What fixed your game today / general repair log

[mecha]

had a K4900 I overhauled last night and put back in the game and it was dead. gamefixer inquired about that plastic clip gimmick that the front of the deflection board slides into, I was never culturally aware there's one of those paperclip jumper gimmicks there that's supposed to carry B+. the jumper was destroyed probably from my struggle to get it back in with a monitor pitched so far backwards. I keep all the cut off cap legs in the tray of my soldering iron holder where the sponge would normally be and conjured up a new jumper.

 

[zenomorp]

had a K4900 I overhauled last night and put back in the game and it was dead. gamefixer inquired about that plastic clip gimmick that the front of the deflection board slides into, I was never culturally aware there's one of those paperclip jumper gimmicks there that's supposed to carry B+. the jumper was destroyed probably from my struggle to get it back in with a monitor pitched so far backwards. I keep all the cut off cap legs in the tray of my soldering iron holder where the sponge would normally be and conjured up a new jumper.

Yup. I mention that on all my 4900 videos. It's also a jumper you remove for the lightbulb test…

 

[parism]

The two most dreaded issues in Outrun repairs are PCM audio issues and bad MASKROMs. I am working on a badly corroded outrun board and I had to repair many legs from the MASKROMs as they simply fell off. Unfortunately, one of those MASKROMs was indeed bad after all.

These MASKROMs are 1Mbit 28pin devices, not readily available. I did not want to do any hacky piggybacking to fit a 32pin IC to the 28pin socket. So, I programmed an AMD AM29F10B TSOP that would fit this adapter. Programming went well but it took me 30 minutes to solder it on the adapter board and confirm it OK. I used a regular chisel soldering tip and a microscope, there is really no other way…

All good now.

p

 

[mwiggett]

Game: Asteroids Version 05 board
Problem: Constant Reset
Fix: ROM 43 & 45 was in the incorrect order. Putting them in the correct order and board is up and working.
I know, not very exciting, but a win is a win.

 

[mdeslaur]

Friend brought over a G05 and an Asteroids PCB from a non-working machine he just bought. He just wants it to work with minimal fixes as he is not keeping it, so no preventative maintenance.

Decided to start with the G05. Put it on my bench. Shit, it's a G05-801...I don't have the cables required to plug it into my pattern generator, and I really hope the voltage doubler thingy on it isn't busted. Order some connectors and made a harness to connect it. Fired it up. Got a nice and bright horizontal line, no Y deflection.

Tested the frame transistors with DMM, pulled the deflection board, tested transistors, diodes, big resistors, etc. Connectors have cracked solder joints. Reflow and clean connectors. Plug it back in, same, no Y deflection. Pull the deflection board out again, hrm, linearity and size pots have factory glue on them...measure underneath with DMM, 3 out of 4 pots aren't making proper contact. Rip off the glue, full-wipe the pots a dozen times with a screwdriver. Plug deflection board back in, monitor fires up and works. Shit, I should have tried the pots first, duh.

On to the PCB. It's a -02 variant, looks clean but some chips have rusted legs. Rummage through bazillion different Asteroids manuals and schematics to find the appropriate ones for -02. Plug it into bench test harness with an oscilloscope in XY mode. Board is watchdogging with fast blinking lights. Pull the 4 Eproms, they test good. Oh eww, all the socket pins are GREEN.

Desolder the 4 sockets, replace with new ones. Stick the Eproms back in. Board watchdogs in game mode. Test mode comes up on the oscilloscope, but with an error code. Decide to pull out the FlukeEmu and test everything at once. Ram tests good, ROM @ F1 tests bad. Read a couple of bytes, coming up as FF. Loop on first byte of ROM, probe chip select signal /PROM0 on pin 20. Stuck high. Probe the same signal on LS139 @ L3. Stuck high there too. Piggy back another LS139, signal is back and rom tests OK. Install socket and new LS139. Game PCB is working.

 

[lilypad19]

I'd picked up a Space Duel board for myself a while back - it made it to the front of the bench.



Triage:

• This is the 'after' shot - but overall a pretty clean board.
• Prior work: analog section had been worked on / socketed
• Once powered up - testing voltages - missing +15V.
• No clock
• Registered a number of bad ROMs
• All RAM checked bad

Started simple and replaced 7815 voltage regulator.
Probing around I found the 12MHz clock coming off the crystal no problem..


The 12MHz was clean going into @F3 pin 11 - and was being pulled up on the other side. The short was to the +5v power rail and was ~6 Ohms. No clock out of @E4 as a result. The down side.. The 12MHz signal hit 15 chips and 17 pins.


