(Topic ID: 326327)

Firepower will not enter diagnostics

By Eytan

7 days ago


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  • 27 posts
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  • Latest reply 2 days ago by Eytan
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20221128_190219_resized (resized).jpg
TC5501P (resized).jpg
s6sch1.pdf (PDF preview)
43915029-7637-447B-8D1B-7179BA68CF92 (resized).jpeg

#1 7 days ago

So my Firepower ( Williams system 6 ) has been working and used regularly for years. The other day it powered on in audit mode. The batteries were completely dead. Changed them but now the game plays with defualt settings ( coin only and 3 balls ). I cannot enter the settings menu or enter diagnostics. Game boots up in game over attact mode and plays fine. I checked door switches ( at the switches and the MCU board connector ) AND grounded the advance button on the MCU board connector ( top left ) but has no effect. If I press diagnostics button the 2 leds blink twice ( passes test ) and the displays blank. door switches do not have any effect and I cannot do lamp test , etc. Any help where I can start troubleshooting would be greatly appreciated. Weird thing is the game is playing perfectly. The door switces did work previously ( a few years ago ). Nothing changed except for my batteries going dead

#2 7 days ago

My Gorgar still has the 40 pin connector and when it acts up I slightly pry the boards apart so the pins are touch at different spots along the connector. Just a thought.

#3 7 days ago

Ya, I actually removed the MCU and Diver boards. re-soldered the 40 pin connecetors as a few were showing signs of cracking. No effect. I beleive it only has to do with the MCU board and not the dirver board and 40 pin connectors as the game plays properly. Thx thhough.

#4 7 days ago

Any corrosion on the board or battery holder where the batteries were?

#5 7 days ago

Not so much near the battery holder, however the board does show signs of age and previous repairs. The green coating on the circuit board is "wavy" in some locations. I went through and inspected for any signs of a bad connection. I even checked the TP1 to TP9 values and they all seem correct ( except TP-1 is 9.?? volts DC rather than 12V DC, but I think this is ok from another post i saw ).

#6 6 days ago

What do you get at TP7?

#7 6 days ago

I get around 4.3 VDC which is what I was told to expect.

#8 6 days ago

4.3 is good.
Any chance one of your door or coin switches is closed?

#9 5 days ago

I don't think so. Coin slot works to add credit. Game stores and updates high score. Game plays great and strong ( i reflowed the 40 pin connector). Door switch to reset high score works. The adjust and auto up do give proper states at jumper ij2 ( 2nd top left connector ) but game won't enter audit or do a diagnostic. Im at a loss as to what more to check.

#10 5 days ago

With door open, i can still add credits with coins and start game. Not sure if that is normal or significant.

#11 5 days ago

Maybe a bad PIA. Do you have a good known PIA you can swap out?

#12 5 days ago

Maybe you already tried to advance diagnostics on the board. I took a quick picture of my board set with diagnostic switches. If you can make out my picture-diagram to test and make sure it the board.

43915029-7637-447B-8D1B-7179BA68CF92 (resized).jpeg

#13 5 days ago

The diagnostic switch inputs go to IC5 you should be able to test the outputs of pins 13 and 10 as you press the advance button or change the up/down switch. They should change voltage (if you have a logic probe even better) as you press each (press and hold for advance, the up/down will lock of course).

If you don't see the outputs changing test the inputs. Pins 11/12 for pin 13's output, pins 8 and 9 for pin 10's output. One input goes to the connector for the switches, and the other is the !IRQ (inverse IRQ) signal. (which is probably ok since the game boots and plays)

#14 4 days ago

Thx guys. I have tried to mimic the switches directly on the board no effect. Ill test IC5 as you recommended and report back.

#15 4 days ago

Sorry Jethro what is a PIA ?

#17 4 days ago

You have 3 PIA's on the board. If they are socketed, try swapping one of the other ones with IC11 and see it that makes any changes. May identify if IC11 is bad.

