Sega Mega-Tech pcb repair

I wasn't planning to log this one which is why there aren't any before pictures but there turned out to be quite a lot wrong with it.

First thing I had to do was clean it as it was filthy, powering it on just gave a black screen. On closer inspection all the sockets needed to be replaced as they were badly corroded.

This got the top screen to work but the games weren't listed or running. This is usually down to bad Sony CXD1095Q chips, I ordered a couple from aliexpress and replaced both of them. This fixed the games not loading / displaying issue but it also revealed new problems.

The graphics were missing and just displaying noise and blocks, this was down to the two video drams that again I had to order. I found some nice new old stock M5M4C264AL-12 on ebay which are the same type and speed rating as the originals.

Now the games were playable but I noticed certain sounds were missing, 'Sega' and the ring collecting sound in Sonic were missing along with a lot of other sounds. This was due to a bad YM2612 which thankfully I had some spares on hand and didn't have to wait a third time.

I also noticed the red output on both screens was quite weak, especially on the main screen. This was due to faulty and leaky transistors, replacing them fixed the problem.

That looked to be everything but I found one final fault, about half the dip switches weren't working. Replacing them with new ones fixed the problem and the board is finally 100%.

 

 

Repair complete.

Atomiswave fan upgrade

I picked up this Atomiswave motherboard in a recent trade, I've been after one for years as I had a Metal Slug 6 cartridge (bootleg) that I haven't been able to play.

It worked great but the original fan was screaming and very distracting.

I used to get some nice silent red 40mm fans from ebay for CPS2 motherboards, this would have been perfect as it would have matched the Atomiswave case. They're no longer available though so I had to find something else, I ended up settling with this one.

Noiseblocker Black Silent XM-2, it is very quiet still moves some air and most importantly was cheap (£7 posted). There is an MX-1 version too which is even quieter but it doesn't move much air so I wouldn't recommend it. The XM-2 is very quiet to the point you won't hear it during game play or if you have the motherboard installed in a cabinet.

As with most things it's not just a simple case of screwing and plugging it in, you'll need to take the original cable and splice it with the new one as the connectors are different.

The third yellow wire on the original fan feeds ground back into the board from the black wire, since the new fans white wire is for sens this won't work and will cause your board to lose sound.

What you have to do is also bridge the second and third pins on the motherboard with a solder blob (this is also covered on arcade-project forums).

That's it, one quiet Atomiswave.

Now to try and track down some more cartridges.

Blood Bros pcb repair

This one was a real headache, it was completely dead with nothing on screen and no sound. After going down many different rabbit holes I checked the previous work that had been done which is the first thing I should have done.

The 74LS04 at U071 had been socketed after removing the socket I could see quite a bit of damage, including the trace from pin 11 to 13 being broken.

After patching the bad trace it would finally power up and display something, but there was no sync and no sound.

The sync issue was fixed by reflowing the SEI0200 custom chip.

I also noticed the LS04 at U053 had been replaced with a HC04, it may have been okay to use a cmos chip here but I replaced it with the proper LS04.

The only issue remaining was the lack of sound and the coin inputs not working. These are linked as the Z80 wasn't running which is the sound cpu and for whatever reason seibu also used the Z80 for the coin inputs.

The main sound eprom was bad but after replacing it the cpu still wasn't running.

I next desoldered the Z80 and fitted a socket so I could hook up the Fluke 9010a and also test the cpu, the cpu was fine.

The fluke was reporting 'Data bits 0 tied' but tied to what? usually it will say ground, 5v or another line. According to a cource notes fluke pdf document I found online some combinations of shorts or when it's multiple lines the fluke cannot always identify them and cannot give you any more details.

Checking with a multi meter I wasn't able to find any shorted lines, I lifted the D0 pins on various chips and wasn't able to find the issue. I just had to start pulling and socketing stuff directly connected to the data bus after pulling the M6295 pcm voice chip the bus test on the fluke passed.

I have seen these fail quite a bit on CPS1 motherboards but never like this where it kills the data bus. It looks like they are getting very hard to find now too. A couple of sellers in China have them but they look remarked so who knows what they really are. Luckily I had a couple of working ones in my spares drawer pulled from scrap boards.

M6295 fitted and the sound and coin inputs are now all working.

Repair complete.

