Hey all,

Need some guidance. Got this machine from my friend. Has run great for years despite nothing been done to it. Lost the sound one day and decided to invest some parts in it. Recapped the SDB and sound board, and replaced the 3.6VDC lithium battery on the MPU board with a 4 AA battery holder with a blocking diode in the 4th position to be remotely mounted. No alkaline damage at all. Lithium battery looks like a retrofit from years prior.

Since doing this, the MPU locks on, solid LED, immediately turn it off and on, then I get two flashes and thats it. Hitting reset button on MPU does nothing.

Here is the kicker, I reinstall the 3.6V lithium battery after waiting 5 minutes or so for the residual charge to dissipate, and whatdayaknow...8 flashes everything boots up great, sound is back, all is good.

So whats up with this? I thought 4.5VDC was okay for the onboard memory? Blocking diode is for non chargable batteries.

My guess is that there is something wrong with the MPU reset circuit? Bad non volatile memory? Or am I way off?

I have rebuilt my entire OEM board set for my Embryon so I'm no stranger to this work or dealing with glitches. This one has me a bit stumped though. Can really use some direction.

Pinwiz

Ill do this and report back to you

Okay, did this two ways. With the 3.6V lithium battery, and the 3 AA with blocking diode. The resistor is fine not burnt measures 83ohms

1. U8 P22, no bat powered up =350mV
2. U8 P22, with 3.6V bat powered up = 4.3VDC
3. U8 P22, with 3.6V bat power off = 2.01VDC
4. U8 P22, with 4.5V bat power up = 5.1VDC
5. U8 P22, with 4.5V bat power off = 4.3VDC

FYI , 4.5V bat measures 4.7V at terminals.

U9 P40 voltage power off is zero volts, when powered on and booted working properly the voltage is 5.4VDC

Cycling the power on and off a few times (not like a maniac but normal interval) I got the board to lock at the 2nd flash, and U9 P40 voltage hung at 3.36VDC. Had to remove battery and wait like 5 minutes before reconnecting it and MPU booted. Wondering if a transistor is starting to go bad or a diode in the reset circuit?

Hope this detail helps the diagnosis.
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Understood. I'll concentrate on the following parts. Resistors I'll check too but they tend to be fine unless they appear burnt. Be in touch soon

Q1, Q5, CR5, CR7, & VR1

Confirmed the RAM chip U8 P22 has 5.3VDC when machine is powered up and no battery attached.Seems there was slight black corrosion that my test lead couldn't measure

I checked all the components of the VPD circuit, and components check out correctly with my DMM. Though I suspect that while the components test good in circuit doesn't mean they are good.

The latest symptom I have now after checking everything, with the 4.5V bat, the machine boots up, goes into attract mode for like 5 seconds, then goes blank resets through all 7 flashes of the MPU, then resets one more time with the displays flickering before everything goes dead.

Seems like from reading the repair guide that its a bad U7 6810 memory chip? It did have black corrosion, so I used fine sandpaper to clean the pins, no change in behavior.

Where do I go from here?

Bump, looking to get direction if i am on the right track before throwing darts/parts at it.

Zener voltage is 6.19v on one side and 5.1v on the banded side. This reading is the same with no battery, 3.6v battery, or 4.5v batteries.

New development: 3.6v battery, replaced 6810 socket, now it boots up. Played 6 games, no problems. Put the 4.5v battery back in, flicker and one flash. Maybe a bad socket on the 5101 ram chip? Intermittent component failing under load in VPD circuit?

Making progress it seems

I measured from ground to each side of the zener. If I measure across it with my DMM I get 8.01VDC. Looks like it is the correct zener, part# 1N4738A.

I left the 3.6 lithium installed, and played a few more games with a half dozen power cycles, and it booted up fine no problems. So that tells me I don't have a chip problem. Its possibly a socket issue (it has AUGAT type installed) or something else.

For s*h*i*t*s and giggles I reinstalled the 4.5v battery without touching the MPU physically. I remotely mounted the 3.6V lithium so there is no risk of it leaking onto the board. Nope, same issue, flicker and a flash, wont boot. Turn on/off a few times, then it will boot, then reboot constantly through all 7 flashes like 3 times then it goes dark. No steady LED.

Reinstall 3.6v battery after waiting 10 minutes for everything to settle, and voila, everything is working again no issues.

At this point its up and running now, but I know that lithium battery will only last so long, and I'd like to get it to work on the 4.5V AA setup with diode.

What else could I check? This is the fun of electronics, things can test good but under load conditions they fail and its a needle in a haystack unless one knows what to look for.

1. I have not done this exactly, I jumpered the junction of R1/R3 to ground to reset the board, and no it does not boot properly.

2. I've tried this, and it will boot, but after about a minute or so, displays go blank, and board stops working.

You may very well be right. I spent sooo many hours on my Embryon during the restore that I simply gave up trying to track down the problems and shotgunned the entire board set which worked. I like this game, but not enough to do that method on it.

Is it possible that the voltage tolerance of the chips was less for some of them? Can transistors which test good when powered off be in a failure condition when powered on? My thought would be yes on this second question but not 100% sure.

You are right, R12 is a diode. I cant tell if the LED is dim or out. Here is a picture of the battery pack, i got it preinstalled as an item. Come to think of it, its backwards i think.

Diode is a 1N5819. Ill remove it, replace it with a jumper and let you know the outcome. Gotta run an errand first.
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It has a reading of 0.188V one way, and INF the leads reversed. I would expect like 0.6V and INF, guess this diode is bad?

If I removed the 1N5819 and connected the batteries directly to the board, the 1N4004 would be the blocking diode?

Got it! So if the machine fails to boot with the 4.5v bats without the diode on the pack, then there is something else causing a problem.