Bosconian Repair from hell...

channelmanic

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Why am I getting all these crazy assed boards!

Whew!

Doing a repair/renew kit on a Bosconian (Same CPU board as Galaga but with an extra chip & ROM)... Replaced all the sockets... resistor packs were the good kind and didn't need replacing.

The board would boot but would come up with flickering on the text and the graphics would get all kinds of glitches and turn blocky. If you tapped on the board it would come and go (which makes the repair all that much stranger!!!) so I redid the solder joints, checked for bad traces/gouges, cleaned the board interconnect socket, and looked it over and over and over until I was sure it was all perfect.

Started probing things to see if I could hear the glitches on the screen with the audio on the logic probe. Found if I put it on pin 13 of one of the LS367 chips that the text would go crazy. Checked the schematics and it went to pin 1 of a 74LS138 and pin 13 on 2 more LS367 chips. Replaced all 4 of those chips.

Now instead of a perfect screen, the text was flickering and flashing all kinds of colors and every other character would flip upside down then right side up repeatedly. If you pressed start the game would crash... but there was no more flickering out to the blocky screen.

If the logic probe hit pin 1/15 on the upper 3 LS367s then the game would crash. These are the select lines to enable the outputs from the address bus to the video board through the LS367s. Replaced the other 2 LS367 on the main CPU's address bus and the game played perfect.

Replaced the other 3 LS367s for good measure.

Yes... the failed ones were Fujitsu chips. And they must've had failed bond wires because I've never seen a chip that failed to where if you tapped the board the symptoms would come & go.

What a strange freakin' repair!

Now to redo the sockets on the video board tomorrow.

RJ
 
Galaga/Bosconian PCBs never cease to invent new and unique ways to fail... :)

Date code on the Fuj LS367s?

Bill
 
Do you sell these chips?

I need some of the 74ls138, 74ls367, and an lm377 (I think) it is a audio amp for the galaxian.


Why am I getting all these crazy assed boards!

Whew!

Doing a repair/renew kit on a Bosconian (Same CPU board as Galaga but with an extra chip & ROM)... Replaced all the sockets... resistor packs were the good kind and didn't need replacing.

The board would boot but would come up with flickering on the text and the graphics would get all kinds of glitches and turn blocky. If you tapped on the board it would come and go (which makes the repair all that much stranger!!!) so I redid the solder joints, checked for bad traces/gouges, cleaned the board interconnect socket, and looked it over and over and over until I was sure it was all perfect.

Started probing things to see if I could hear the glitches on the screen with the audio on the logic probe. Found if I put it on pin 13 of one of the LS367 chips that the text would go crazy. Checked the schematics and it went to pin 1 of a 74LS138 and pin 13 on 2 more LS367 chips. Replaced all 4 of those chips.

Now instead of a perfect screen, the text was flickering and flashing all kinds of colors and every other character would flip upside down then right side up repeatedly. If you pressed start the game would crash... but there was no more flickering out to the blocky screen.

If the logic probe hit pin 1/15 on the upper 3 LS367s then the game would crash. These are the select lines to enable the outputs from the address bus to the video board through the LS367s. Replaced the other 2 LS367 on the main CPU's address bus and the game played perfect.

Replaced the other 3 LS367s for good measure.

Yes... the failed ones were Fujitsu chips. And they must've had failed bond wires because I've never seen a chip that failed to where if you tapped the board the symptoms would come & go.

What a strange freakin' repair!

Now to redo the sockets on the video board tomorrow.

RJ
 
Why am I getting all these crazy assed boards!
Yes... the failed ones were Fujitsu chips. And they must've had failed bond wires because I've never seen a chip that failed to where if you tapped the board the symptoms would come & go.

Have seen some odd behaviour with Fujitsu chips lately, ones that test bad on the board with floating outputs, that also fail a comparator test on those pins but when desoldered test fine. I can only assume the heating of the desoldering fixed the bond wire joint internally, either way they went in the scrap jar.

Date code on the Fuj LS367s?

I don't think you can judge F chips based on date, I have seen the exact same ways to die from Fujitsus on Konami boards from 1984 (Mikie) through to TMNT (1991), same mode of death, floating outputs, or stuck outputs (which are probably due to internally disconnected outputs), or bat-shit crazy behaviour, highly sensitive to touch, which is possibly disconnected 5V or ground internally.
 
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Do you sell these chips?

I need some of the 74ls138, 74ls367, and an lm377 (I think) it is a audio amp for the galaxian.

I have 'em in stock... not sure if I have the inventory on the web site up to date on 74xx logic though. Will check later tonight.

On the LM377, I don't recognize the # as something I'd have. I can get it though.
 
I have 'em in stock... not sure if I have the inventory on the web site up to date on 74xx logic though. Will check later tonight.

On the LM377, I don't recognize the # as something I'd have. I can get it though.

Just checked it is the lm377 and was wondering if the heat sink comes with it.
 
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