Super Off Road (Ivan Ironman Stewart's) repair and notes

A Super Off Road board came in for repair, the first thing I had to do was make up a basic power and video harness to test it. It was completely dead, a look over the board revealed it was two non working pcbs (different serials) from different sets connected together with a big X in marker on each.

It had also been stored in a damp place so it had some corrosion and every socket on the board needed to be replaced, a lot were single wipe rubbish that would have to be replaced anyway. Apparently Atari made these boards or at least assembled them, I'm not sure if this is true but it would explain the sockets.

This board uses a LOT of PLDs (Programmable logic devices), all secured and none have been dumped or replicated from what I can tell. This was my main concern as one bad PLD and I wouldn't be able to get it going.

Top Board PLDs

Location   Device          Name
U9            PAL20L10    38-01
U42          PAL16R6      37-01
U43          PAL16R4      36-01
U44          PAL16L8      35-01 - Bruteforced, jed file available at wiki.pldarchive.co.uk.
U54          PAL16L8      41-02 - Bruteforced, jed file available at wiki.pldarchive.co.uk.
U55          PAL18P8      39-01
U68          PAL18P8      40-01
U74          PAL16R6      19-01
U75          PAL16R6      18-01
U82          PAL16R6      21-01

Bottom Board PLDs

Location   Device          Name
U16          PAL16L8      03-01 - Bruteforced, jed file available at wiki.pldarchive.co.uk.
U17          PAL16L8      04-01
U19          PAL20X10   06-01
U21          PAL20X10   05-01
U22          20X8                       Programmed to behave like a 74LS461 which can be used instead.
U23          20X8                       Programmed to behave like a 74LS461 which can be used instead.
U26          PAL16R8     10-01
U27          PAL16R8     11-01
U40          PAL16R8     09-01
U42          PAL16R4     08-01
U43          PAL16R8     07-01
U45          20X8                       Programmed to behave like a 74LS461 which can be used instead.
U56          20X8                       Programmed to behave like a 74LS461 which can be used instead.
U60          20X8                       Programmed to behave like a 74LS461 which can be used instead.
U85          PAL16L8     02-22
U96          PAL16L8     01-01 - Bruteforced, jed file available at wiki.pldarchive.co.uk.

I bruteforced, created jed files and tested the four PALs I could, this still leaves a lot that cannot currently be replaced but it's a start.

On to the repair.

The board would boot from cold and display the title screen but it was cut up into pieces and then would crash. Trying to boot the board again or pressing the reset button would result in vertical lines and the slave cpu resetting.

When replacing sockets I tested every chip I removed and found two bad 6116 rams and two bad 41464 rams which I replaced. I also found that R1 resistor next to the CPU socket U1 on the bottom board was only soldered on one end and the other end was just touching the pad, it must have been like this since it left the factory, so I soldered that on properly.

It still behaved the same though, next I found a bad 74LS374 @ U18 on the bottom pcb, replacing this fixed both the graphics and crashing issue.

I'll also replace the original battery from 1989 with a new CR2032 coin battery and holder.

The sound and digital controls all work but I haven't been able to test the steering as I don't have the 'opto coupler' board but hopefully this repair is complete.

Guide: Make your own desoldering gun / station filters.

Since Hakko put the price of their filters up for my desoldering station (and other models) I've been looking for alternatives.

RS sell some cheap filters for their rebranded Pro'sKit SS-331H station and the cleaning rods are very good too (much better than Hakko's version). The filters are slightly larger than the ones used on my 474 station though.

CDJump on the KLOV forums came up with a great solution, using a metal hollow punch meant for leather and a ceramic paper blanket from china (ebay) to cut his own.

I got two hollow punches to cut down the RS filters, this worked great for the 3mm x 16mm filters used in the station. The filters used in the gun should really be more like 5/6mm thick though. Also the blanket has since sold out so I went looking for something else.

I found some 3mm and 5mm ceramic paper sheets (A4 size) on ebay which are perfect. A search for ceramic gasket should bring up something similar.

From a single sheet I was able to make over 200 filters.

Considering 10 filters from Hakko are £10.75 + £7.50 postage and a sheet that made over 200 was £4.99 including postage, it was quite a saving.

The hollow punches can also be picked up from ebay for about £5 each.

 16mm x 3mm (not 15mm as stated on their web site)

17mm x 5mm (or 6mm, if you can find it).