Williamsburg, KY
Quoted from GRUMPY:If this is on the bench, then you need to lift a leg of C-75, ZR-8, pin-2 U-49 or pin 2 U-50 until the ground short goes away.
It is removed from the game. I will start checking those this evening. Thanks
(Topic ID: 242657)
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I pulled C-75 and zr8 legs and the short was still there. I went to pull u50 and noticed that it was cracked. I pulled it and replaced it and the ground short stopped. I put the board back in and the coils still locked on. I guess I need to pull the board back out and see if the chip has failed again?
You don't need to connect j-19 just to see if it's fixed. Just use your ohm meter or logic probe. Locking on the coils each time will kill the diodes and driver's.
Quoted from GRUMPY:You don't need to connect j-19 just to see if it's fixed. Just use your ohm meter or logic probe. Locking on the coils each time will kill the diodes and driver's.
So I am learning as I go on all of this. How would I check to see if it is fixed with my ohm meter.
Quoted from jmountjoy111:How would I check to see if it is fixed with my ohm meter.
With J-18 and J-19 off the board, power on the game. After the Cpu boots, first check switch inputs J-18 with the voltmeter, pins 2,3,4,5,8,9 should have 5 volts while in attract mode. Any pin that is lower then 2 volts will trigger U-45 and U-50 and turn on a driver transistor when you start a game. Once the switch inputs are good you check the driver outputs on J-19. Pins 3,4,6,7,8,9 resistance should read O/L in attract mode to ground. Then start a game and retest J-19, all should read the same as before until you trigger a switch input during a game or run coil test. Now before you connect J-19 again you need to replace all SS coil diodes.
pb cpu (resized).PNGQuoted from GRUMPY:With J-18 and J-19 off the board, power on the game. After the Cpu boots, first check switch inputs J-18 with the voltmeter, pins 2,3,4,5,8,9 should have 5 volts while in attract mode. Any pin that is lower then 2 volts will trigger U-45 and U-50 and turn on a driver transistor when you start a game. Once the switch inputs are good you check the driver outputs on J-19. Pins 3,4,6,7,8,9 resistance should read O/L in attract mode to ground. Then start a game and retest J-19, all should read the same as before until you trigger a switch input during a game or run coil test. Now before you connect J-19 again you need to replace all SS coil diodes.[quoted image]
Learn something new everyday. I’ll replace those diodes tomorrow and get back to it.
Quoted from jmountjoy111:Any one know a source to buy legit 6821 chips.
These new replacements are great and are used on Alltek MPU boards. I have used 20 of them with no issues on various DE and Williams MPU boards.
Quoted from PinballManiac40:These new replacements are great and are used on Alltek MPU boards. I have used 20 of them with no issues on various DE and Williams MPU boards.
https://www.mouser.com/ProductDetail/Western-Design-Center-WDC/W65C21N6TPG-14?qs=%2Fha2pyFaduiPoUewmeSNS2DLBidqhFEucYPYqS2dsIcf7XyqMCXSA%252B5L3vKQVQ4u
Awesome thanks. I had looked at mouser and just saw they didn’t have 6821. I didn’t know these were a replacement
I have replacement for my 6821s on order. I’m going to try and replace those diodes this evening or tomorrow morning.
Quoted from GRUMPY:With J-18 and J-19 off the board, power on the game. After the Cpu boots, first check switch inputs J-18 with the voltmeter, pins 2,3,4,5,8,9 should have 5 volts while in attract mode. Any pin that is lower then 2 volts will trigger U-45 and U-50 and turn on a driver transistor when you start a game. Once the switch inputs are good you check the driver outputs on J-19. Pins 3,4,6,7,8,9 resistance should read O/L in attract mode to ground. Then start a game and retest J-19, all should read the same as before until you trigger a switch input during a game or run coil test. Now before you connect J-19 again you need to replace all SS coil diodes.[quoted image]
Ok I replaced the diodes on the coils. I replaced the 6821 chips with the replacement that was mentioned above.
I tested j18 and all the pins were at 4.9.. v except pin 3 which read 162mv
I did not test the j19 because you said I needed to line out j18 first or at least that is how I read it.
Quoted from jmountjoy111:at least that is how I read it.
Correct.
Quoted from jmountjoy111:except pin 3 which read 162mv
This will lock on the coil when you start a game. Is the connector J-18 on or off the CPU?
I removed the board and zr6 measured at 12 ohm. I replaced it and u45 (since I had already done u50) for good measure. I removed u49 and the ZR measured correctly with it out of the board. I tried a different 7407 in u49 and all zeners measured correct so I then put the board back in. Pin 3 on j18 now measured correct at 5 Vdc but now pin 8 is at 162 mv. Is it possible both chips are just bad? The old one and the one I thought was good? I do not have another 7407 so I will have to order one
Quoted from jmountjoy111:Is it possible both chips are just bad?
Anything is possible with the number of times the coil were locked. Are U-45 and U-50 in sockets? If yes, pull both chips and then test J-18 pins, all should be 5 volts.
That was with u45 and u50 still in. They are socketed and would be easy to remove and test but I didn’t know if I needed too with having 5v on everything with u49 removed
Quoted from jmountjoy111:That was with u45 and u50 still in. They are socketed and would be easy to remove and test but I didn’t know if I needed too with having 5v on everything with u49 removed
Your making good progress, try a new U-49 and retest. The end is in sight.
