Sys 80 Non CPU boot/IRQ issue

[The pinballist formally known as Dean Morgan]

OK, so at the moment, A12-J4 is NOT plugged in.  There is a red connector (fits) coming from backbox without a label.  Its the only red one...
So should they be connected together....(just cautious don't want to plug wrong shit in and really make a mess)

Yes it needs to be plugged in...however, site unseen I cannot comment on if thats the correct plug to plug it into...but if it fits it most likley is!

[MartyJ]

Some progress...

Not smoke or bang.

P1 is showing roughly in the middle what looks to be a no. 6 (perhaps with a 1 locked on) and P3 is showing a 0.

[The pinballist formally known as Dean Morgan]

Some progress...

Not smoke or bang.

P1 is showing roughly in the middle what looks to be a no. 6 (perhaps with a 1 locked on) and P3 is showing a 0.

Sounds good, I must go for today.  Try swapping Player 1 and 3 displays and see what happens.  Good visual way to tell if the processor is running is to see if the displays cycle from high score to date to last score played.  If you leave it on should cycle ever 5 to 10 seconds or so.

We will get there in the end

[MartyJ]

Some progress...

Not smoke or bang.

P1 is showing roughly in the middle what looks to be a no. 6 (perhaps with a 1 locked on) and P3 is showing a 0.

Sounds good, I must go for today.  Try swapping Player 1 and 3 displays and see what happens.  Good visual way to tell if the processor is running is to see if the displays cycle from high score to date to last score played.  If you leave it on should cycle ever 5 to 10 seconds or so.

We will get there in the end

Thanks for the help thus far.  Two steps forward....

Well at least I know now the CPU is not booting....

[MartyJ]

Thanks again Dean,

Now armed with a new Fluke so I can trust DMM readings a bit more.  I emailed Clay too about that some DMM's may give readings on his Sys 80 guide (MPS-U45's) that they are bad, but if the DMM has less than 2.000v on the diode test will continue to give bad readings.  Not bad transistors, just DMM not enough grunt to give his readings!  Hopefully may save someone else a headache down the track..

I've been going through the http://www.geocities.com/kirbseepe/repairCPU.html guide as well.

From the start, my Z26 (pin 12) is definately not giving 5v at all.  Somewhere to start at least!

[MartyJ]

The logic probe (I think) is starting to become handy.

It also appears that my IRQ is stuck LOW (pin 4 U1).

I've replaced U4 and U5 RIOTS....

[ddstoys]

DOes that have something to do with the game rom not working from memory?

[MartyJ]

DOes that have something to do with the game rom not working from memory?

Not 100% sure as yet.  I'm chasing my tail a bit as problems are somewhat intermittant.  For example, this morning, IRQ was stuck LOW and had funny displays on screens.
Tonight, IRQ is getting stuck HIGH.

According to Clay's guide, it may be issues with U2/U3 game ROMs.

I'm hoping for someone who may be able to guide me in this area.

Reset appears to be functioning correctly, I've replaced crystal and Z2 & Z3 just to be sure.  U4 & U5 also changed.  U1, U4, U5 & U6 all appear to be getting clock signal too.

[ddstoys]

Well i didnt get mine goig but when i replaced the game rom u2 it fixed the irg maybe try removing the chip and reseating it since its intermitant?

[MartyJ]

Not an option.

On my breed of Sys80 board both U2 & U3 are NOT socketed!...

Looking at other options at this stage...Are they expensive to get?

[MartyJ]

U5 reseated again.

Out of about 10 powerups, IRQ is constantly getting stuck high.

I am happy to replace U2/U3 if required.  Is there anything I can check before pin 4 on U1 if it is causing issues with the IRQ?

[Strangeways]

Marty - I have not spent enough time on system 80 MPUs to assist here, so I'm a little "out of my depth" - But - If you need ROMs and you want to "dig deeper" with the board - Try Ed at GPE ;

http://www.greatplainselectronics.com/proddetail.asp?prod=120-102

I'm thinking of getting a Quickscan - Just for a "play", as I have quite a few Sys80 boards I need to fix. Clay gets dirty in his guide;

http://www.pinrepair.com/sys80/index3.htm#testrom

ROMS

http://www.greatplainselectronics.com/proddetail.asp?prod=140-101

I might have an untested board you can use for testing.

[ddstoys]

Hey Marty
                 The rom for rock cost me around $70 with postage etc.  Mine has an adapter so i cant even lend you mine for a test.

[MartyJ]

Marty - I have not spent enough time on system 80 MPUs to assist here, so I'm a little "out of my depth" - But - If you need ROMs and you want to "dig deeper" with the board - Try Ed at GPE ;

http://www.greatplainselectronics.com/proddetail.asp?prod=120-102

I'm thinking of getting a Quickscan - Just for a "play", as I have quite a few Sys80 boards I need to fix. Clay gets dirty in his guide;

http://www.pinrepair.com/sys80/index3.htm#testrom

ROMS

http://www.greatplainselectronics.com/proddetail.asp?prod=140-101

I might have an untested board you can use for testing.

Thanks Nino,

I've sent Ed an email for a couple more spare parts.  He is a System 80 guru.  He is out of stock of the Quickscan's, but I'll wait for his response to see what he recommends.  I am thinking it would be a good purchase either way. (hmm, maybe a HH too one day!)..

[The pinballist formally known as Dean Morgan]

If the tests are done correctly then it is a good chance that U2 or U3 is bad.  Also try it with the game prom removed. and test the IRQ then to ensure this is not dragging it down.