Screwed up big time....... MCR Stack

jetusenet

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Hi,
Working on a Spy Hunter MCR stack. Received the A7 A8 errors and after confirming the ROMs and RAM were OK, replaced those 3 IC sockets, capped all three PCB's and replaced the ribbon cables, was starting to go over my work and my 8 yr old son comes down to help..........

Long story short, I did not in fact get to check my work and after powering up the rack and getting no voltage reading on the DMM, pulled it only to find that on one of the ribbon cables, I was off by one!

Well, I correctly installed that cable and now just get a bunch of blocks on the display so I fried something. I tried the test switch but that did nothing to change the display

I checked all three boards and cannot see any physical damage so there must be some IC damage, AFAIK.

Can anyone shed some light on this issue which I created for myself??

Thanks in advance

Jeff
 

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Send them to CDjump hear on Klov...He's very good on MCR boards and very fair...
 
I know, he has helped me in the past but since I killed it I would like to fix it - if possible,,,,,,
 
video board seems operational. check the cpu if it is getting power. check its reset pin. is there any activity on the address lines?
 
bummer... I would check the pinout of that connector, see which pins had supply voltage(s) going across and which direction, and start following the traces/schematic from the pins that you accidentally sent that voltage to

good luck
 
Connector

If you don't have the cable keyed, insert a spacer in the key hole or use some epoxy to fill it so this doesn't happen again. Hopefully you will be able to trace the pinouts and find out which way the cable was inserted incorrectly and figure out which components are fried.
 
Jet, go buy some of Madrit's cables. You can't easily be off by one with those and they're great cables and they're cheap.

You shouldn't run with anything else.

Bob's 25x2 cables work fine but make it very easy to do this...
 
Jet, go buy some of Madrit's cables. You can't easily be off by one with those and they're great cables and they're cheap.

You shouldn't run with anything else.

Bob's 25x2 cables work fine but make it very easy to do this...

dude F those SCSI cables. it was weird, I was checking continuity between boards to see if I got them back on right and there just so happen to be several pins on either end of the cable that will read continuity on different rows. I plugged that in and I think it crossed +5 and ground on one of the wires and simply burned up that one wire. it didn't damage the board. in fact when I researched it people said it shouldn't kill it.

these are incredibly particular about how the chips are plugged into the original sockets, make sure you have the legs straight. past service I've found people pulled the chips one sided and half the legs will be bent. the game will probably work fine for awhile but then it won't in this condition.

the things we encounter.
 
I cant imagine why but the three Spy Hunter Manuals I just looked at online dont have the CPU board in them.

I'd check your power supply, make sure you didnt toast the rest or VBatt circuit. Looking at a Tron manual it doenst look like that connector contains any "lethal" voltages. Any by lethal I mean -5 where +12 or +5 should be.
 
I see you reflowed the header... it's hard to tell from the pic whether that's flux or solder bridges, but you should check to make sure none of the pins are bridged.

DogP
 
I see you reflowed the header... it's hard to tell from the pic whether that's flux or solder bridges, but you should check to make sure none of the pins are bridged.

DogP

Jet's soldering does not meet your standard of excellence, eh? :28:
 
dude F those SCSI cables. it was weird, I was checking continuity between boards to see if I got them back on right and there just so happen to be several pins on either end of the cable that will read continuity on different rows. I plugged that in and I think it crossed +5 and ground on one of the wires and simply burned up that one wire. it didn't damage the board. in fact when I researched it people said it shouldn't kill it.

these are incredibly particular about how the chips are plugged into the original sockets, make sure you have the legs straight. past service I've found people pulled the chips one sided and half the legs will be bent. the game will probably work fine for awhile but then it won't in this condition.

the things we encounter.

That's really odd. Mine were perfect and he's sold hundreds of sets and I've not heard a single complaint, only glowing compliments.

You are talking about Madrit's cables, right?

It's super easy to be off one pin with Bob's scsi cables and now I'm thinking that's what you were talking about.
 