#18 4 days ago
Quoted from slochar:

The diagnostic switch inputs go to IC5 you should be able to test the outputs of pins 13 and 10 as you press the advance button or change the up/down switch. They should change voltage (if you have a logic probe even better) as you press each (press and hold for advance, the up/down will lock of course).
If you don't see the outputs changing test the inputs. Pins 11/12 for pin 13's output, pins 8 and 9 for pin 10's output. One input goes to the connector for the switches, and the other is the !IRQ (inverse IRQ) signal. (which is probably ok since the game boots and plays)

OK, so I think there is a problem with inputs to IC5. Here are results from testing:
Pin8 is 4.8V no press (adjust) 0.12V with press ( adjust)
Pin9 is 4.8V No press 4.8V with press
Pin10 is 0.19V no press 0.23V with press

for pins 11,12 and 13 I might have my adj/man switch upside down ( reversed)
Pin11 is 4.8V switch up 4.8V switch down
Pin12 is 4.8V switch up 0.12V switch down
Pin 13 is 0.29V switch up 0.13V switch down

For an inverted nor gate I require both inputs to be 0V to get 5V at output I believe.
Pins 8 and 12 are changing states but pins 9 and 11 are staying HIGH.
Pins 9 and 11 are tied together and seem to be the IRQ line. I am only using a multimeter to measure voltage on the pins. perhaps I can't detect IRQ going low ? This is TP5. is there a way to further test this ?

#19 4 days ago

Here is the schematic for CPU board I'm referencing.

s6sch1.pdf
#20 4 days ago
Quoted from JethroP:

You have 3 PIA's on the board. If they are socketed, try swapping one of the other ones with IC11 and see it that makes any changes. May identify if IC11 is bad.

JethroP, I think you hit it. I just noticed IC11 output is the input fed to Pins 9 and 11, which I believe are not behaving after analyzing IC5

So TP5 seems to be this IRQ line which is the output from IC11. Can I tie that to 0V to test or is that a really bad idea ??

#21 4 days ago

The main thing I was looking for is for the output pins on U5 to transit, and they don't, the IRQ signal is likely missing/not transitioning as you say, I would not tie that signal low as it would likely crash the system just to test U5. Signs are pointing towards the 6821 at IC11.

#22 4 days ago

Ok so unfortunately the PIA in the CPU board is soldered in. There are 3 - 6821 pia's in sockets in the driver board as it was probably previously repaired by someone.

I guess I'll order a 6821 chip ( I read somewhere I should replace with 6821 rather than 6820 ) and a 40 pin socket and hope...

I must say everything on the cpu board looks in excellent shape and orriginal except IC19 seems to have been replaced. solder work looks so so.
Could this chip have any affect on my issue ( cmos ram address ?? ). I also noticed that the spec sheet calls for a 5101 CMOS Ram chip, but the chip installed is a Toshiba TC5501P chip. ( I'll attach a pic).

TC5501P (resized).jpg
#23 4 days ago

You’re not replacing the soldered in PIA on the MOU board. Replace IC11 on the driver board. It’s already socketed. If you want, just swap it with one of the others on that board and see if you can get into diagnostic test to verify that’s the problem

You can replace 6820 with 6821. There are other substitutes as well.

#24 3 days ago
Quoted from JethroP:

You’re not replacing the soldered in PIA on the MOU board. Replace IC11 on the driver board. It’s already socketed. If you want, just swap it with one of the others on that board and see if you can get into diagnostic test to verify that’s the problem
You can replace 6820 with 6821. There are other substitutes as well.

Ok, so if I understand correctly, you are thinking it's a problem with IC11 on the driver board.
Yes I can swap IC11 with one of the other PIA's on that board. I'll try that tomorrow night after work.

Thanks again for your help.

#25 2 days ago

Ok so I have more info. I swapped IC11 PIA with the lamp PIA beside it. Turned the machine on adjust button still has no effect. Everything seemed the same. I did a close scan of all components and touched all chips for heat. I then noticed the 8A 18V lamp fuse was blown and play board lamps were out. I changed the fuse with a 7.5A ( didn't have an 8A ) and lights came on. fuse did not blow again ( prob old and weak ), BUT I decided to try and play a game and although it played normal the playboard lamps were all ( or mostly ) on where they should not have been. So I guess that chip is bad, but why did it not allow me into diagnostics after the swap ???

#26 2 days ago

Maybe a bad socket or two?
Are the chips AMI brand by any chance? If so, they have a history of going bad and would be well to replace.

#27 2 days ago

The one chip for the solenoids which I did not touch is a motorola 6821P
The other 2 that I swapped I don't recognize the logo. here is a pic. Possible SGS Thompson ?
So are you thinking there could be an issue with the IC socket as well as with the actual chips ?

20221128_190219_resized (resized).jpg

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