PCB Repair Logs – Page 57

Raimais repair log

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Oct 052016

Got for a repair this Raimais PCB , an obscure maze game released by Taito in 1988 :

100_8907

Board played fine but sound was totally missing.If I put my fingers on solderside of the amplifier I could hear some noises, sign that it was still good.Someone replaced invain the YM3016 DAC but this was not the cause.Ruled out a problem is the analog section, I went to check the digital circuitry.Sound CPU is a Z80 with a ROM and a RAM.When I went to check the RAM @IC25 (a Toshiba TMM2063, 6264 compatible, almost prone to failure in my experience like Fujitsu TTLs) I found irregular activity on some data pins (on the left of the below picture an healthy signal) :

data_lines_comparison

I desoldered the chip:

100_8906

and tested it out-of-circuit where it failed (my programmer went in protection due a possible short , indeed I could measure few Ohms of resistance across VCC and GND pins of the chip)

tmm2063ic25

Fitted a good chip restored the sound.End of job.

Fire Shark repair log #1

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Oct 052016

Received today this Fire Shark PCB for a repair:

100_8995

According to the owner, board would sit on a “OBJECT RAM ERROR” but instead, once powered up, the board entered in game but sprites were almost absent,spread on screen in form of lines and garbage:

Like many other Toplan games, also this one uses the ‘FCU-2’ custom ASIC sprites generator which , due its package, is the first thing to check if you have sprites issue:

100_8998

Visually I couldn’t see anything wrong with it but when I tested the soldering of each pin with a needle, I found some loose legs on a side :

100_8996

I promptly reflowed them and sprites were back properly formed:

100_9005_

The other issue reported by owner was that player 2 controls were not responding except for BUTTON#2, COIN and START.The screen of the TEST MODE clearly showed the stuck inputs:

I traced these inputs back to a 4.7K Ohm resistor array used as pull-up and I found it was cracked in two:

100_9001

The scope confimed that half of pins were floating and not in high state like they should be :

I removed the broken resistor array:

100_9002

and, after installed a good one, all the player 2 inputs were correctly working again.Board 100% fixed.

Golden Axe 2 – The Revenge of Death Adder repair log #1

Oct 042016

Got this Golden Axe 2 rom board (here plugged on a working Sega System 32 mother board from an Arabian Fight) with a black screen on boot:

goldenaxe2-1

I borrowed a friend’s working Golden Axe 2 rom board for tests and found out that the security board was the faulty part:

goldenaxe2-2

This board uses an encrypted V60 CPU to prevent conversions by swapping ROMs between boards. For example, there is the exact same board on Arabian Fight but CPUs have different IDs:
– 315-5533-01 for Arabian Fight
– 315-5533-02 for Golden Axe 2

So obviously, putting the security board from Arabian Fight didn’t make the game working, even with the EPROM from Golden Axe 2 plugged in.

ROM, PAL, oscillator and 75HC04AP were tested good but I found a few address lines which looked inactive with the scope. So the faulty chip could be either the CPU @U2 or the RAM @U1. As the encrypted CPU cannot be retrieved anywhere else than another Golden Axe 2, replacing the RAM was my only chance to repair it.

The RAM is a Fujitsu MB8421 (16 kb CMOS).

goldenaxe2-3

I bought a new one (got a MB8421-90L instead of the original MB8421-12L but not a problem as it is a faster 90 ns instead of the original 120 ns), replaced it and luckily the game booted with no other issue. 🙂

goldenaxe2-4

Out Zone repair log #5

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Sep 292016

Another Out Zone on the bench and with this one we have five repair logs of this PCB.

Board came in not so great condition, quite dirty :

100_8856

Like all the Out Zone I have troubleshooted, also this PCB suffered from sprites issue, they were garbled and misplaced :

Having a good knowledge of this hardware, I went to probe the involved circuit.All was fine until my logic comparator reported issue on a couple of outputs of a 74ALS163 @17B:

100_8858

The scope confirmed the outputs were floating compared to inputs:

74als163_inputs_outpus_comparing

I removed the IC and the out-of-circuit testing failed miserably:

74als16317b_failed

Another Out Zone saved.See you at the next repair of this great game by Toaplan!

P.O.W. – Prisoners of War repair log

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Sep 292016

Got this P.O.W. – Prisoners of War PCB since a long time, bought in a lot of faulty boards from USA :

100_8798

Board was marked by a piece of tape with the words “SPRITE ERROR”.When I first powered the board up, picture could not sync properly on the Philips CM883-II monitor of my supergun (but it did on my Astro City):

I found a workaround by replacing the 100 Ohm resistor connected in series with the SYNC pin of edge connector with a 10 Ohm one.So the sprite error materialized :

As usual I did my visual inspection and found a severed trace on the solderside (involved in the sprites RAM data bus).Patching it cleared the error so game finally booted showing this issue :

100_8729

I noticed that if I shorted some address/data lines of a row of eight 2018 RAMs, further lines were displayed so this was the part of circuit involved.

100_8733_

I went to probe each RAM with my scope and found some irregular activity on data lines of the chip @9K, here is a comparison with a good signal (on the left of the below picture)

data_line_compare

Time to desolder the chip:

100_8946

The out-of-circuit test failed :

20189k_failed

A good RAM chip fixed completely the game.

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