Help testing a MSU-2 Game Plan Board

anubisdeath6

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I'm trying to get my MPU-2 Board to boot. So far when turned on, I get no flashes of the LED. I'm getting correct voltages everywhere except for TP4 and TP3 (both have to do with the reset). Pin 26 on U11 is reading less than 4, which means the reset is bad? I read that jumping U11 pin 25 to U11 pin 26 will bypass it and allow the rest to boot. But when I do that, I still get no flashes.

Any suggestions?


EDIT, sorry, I titled it MSU not MPU and can't change it.
 
Thanks, but I've already read through that entire thing multiple times, and did everything it said and still no flashes. I'm getting weird readings from TP 3 and 4 and all 4 of the transistors check out fine.
 
"# TP4 (located below U7, reset circuit). RESET Test Point! Should be 5 volts. If not suspect one of the reset transistors QA,QB,QC (2N3904) and QD (2N4403). Also U3 (74LS04) or U5 (74LS32) could be bad.
# TP3 (located below U8, reset circuit). Should be 0 volts. This is the "Anti RESET Test Point", that is if Reset is high (as it should be), this test point will be low. If not suspect one of the reset transistors QA,QB,QC (2N3904) and QD (2N4403). "

and....

"The Gameplan MPU board uses a number of (usually) green 104 (.1 mfd 16 volt) disc capacitors. Just be aware that these can short and drag the 5 volt bus down, giving strange boot up results. These caps can not be tested in circuit. So if there is any questions about them, just replace them all (they are inexpensive). "

we're talking like $2 worth of parts here. just change 'em.
 
Reset should go low briefly before going high when you apply power to the board. If that doesn't happen the board will never boot. If you find a problem with the reset circuit your best option is going to be installing a Dallas DS1811 in place of the original reset circuit.

The next thing to check after the reset is the clock circuit and then move on to sockets, Possible bad ICs, ROM, RAM, etc...
 
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Yeah I checked that and that wasn't the case. The board is being shipped to someone for repairs tomorrow (I'm not paitient enough to do circuitry, I MUCH prefer working on EM games.)
 
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