Fixing a few more boards for Vamino.
Thought I would start with a simple one but boy did it give me problems.
First was a blank screen.When I first switched on I got brief garbage but turning it on after that it just came up blank-It was syncing but showing no graphics.
My video probe on the last proms showed graphics so I know the fault was later. Found the last buffer in the video output had gone (7407 at IC40).
Replaced that and found the CPU was dead.
Swapped in mine from my bootleg Phoenix and tried the test rom but was getting memory errors. Unfortunately kept getting different results so I wasn't sure which ram to replace but then the test rom wouldn't even run.
It just started to boot to garbage with no sign of the test rom running.
Using my Phoenix as a test I found that if the 1st four rams were bad it would give a static screen so I socketed the 1st four 2114 ram chips (40,41,42,43 on the video board).
I put known good ram from my phoenix in but go no change and the ram from this board worked fine in my bootleg.
Got errors coming from the LS374 (IC1) that handles the data so changed that but still no boot.
Checking the 2716 test rom I found that pin 19 (A10) was showing as not connected. checked and it had continuity to pin 11 of the LS125 at IC10 on the CPU board so I checked that chip and also got errors. A piggyback of the LS125 booted the board and the test ran without errors.
Replaced the test rom with the game rom and games appears to be working now.
Just need to check controls and later levels.
So in the end it was a bad LS125 that handled the higher address lines that was the main fault.
I got the game running by grounding the credit and start buttons and was surprised to hear background music.
Never played a Pleiades that had background music before and I recognize the tune as the same one as plays in the background of space demon (A space firebird clone).
Were all the Pleiades I played back in the day boots I wonder?
Thought I would start with a simple one but boy did it give me problems.
First was a blank screen.When I first switched on I got brief garbage but turning it on after that it just came up blank-It was syncing but showing no graphics.
My video probe on the last proms showed graphics so I know the fault was later. Found the last buffer in the video output had gone (7407 at IC40).
Replaced that and found the CPU was dead.
Swapped in mine from my bootleg Phoenix and tried the test rom but was getting memory errors. Unfortunately kept getting different results so I wasn't sure which ram to replace but then the test rom wouldn't even run.
It just started to boot to garbage with no sign of the test rom running.
Using my Phoenix as a test I found that if the 1st four rams were bad it would give a static screen so I socketed the 1st four 2114 ram chips (40,41,42,43 on the video board).
I put known good ram from my phoenix in but go no change and the ram from this board worked fine in my bootleg.
Got errors coming from the LS374 (IC1) that handles the data so changed that but still no boot.
Checking the 2716 test rom I found that pin 19 (A10) was showing as not connected. checked and it had continuity to pin 11 of the LS125 at IC10 on the CPU board so I checked that chip and also got errors. A piggyback of the LS125 booted the board and the test ran without errors.
Replaced the test rom with the game rom and games appears to be working now.
Just need to check controls and later levels.
So in the end it was a bad LS125 that handled the higher address lines that was the main fault.
I got the game running by grounding the credit and start buttons and was surprised to hear background music.
Never played a Pleiades that had background music before and I recognize the tune as the same one as plays in the background of space demon (A space firebird clone).
Were all the Pleiades I played back in the day boots I wonder?
