[Techtoolslist] Midway Sea Wolf with Fluke

[John Robertson]

On 04/08/2013 11:00 AM, Theron Troxel wrote:

> Just started using my Fluke for the first time.  Decided to work on a Sea Wolf that quit working on me.  Ran a bus test, which came back fine.  Then did a short RAM test, and got the following errors:

>

> Range 0000-1fff

> R/W ERR @ 0000 BTS FF - loop?

>

> Range 2000-3fff

> RAM DCD ERR @ 2000 Bit 11 - loop?

>

> Range 4000-5fff

> R/W ERR @ 4000 BTS FF - loop?

>

>

> Looking into the manual, I found the errors, but not quite sure what they are telling me.  I somewhat get the RAM DCD error.  It's saying at 2000 there is a problem with the address 11, which would be pin 3 on the RAM.  Is that correct?

>

> One of my questions, is how do you know what RAM goes with what error?  If there are 16 RAM chips on the main pcb, how do you tell which ones are between 0000-1fff and which one goes with 0000?

>

> Not sure what the R/W error is stating.

>

> Any help would be greatly appreciated.

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Back on February 19 Andrew Welburn said:
/
//IIRR There are two resistors on the clock signals coming from the 
clock generator IC for the 8080 ... from memory, they should be 150ohm, 
but you might find different values loaded (taitos are different to 
schems, and had 750's). //
////
//You can temporarily short the resistor or change for 100ohm so the 
clock signal goes straight through to the CPU or near enough. the fluke 
pod will then run UUT. //
////
//This problem stumped me for months about a decade ago. I just resigned 
myself to the fact you couldn't run uut on 8080 pcbs. I finally came 
across a Taito SI with bad clocks and thats when i noticed the clock 
signal differences before and after the resistors, and the difference 
from the schems. //
////
//I will say though, this problem is not really apparent on Midway pcbs, 
rarely do i get UUT run problems, maybe one in the last 30 or so i've 
fixed? I do sometimes get crashing or ram dots appearing, but i tend to 
ignore these because i know this is an artifact of the pod, its not 
worth modding every pcb if i pop a good cpu in and it runs fine. Most of 
the time i dont see it tbh, but ymmv. /

Perhaps relevant to your problem?

John :-#)#

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