The vast majority of the connections were here. I let the board run a while and found one burning hot chip @F8. Removed it - but still had a short. I used a laser thermometer and the next 'warmest' chip was @C8. Pulling it eliminated the leak to +5V. Clocks were now running! A thermal camera could come in handy...

Some of the ROM and all of the RAM checked bad. One by one I removed RAM and socketed it.. and one by one the RAM checked good.. All 6 RAM were bad. After that only one ROM checked bad.. Replacing it got all RAM and ROM checking good.

Next up the Vector Generator. It was stone dead. Probing around found yet another leak.


This time it was LATCH1 but it was being pulled to ground. An 8 Ohm leak. It hit ~9 chips. Since I had 2xbad LS194's above, I removed the remaining 4. 3 of the 4 were bad in the chip tester.. But none of them were the cause of the leak. The 74S00@E7 was the problem child. Once I pulled it - the leak was removed.

I've run into this enough times now that a Leakseeker will be here in a few days.

Replacing all the chips restored operation of the Vector Generator!


Game running. This issue was in the analog section. Prior work helped me here. The TL082@D/E12 was already socketed. Replaced/easy fix.

The last problem could have been a rat hole. Game would run in attract mode for about 5-6 seconds and restart. If I coined up - it would still run 5-6 seconds and restart to attract mode. Therefore it was rebooting and it wasn't the VG flaking out. If I moved quick - coined up - started the game and then got into game play. It was stable. I could play an entire game. All the RAM had been replaced, but I swapped in another set to be sure.. All the ROM checked good, but swapped in another set to be sure.

I decided to see if it was a watchdog reset and it looked like WDCLR was not getting signaled and the game rebooted itself. It was a software issue for sure.


Checking the interrupts - the 3KHz clock into LS161@J4 was coming in at 6KHz.

Working backwards...


LS393@F4 pin 8 was feeding 2x the clock doubling the output frequency on Pin 6, Pin 4.

Replaced LS393 - 3KHz and 12HKz clocks restored. No more crashes!


Board Works!

 

[VectorCollector]

I have a LeakSeaker and never found it to be useful.
I have a DVM/thermal-camera FLIR and have found it very useful in finding shorts (including low-ohm ICs) etc. (See some of my repair posts). Very useful tool.

YMMV

 

[lilypad19]

I have a LeakSeaker and never found it to be useful.
I have a DVM/thermal-camera FLIR and have found it very useful in finding shorts (including low-ohm ICs) etc. (See some of my repair posts). Very useful tool.

YMMV

I knew I should have pinged you... I saw that you had one.. I watched the @douglasgb videos and it looked like it would help.. May still end up with a camera..

 

[VectorCollector]

I knew I should have pinged you... I saw that you had one.. I watched the @douglasgb videos and it looked like it would help.. May still end up with a camera..

We all have our own way to debug and repair. That includes test equipment.
Just because I find the thermal camera to be useful for boards repair, does not mean everyone will find it so. (NOTE: thermal camera is good for other uses too).
(Same is true for using an oscilloscope (analog and/or digital), or microscope, or HP comparator, or HAKKO desoldering gun etc).

Try out the LeakSeaker ... make the decision yourself if it is a good tool for YOU.
Let us know your findings.

For dead shorts, I still like to find them by using a current-limited power source and let the short heat up. Then use my finger or thermal camera to check the components.

 

[lilypad19]

I'll never be accused of not buying tools - "My name is Lilypad19, and I'm a tool-aholic"

 

[jacklick]

I knew I should have pinged you... I saw that you had one.. I watched the @douglasgb videos and it looked like it would help.. May still end up with a camera..

I just watched his videos as I have these waiting for a use case but hadn't seen them used before. Maybe one day I will find out if they work.

 

[Terrypro]

Not a ton of info out there for this pcb, so figure I'll share a quick fix.

Game PCB: Superman (with daughterboard)

Symptons:
#1 - Lines through sprites
#2 - No black
#3 - Green blocks around sprites

Steps & Repair:
For #1 & #2 - Thankfully I have a working board for this game as well, so we started playing around with the roms. Swapping
U45-H on the daughterboard with the one from my working board fixed both issues - sweet! Since the rom files for the daughter board version aren't online, we ripped the code from the working board and sent it to Hobby Roms to burn it on a new AM27C400.
For #3 - When we got the new chip and put it in, the blacks came back and the lines were gone, but it gave us green blocks around the sprites. No idea why or how, the other chip with the exact same code fixed all the issues! Anyways, the fix goes on… Bought a rom eraser, bought the mod to program this type of chip and grabbed the rom file that corresponds to U45-L and U45-H from the non daughterboard version - B61-17.k1. Took a shot in the dark and burnt it onto an AM27C400 and voila, working perfectly.

Thanks!

