We had two separate files for M92-b-2l.
One was just labelled for M92 hardware and the other was for Ninja Baseball Batman.
I deleted the entry for M92 as the Ninja Baseball Batman dump was from an actual unlocked PAL chip.
End user will not notice any difference, this update is to keep a record of what has been done and when.
I got an M92 PCB here that uses MASKROM’s from SHARP.
These MASK’s in particular are pin compatible for either 27C020, 27C040 or 27C080 EPROM’s.
It is possible to determine which to dump these as from the markings on the chip. They all begin with the ID LH53#, where # is the identifier of the size.
“LH532” = 27C020 dump
“LH534” = 27C040 dump
“LH538” = 27C080 dump
The remaining letters/numbers of the markings are unique to the game and location on the PCB.
After fixing a couple of Pac Man PCB’s recently, the owner of them very kindly let me keep one of the boards. The only problem was it had been stripped of the ROM’s and customs.
Now the customs are no longer a problem for me but the ROM’s are of the 2532 variety and I only have a couple of them free.
As luck would have it user ‘philmurr’ on the UKVAC forums has made a nice little drop in replacement that fits in the Z80 socket and lets you use a single 27c128 EPROM in place of the 4 x 2532 program ROM’s.
I got it today, assembled and fitted it without issues.
Game plays as you would expect.
A couple of caveats. There are a few wire link mods needed to the PCB due to an error but these are well documented in the instructional PDF and the boards are so nicely priced that it really doesn’t matter too much, at least not to me.
The other potential issue is that if your PCB is fitted with the TTL custom replacements then this board just isn’t going to work for you as the custom covers the original Z80 socket.
Really happy with this so thanks to Phil.
I’ve uploaded the updated version of QuickTools 2.0 (formerly Fluke 90 Controller).
There are quite a few differences. The main ones are its quicker, has some status indicators for the Trace functions and has preliminary script support (which doesn’t work too well right now).
If anyone has the Z80 version of the Fluke 90 for sale then I would be interested in buying it if the price is right.
Got the second board fixed up today.
This one had a lot more wrong with it and all caused by a previous repair attempt.
Visual inspection immediately revealed this.
I confirmed these wires were going where they should be and neatened them up a bit.
As with the first board all I got was a blank screen with the board not playing blind. At this point I had my smaller custom replacements verified so could do away with stacking the TTL riser and could just plug the Fluke straight in.
ROM checks were all good but the RAM checks failed straight away.
With the previous repair still fresh in my mind I knew where to look. the 74LS245 at 4H. This had a turned pin socket fitted and a 74HC245 chip inserted. The HC variation means its CMOS logic levels and typically aren’t an ideal replacement for LS parts. If you are going to swap them out you can use the HCT variety which are TTL compatible.
I replace this chip with a 74LS245 but it did not fix my issue. Checking the outputs of the 245 to the RAM led me to suspect a poor desoldering job of the previous chip as several pins weren’t connected to the RAM. I desoldered the socket and found this mess.
You can clearly see a the traces that have been ripped through. I patched these, fitted a new socket and continued my checks.
The Fluke now reported this.
Knowing the chip was good and the connections to the RAM were good I focused my attention on the CPU side of this chip.
I knew my custom chips were good and I could correctly read the ROM’s so new the CPU socket was good. This didn’t leave me with many places left to look. I could almost certainly rule out some places as data bits 2 and 6 were across two different chips and the chances of both of the chips shorting together was a bit low. This left me with an 74LS273 at 4D and also to the dreaded crusty flux issue. Cleaning the flux cleared my short.
Now the game would boot but I get this
Only the score and credits were showing. If I started a game the lives were also showing at the bottom.
My attention immediately went to the 4 x 1bit RAM chips at 2A-2D and found there wasn’t a great deal of activity and some missing signals.
My heart sank right away as I could see turned pin sockets had also been fitted for all of these which most likely meant the same person had replaced them.
Sure enough there were several traces cut. I did remove one of the sockets just to see what I was up against.
Some severed traces here and doing a continuity test revealed more and more. I also found one pin not soldered.
A bit of time later after patching and verifying my work I fired it up and was all ready to feel pleased with myself on a job well done but the same fault was still present.
Confident the fault was still in the area I was already working I set back to work checking continuity and found the ‘Data In’ pin (pin 15) of a RAM at 2A was shorted to pin 1 of the RAM at 2B. Looking back at the picture I had taken I noticed a bit of stray solder bridging the trace that ran adjacent to pin 15 that I had missed earlier. I managed to remove it with a pin and a bit of patience.
After that the board fired right up and plays fine.
