Davewellington: moved Terra Cresta by Paul Swan to Terra Cresta Repair Logs

2012-09-07T01:03:57Z

moved Terra Cresta by Paul Swan to Terra Cresta Repair Logs

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Repairer: Paul Swan

BOARD NO: 0111 
GAME: Terra Cresta 
MANUFACTURER: Nitchibutsu 
DATE: 1985 
HARNESS: NITCHIBUTSU-S 
 
SYMPTOM (21/07/96) 
------- 
No initialization. 
 
SOLUTION 
-------- 
Using a scope to have a look around the 68K indicated that all the address/data pins were floating. Using a pulse injector on the 68K RESET pin 18 started the game but the game would not start from power on. The 68K reset line was output from an LS14 hex inverter at location 3A and the complete reset circuit as it was on my game is as follows:- 
 
<nowiki>
Vcc 3A
^ 13|\ 12
| +-----| >0----->RESET1~ (to 68K)
| R3 | |/
+-------/\/\/\-----+ | LS14
| 100R | |
| | 3A | 3A
----- R4 | 3|\ 4 | 11|\ 10
|PST|-----/\/\/\-----+-----| >O----+-----| >O----->RESET2~
----- 10K | |/ | |/
| | LS14 | LS14
| C2 | |
| | |+ | | 3A
+--------| |------+ | 9|\ 8
| | | +-----| >O----->RESET3~
| 100uF |/
= LS14
GND
</nowiki>
 
The three legged device "T518B" designated PST is presumably a three terminal reset generator chip. This circuit, as it stands, won't work very well and what has probably happened is that R3 and R4 have been swapped accidentally during manufacture. Swapping R3 and R4 over fixed the game completely. It's possible that other board sets in the same production run may have the same error and for reference the serial number of my board is "CA2906" and "85-06080"
[[Category:Repair Logs]]

Terra Cresta Repair Logs - Revision history

Davewellington: moved Terra Cresta by Paul Swan to Terra Cresta Repair Logs