As pin 1 and 3 should be reverse-images of each other, knowing what the voltage of both are will tell what the range the middle one/wiper should be.

I normally would consider pin 1 will have 0 ohms (or close to 0 ohms) to pin 2 (wiper) when the knob is rotated all the way to the counter-clockwise direction. Likewise pin 2 would be 0 ohms to pin 3 when the knob is rotated in the clockwise direction. Hopefully this will kill some ambiguity at least in what I call what pin

The key numbers: pin 2 voltage needs to be between the voltages at 1 and 3. It could be equal, but only if rotated fully clockwise or counterclockwise.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Before we go any further, which pin is 1 in the potentiometer? Maybe I'm measuring pin 3 as pin 1....

If you swap the measurements between pin 1 and pin 3, would the diagnosis change?

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

With M1 disconnected/removed, can you adjust the voltage all the way to a low voltage on the middle pin of RP7? That needs to be ascertained before anything can be done...

Based on the other link, it seems that there are multiple problems that cause the LM741s to die, unfortunately it looks like you may have a few more dead LM741s...

Did you replace the LM324? Can you leave the LM324 out while debugging (or disconnect the coils to the relays)? This should help save the LM741s while debugging....

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

I just swapped the IC's, still got the same problem.

I didn't do anything, I use the power supply to find shorts in motherboards. I remember turning it on once and got this problem.

I found someone with a related problem: https://electronics.stackexchange.co...y-stuck-on-48v

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

I think adding C13 in, as well as adding a resistor in series with the wire you disconnected may be the things you could do to help prevent damage to the IC. This mod will slow down the slew rate of the potentiometer.

A cheap/FREE solution would be to change how the operator uses the knobs - to not turn the knob (specifically RP7) rapidly If you make slower adjustments to the knob, not letting the knob voltage go way too out of sync with the voltage on the meter, it will help protect the IC. This is especially important if you connect additional capacitors outside the PSU.

Otherwise, make sure you have a good socket there, and replace them if it goes bad with the same symptoms again. Unfortunately this may mean you may be powering something with 50 volts. (What were you doing with the PSU when it broke?)

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Hahaha, I bought a lot of 10 pieces, for now I will swap the IC's and report back.

What is your suggestion to protect the IC against the bad design of this PSU?

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Whoops made a mistake on post 24, the middle/wiper of RP7 should be connected to pin 3 of M1 - as the schematic says, not pin 2.

Okay, based on this information, it seems M1 is bad - the input somehow is shorted against something inside the IC and passing voltage out instead of being high impedance. I would hesitate to swap M2 with M1 but if you want to try it, go ahead (or simply leave M2 out; it should still work without it - but without current limiting.)

I would think LM741s are cheap, perhaps you should have bought a tube (or perhaps whatever the first discount batch) of them