Friday, 5 June 2020

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 will be on soon.
U54          PAL16L8      41-02 - Bruteforced, jed file will be on soon.
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 will be on soon.
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 will be on soon.

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.

Thursday, 20 February 2020

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).

Thursday, 10 October 2019

Street Fighter 2 CE / HF to HF Turbo conversion

It's quite well known and documented that you can convert Street Fighter 2 Champion Edition to Hyper Fighting by simply replacing the three program eproms (6F, 7F and 8F).

Turbo Hyper Fighting upgrade / conversion isn't quite as simple, it also requres three graphics roms to be replaced. You will need the sf2hfj rom from mame (and sf2hf if going from CE).

First burn the program rom 23 location 8F on to a 27C4096/27C4002. Next burn the four graphics roms 3C - 6C on to 27C400 eproms and now for the part that caused me some confusion, roms 4C and 5C need to be swapped, so 4C in 5C and 5C in 4C.

If you started with a Champion Edition board you'll also need to replace eproms 21 and 22 (6F, 7F).

I also suggest installing a 12mhz oscillator in place of the original 10mhz if you don't have a 'dash' motherboard, so that the game runs are the correct speed.

Tuesday, 27 August 2019

Punch-Out! pcb repair

This board was mostly working but had a messed up background and no sprites on the bottom screen. The top screen was perfect apart from the missing logo.

Most times powering on the board it also had what looked like an interference issue.

As you can see (just about) the background is now fixed, this was a bad 74LS244 @ 3K on the back / small pcb.

The rest of the issues were on the middle / graphics pcb, first replacing a bad 74LS273 @ 1N brought back glass joe and the main logo.

I also found two 74LS04s with floating outputs @ 1J and 4E replacing these fixed the 'interference' issue.

Replacing two more 74LS273s @ 7H and 8J brought back the player (green guy).

This just left one small intermittent graphics issue with glass joe and the logo flickering and having black lines through them every so often.

I noticed some previous work on the board, someone had replaced the four 74F161s @ 1F,2F,3F and 4F with 74S163s. The one at 1F was rusty and when removing it from the socket one of its pins fell off, I soldered on a lead from a resistor just so I could test it and sure enough it failed.

I replaced all the 74S163s with proper F161s, they seemed to be working okay but I have a bunch of the correct F161 anyway.

In the same area of the board three 74F283s had been replaced with standard 74LS283s, I removed these and installed the correct F (fast) chips to finish off the repair.

I hadn't worked on a Punch-Out pcb before, this is the basic adapter I knocked up. It uses a Mike's Arcade Nintendo jamma adapter to invert the colours and amplify the audio. I basically copied what Adam @onecircuit came up with for his setup. :)

The switches are to flip between top and bottom monitors and the other switches between the two audio channels.

Saturday, 1 June 2019

Sega self test mistakes

Thought I'd note this quickly as it has caused some confusion on a couple recent board repairs.

Outrun - IC75 in self test is actually IC57.

GP Rider / Afterburner - IC30 in self test is actually IC37 (315-5248).

Friday, 3 May 2019

Missile Command - 4164 RAM upgrade

Purists look away.

Missile Command originally uses 8 x 4116 rams, and 4116 rams are terrible. They don't just die (a lot) they often take out other parts when they die. It's best to replace them with 4164s which run a lot cooler and are far more reliable, they also don't require +12v and -5v like 4116s.

It's already common practice to replace them on Williams boards but doesn't seem to be so common on Atari boards, not yet anyway.

Since there's no tried and tested mod for Missile Command I spent some time looking at the board to see the cleanest and most reversible way of doing the modification. You can mod the ram itself but this looks awful and not practical for some collectors to replace them where as anyone can drop in a stock chip.

Here's how I did it.

The cuts need to line up with the via on the back of the board where the 12v and -5v come through, if you hold the board up to light you can see it a lot clearer and mark where you need to cut with a sharpie.

Saturday, 23 March 2019

Outrun pcb repair

I did this repair a few days ago now and forgot to take certain pictures but I'll document what I can. This Outrun was watchdogging (resetting) and had a smeared red and blue image on screen which I forgot to photograph.

Firing it up with the extremely helpful test roms and a known working video board I could see a lot of bad rams on the CPU board, the watchdog was kicking in before the test would finish but I could see all I needed to for now. IC55 was failing every so often too so I replaced them all apart from IC114 and IC130 which are made by Fujitsu and hold up very well (unlike their TTL).

Swapping back to the original video board I could just about see that both palette rams (IC92 and IC95) were failing. With these replaced I got this image.

This was caused by two bad roms opr-10267 and opr-10268 if I remember correctly.

With these replaced the image was perfect apart from there being no road on the left side (again I forgot to photograph this).

The road issue was fixed by replacing a bad rom on the top board opr-10186 at location IC47.

This fixed everything graphically and the controls worked too.

Now the problem was the lack of sound, nothing completely quiet. The clock signal for the Z80 was stuck. Looking at the schematics I see the last thing I want to see.

That the clock is created by the 315-5218 surface mount custom chip. I tried a little experiment and created a 4mhz clock from the 16mhz clock using a 74LS74 and fed it into the Z80 to see if there was any life left in the custom but unfortunately there wasn't.

Here's the custom removed and pads cleaned up ready for the donor.

The new custom fitted, originally from a System X board.

Still no sound whatsoever but the clock was back and the Z80 was a lot more active. I decided to hook up the Fluke 9010a to the sound cpu (Z80) and see if the ram was good. First thing I do is a bus test and it reported A15 stuck high, this was caused by the main sound eprom epr-10187 which is interesting as the eprom programmer had no issue with it.

With the rom replaced there was still no sound, the fluke reported that the ram was fine so I moved onto the PCM eproms and rams. The two rams failed out of circuit testing and were replaced and the maskrom at IC70 failed and was replaced too.

This finally brought back the PCM sounds that were slightly too fast and getting cut off early but finally I could hear something.

I used a sound probe on the op-amp TL084 (IC125) and nothing was going in, this traced back to the YM2151 and sure enough nothing was coming out of it. I took a replacement from a System X donor board and all sounds were back and everything is working perfectly.

Repair complete.