Bench PS Problem (Volteq HY3010D)

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

BTW, in order for the voltage to drop to zero or something that's usable by typical digital electronics, V16 needs to be lit. If neither LED will ever turn on, that's another data point that will help tremendously to debug this problem, all without an external voltmeter...

The only thing to make sure is that either the LED lights up, or is not open circuit in both directions.

But the data given about the potentiometers is really messed up. Please carefully remeasure and make sure there's nothing in parallel that will skew the results. Potentiometers do not fail shorted, they fail open.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Oh cool, did not realize V16 was an LED on the front panel... I assume V15 is the other LED though it's obscured by the wire. Are these LEDs lit at any time? I also wonder if they're still good too...

[kaboom]

Re: Bench PS Problem (Volteq HY3010D)

ckt = circuit?

yes

The test was done outside of circuit (soldered out). Forgot to mention that.

Ok. Try putting each wiper in the center of its rotation. Then check from 1-wiper and 3-wiper. Each should measure 1/2 of what 1-3 reads.

ASSuming linear taper, a 10k nominal should be ~5k in each half-element/wiper check. All pots have some end resistance, don't expect zero ohms from end-to-wiper when fully turned to one side.

And don't buy cheap/fake stuff from aliexpress. Mouser/Digikey are a better value overall, especially when you consider wasted time for "repeats."

You can pull the 324 and disable the tap changer. You'll then be at the lowest range of raw DC before the regulator.

Check the opamp supplies, with respect to the positive output terminal (black meter lead on + output).:

M1/M2, 4(-6.2v) & 8(+12v)
M3, 4(+12v) & 11(-15v)

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

ckt = circuit?

The test was done outside of circuit (soldered out). Forgot to mention that.

[kaboom]

Re: Bench PS Problem (Volteq HY3010D)

RP7 resistance test failed, pin1 with pin3 resistance is way too small for the sum of 1-2 + 2-3.

Because you're checking them in ckt. Pull em and try again.

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

I attached photo with the pots locations circled.

RP7 resistance test failed, pin1 with pin3 resistance is way too small for the sum of 1-2 + 2-3.

It's the potentiometer then?

EDIT: What's the part number for these pots? I want to order from Digikey.

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

Can you take a better picture of the board/pots and annotate which wire goes where? Each of the voltage and current settings have three pots apparently - fine, coarse, and calibration PCB pot...

When out of circuit do RP5 and RP7 change resistance as described when rotated?

[orientalsniper]

Re: Bench PS Problem (Volteq HY3010D)

mmmm what should my next step be? do they sell these boards?

[eccerr0r]

Re: Bench PS Problem (Volteq HY3010D)

In RP1, RP2, RP6, and RP4 - there should be a connection between the middle pin and one of the side pins when in circuit. However RP5 and RP7 should not -- that is, if the schematic is accurate.

[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.

[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)

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)

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)



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)

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...

[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.

[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.

[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)

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


What about RP1, RP2 and RP9?

[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.