Thanks guys for the suggestions and links, I will have to check the traces and see to where that voltages went.

I was thinking the reset circuit as the display is just static and from my limited knowledge with the MCR stacks, it looks as good as any place to start.

Onto the P/S to check for reset......

BTW, although I always clean the flux from a socket / IC pull / install, I just went around the header connections with a pin to break away and residual flux. Don't hate me, I just do not have the time to always be as neat as I would like to be........

Thanks again and I will report back once I check the set.
Jeff
 
For the record, Mecha clarified that he wasn't talking about Madrit's cables that are excellent.
 
Jet's soldering does not meet your standard of excellence, eh? :28:
Heh, nah... just from the reflection of the light in the pic, I couldn't tell if there were solder bridges or flux.

I cant imagine why but the three Spy Hunter Manuals I just looked at online dont have the CPU board in them.

I'd check your power supply, make sure you didnt toast the rest or VBatt circuit. Looking at a Tron manual it doenst look like that connector contains any "lethal" voltages. Any by lethal I mean -5 where +12 or +5 should be.
Yeah, it seems several of the MCR manuals are crap... Spy Hunter is missing the CPU schematics, and DOT doesn't have any. I personally grab the troubleshooting guide: http://arcarc.xmission.com/PDF_Arca..._Midways_MCR_II_&_III_Systems_(July_1983).pdf , and the MCR III CPU schematic is on the last page.

From the pic, I believe J3 is offset down by 1 pin (i.e. pin 1 was hanging off the end of the connector). I wouldn't expect that to be a fatal mistake. It would short +5V to GND, which is obviously bad for the power supply and the connector/wire shorting them... but if +5V came back after moving the cable back, I don't think any of the other signals would cause any real damage. I believe that connector goes to the SSIO board, so you could trace some of those signals to verify nothing looks messed up.

Since you did other work on the board, I'd double-check all of your work... and make sure the DIP switches are set correctly (I believe there's a freeze video DIP, and other test DIPs, which might keep it from booting if they got bumped to the wrong position).

DogP
 
I used the schems from Tapper, clear as a bell.

From what I can tell, you are correct, I shorted the +5vdc to GND.

Also I shorted FLIP1 to uRESET - that is the only other "bad" connection made as the others would just mix up the buffered data bus.

I did visually check out the boards and there is no physical damage that I can see so once I get the chance to reassemble the rack, I am going to try a different linear P/S in case I killed the reset circuit on mine. Also check the DIPs (thanks for that as well).

If that does not work, I am going to have to bench the rack and give it a try.

Thanks for the suggestions.....

Jeff
 
Jet, go buy some of Madrit's cables. You can't easily be off by one with those and they're great cables and they're cheap.

You shouldn't run with anything else.

Bob's 25x2 cables work fine but make it very easy to do this...

Those aren't 25x2 cables, kiddo.
The ribbons have .1" spacing, not .050", so they're single row.
 
OK, no dice on the new P/S so the issue is with the rack.

Originally the game "kinda" played, with various issues, especially the soundtrack (but that seems to be another problem all together). When booting the game, I would get ROM errors A7 A8, so I had pulled the RAM and ROM in those 3 sockets and tested. The RAM came up good and the 2 ROMs (A7+A8) matched their respective check sums.
Since proving the IC's good, that's when I decided to replace the IC sockets at A6 A7 A8. While I was at it, I capped all 3 PCBs, replaced the ribbon cables and reflowed all headers.
That's when I screwed up the one ribbon cable connection...........

Anyway, since the new P/S did not help, just for the heck of it I ran the RAM/ROM test using the DIP switches and lo and behold, I got the quick blinking LED which indicates ROM errors....... Does that mean ROM errors on the SSIO or could that also mean ROM errors on the CPU or Video PCB's as well?

Next up, disassembly and bench.

I will figure out what happened, one way or the other.

Thanks for the assistance
Jeff
 
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