JAMMArcade.net – Page 62

Bubble Bobble repair log #4

PCB Repair Logs Comments Off

Sep 122017

Received this original Bubble Bobble PCB for repair.Set is made of a CPU board :

and a VIDEO one :

Game played blind, no RGB output, only SYNC was present on edge connector pins.Each colors is generated by a single ‘PC040DA’ custom (a 6 bit DAC)

Probing them revealed that pin 10 was stuck, this is the vertical blanking signal called /VBL on schematics:

Tracing back the signal lead me to a counter 74LS163 @IC11:

Clock on its pin 2 was present but all outputs were stuck low:

The IC failed the out-of-circuit test:

I replaced it and finally had output on video but all was displayed with the only red color, green and blue were missing at all:

I checked the two involved PC040DA customs @IC85 and IC86 and found that their output pin 3 was clearly dead compared with the active one of red color:

I removed them and installed sockets:

I took the donor parts from a Rastan PCB and installed them:

Colors were restored and board 100% fixed.

P.S.

‘PC040DA’ DAC could be the next candidate for a reproduction although someone has already did it:

https://www.gamoover.net/Forums/index.php?PHPSESSID=f9cba7f099937c197dceb458d0b6a897&topic=27336.0

Commodore 1084S-P1 repair log (part 3)

General, Monitor Repair Log 2 Responses »

Sep 112017

During my Hypersport’s repair I discovered a problem with the display of my Commodore 1084S monitor. Notice blue missing for “3 LONG HORSE” and “7 POLE VAULT”.

This will be the third time I’ve performed a repair on this old monitor which I’ve had since the early 90s for my Amiga 500 and 2000. At first I would suspect the AV7000 Supergun as the culprit. But subsequent tests would prove otherwise.

There’s definitely a better picture with composite or svideo from my c64 and Atari 8 bits but there seems to be a problem showing blue on the RGB input even though some blue is there ( turquoise , cyan.. etc ) in other images. Adjusting the blue gun and turning up the contrast just makes the backgrounds in Puzznic more blue. Where blue is supposed to be on the screen, it seems to not be present as though the signal were being cancelled out. With no RGB signal to the monitor at all, it defaults to a blue screen instead of a white one.

Apologies for the sync bands.

I suspected the neck board transistors, so I pull out the one responsible for blue and tests with my multimeter show it’s fine. I even swap the transistors around to see if the problem would move to the other gun…. but it doesn’t.

I found this really good post on eab [ English Amiga Board ] by Loedown

https://eab.abime.net/showthread.php?t=59401&page=2

IC502 TDA 3505 pins 12, 13, 14 are RGB in from Euro Connector /SCART, check voltages there to begin with when inputting a perfectly white screen. Then follow the voltages through to transistors TS604 – 606.

The schematic shows the analogue inputs go directly from the RGB connector to the Philips TDA3505 IC via some 100nf caps. Pins 12,13 & 14 are the input RGB signals. I measured 4.3v for red and green but 9.1v for blue. That seems a little too high for blue and the schematic indicates 4v for those signals.

I order some TDA3505s on eBay from atarifreakz and my package arrives a few weeks later.

Not wasting any time. I replace the chip and the picture is now perfect!

The Taito logo and blue shadow around the Puzznic logo is now visible. Notice the bricks and backgrounds are also showing up right compared with the previous screenshot.

I wonder if there will be a part 4 🙂

Michael Jackson’s MoonWalker repair log #2

PCB Repair Logs Comments Off

Sep 072017

Got this Michael Jackson’s MoonWalker PCB (Sega System 18) for repair:

Board booted but sound was missing at all and game behaved strangely, you could no longer move your character whenever you pressed the buttons or being hit by enemies :

At first glance I thought the FD1094 custom CPU module was slightly suicided so I swapped it with a good one along with the i8751 MCU but with no luck.I began to think of a correlation between the lack of sound and freeze.Probing the Z80 sound CPU revealed /HALT line was asserted while the /INT was floating.The latter comes from one of the two YM3438 FM sound generator @IC88 :

I removed the chip and tested it on a good motherboard, it was bad.But replacing it made no difference, the shared data bus of the two YM3438 was still inactive.So I pulled the other one @IC87:

It was bad too.Replacing it fixed the board.

Cabal (bootleg) PAL dumps added

PAL Updates Comments Off

Aug 292017

Today I dumped the two PALs from a working bootleg of Cabal.Original devices were two secured PAL16L8 which I reversed and successfully tested onto GAL16V8.

ROMCMP Frontend

General Comments Off

Aug 272017

In an attempt to help more people start using MAME’s fantastic ROMCMP utility I have made a simple GUI frontend for it.

Program can be found in the Downloads section under “PC Software”

Older Entries Newer Entries