 

[jacklick]

I don't know if I posted for help here but 5 years ago I posted on neo-geo forums and was like this is way too hard and put it away.
Game PCB: Neo-Geo MV2F (2 slot later revision I think)
Symptom: Lines through sprites on slot1, lines through neo-geo logo on both slots.
Steps: continuity check line in and around the battery area (mostly zmc2 and neo 257 chips)
1) One trace was obvious on the top side going to pin 19 of zmc2 (aka C1)
2) It took a bit but eventually I started doing continuity checks on bottom of board. Found an extremely small break going to zmc2-p10 (aka GBD0)
3) This was the bitch of the bunch. A through hole issue on 257-p64 (aka CR15) The through hole seems to be right where the corner pad is. I managed to get enough wire and solder in the hole to make contact with something.
Repair: General battery corrosion clean, fix and repair traces, etc.
After fixing it, I don't regret putting it aside for 5 years. big pain in the butt I need to practice some smd air desoldering and stuff as it would be a nice skill to have on these boards.

 

[lilypad19]

Longish post - But got to try my new Leakseeker for the first time..
Got an Asteroids board in for repair:

Initial inspection:

• Had to temporarily remove Braze kit to work on the board
• RAM tested good
• ROM tested good
• Vector generator tested good
• Bad Y output (to start)

Testing 4016B on the Y side showed it was pulling down the 8.2V to about 4V on pin 14. Replaced that.


While working on it I noticed the 7815 voltage regulator was really hot, even though it was outputting proper voltage.


Put a new one in after looking under it. I was having issues with the switches on that side anyway. The TL082@A12 had been socketed in the past - socket was bad.
Finally got to some test screen output:


After poking around a bit, determined the 7404@H11 appeared to have issues.


Good clock going in - bad clock coming out. I swapped the chip - but it was not the issue.


One of the LS191 counters has an issue on pin14 pulling down the clock output. Time to finish assembling and use the Leakseeker I picked up. I've run into this situation enough times now that a new tool could be helpful.


The counters in question are physically 2 inches apart and pin 14 is a straight line between them. The Leakseeker quickly determined that LS191@H10 was the likely culprit...


I'm impressed.. I'm looking forward to the next one.

 

[lilypad19]

The last issue was this....


Graphics distorted on the top half of the screen, but if they moved to the lower half of the screen - they corrected themselves... I was thinking it was a bad high bit on a Y counter for a while and even replaced the LS191@F10 since H10 was bad.. But no... In hindsight - it made no sense - the distortion could not have been a missing bit.

I should have done this sooner - I flipped it into cocktail mode to see if the problem stayed or moved.


It went away - but introduced a new distortion. Turns out I got a batch of bad analog switches mixed in with my good ones. I'd already replaced the 4016 analog switch - which is why I didn't go back to it initially. Problem cleared up.
Board works!

 

[cwilkson]

Not a game, but a tool.

I needed to service my Skilsaw. It needed a new power cord and an oil change. No really! Big saw. Big motor. Worm drive. --> needs heavy motor oil! I haven't used it enough to really justify an oil change, but the cord really needed to be replaced so what the hell. The oil was at least 17 years old and probably much older. I don't know when my dad last changed it. I got those parts and new brushes (just in case) on Saturday. Sunday night I took the handle apart only to find that it's busted inside. So I need a new handle. Ok. I can replace that. They are available. Annoying, but it only adds a couple of days of delay. The more alarming discovery was that the insulation on the field winding leads had turned to jelly in a couple of spots. So I decided to do a deep clean since I needed to take the motor apart anyway. Good news is the old brushes are basically new. Did I already change them? Did dad? Dunno!

Taking the saw apart...
I broke a blind screw taking off the blade guard. (DAMN IT! )

The head was moving but the body wasn't. Of course you don't know that until you feel the ***SNAP***! Apparently it had thread sealer. From 1985. Damn it. Luckily, it broke with about 3/16" of thread showing so I was able to grab it with Visegrips. After a couple of hours of persuasion with PB Blaster and a hammer I was able to remove it without any damage to the saw. But now I have to find a magical replacement for a screw with this type of head:



What do you even call that? A Torx combination pan head? Hexalobular with continuous slot pan head? And it looks like it's thread forming (the threads may be triangular instead of round). I can probably get by with normal threads. The hole was already nicely tapped decade ago after all. But damnit it's not original!

I have the great good fortune to have a Model 77 Type 16. The last made-in-USA Skil Saw. Sadly, it's also the only one without a manual online.
Type 13,14,15 are available. Type 17 and up. But not the 16. So...no parts list, no exploded diagram, no nothing. The only exploded view in existence online is not quite readable. So I can't tell which screw is actually needed. Also...the saw is almost 40 years old. Parts are scare anyway. Even if I knew which screw to order. I know for a fact that some are obsolete and unobtainable.

