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WPC-S MPU issue~ advice appreciated

Game On

Game On

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Mar 10, 2020
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127
Location
Cheltenham
Help please from you lovely people I am treying to help my brother who has a Roadshow. He tells me that all of a sudden the game stopped working with no apparent symptoms. When I asked further he confirms the game does not even boot. no Displays etc. He lives in Chester so he sent me the MPU and driver board as I requested. I initially though it would be the usual driver board issues with the Capacitors and 5 volt regulator but no the power board is fine and works perfectly in a Flintshtones I currently have. i have the mpu on the bench connected to a computer PSU delivering a stable 5 & 12 volts. When I connect it All 3 LEDs illuminate and stay on. There is no apparent damage or burning on the board. I took a risk and one by one put the Processor, NVRAM, ASIC, Game Rom & Security Chip into my Flintstones board and all are fine and boot normally I have not connected the switch matrix connectors so I get the usual "Check Fuses 114 &115" on the DMD but everything else runs ok so I know all the important IC's are good . with all these IC's out of the board D20 &21 stay on if I put in the known good ASIS D19 comes on and stays on as well. Can any of you good people point me in the right directions as to why all the LEDs are permanently on I expect the bottom one D21 to be on as it is the 5 volts but I understand D19 is the Strobe and D20 the diagnostics why do they say on HELP!!
 
How are the sockets? I've had corroded connectors behind the ASIC chip stop a boot.
 
Dex-Jay said:
How are the sockets? I've had corroded connectors behind the ASIC chip stop a boot.
Click to expand...
It is not even getting to that stage ALL THREE LED.s light when the board is plugged in to a 5 & 12 Volt PSU All the main IC are known good but not even in the game yet LED 20 is supposed to be the diagnostic and flash accordingly just comes on and stays on and I do not know why?
 
The only other thing I can suggest is give that ASIC chip a push while powered on. If that isn't right you wont get the flashing lights and that's all it takes.
 
Logic probe time. that asics is a bit of a black box not sure what signals the cpu sends to it in order to alter the blanking line state and the diagnostics led line too.
 
I cant understand how the ASIC chip can ge causing the balnking and diagnostic LED's to light on powrr up on the bench when it is not even installed in the game plus I have tested the ASIC in a different game and it is fine!
 
The ASIC seating is what we are highlighting might be an issue. The socket could have a pin that is slightly corroded or the chip isn’t seated properly. I had this with a game and the lock light stayed on. Removed, cleaned, put back, board started to work and then I went on to fix it’s other issues.
 
This from Clay's guide may help a bit, though it sounds as if youve checked the ICs, the issue may be with the sockets or elsewhere:

Bad socket at U9.
The large U9 WPC square chip can have a bad socket. It's not much fun to replace this
84 pin socket! Radio Shack sells replacement sockets, part number RSU 11354453,
$1.99, but they may not stock it. Use your DMM and check for continuity with the chip
installed before you replace this socket.
Shotgun Approach.
The chips are U1, U2 (74LS244) and U3 (74LS245) are the ones that affect on a dead
CPU the most. If replacing those yeilds nothing, then try replacing U5 (74LS14). Also
check resistors R95 and R99 (1 meg ohms) to make sure these are the correct value.
Finally U10 (a MC34064 transistor that is part of the startup circuit) can be replaced.
Using a logic probe, also check for a good clock signal on pins 34 and 35 of U4 (6809
 
Ped said:
This from Clay's guide may help a bit, though it sounds as if youve checked the ICs, the issue may be with the sockets or elsewhere:

Bad socket at U9.
The large U9 WPC square chip can have a bad socket. It's not much fun to replace this
84 pin socket! Radio Shack sells replacement sockets, part number RSU 11354453,
$1.99, but they may not stock it. Use your DMM and check for continuity with the chip
installed before you replace this socket.
Shotgun Approach.
The chips are U1, U2 (74LS244) and U3 (74LS245) are the ones that affect on a dead
CPU the most. If replacing those yeilds nothing, then try replacing U5 (74LS14). Also
check resistors R95 and R99 (1 meg ohms) to make sure these are the correct value.
Finally U10 (a MC34064 transistor that is part of the startup circuit) can be replaced.
Using a logic probe, also check for a good clock signal on pins 34 and 35 of U4 (6809
Click to expand...
Ped said:
This from Clay's guide may help a bit, though it sounds as if youve checked the ICs, the issue may be with the sockets or elsewhere:

