Repair Logs – Page 67 – JAMMArcade.net

ESP Ra.De. repair log #1

Jun 122016

Got an ESP Ra.De. board with faulty graphics:

esprade2

While looking for some suspicious signals on the GFX area, I found two PALs at locations U31 and U34 that got nothing on their output pins. U31 had healthy looking pulsing signals on its input pins but U34 had some input pins with no signal. These were in fact coming from U31 so that was totally normal.

These PALs are soldered and weren’t dumped yet so I needed to find a working board, desolder the PALs and dump them which was not easy due to the rarity of that game.

Anyway, I desoldered the two suspicious PALs from by board.

esprade1

I tried to dump them but got an error at pin #20 which is the +5V pin. Sounded they really were faulty as they got no power in order to work properly.

Finally, a good friend got a working board and kindly lent it to me so I could dump the PALs (they were unprotected).

I put sockets on my board, plugged new reprogrammed GALs in place (PALCE16V8 are compatible with GAL16V8). Everything looks perfect now:

esprade4

There is a total of 4 PALs on this board. I dumped all of them. They are available on JAMMArcade.net

Here’s a picture of the board with the two replaced PALs highlighted in red:

esprade0b

HP10529A repair log

Equipment Repair Logs Comments Off

Jun 112016

Got myself a new HP logic comparator which had a fault on it.
The fault was with pin 11 on the LED’s.

The schematics for this are available but its so small its pretty easy to trace out just by looking at it.
Using the scope I found all the outputs of the 74L04 hex inverter at location U4 were stuck at around 1.7v. I replaced with with a 74LS04.
hpcomp

While I was poking around I also found the zener diode CR3 had a dry joint so resoldered that too.
Now its all working.

(Ignore the sound, had kids TV playing on Netflix while doing this)

Pyros repair log

PCB Repair Logs 2 Responses »

Jun 072016

I got this faulty Pyros (US version of Wardner) PCB from Ebay :

DSCN3385

It was not really cheap but it was worth the buy since, on the basis of the seller description, I was confident it could be an easy fix.Board showed an ‘I/O ERROR’ upon boot:

DSCN3384

I knew from my experience that this board produces the mentioned error when, indeed, there is some troubles with the inputs during the startup sequence (also a simple buttom pressure would cause it).So for first I went to check with my logic probe all the inputs probing pins on the JAMMA edge connector.All of them were high except the ‘COIN 2’ (pin 16 solder side) which was stuck low.I could trace it back to pin 17 of a 74SL240 @20N :

74LS240@20N

I could measure only few Ohms of resistance between this pin and ground, this meant internal junction was nearly shorted to GND:

DSCN3387

Once desoldered the chip, it obviously failed the test:

74LS240@20N_testing

With a good chip, the board entered in game with no further issue.

DSCN3392

Teenage Mutant Hero Turtles repair log #4

PCB Repair Logs, Repair Logs Comments Off

Jun 062016

tmnt0

1) It was stuck on a white screen on boot.

After looking for a suspect chip, piggybacking, etc… with no luck, I finally found out that the reset signal was going to high level too quick to let enough time to the 68000 for proper initializing.

Thanks to the schematics, I could see that the reset was generated by a custom Konami chip labeled 051550 located at B19. Like many boards of that era, a capacitor is used to create a temporization when you power up the board and let the 68000 initialize after everything else is ready.

The capacitor takes one or two seconds to fully charges then the chip responsible for generating the reset switches to high level. You can see when powering up the board and looking at the signal on the + pin of the cap with a scope the voltage slowly raising before stabilizing. Here, the ceramic capacitor located just below the 051550 chip didn’t seem to charge slowly and got suddenly to high level when powered up. The cap was a bit hidden under the 051550 chip that was bended over it so I softly pushed it and it went like that:

tmnt1

This chip is a small ceramic board populated with SMC chips recovered by a black material. It was cracked but that was almost unnoticeable before pushing on it. It is used on many Konami boards of that era and luckily I could find a good one on a spare board. Here is a closer look at both desoldered:

tmnt2

After replacing the chip, it booted, got the RAM/ROM test with everything OK:

Then the white pattern:

tmnt4

Then it rebooted and repeated that again and again…

2) I inspected the signals near the CPU part, RAMs, TTLs, but everything looked fine… Retried piggybacking the RAMs with no changes…

Sometimes it may happen that a minor error in the data or address lines cannot be clearly visible with the scope so I desoldered the two CPU RAMs, a pair of Fujitsu MB8464 (64kb) at J13 and L13 and tested them on my programmer. And the one at L13 didn’t pass the test:

tmnt6

I replaced it with a new one and the game launched. Everything else works perfectly.

tmnt5

Thunder Fox repair log

PCB Repair Logs, Repair Logs Comments Off

Jun 032016

Got this Thunder Fox PCB from a friend to repair.

thunderfox1b

It had 2 issues:

Vertical lines on some sprites.
No sound.

thunderfox2

I had a working Thunder Fox PCB with me so I started the easy way to swap sprites ROMs between the boards and got the sprites working again with replacing the one labeled c28-03 at location IC29 (#1 on the PCB picture above). I reburned a 27C400 EPROM as a replacement.

thunderfox3

For the sound part, I could notice there was no analog output signal at pin 27 on the YM2610 sound chip but all its data inputs and data lines on the sounds ROMs were pulsing. I also noticed the signal on the IRQ (pin 56) was stuck low (it was pulsing on my working board). The IRQ signal is an output so it made me think the YM2610 was clearly the faulty one so I replaced it but with no change…

The IRQ pin was still stuck low so I traced it to pin 16 of the Z80. Strange because it is an input pin on it but sometimes if a pin is dead it takes over and pushes down the data that comes from an other chip. So I tried replacing the Z80 (#2 on the PCB picture above) and finally got the sound working. That was it !

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