(Topic ID: 260701)

Bench Testing Data East cpu board problem


By maddog14

61 days ago



Topic Stats

  • 13 posts
  • 7 Pinsiders participating
  • Latest reply 32 days ago by maddog14
  • No one calls this topic a favorite

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#1 61 days ago

Bench testing data east CPU board. As soon as I attach the 5 volt from bench power supply, the 5 volt goes down to 3.8 volts.
Is a shorted out chip causing the 5 volt to get pulled down? If this is the case, is there an easy way to find out which chip?

The 5 volt and pia light are on, but no booting of cpu.

#3 60 days ago

If there is a problem with the CPU when the game is turned on, the PIA LED will usually stay on, and not turn off (and the Blanking LED will not turn on). Here is what this means:
PIA LED turns ON (and stays on), blanking LED never turns on: EPROM at location 5C and/or 5B is bad.
PIA LED turns ON, turns OFF (and stays off), blanking LED never turns on: EPROM at location 5C and/or 5B is bad (this LED sequence is very rare).
PIA LED turns ON, turns OFF, then turns ON (and stays on), and blanking LED never turns on: 6264 RAM at location 5D is bad.

Copy and pasted from flipperwinkel.

#4 60 days ago

Thanks, But that is where I was able to get the bin file for the leons test chip. So sadly for me, I was already there. While informative, I did not really follow what was stated.

Quoted from mikat11:

If there is a problem with the CPU when the game is turned on, the PIA LED will usually stay on, and not turn off (and the Blanking LED will not turn on). Here is what this means:
PIA LED turns ON (and stays on), blanking LED never turns on: EPROM at location 5C and/or 5B is bad.
PIA LED turns ON, turns OFF (and stays off), blanking LED never turns on: EPROM at location 5C and/or 5B is bad (this LED sequence is very rare).
PIA LED turns ON, turns OFF, then turns ON (and stays on), and blanking LED never turns on: 6264 RAM at location 5D is bad.
Copy and pasted from flipperwinkel.

Yes, I have a copy of this. This information does not appear to be accurate. As stated, I have tried the Leon's test chip as well. I do appreciate the effort though. Thank you.

#5 54 days ago

Bump for more help. See original updated post.

#6 54 days ago
Quoted from maddog14:

Bump for more help. See original updated post.

i dont understand what you are saying is happening. Did you install Leons test eprom and nothing happens? did you make sure you had the right size eprom and the settings on the board set up for that size eprom?

#7 54 days ago
Quoted from maddog14:

Is a shorted out chip causing the 5 volt to get pulled down?

Yes.

IMO - First test would be to remove all chips that are in sockets (ROM/RAM/CPU,etc) and see if the 5v is OK.

#8 54 days ago
Quoted from Neal_W:

Yes.
IMO - First test would be to remove all chips that are in sockets (ROM/RAM/CPU,etc) and see if the 5v is OK.

Bingo. First order of business is to find out what is dragging your 5VDC down.
Any chip on the MPU board could be the culprit.
Start with the easy techniques as neal_w mentioned by removing socketed chips.
After that, leave the board powered for a while. Place your finger on each chip. Does one of them seem abnormally hot?
After that, you are left with educated guesses, and removing chips one by one.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#9 54 days ago

After that, leave the board powered for a while. Place your finger on each chip. Does one of them seem abnormally hot?
After that, you are left with educated guesses, and removing chips one by one.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

I was afraid it would be like that. Removed all the socketed chips. Brought the voltage up a couple of tenths.
The board has been extremely worked on before. Does not look too proffesionally done. I bet it will come down to fixing previous work.

Quoted from Neal_W:

Yes.
IMO - First test would be to remove all chips that are in sockets (ROM/RAM/CPU,etc) and see if the 5v is OK.

Only a couple of tenths.

#10 54 days ago

Any of the remaining chips getting hot?

#11 54 days ago
Quoted from maddog14:

Does not look too proffesionally done. I bet it will come down to fixing previous work.

That is unfortunately the reality that I confront with almost all boards sent to me these days.
I'll often remove all prior rework, just to establish a known baseline of board function.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#12 53 days ago

Any new progress? I'm in the same exact situation, love to hear if you solved it and how. I even started a thread before I noticed this one.
I'd love to hear more tips on how to further narrow down really tricky stuff when normal methods like heat check & diode testing for shorts on logic don't help.
I agree with Chris 100% on removing prior work. That is usually where I start.

3 weeks later
#13 32 days ago
Quoted from thedefog:

Any new progress? I'm in the same exact situation, love to hear if you solved it and how. I even started a thread before I noticed this one.
I'd love to hear more tips on how to further narrow down really tricky stuff when normal methods like heat check & diode testing for shorts on logic don't help.
I agree with Chris 100% on removing prior work. That is usually where I start.

Sadly for the knowledge base, this was a customers board. I cut my loses of time and had him get a rottendog board. Boom like magic. The machine works.

I removed a few chips and got the voltage to go up a few tenths. There were several chips that were noticeably warmer. There was just too much potentially wrong with the board. For my own game, sure I would have fixed it. But how do you charge a customer for all of that time? Plus, how reliable will it be at the end of the day.

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