(Topic ID: 269921)

Have I Fried My Rottendog MPU327 & Pharoah

By cooked71

1 year ago


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  • Latest reply 1 year ago by cooked71
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DAD2FB80-B908-4D78-B390-22C330505613 (resized).jpeg

#1 1 year ago

I purchased a nice Pharaoh about a year ago and have only just got around to setting it up.

Im a bit of a newb when it comes to early 80's SS games.

This game has a complete set of Rottendog replacement boards including the MPU327 driver/cpu board and Rottendog display board and number displays. This is my first experience with a Rottendog board.

On reconnecting all the connectors I think I accidentally had the 1J2 and 1J6 connectors mixed up since they are keyed the same. I should have checked the Pharaoh manual but of course only did that afterwords.

Anyway after correcting the connectors, surprise surprise, the displays don't work now. Have I completely fried the boards? How do I test to determine where the fault is? Can I fix them?

Funny thing is when I had the 1j2 and 1j6 swapped in the incorrect positions, I played a couple of games - everything worked fine - even the displays worked, but showed only a few numbers - not the score, but they were active. Only after I swapped the connectors to their correct positions did the display stop working altogether.

Rest of the game plays fine.

#2 1 year ago

contact Rottendog

#3 1 year ago

You have sent 12v down strobe #10 by doing that. The 74154 at IC6 on the MPU is probably fried. The 74 series chips do not like over voltage. Nothing else likely be bad on the MPU/Driver. If that 74154 is in a chip socket it would be pretty noninvasive to try a new one. If the board is in warranty see what the manufacturer says.

Master display board is probably ok. 12v pin would have been floating and the others are just 5v or ground going to strobe inputs.

#4 1 year ago
Quoted from barakandl:

You have sent 12v down strobe #10 by doing that. The 74154 at IC6 on the MPU is probably fried. The 74 series chips do not like over voltage. Nothing else likely be bad on the MPU/Driver. If that 74154 is in a chip socket it would be pretty noninvasive to try a new one. If the board is in warranty see what the manufacturer says.
Master display board is probably ok. 12v pin would have been floating and the others are just 5v or ground going to strobe inputs.

Thanks barakandl , sounds like a good place to start.

Would that just be a standard chip I could order and replace? I can see chips matching that number available online.

#5 1 year ago
#6 1 year ago

Several versions of 74HCT154 will work. Just make sure to get the DIP-24 package instead of a surface mount part.

#7 1 year ago
Quoted from G-P-E:

Several versions of 74HCT154 will work. Just make sure to get the DIP-24 package instead of a surface mount part.

Thanks Guys - will look into it. Would order from you G-P-E but shipping from US to Australia at the moment is a nightmare.

#8 1 year ago
Quoted from barakandl:

You have sent 12v down strobe #10 by doing that. The 74154 at IC6 on the MPU is probably fried. The 74 series chips do not like over voltage. Nothing else likely be bad on the MPU/Driver. If that 74154 is in a chip socket it would be pretty noninvasive to try a new one. If the board is in warranty see what the manufacturer says.
Master display board is probably ok. 12v pin would have been floating and the others are just 5v or ground going to strobe inputs.

Chip is socketed so that’s good. Going to order a new one now and see what happens- fingers crossed.

The numbers on the chip are slightly different than G-P-E mentions. Does it matter as long as it’s not surface mount?

DAD2FB80-B908-4D78-B390-22C330505613 (resized).jpeg
#9 1 year ago
Quoted from cooked71:

Chip is socketed so that’s good. Going to order a new one now and see what happens- fingers crossed.
The numbers on the chip are slightly different than g-p-e mentions. Does it matter as long as it’s not surface mount? [quoted image]

Go with what Ed from GPE mentioned, generally speaking it doesn't matter.

#10 1 year ago
Quoted from cooked71:

Chip is socketed so that’s good. Going to order a new one now and see what happens- fingers crossed.
The numbers on the chip are slightly different than g-p-e mentions. Does it matter as long as it’s not surface mount? [quoted image]

74154, 74LS154, 74HCT154 will all work. The 74HC154 will work if the decoder is wired up to CMOS ports of the PIA.... i am not sure from memory if it is.

I think they also make this chip in a narrow through hole package with 0.3" between rows which you don't want. Get through hole wide part 0.6" between rows.

#11 1 year ago

Ignore the prefix - it's just the manufacturer.
E.g. -- Most common:
SN prefix is most oftenly used by Texas Instruments but also occasionally Motorola during 1980s/1990s.
CD prefix was used by RCA, Harris and eventually Texas Instruments
Philips and NXP often didn't use a prefix.

Suffix states the type of part.
"N" and "P" are often used to indicate Plastic DIP type package.

The one in the photo is a 74LS154. Can use a 74HCT154 or 74154 although the 74154s are more difficult to locate.
74HC154 is a maybe. Like barakandl said -- depends on how it's used. If in doubt, safest bet is to avoid the 74HC154.

4 weeks later
#12 1 year ago

Just thought id put a cork in this thread. All you guys were spot on. Received the replacement chip last week. Badly packaged and a couple of pins broken - but soldered on some replacement pins, popped her in and boom - works perfectly!

Anyway, I'll chalk it up to a good lesson for next time.

Thanks again all!

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