SUPER CD ROM spinning inmediately after power on

[JayDecay]

Hello everyone.

I have a problem with the Super CDROM2. It was working ok, with some audio skipping (originals and CDR) and no audio in the av output but I hoped it will be solved with a future recap. One day, just after switching the power on of the CoreGrafx I, the CD started to spin very fast, even with the lid open. It shows the Bios screen ok but after pressing Run it shows the message Please Set Disc and continues spinning. The power brick has 2 Amps.

I searched in the forum but I could only find some answers related to the CD unit. After checking the PCB there were signs of corrosion in capacitors c136, c163 (console5 schematic) so I changed that group of capacitors (136,163,200,201,133,129,127) and also 311,310,304,302,303. There was a missing trace that I bridged but it didnīt fix the spinning problem. The remaining capacitors look ok but I'll try to replace them once I solve this issue.

Luckily another user asked a similar question in this post:

https://www.pcenginefans.com/forum/index.php?topic=23724.0

and I thought it could be the same problem as I believe they share the same chip for the CD Digital Signal Processor. But I couldnīt find a via the same size as the PCE Duo one and I couldn't follow the trace back to find the equivalent via in the Super CD Rom PCB.

I have attached a picture of the area in the hope that someone could point the problematic via or any other idea that could help.

Thanks a lot for reading.

[Keith Courage]

Most likely corroded Via holes since the CD drive was working fine before the recap. Look at the Via holes in the area with all the Larger High value capacitors near the 7805 Heat sink. You will probably see a few via holes with Black gunk in them from the capacitors leaking. Solder an extra capacitor lead on each side to repair or run a wire where needed from the bottom side of the board.

Another area that could have a bad trace or corroded via would be in the two rows of 4 capacitors just above the BA chips near the gray CD stop switch wire.

[JayDecay]

Thank you very much for your quick response. Let's see if I can find the guilty via.

[JayDecay]

I checked all the vias from top to bottom in that part of the board. Starting near the CD stop switch wire and ending near the 7805. I also checked the vias close to the Sony ICs. I couldn't find a single one bad (I was hoping to find one like the user in the pce duo post but no luck). All of them make contact with the other side. I cleaned the area again but after reassemble it keeps spinning inmediately. I don't if it's related to the spindle motor on/off control output pin or any other spindle control pin in the chips but the traces seem ok. 

Next thing I would like to try is to change the SMD capacitors in that place (114,113,119,122,110,105,164) there are no corrosions signs but right now I don't know what else to do.

Thanks again.

[michellybells]

Did you check those vias with the unit on to see how many volts were running through it? On my Duo, one of the things that helped me figure out exactly which via was damaged was to use a multimeter to measure voltage along to path towards the CD control IC. What I found was 2v instead of 5v all the way back to where the one via was broken. On the other side of that via was 5v (which it should be) so I knew that via was the issue. Maybe check all the voltages around that area and see if you're getting 5v. If you aren't but also no vias are broken, then you know the problem is some other component. Plus tracing the voltage along its path might help you figure out where the damage is. Just a thought.

[JayDecay]

Thank you very much for your reply. This weekend I replaced some of the SMD capacitors in that area and cleaned again the corroded capacitor vias near the BA chips and the voltage regulator ones, scraping some zones to make sure they make contact so I think that part should be ok.

Today Iīve been checking with the multimeter some IC pins.

A few readings I have had:

Voltage regulator 4.95 v / 11.10 v

CXA1082BQ pin 1: VC 2.44, pin 37: DVcc 4.94

CXD1167Q pin 2: spindle motor on/off control output 2.22 pin 33: VDD 4.89 pin 73: VDD 4.73 pin 53: Crystal Osc. Input 2.30 pin 54: Crystal Osc. Output 2.20
(i've checked those pins (53 and 54) because they're near the broken vias in the Duo that gave you 2v that Keith Courage pointed in the other post, but I couldn't tell in that picture which pins were affected)

CXA1081M pin 30: VCC 4.94 pin 9: VC 2.44 (single power supply half the Voltage)

D78C14GF pin 58 VDD 4.90 pins 8,9 and 10 1.60 (the lowest values I've found)

In some cases it is hard to follow the trace because the via lies under an IC and I canīt test it but in the ones that I've tested it was the same reading in both sides.

Sorry for the long post. If I can make any other test to find the problem Iīll be happy to do it. It has been a really fun project and I hope it would be fixed soon.

Thanks again.

[michellybells]

If you look at the datasheet for the CXA1082BQ, it looks like pin 1 should have 5v, though it can handle a range. However 2.2v is below the minimum operating voltage for that power input pin, so I'd just start tracing backwards from there and see if you can find any via issues or somewhere where power is being lost.

https://console5.com/techwiki/images/1/14/CXA1082B.pdf

[JayDecay]

Yes, when I tested that pin I thought "this is the one bad" but I find the same value in CXA1081M and it looks like it's some kind of reference voltage (VR in the specs) when the chip is using a single power supply (page 30 in the chip schematics) and itīs exactly half the value of the voltage. Pin 37 is 4.94 and looks ok.

There a few values in that datasheet electrical characteristics so I'll try to check with those numbers and I'll search in the forums to find more values to compare with.

Thanks again for your input.