Tempest

[DanP]

Symptom:
Brightness issues. Sometimes it
would be fine, sometimes dim or too bright.
Fiddling with the brightness control on the HV box would get it
settled. As time went by the brightness
would flicker.

Fix: Eventually found the connector pins from the two
wires coming from the Brightness/Focus block had poor connections. Replaced the pins (and soldered them in) and
all is fine.

 

[Equites]

Symptoms:
PCB was dead, constantly watchdogging.

Fixes:
Found two bad ROMs, PCB now boots to TEST (shows 'M' for Mathbox problem), GAME does not start, watchingdogging.

Checked ROM sockets, these were fine. However, it seemed that the GAME could not start due to not being able to read program ROMs. Check 8403 buffers, these checked out fine.

Checked the multiplexor LS139 at C1. I had previously probed this IC, but had made the fatal mistake of leaving the PCB in TEST mode where the pin would not be active anyway. Hence, I never spotted that pin 6 was stuck HI, and therefore it could never select the ROM during game mode.

Swapped in a fresh LS139 and GAME now starts but with bad vectors due to Maths box problem. This was due to a bad ALU and PROM - all working 100% now.

Equites2013-01-29 23:06:14

 

[tb lilley]

Still working too.

 

[Equites]

Symptoms:
PCB constantly watchdogging, game would not start, vectors randomly drawing quickly. Test mode did not work either. No beep indicating bad RAM.

Fixes:
I checked the ROMs, but these all checked out good, including the one ROM which is used for the SELF TEST. The ROM select circuitry seemed to be fine.

Problem turned out to be two bad 2114 RAMs that are used as a scratchpad. SELF TEST did not report bad RAM because the sound was not working! Damaged resistor and Capacitor was replaced in the sound circuit.

GAME now starts but with bad vectors due to Maths box problem. This was due to a bad ALU socket - all working 100% now.

 

[IDCHAPPY]

Well done buddy