Bad socket at U9.
The large U9 WPC square chip can have a bad socket. It's not much fun to replace this
84 pin socket! Radio Shack sells replacement sockets, part number RSU 11354453,
$1.99, but they may not stock it. Use your DMM and check for continuity with the chip
installed before you replace this socket.
Shotgun Approach.
The chips are U1, U2 (74LS244) and U3 (74LS245) are the ones that affect on a dead
CPU the most. If replacing those yeilds nothing, then try replacing U5 (74LS14). Also
check resistors R95 and R99 (1 meg ohms) to make sure these are the correct value.
Finally U10 (a MC34064 transistor that is part of the startup circuit) can be replaced.
Using a logic probe, also check for a good clock signal on pins 34 and 35 of U4 (6809
Click to expand...
Thank you for the practical advice I will try it. I dont think it is the ASIC socket as I have carefully removed the ASIC (using the proper tool) and thouroughly inspected with a magnifiing lamp the socket and board. Just to be sure I hav=d the board in an Ulrasonic Tank for 3 hours and it has come out gleaming but no change. Will try the 74LS circuitry next. I will NOT give up on this and get back to the forum.
Ped said:
This from Clay's guide may help a bit, though it sounds as if youve checked the ICs, the issue may be with the sockets or elsewhere:

Bad socket at U9.
The large U9 WPC square chip can have a bad socket. It's not much fun to replace this
84 pin socket! Radio Shack sells replacement sockets, part number RSU 11354453,
$1.99, but they may not stock it. Use your DMM and check for continuity with the chip
installed before you replace this socket.
Shotgun Approach.
The chips are U1, U2 (74LS244) and U3 (74LS245) are the ones that affect on a dead
CPU the most. If replacing those yeilds nothing, then try replacing U5 (74LS14). Also
check resistors R95 and R99 (1 meg ohms) to make sure these are the correct value.
Finally U10 (a MC34064 transistor that is part of the startup circuit) can be replaced.
Using a logic probe, also check for a good clock signal on pins 34 and 35 of U4 (6809
Click to expand...
Hi there Where is there a Radio Shack in Cheltenham. I thought they went years ago along
 
Game On said:
Help please from you lovely people I am treying to help my brother who has a Roadshow. He tells me that all of a sudden the game stopped working with no apparent symptoms. When I asked further he confirms the game does not even boot. no Displays etc. He lives in Chester so he sent me the MPU and driver board as I requested. I initially though it would be the usual driver board issues with the Capacitors and 5 volt regulator but no the power board is fine and works perfectly in a Flintshtones I currently have. i have the mpu on the bench connected to a computer PSU delivering a stable 5 & 12 volts. When I connect it All 3 LEDs illuminate and stay on. There is no apparent damage or burning on the board. I took a risk and one by one put the Processor, NVRAM, ASIC, Game Rom & Security Chip into my Flintstones board and all are fine and boot normally I have not connected the switch matrix connectors so I get the usual "Check Fuses 114 &115" on the DMD but everything else runs ok so I know all the important IC's are good . with all these IC's out of the board D20 &21 stay on if I put in the known good ASIS D19 comes on and stays on as well. Can any of you good people point me in the right directions as to why all the LEDs are permanently on I expect the bottom one D21 to be on as it is the 5 volts but I understand D19 is the Strobe and D20 the diagnostics why do they say on HELP!!
Click to expand...
just checking have you tried booting the MPU with nothing connected to it? Another reason for non-booting can be the ribbon cables.
 
Game On said:
Hi there Where is there a Radio Shack in Cheltenham. I thought they went years ago along
Click to expand...
That's a direct quote from the guide so I guess that was referring to the USA . Not sure there's ever been one in Chelt - there was a Maplins at one point but they're all online now
 
Neil McRae said:
just checking have you tried booting the MPU with nothing connected to it? Another reason for non-booting can be the ribbon cables.
Click to expand...
As mentioned I have the MPU on the bench only connected to a PC PSU delivering exactly 5 &12 Volts there are no other cables connected at all. I have run it with both the Proccessor, ASIC , ROM, RAM & Security chips both in and out and all 3 LEDS light and stay on in both situations. It simply cannot be anything to do with the rest of the machine and any of the removable IC's I rekon I am gonna start checking every component and replace all the 74 LS logic chips as the whole lot should cost less than a tenner.. I WILL find this barsterard fault, (eventually), and relay what I find on the forum
 
Ped said:
That's a direct quote from the guide so I guess that was referring to the USA . Not sure there's ever been one in Chelt - there was a Maplins at one point but they're all online now
Click to expand...
Yeah I was only "joshing" with you I dont think you can buy electronic components in a retail shop over the counter anywhere in the UK now since Tandy Radio Shack went and Maplin went bust. RS have a few Trade counters but even they are not easy to deal with these days
 
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Game On said:
Yeah I was only "joshing" with you I dont think you can buy electronic components in a retail shop over the counter anywhere in the UK now since Tandy Radio Shack went and Maplin went bust. RS have a few Trade counters but even they are not easy to deal with these days
Click to expand...
Did you resolve this? What was it in the end?

Oh, he's banned? I won't get a reply then! :/
 
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