They were !
We had a great day and I'd like to thank Polder and Robin very very much for their help !!!
We first hooked up the Gonbes CGA/EGA to VGA converter and a VGA LCD. The thing is a brilliant little device for an amazingly low price !
However, when you buy it, the menu's are all in Chinese. Through a nice Youtube video we found out we had to select option 4 to switch it to English. (The manual doesn't tell you this ....)
We started working on the machine with the closest to working hardware. One of the nice things of (a bit) more recent hardware is that the testing options are more extensive and reliable. The test indicated three bad RAMs on the main board.
(This is an older picture done by the seller, monitor looked much better then !)
So we piggy-backed the indicated RAMs with new ones (had bought 5 from e-bay) and to our slight surprise 2 of the 3 turned to green, which meant they passed the test.
Our conclusion was that the third bad one probably had a short preventing the piggy-backed RAM to work properly. Then Robin had an idea I had never thought about before and he cut out the bad RAM as close to the body as possible and THEN piggy-backed the new RAM to the "left over" pins ! (Of course this was all just for testing)
And it worked !! It passed the tests and we successfully went into attract mode. We could start a game, but clearly there was a problem with the gas-pedal as couldn't get the car to move. But all of the problems with the controls will be investigated later, first we need reliable board-sets.
SO we went to the other HD. This one had showed some nice lightning storms around the HVT of the monitor and I couldn't resist powering it up again. Now there was a nice flame coming out of the top of the HVT. I tried to film it but....I kinda messed up with the camera...
Didn't want to burn it down completely so we disconnected that monitor.
This board also had 4 bad RAMs on the main-board. We used the same tricks again and got all of them working.
However, on this set there were also bad RAMs reported on the ADSP board.
These are rather rare 4kx4 Static CMOS RAMs. The schematics indicate them as 8168D45 but on the board there are hm3-65768m-5
I found a source for hm3-65768BK-5 RAMs in Europe for a reasonable price but will these work ? I found a data sheet for the hm3-65768m-5 and it lists the hm3-75768k-5 but not the BK. The K is faster than the M so I figure it will be OK.
Further, we removed the monitor chassis, the "hood" can be shifted backwards to work on the monitor:
This looks pretty impressive IMHO, it looks more like a car-workshop
So gonna examine the monitor chassis, bad solderings, caps, pots etc. ALso need to order a new HVT I guess
