Bench PS Problem (Volteq HY3010D)

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Yeah. 25V-0V-12V for the 3 pins. Heatsink is very hot, is it normal?

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Well, other than drawing a lot of current, think it's doing fine. It only needs to draw 0.5A or so to get quite warm, with three relays all 'on' it can get there...

As long as it's not hot "OUCH" to the touch...

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

I think it's a new symptom since I took out M2 IC unless I haven't noticed it before because the glue near the heatsink is melting.

Check the attached photo please. Is R16 looking fine? It's got 0.433K ohms

I'm worried leaving it on for more than 15 seconds to do the other tests.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

This is weird. What's the output voltage of the PSU now? Oh gosh... that's also unexpected R16 overheating... hmm. need to check my other computer to think about what's going on with it now. At least you had a picture of the resistor before it heated up!

But anyway, what is the voltage on the output of the PSU now with that bottom LM741 out (Note that both of them are silkscreened N2, so be careful. I think you got the "right" one in terms of the voltage feedback unit versus the current feedback unit.)? If it's not 0V, could you do that short test on V13 - solder a wire between base and emitter of the transistor and check the voltage output real quick when turning it on.

In theory the output should be and remain at 0 on the panel, and all the relays should also be off - and thus that N3 regulator as well as pretty much all the semiconductors should also stay cool.

---

OH FSCK THAT'S WHERE R16 was... this is that resistor on top of the stack and it was a 47 ohm resistor which does NOT match the schematic with a 56Ω resistor.

*** DONT TURN THE PSU ON UNTIL YOU FIGURE OUT WHAT'S GOING ON!!! ***

This means the potentiometers are also passing a lot of current - in which they should NOT. Did you inadvertently short RP7's center pin/wiper that's normally connected to pin3 of the LM741 you removed, to GND? (or pin 4?). That could cause RP2 to fry if RP7 is turned all the way up... DANGER DANGER DANGER!

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Yeah, I was a bit hesitant to leave the PS on for long period of time since I saw glue smoking off. Don't want a PS blowing up in my face.

I will double check tomorrow, I might have left RP7 wiper shorted to GND. I think I'm gonna put some safety glasses on.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Well, the worry is not necessarily something blowing up, it's damage to the potentiometers, they are not meant to handle that much power and well, kind of expensive to replace!

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

I screwed up, wiper was grounded, check photo.

Tests done for post #51

Voltage measurements for M1 with M2 pulled out. PS (+) with MM (-):
-6.2
0
0
-6.2
-6.2
-0.5 (jumps a lot)
12
0

I will report back with the tests that follow.


EDIT: THERE WAS A BLOB OF SOLDER UNDER M2, MESSED UP THE READINGS.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

For post #52

PS (+) with MM (-):

Pin 4 of N4: 12V
Pin 8 of M1 and M2: 0V
Pin 11 of N4: -15V
Pin 4 of M1 and M2: -6.2V

R2: -6.2V and -27.8V
R39: 0V and -27.8V

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

For post #58

PS (-) with MM (-):

With RP7 wiper disconnected and MM (+) on it I could get from 18V to 37V by turning the potentiometer from one side to the other.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Well, you were getting -15V on the LM324 pin 11, so that R39 reading of 0V is suspect.

The op amps are all getting power (and keep in mind V+ of the LM741's is pin 7, V- is pin 4). Looks like you got the V- pin 11 and V+ pin 4 of the LM324 right.

Unfortunately the schematic does not annotate the pins of the op amps to the actual schematics, which makes things a bit more difficult...

BTW, is the voltage on the output higher or lower now, or no change, with the LM741s removed? (expected: no change, should still be sky high). With the LM324 removed, the voltage should drop because the relays can't switch in the higher voltages.

Now that you got the shorts cleared (was that short there from the beginning? The back of pots picture is kind of small, can't really see what's going on there) can you do the "experimental" shorts to see if you can get the voltage down on the output?

