Jump to content
Due to a large amount of spamers, accounts will now have to be approved by the Admins so please be patient. ×
IGNORED

Dug one of my old logs up :)


Recommended Posts

Double Dragon - Original PCB

Fault: No foreground characters – Men remaining and score.

Tools: Multi meter, logic probe

No Schematics

Problem known to be on top board – bottom board tested with known good set

A bad 74LS174 at position 5F and a bad 74LS157 at position 4E. Replaced and the foreground characters are back!

Tiger Heli – Original PCB

Fault: No sprites

Tools: Multi meter, logic probe.

No Schematics

Problem known to be on top board – bottom board tested with known good set

 

Repaired three burnt tracks on underside of top board. This bought back the graphics, but some characters were messed up. The helicopter on the title screen was missing every second character. Probing around found the 74ls161 at location C7 had no signal on some pins. Replacing this restored all graphics.

 

Tiger Heli – Bootleg PCB

Fault: Constantly resetting. Audio Thumping

Tools: Multi Meter, logic probe

No Schematics

Problem known to be on top board – bottom board tested with known good set

 

When plugged into my test rig, the Z80 that controls the sound was getting read hot. I socketed and replaced this and the 6116 ram next to it. I clipped out the audio amp as this was getting hot as well, and the caps next to it had the legs pulled out so I removed these as well. The audio stopped thumping.

Now I was getting ROM ERROR 0 and the game would freeze there. Poking around the general area found a bad 74LS74 with a stuck output. Also a 74LS138 was found that had no inputs. When these where replaced, the rom error disappeared. No the game was just constantly resetting. Tracing the reset line back to a 4020 at 8A found there was no output on pin 3. This feed the reset circuit. Not having a 4020 on hand, I pulled a signal from pin 2 on 1A and feed it into pin 3 and 8A. No we have a game!!!

The colours are a bit screwy and there is no sound yet.

The colour was screwed up because someone along the way had the blue and green proms in the wrong sockets! Swapping them over restored the correct colours.

Replaced the amp and a few caps in the audio section – sound works know but is slow. This is due to the patch I did for the reset circuit on 4020- I have verified this as I have clipped it out and know I’ll have to replace it.

Replaced the 4020 binary ripple counter today. Game starts normally and the sound is at the correct speed. The ripple counter gets a feed from the clock to activate the sound Z80 through the NMI input which shares the same data bus as the main cpu. When the sound CPU was not being held off the bus, it was conflating with the main CPU causing the resets. The feed from the 4020 ripple counter also sets the sound timing.

 

 

 

Bosconian

Fault – One of a batch of dead boards from an operator.

Tools: Multi Meter, logic probe

No Schematics

 

OK, wired up a loom for the power and the video and I am nothing! OK, no crystal on the main PCB. Tried a few values and a 18.432mhz gives video. Now it goes thru the ram test then resets. Replaced all three Z80’s on the main board, and it works.

Now there are no stars. I will have to look into this.

Sounds now fixed after having a poke around all the roms on the vid board and figuring out which were the roms for the sampled speech. Roms 5L, 5M and 5N store the data for the speech. Turned out that the rom in position 5N had a couple of broken legs. Reburnt a rom and replaced it and the speech is now fine. Now to do something about the stars.

Seems Bosconian uses a custom chip for the starfield generator. Pulling this chip and I find a bent pin!. Straightened the pin carefully (these chips are known for there bad legs) and reinstalling it, and we have stars.

 

Xain Seleena

Fault – No Sound

Purchased the PCB off Ebay with the known fault. Probing around with my remote amp, I could pick up the unamplified sound, so the fault was in the amp section. Changed all the caps in the section, no change. Changed the amp, no change. This was getting frustrating. Had another good look at the pcb, and it turned out there was no path for the speaker ground!! My test rig only connects the speaker the speaker + and – on the jamma edge connector. Adding a speaker ground to the pcb and the sound works!. Strange, but true.

 

 

 

 

Bank Panic

Fault – Dead board

Another Ebay purchase. This was bought as untested. I gave it a quick look then made a jamma harness and plugged it into my test bed. Nothing. Another look, and I found a broken trace next to IC 1J. Repairing this trace bought it to life. When I hooked up 12 for the sound, the amp blew. I didn’t have any HA1377 amps, but quick look showed these to be close in pinout to a common HA13001 amp. Pins 7 to 12 are the same and the others where jumpered to the correct place. The sound tested fine after that.

 

IPM Invaders (aka Solar Warriors)

Fault – Dead board – No roms

This is a game I always wanted to get my hands onto!. I have gotten a pcb from an op that stripped the roms (*sigh*) for another board. Getting a hold of the roms is no easy feat. I did get what I think is a set of the Guru’s web site for unemulated mame games. I hope they are the right ones.

First to try and find out what goes where on the edge connector. This PCB has 4116 rams on it so it uses +5, +12, -5 and -12v.

 

Turned out, this is a Red Alert PCB, so I will be revsisting it oneday.

 

Bombjack

Fault – Missing sprites and top half of Bombjack on title screen.

Replace 74ls157 @

Constanly watchdogging

Replace 74ls283 @

Bar Ram 4

Replace 6116 ram @

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...