Tuesday, 6 November 2018

Phoenix pcb repair

This board appeared to be completely dead at first but it turned out to be running blind. I narrowed this down to the 7407 near the edge of the board, the resistor network it is connected to was getting very hot.

After removing and replacing the 7407 with a good one I got a monochrome image.


I traced this back to the prom at ic41, the green pin was pulsing away but the blue and red pin were both stuck low. The bad 07 obviously took out the prom too.


 With a new prom burned and fitted...


The board is now fully working, repair complete.

Tuesday, 16 October 2018

TMS5110ANL sound chip adapter pcb

The TMS5110ANL sound chip was missing from one of my Bagman pcbs, I ordered a replacement from utsource but it didn't have a picture or any details. Once it arrived it turned out to be a shrink dip version which seems to be much easier to find than the standard dip version and cheaper too. It won't work in a Bagman pcb though, well not without a little help.

Instead of tracking down another one I made a very basic adapter in eagle and had oshpark make me some pcbs.


I ordered some 28 pin sdip sockets from China, not really necessary but makes it easier to swap the chip out if it fails.


Here it is installed in the Bagman pcb and now all speech is working.

Like I said the design is extremely basic but if anyone else wants to have some made up you can order them here.

Wednesday, 19 September 2018

Sega System X (After Burner) pcb repair

This board was completely dead I had sync but that was about it, after an inspection it soon became clear why.


Two nasty gauges on the back of the board taking out many traces, I removed the solder mask either side of the breaks with a fibreglass pen and repaired each trace using a single strand from some multi core wire, just like in a previous Sunset Riders Repair.


Liquid solder mask applied to protect the repair.

The board then booted right up and worked perfectly or so I thought. After I finished my harness to test it fully I could see that the analogue controls (joystick and throttle) weren't working. This turned out to be a bad ADC0804, I pulled a replacement from a scrap system x board and replaced it which fixed the issue.

This was actually a GP Rider to start with but after a rom / pal swap it's now an After Burner.


Up and running in its new home.

Tuesday, 21 August 2018

Bagman pcb repair notes.

 

I've labeled this one as notes rather than a repair log as it was three different boards I repaired at once and not everything is covered. A lot of TTL needed to be replaced to get these up and running.

Some issues I noticed across all three boards were that the Z80 cpus were bad and when removing them from their socket some of the pins broke off and stayed in the socket.

Missing player / enemy sprites on two of the boards was down to a bad 74LS163 @ M2
Can also be caused by a bad 74LS32 @ 2P

No speech (TMS5110A was ok) on one board it was a bad PROM @ R6 and on the other a bad 74LS151 @ S6

Bad PROMS in general, on one of the boards all three were bad. This causes colour issues and no speech.

An issue across all three boards was bad / missing video sync. This was a combination of bad 74LS161s @ A4, A5, B4 and B5.

Bad 74LS283s @D2 and D3 again on all three boards.

Certain controls not working 74LS245 @ 9A or 2B

The four sprite rams (27LS00) were fine on all three boards.

One final note, the PAL @ P6 is used for 'guards controlling' according to mame, which I guess is a cryptic way of saying controls the enemies. With the PAL removed the enemies seem to behave the same but I am guessing later in the game they behave differently and that it might make the game harder with it removed.

A similar security measure to what Bubble Bobble used maybe?


Download the full size image here

To help with my repairs I took the existing pdf scans of the schematics which are split up over several pages and combined them into a single page using photoshop. There's still quite a few areas that aren't legible unfortunately but I don't think the originals were that good to begin with.

Monday, 6 August 2018

Final Fight pcb repair

This original CPS1 Final Fight pcb was working fine apart from no sound.

The most likely causes were the Z80 cpu (capcom fitted Z80 instead of Z80A), 6116 work ram for the Z80, sound eprom on the B board and less likely but also possible the amplifier or oscillator.

I started with the sound eprom for some reason this one always seems to be missing a label on many CPS1 games which lets the bad UV light in. This was fine though, next I had a close look at the board it was very clean and looked like it had been well looked after.

The 6116 ram on the other hand had corrosion on several of legs, I have read that some early 2K X 8 rams contain electrolyte which eventually leaks. I am not sure if this is true but it would explain why these Sony rams often fail and the corrosion on the legs which was no where else on the board.



With a socket and new old stock compatible ram fitted the sound was fully restored.

Saturday, 2 June 2018

Sunset Riders pcb repair

This was just sold as faulty so I wasn't sure what to expect with this one. First of all a visual inspection, I noticed right away a deep scratch on the bottom of the board that had taken out several traces. Someone had taken off some soldermask and figured out which were the bad traces but not made any attempt to repair them.

I was going to use kynar wire but this was too big, the traces are extremely small and close together. So I ended up taking some multi core wire and using a single strand about the size of a hair.



With the micro surgery complete and no other visible issues I powered the board up. At first all I got was a black screen so didn't think it was running but then the music kicked in and part of the title screen appeared.


I fixed another Sunset Riders pcb recently that didn't end up getting logged but it gave me a good idea where the issue was. The other board wasn't as bad but had colour and background issues caused by a bad 053251 konami custom.

By touching certain pins on the custom chip I was able to get it to display slightly more of the background.


I took a donor 053251 from a Golfing Greats pcb.


Not quite there yet but better.



Time to check the maskroms as these are another common failure on this era konami board. I went into test mode but wasn't able to read which was the maskrom test, I used mame to see what I should be seeing. Then I could see the bottom two turned red which again in mame I could see was 16K and 1D, 16K maskrom contains graphics data and D1 contains the audio. This explained the lack of shooting and certain other sounds.


I then replaced the two maskroms with eproms (27C400 and 27C800). Luckily they were all in sockets from the factory, usually they're soldered directly into the board.





A blob of liquid soldermask to protect the repaired traces on the bottom and the repair is complete.

Tuesday, 29 May 2018

Popeye pcb (bootleg) repair

I bought this Popeye bootleg pcb in a lot of faulty boards, it included the worse jamma adapter I've ever seen. It's made from another cut up pcb, anyone know what game it was?


The board was working apart from the character layer of the graphics, making the text scrambled and blue blocks appear over the background and other sprites.



I didn't notice at first but blue and green were also switched, this was an issue with the adapter though and not the board.

The first thing I did was dump all the eproms and make sure they matched the ones in mame. Eprom 5 failed but this was a red herring as it was fine even though it's not in mame. :)

This did lead me in the right direction though as the data causing the issue is stored on this rom, it looked much better with it removed from the board. So I started looking around this area, I piggybacked a 2114 ram @ F8 and things looked much better, leaving the ram in place and power cycling the board completely fixed the issue.



I replaced the bad ram and made a new jamma adapter.




The colours are now correct, repair complete.