VUPPM500 KIT Build Thread

[hasanova]

All 10x 100R resistors measure the correct resistance value.

I've compared 4x VUPPM mdules. There seems to be continuity between a group of 3 solder links (between the main pcb and display pcb). See picture.

What should I do next? Maybe swap CPU between faulty and a working module? Or should I make some more measurements?

Continuity VUPPM.png

Main CPU PCB - close up 10x100R.png

Main CPU PCB.png

[hasanova]

By the way, these are the 4 I've compared.

The input signals went through different line-amps, with different gain settings, just to compare the LED brightness. LOW brightness mode on all.

Not very clear on the pics, but on the faulty module, the second blue LED from top is also more dim then the others.

[hasanova]

Here's some pics of the solder side.

Main CPU PCB solder side.png

Main CPU PCB solder side - EDGE.png

[Joe Malone]

By the way, these are the 4 I've compared.

The input signals went through different line-amps, with different gain settings, just to compare the LED brightness. LOW brightness mode on all.

Not very clear on the pics, but on the faulty module, the second blue LED from top is also more dim then the others.

The 3 x 100k resister to those 3 links are for the blue LEDs and the 100k at the bottom for the 4th blue led.

Yes swap cpu to see if the problem follows the cpu or not

[hasanova]

I've swapped the CPU, but the problem stays with the same module...

Did you, or anyone else, see anything unusual on the pictures I've sent?

Thnx,
H.

[Joe Malone]

I've swapped the CPU, but the problem stays with the same module...

Did you, or anyone else, see anything unusual on the pictures I've sent?

Thnx,
H.

OK in colour test mode (pressing the outside 2 switches together) are the same leds dim in all 3 colours or only one colour?

Also does the 3 brightness levels change anything?

[hasanova]

I thought I already these pics, but yes, the same LEDs keep being dim in all 3 brightness settings. It's way more visible than the pics show. Check page 3 for more pics. Also, the brightness does change indeed.

LOW brightness LED.png

MEDIUM brightness LED.png

HIGH brightness LED.png

[Joe Malone]

I thought I already these pics, but yes, the same LEDs keep being dim in all 3 brightness settings. It's way more visible than the pics show. Check page 3 for more pics. Also, the brightness does change indeed.

LOW brightness LED.pngMEDIUM brightness LED.pngHIGH brightness LED.png

I was just wanting to see the led test for all 3 colour tests. Am I correct that only the 10,20,30 row leds that are dim and not the 40th row?

[hasanova]

I was just wanting to see the led test for all 3 colour tests.

Sorry, you're right, I didn't send all modes!

LED red.png

LED orange.png

LED green.png

Am I correct that only the 10,20,30 row leds that are dim and not the 40th row?

No, it's the 1st of every 10, 20, 30 & 40 row LEDs that's dim.

[Joe Malone]

I was just wanting to see the led test for all 3 colour tests.

Sorry, you're right, I didn't send all modes!

LED red.pngLED orange.pngLED green.png

Am I correct that only the 10,20,30 row leds that are dim and not the 40th row?

No, it's the 1st of every 10, 20, 30 & 40 row LEDs that's dim.

Yes I see that in the colour test only green is affected on row 10, 20 , 30 & 40. Need to know what blow the 10R on the 5v rail to give a clue to the problem. The TL074 pin out would only effect the +/-16v rails for the opamps. Because red is ok it means all the 100R are ok and since green is not stuck on it shouldn't be any of the bc639 transistors as it would mean 8 of them are faulty in the same way which is very unlikely.

If you bring up a 1khz tone in different modes do the leds raise up one level at a time with no random leds lighting anywhere?

[hasanova]

If you bring up a 1khz tone in different modes do the leds raise up one level at a time with no random leds lighting anywhere?

Yes, when I slowly bring up a 1 kHz tone, the LEDs raise up one level at a time, in all modes. No random LEDs visible.

[hasanova]

I've reached a dead end. Is there any follow up?

I've just received 2 more new kits in the mail. If there is anything I could test with these fresh parts, please, let me know.

By the way, is there any significance that there is lower intesity in these LEDs in "RED"?
I could not tell with naked eyes; only visible on the pictures.

Screenshot_20250823-120400.png

[Joe Malone]

I've reached a dead end. Is there any follow up?

I've just received 2 more new kits in the mail. If there is anything I could test with these fresh parts, please, let me know.

By the way, is there any significance that there is lower intesity in these LEDs in "RED"?
I could not tell with naked eyes; only visible on the pictures.

Screenshot_20250823-120400.png

If the red is dimmer as well than changing that rows 100R to smaller R like 50R may fix the problem. It would be the first thing I would try by putting a extra 100R under the pcb in parallel with the fitted 100R to see if it is better or not.

Let me know what you find

[hasanova]

I added a 100R resistor in parallel with the 100R that's already in place. I measure 49R.

It's already better than before, not completely there, but I think we're on the right track. Difference in colour/intensity is less than before in all modes, bit still visible.

[hasanova]

I removed both resistors and placed a trimmer.
I've dialed in a sweet spot where I didn't see a difference in GREEN LEDs, hardly in ORANGE and a little in RED mode.

I've measured 15R.

Before, was the most visible difference in GREEN, now it's in RED, but still, way less obvious then it was before in GREEN mode with 100R.

Still no idea why the 10R burned twice on the EDGE card...

IMG_20250824_102213320 (1).jpg

IMG_20250824_102218604 (1).jpg

IMG_20250824_102223182 (1).jpg