Sigh.

So to wrap up for Saturday night, I put heat shrink on the field leads and reassembled everything. Except for the missing screw. I didn't do the oil change because I was afraid to run the saw with a screw missing.

Today I stopped by Homie's Depot and picked up a temporary replacement screw. #10-24 x 5/8 zinc combo head. Yuck. Way too shiny. Wrong head. Super easy to strip out. Not original. LOOKS WRONG. It looks like an LCD in a Star Wars cockpit, FFS! But it's good enough for now. It allowed me to get the blade guard back together tonight.

Tonight I ran the saw for a couple of minutes to warm up the oil and then drained it. Yep. Dirty brown used motor oil. And thick like syrup. The new stuff is also thick like syrup, but it has that weird indescribable yellow-blue-green gear lube color. Oil change complete!

The brushes are sparking. I hope it's just the brushes re-breaking in and not some kind of armature damage. Time will tell!

Next steps...
New handle and un-namable-type replacement screw to be ordered.

 

[Kaworu5]

I have been spending a lot of mental power to try to help with 2 cranky vector machines and while progress is being made, we are still no where near a solution. So this week, I decided to put on some tunes and just play my Tempest for an hour. As much as I love to repair and poke around at these machines, I was really grateful to kick back, lean against the control panel and just get lost in the game... until I got to the red levels... f--- those pulsars!

- Jon

 

[mwiggett]

Got an Asteroids board -06. Board played blind, but not resetting. Noticed GO was being pulled high, but not high enough on my scope. Looking at traces, found a piece of stray solder was bridging two traces. Cleaned the solder and now had display on the scope and monitor, but looked like the picture. All signals going to the Z output looked good on my scope, until I got to the collector side of Q8, That showed the pattern below. Replacing Q7 fixed the screen issue. All that was left to do was replace the 4016 for the saucer sound that was stuck on, and C33 for no thump noise.

 

[jacklick]

Game PCB: Sinistar
Symptom #1: vertical lines on screen. Boot to some type of error either RAM or ROM but couldn't read it and then would reset. ROM LED read 0-3-3.
Steps:
1) looked at manual for what 0-3-3 meant. Well ram error is documented as 1-row-ram in manual so no idea. Sinistar's LED codes are wacked. see thread https://forums.arcade-museum.com/threads/sinistar-mystery-backwards-c-on-led.473716/
2) hooked up FPGA Catbox and could see data bits 2-7 were bad but which row? (actually I was on a bit of a goose chase because initial config wouldn't verify roms)
3) messed with FPGA Catbox some more and got a good working config file and it showed row 3 data bits 2-7 were bad. I also noticed they were "cold" to the touch.
Repair: Replaced bad ram.

Symptom #2: Image was dim. During Color RAM test instead of flashing different intensities of Red, Green, Blue the screen was just blank.
Steps:
1) Checked outputs of 7489 RAM at 1B and 2B. They looked fine. Check LS374 @ 1A which seemed fine as well.
2) Had a working board to compare to so put it in the same test mode and could see what the signal should look like on the 2n4403 transistor collector. Since the blank screen during test was common to all colors, started focusing on Q4 and 7400 at 4B which feeds it.
3) Ended up pulling all the 2n4403s but they tested fine.
4) 4B-11 (might be blanking signal not sure) looked ok but was only reaching @ 3 - 3.5Vpp vs working board which was getting to good 4+Vpp. I measured the resistors r18 (470ohm) and r17 (1Kohm) and they looked good out of circuit but were being brought down to like @ 410ohms and 750ohms respectively when in ckt. Assuming something was off internally with 7400 at 4B (Fairchild chip), I replaced it.
Repair: Replaced 7400 at 4B

 

[jacklick]

Game PCB: Gorf RAM (DRAM) Boards
Symptom: Various...but typically lines through screen. I was testing six ram boards using the super convenient Test RAM (Dave and then Mark) which was patched by @mdeslaur here: https://forums.arcade-museum.com/th...mming-and-other-fun-stuff.419492/post-4020723
Steps:
1) Test Tantalum Capacitors for ESR and Shorts. Even with this pre-power check, one 12v cap exploded on me in spectacular fashion.
2) I usually put board to be tested in slot 6 and just use the test rom. Using RGB hook up or cabinet does make text more readable. I was having issues with sync and sometimes couldn't read the text using composite signal.
3) The test rom didn't fail me once. I spot checked a few reported failed ram in NeoLoch and they tested bad.
Repair:
Socketed and replaced bad 4027 DRAM. 6 Boards. Three were good, one had 3 bad dram, and two had 1 bad dram each.