MV-1B stuck on green error

HeavyMachineGoob

My poontang misses Lenn Yang's wang
10 Year Member
Joined
Apr 3, 2011
Posts
5,813
Model: MV-1B (1996)
Symptom: Stuck on green screen (calendar error)

This board still has its original battery, seems to be working ok, no leaking. I've replaced the 32.768Khz oscillator, no change.

I've checked the voltages on the work RAM chips, they are at 5v. The backup RAM chips, the D4990 RTC chip and the logic chip all are at about 4.2v. I've been trying to figure out what could causing the drop in voltage but I'm not sure where to start looking, the MV-1B has so few passive components. Does anyone know where voltage is fed into the battery section?
 

BIG BEAR

SHOCKbox Developer,
20 Year Member
Joined
Dec 14, 2001
Posts
8,230
Probably a bad d4990 or broken trace to it.
BB
 

HeavyMachineGoob

My poontang misses Lenn Yang's wang
10 Year Member
Joined
Apr 3, 2011
Posts
5,813
I figured I didn't have much to lose so I tried directly supplying 5v to the D4990 and RAM chips without the battery and there was no change either. I'll order a new D4990 chip and try that.
 

Xian Xi

JammaNationX,
15 Year Member
Joined
Dec 1, 2005
Posts
27,748
Don’t forget that the BRAM is powered through a diode.
 

HeavyMachineGoob

My poontang misses Lenn Yang's wang
10 Year Member
Joined
Apr 3, 2011
Posts
5,813
Is that something I should check? Which diode? I'm not sure why it is the battery section on this board is underpowering using the JAMMA interface. The +5v rail is usually at 5.02v.
 

Miketage

n00b
Joined
Jul 10, 2019
Posts
23
I'm having the same problem. I'm ready to send mine off for a pro to handle so I don't make it worse.
Any recommendations? I've read channelmaniac is one of the best.
 
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