Quoted from PinballManiac40:If you have an Fry's Electronics store near you, they may have a NTE7407 equivalent part.
I sadly live near nothing lol. I like living in a small town but it definitely has it’s downfalls.
Quoted from GRUMPY:Your making good progress, try a new U-49 and retest. The end is in sight.
I ordered some chips last night. I will install them and test as soon as they come in and report back what the finding are.
Quoted from jmountjoy111:I like living in a small town but it definitely has it’s downfalls.
So do I, but more benefits then downfalls.
Quoted from GRUMPY:So do I, but more benefits then downfalls.
I couldn’t agree with you more.
I got the new 7407 chip in from Great Plains and I put it in the game. All pins except pin 8 on j18 are 5v. Pin 8 is reading 62mv
Quoted from jmountjoy111:with u 49 removed I am measuring at 1.39 vdc at pin 1
The needs to be @ 5 volts, check the traces and solder joints of both chip sockets and the resistor pack.
Quoted from GRUMPY:The needs to be @ 5 volts, check the traces and solder joints of both chip sockets and the resistor pack.
Do you mean the u45 and u50 chips?
U-49 pin 1 should always be 5 volts unless in coil test on this particular special solenoid. Then it would be a high with low pulses. Since you are reading 1.39 volts I would guess that if you measure at the resistor pack it maybe 5 volts. But a poor solder joint on the pia or U-40 chip socket maybe causing the voltage to drop under load. Your real close to finding the problem here so stay after it.
Quoted from GRUMPY:U-49 pin 1 should always be 5 volts unless in coil test on this particular special solenoid. Then it would be a high with low pulses. Since you are reading 1.39 volts I would guess that if you measure at the resistor pack it maybe 5 volts. But a poor solder joint on the pia or U-40 chip socket maybe causing the voltage to drop under load. Your real close to finding the problem here so stay after it.
Awesome. Hey if nothing else I’m learning a bunch. I really appreciate the help. It may be tomorrow before I can test it further but I will check it out and post back.
Quoted from jmountjoy111:It may be tomorrow before I can test it further but I will check it out and post back.
Not to many items to check here. How are the traces?
pia (resized).PNGSorry. I just got to the machine.
I have continuity from u54 pin 19 to sr-19 pin 10 and to u49 pin 1.
Quoted from jmountjoy111:I have continuity from u54 pin 19 to sr-19 pin 10 and to u49 pin 1.
Do you have five volts at SR-19?
pia (resized).PNGQuoted from GRUMPY:What does pin 1 of U-49 read if you remove U-54?
I have not replaced u54 so it isn’t socketed. I will remove it and add a socket and test
With no chip in u54 there is 5v to pin one on u49. Should I put a new 6821 in and test the power then?
Quoted from jmountjoy111:With no chip in u54 there is 5v to pin one on u49. Should I put a new 6821 in and test the power then?
I think so.
Ok so I replaced u54 and u49 pin reads 5v. I replaced the 7407 in u49 and pins 2,3,4,5,8,9 on j18 all read 5v.
Do I need to plug j18 back in to test j19?
Quoted from jmountjoy111:I replaced the 7407 in u49 and pins 2,3,4,5,8,9 on j18 all read 5v.
Quoted from jmountjoy111:Do I need to plug j18 back in to test j19?
I would put the board in the game and reconnect every connector but 1J-19.
I would then turn on the power and the check resistance from ground to each of the 6 SS TIPs metal tabs. Should be high resistance. If OK, then I would start a game and retest the 6 SS TIPs. If OK then I would replace the 5 coil diodes and check the coil resistance. Then I would reconnect 1J-19 and do a coil test to see if every thing is all good.
Quoted from GRUMPY:I would put the board in the game and reconnect every connector but 1J-19.
I would then turn on the power and the check resistance from ground to each of the 6 SS TIPs metal tabs. Should be high resistance. If OK, then I would start a game and retest the 6 SS TIPs. If OK then I would replace the 5 coil diodes and check the coil resistance. Then I would reconnect 1J-19 and do a coil test to see if every thing is all good.
All specials are reading correctly except the upper jet bumper. The others read some resistance to ground when I connect to their corresponding pin on j19 until I engage the switch. Then they read o/l. The upper jet reads o/l at all times
I replaced q79 and the 4401 driver for it just for good measure and now ALL special solenoids are working properly!!!!
GRUMPY thank you so much for your help. I’m sure you get told all the time but you are such an asset to the pinball community. I really do appreciate all the help and patience with my pinball ignorance lol
Since you have some of the PIAs in sockets now, are you going to test the counterfeit PAIs one at a time to see if they are working chips?
Quoted from GRUMPY:counterfeit PAIs
I see what you did there. Most like a typo though. Still funny.
Quoted from GRUMPY:Since you have some of the PIAs in sockets now, are you going to test the counterfeit PAIs one at a time to see if they are working chips?
Would it be safe to just insert them in and see?
Quoted from jmountjoy111:Would it be safe to just insert them in and see?
Yes. That is what he meant.
Quoted from PinballManiac40:Yes. That is what he meant.
Then yes of course I will test them all. I didn’t know and certainly didn’t want to mess this thing up again lol.
Quoted from jmountjoy111:Would it be safe to just insert them in and see?
But disconnect J-11,J-12 and J-19 so a coil wont lock on.
Quoted from PinballManiac40:Still funny.
Your the only one who understands my weird sense of humor.
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