Hello.
Space shuttle.
I’ve got 4.90 volts running throughout the board. My reset voltage is only 3.63volts. I can’t figure out what is bringing it down. R170 specs at 4.7k ohms out of circuit, but when I measure resistance in circuit it reads way off. The same is happening around Q52. The 10k ohm r172 resister reads 10k out of circuit but reads 5k ish in circuit. I’ve been fighting with this board for some time now. I feel it is in the reset or logic that feeds into the reset. If I sever the trace before R173 (which feeds Q52 collector pin) I will get 2.6 volts back feeding down the 5v trace to the point I severed it. LED shows a faint 8 with the center segment slightly brighter. This is all on a bench set up using a pc power supply. Thanks for any help.

I do have a logic probe. Have very limited knowledge of using it.

I am not certain if it is reset or blanking. I am using the modified reset circuit from pinwiki that uses the MCP 120 reset generator chip in place of Q4 and the jumper. I’m starting to get a feel for Logic, but I am uncertain as to testing for it. I do have a logic probe. I get no boot up what so ever. My reset circuit voltage is only 3.63 volts. Something is pulling it down or bleeding it off to ground somewhere. That’s what I have been trying to locate. I feel it is somewhere around Q52 ( which is new) and several of the Logic chips in the neighborhood u41 , u42, u43(replaced) , u16, u33, 36, 37.
I’ve got 4.90 volts on the bench throughout the 5v circuit. The machine power supply puts out 5volts, but here is the mystery. When I connect it to the cpu board, the voltage drops to zero. Power supply has been rebuilt.

Logic probe results. I compared my machine with my friends working Sorceror.
Mine is benched. His is turned on waiting for a credit to be assigned.
Reset. Clock (E)
PIAs Mine. His. Mine. His
U15. Low. High. High. High low
U14. Low. High. High. High low
U5. Low. High. High. High low
U13. High. High. High. High low
U4. No signal. High. High. High low
CPUs. IRQ.pin 4 VMA pin 5
U11 High. High. High low. High low. High. High. High. High low
U17. High. High. High low. High low. High low. High ow. High low. High low
Blanking
1J3 p12. Low. High
555 p 7. Low. High
555 p 3. Low. High

Note. All PIAs had been replaced prior to testing as well as 555 time chip and clock crystal. Not sure about cpu chips
U59p9. High. High