----

Okay it looks like you can drop the pot voltage to 18V, so at least it's partially working, but not what it should be... This is with PSU OUT+ still stuck at 37V? This would mean reference is ~40V. Also do you have RP6 turned all the way down? With this turned all the way down, RP7 should be able to hit or close to hit 0V. Take a measurement of the other RP7 and RP6 pins again to see where they stand now without the effects of the op amp.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Yeah, RP4, RP5, RP6 are all turned down.


What about RP1, RP2 and RP9?

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

BTW these are all depending if the schematic is correct:

RP2 to get the lowest output, needs to be turned "up" (highest resistance). However this is a calibration pot, should try not to touch it if possible. I think RP1 likewise is a calibration pot for current, so we don't need to worry about this one for now.

RP9 I don't know because I've not located it on the schematic...

At this point I'm kind of doubting the schematic vs real circuit. Need better pictures of the real circuit, traces and all to be sure. Same with the potentiometer front panel board and wire connectivity to see if there's any additional trickery going on...

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

I think I'm gonna wait for the UA741 to arrive and see if they are gonna fix the problem first.

[redwire]

Re: Bench PS Problem (Volteq HY3010D)

If the output is stuck at high voltage, this circuit will naturally cook the op-amp and then the voltage adj. potentiometer, smoke the 47R resistor too.
This is because the PSU design assumes the output is never way above the setpoint.

Consider the similar BK 1630 bench power supply, note the extra protection diodes and resistors:
D102, R113, R110 (across V control op-amp U104 inputs)
D112 across pass transistor C-E for backfeed protection.

I would add this before cooking a new LM741.
Otherwise the smoke and problems will just keep repeating unless the design cheapness is fixed.
Again, make sure your pass transistors and driver are not shorted.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Yes please remove RP7 and test it out of circuit, it may very well be fried at this point.

I think there's enough resistance there the potentiometer should just barely survive but it definitely will get toasty. The 47R resistor should normally be fine, the potentiometer will take most of the drop. That is, unless someone accidentally shorts it out...

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)



I just replaced both UA741 and RP7 potentiometer out of circuit is not shorted in all 3 pins. What's the problem with this?

Is there a DIY board with a better design so I can just solder in the good components in this board?

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

RP7 coarse potentiometer, and potentiometers in general, usually fail open -- not shorted. Make sure the characteristic resistance (the two outside pins) is about the same as in the schematic, somewhere around 10KΩ. Need to make sure that the middle pin can be adjusted through the whole range and you can shut off the power by the experiments described in the previous posts, to help locate the problems.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

Resistance of RP7 soldered out:

Pin 1 with 3: 18K ohms

Pin 2 with 1 and 3: 26K ohms 18K ohms

EDIT: There's a short between Pin1(?) and Pin2 of RP7 while in circuit.

EDIT2: I finally got what you mean by sockets, it's IC sockets you were referring to like this https://www.aliexpress.com/item/66PC...799809293.html I just ordered it, I could had save a lot of time testing the power supply with one of those sockets.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

A potentiometer has those three pins, 1 2 and 3. If pin 2 is the center/wiper/adjuster, the resistance between 1 and 2 plus the resistance between 2 and 3 should equal the resistance between 1 and 3. As you rotate the pot, resistance will get traded between 1-2 and 2-3, but the resistance between 1 and 3 should remain constant. If you rotate the resistor all the way clockwise or counterclockwise, one of the two sets will be 0 ohms.

In any case, need to find that short, unless it's because you have the knob rotated all the way in one direction.

Yes, the sockets are very helpful when working with ICs. The 'machine pin' sockets are the best quality sockets. The second best are the dual wipes which appear to be the ones you pointed at.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

There's a short in all 4 potentiometers in pin1 (or 3??) with pin2 in circuit: RP4, RP5 (current) and RP6, RP7 (voltage).

EDIT: The short is in each individual potentiometer, testing pins between 2 potentiometer (for ex, RP6 and RP7) the short is gone.

EDIT2: Moving the knobs has no effect on the shorts.