Stern Solenoid/Driver Board - RevC

[Sinbad79]

yes criss i also suspected that as he still has the 4 eproms installed

interesting, should i be trying something different with these proms?
I have an Eprom burner so can try a few things tonight before i head up tomorrow - any pointers?

[studley67]

the eprom x 4,mpu,pia x2,ram,rom will probally all need to be replaced with new machined pin sockets.

[studley67]

not yet even.but you can bring it with you and teach me how to use mine nfi

[Sinbad79]

OK i'll do that tonight in prep for tomorrow's visit

[studley67]

do you have an antistatic wrist strap?

[Sinbad79]

nope!

[studley67]

without using one you run the risk of destroying chips on removal and re-install.especially the ram as it is a cmos device.

[Sinbad79]

would you prefer to do it, im just thinking of your time is all.
I use an IC removal tool to remove the chips, and try not to touch the legs.

In all honesty, the IC sockets seem OK, they've all tested fine for continuity with a DMM and so have the chips when installed in them.
I would say that some of the IC's are bad anyway - previous owner has probably had these in and out a hundred times before anyway - probably why it doesnt boot.

[studley67]

the sockets loose there tension on the legs and become unreliable,remember they are 35 yrs old

[Sinbad79]

I'll grab an earth strap tonight and do the work so we can focus on diagnosis tomorrow

[Boots]

Pinrepair Guide:

No Flashes: the LED is Permanently On.
If you turn your Bally game on, and the LED stays on continually, this is one of the hardest problem to fix on these boards. A stuck on LED can be caused by any (or all!) of the following:

    * The reset circuit is damaged (after all, it's in the battery corrosion area!) This includes transistors Q1 and Q2 (both 2N3904), Q5 (2N4403), and diodes CR5 (1N4148 or 1N914) and VR1 (1N959B or 1N4738A).
    * The program ROM (read only memory) at U6 is bad.
    * The ROM jumpers are incorrectly set for the U6/U2 ROMs installed.
    * The U9 CPU microprocessor is bad.
    * The U11 PIA (peripheral interface adapter) is bad.
    * ANY of the sockets for chips U6, U9, U11 are bad.
    * The ground trace to U11, U6 or U9 are bad. U11 is especially important to check the ground trace, as it's right in the corrosion zone. And corrosion just loves to travel up the ground traces. Use a DMM set to continuity to check ground at U11 pin 1 (and U11 pin 20 for +5). Also check U6 pin 12 for ground (and U6 pin 24 for +5). U9 pin 1,21 (gnd) is less of a problem as it's well outside the corrosion area.

The first and last two points are probably the most common problems.

[Sinbad79]

Thanks Boots
i've checked most those, even rebuilt the reset section of the board - tested the boot voltage on U9 and it seems to be fine. I dont think its a reset relate issue.

Is there any way to verify the program rom? ie can i read-out the chip contents and verify against an online bin file somewhere?

I have noticed that the VMA voltage on U9 is too high, so if i was a betting man i'd suggest the issue lies therein...
Check U9 Pin 5. This is the VMA line. It is a pulsing signal and reads about 2.8v with a DMM. If incorrect first try a new U9. Next check U14D, U15C, U19B. U15 is the most likely IC to have failed.

A legible M200 Schematic would be of help- those available on the net are very poor quality

[studley67]

if you know how to use your eprom reader/writer ? then you should be able to check the checksum against a known goodone.or just re-program

[studley67]

by just changing all the sockets should fix your prob.if you dont introduce further damage.lol

[Sinbad79]

I highly doubt thats the issue - but hope it is