Williams Woes

r2084

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Trying to get my Robotron PBC working, here's the skinny:

The PCB was installed in a Jamma cab with a switcher/new PS and was working fine for a long time.

Hooked it up recently (in same configuration) and I get nothing, blank screen and no numbers on the LED readout.

Added a 4164 RAM kit and adapter AFTER the blank screen problem, hoping that was the problem, but still the same.

Where should I start in diagnosing the problem?
 
I'll try and check it out tonight or tomorrow night. The PS has a small adjustment range, what voltages should I be getting? Is it best to have a little more than 5V or less?
 
Try pulling and reseating the ROM card ribbon cable if the voltages seem correct. The ribbon cables are very touchy after 30 years and may need to be recrimped to reseat the IDC connections.

ken
 
First of all, thanks to all who have taken the time to help me so far, big TY to you all.

OK, checked the voltage at the board, showed 5.08V. I disconnected the ribbon cable on the main board side and reseated it and now I have a 1-3-1 code showing, so I guess that's progress! Pushed the reset button on the sound board and it started making wonderful Williams sounds. The screen still is blank, kind of a red tinge in color, but now I see an occasional grid of vertical black lines and dots pop on once in a while.

Is error code 1 3 1 a RAM problem? Where should I look next?
 
If the header pins for the power connections to the main board and the rom board are questionable then that can cause a 1-3-1 error. Did you measure the power on the rams or at the power supply? If the rams aren't getting good power it will error on the 1st ram as that indicates. Since you say it worked before I'd check there.

First of all, thanks to all who have taken the time to help me so far, big TY to you all.

OK, checked the voltage at the board, showed 5.08V. I disconnected the ribbon cable on the main board side and reseated it and now I have a 1-3-1 code showing, so I guess that's progress! Pushed the reset button on the sound board and it started making wonderful Williams sounds. The screen still is blank, kind of a red tinge in color, but now I see an occasional grid of vertical black lines and dots pop on once in a while.

Is error code 1 3 1 a RAM problem? Where should I look next?
 
Voltage was measured at the input of the main board where the wires enter the connector.

Measured the voltage on the RAM, the legs farthest away from the semi circle punch mark (sorry don't know what it's called) were 5.05V, the other legs were less. Randomly checked other RAM chip voltages and they seemed consistent to each other, 5.05 at the farthest legs.

The screen is solid red and there are random times when I see black vertical bars and square dots appear briefly. I tried tapping on the ribbon cable and thought I saw some yellow for a split second, but was unable to repeat it.
 
You need to test the voltages at the RAM chips to be sure about CPU board voltages. It is not uncommon for cracks at the headers or bad filter caps to drop the voltages dramatically in the RAM chips.

Measure the voltage at the 4 corners of one of the RAM chips.
The voltages should be
Pin 1 = -5V,
Pin 8 = +12V
Pin 9 = +5V
Pin 16 = Ground
The pins are numbered starting in the upper left corner (the side with the notch), going counter clockwise. If any of them are low or are fluctuating more than 0.1 V you need to check your power supply.


ken
 
The RAM has been changed to the 4164 type (5V) and running an adapter, so pins 8 and 9 should read +5V, right? What should voltage at pin 1 be in this case? Will test and let ya know the results. Thanks.

You need to test the voltages at the RAM chips to be sure about CPU board voltages. It is not uncommon for cracks at the headers or bad filter caps to drop the voltages dramatically in the RAM chips.

Measure the voltage at the 4 corners of one of the RAM chips.
The voltages should be
Pin 1 = -5V,
Pin 8 = +12V
Pin 9 = +5V
Pin 16 = Ground
The pins are numbered starting in the upper left corner (the side with the notch), going counter clockwise. If any of them are low or are fluctuating more than 0.1 V you need to check your power supply.


ken
 
The RAM has been changed to the 4164 type (5V) and running an adapter, so pins 8 and 9 should read +5V, right? What should voltage at pin 1 be in this case? Will test and let ya know the results. Thanks.

Sorry, I missed the reference to 4164. Pis 8 & 9 should be +5V. Pin 1 should be 0.

ken
 
Hope my location IDs are correct, in my following reference, position 3-8 is closest to the batteries and outside edge of the board.

Pins 8 and 9 measured 5.1 and 5.17V consistently throughout all locations, Pin 1 was strange, in position 1-1 it was +3.5V then progressively less until at 1-8 it was +.6V, in 2-1 it was +2.7V also progressively less until 2-8 was .6V, and 3-1 was 2.4V going down to .6 at 3-8.



Sorry, I missed the reference to 4164. Pis 8 & 9 should be +5V. Pin 1 should be 0.

ken
 
Hope my location IDs are correct, in my following reference, position 3-8 is closest to the batteries and outside edge of the board.

Pins 8 and 9 measured 5.1 and 5.17V consistently throughout all locations, Pin 1 was strange, in position 1-1 it was +3.5V then progressively less until at 1-8 it was +.6V, in 2-1 it was +2.7V also progressively less until 2-8 was .6V, and 3-1 was 2.4V going down to .6 at 3-8.

To clarify:
all pin 8's were measured at 5.1V
all pin 9's were at 5.17V
 
To quote Samuel L. Jackson in "The Spirit",

That is just damn weird!
attachment.php


I pulled a board with 4164's and all the pin 1's read 0V. That pin was -5V with 4116s so if your adapter was wired wrong, I would expect a negative voltage.

ken
 

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Last night I tried swapping the switching PS for a newer one to see if it made any difference. I noticed that on first powering up it's giving a 1-3-2 error, followed by 1-3-1. The 1-3-1 continues but the 1-3-2 only comes up once at power up. Does that indicate something?

Also, this is a big DUH, but I realized that the voltage readings I was getting at RAM pin 1 was mV not V. Sorry, I realized it when I remeasured after the PS swap. This is all new to me, but I should have noticed the little m in front of the V. Since it's mV is that close to being 0 or should it be exactly 0 V at pin 1?
 
3.5mV = 0.0035V. That should be close enough to 0. You were probably measuring some induced voltage based on proximity to an AC appliance.

ken

PS: Sorry for the freakin' huge picture. That's what I get for just linking it :(
 
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