Voltages are nearly the same:

1-.03
2-2.90
3-3.69
4-4.32
5-3.69
6-.18
16-4.49

I see 4081, I had checked the resistor..

 

Bad board: R163 has -12v and pin14 on 4081 has 3.71v pin6 has -1.00

Good board: r163 -12v and pin14 has 4.48v pin 6 -1.05

 

You still need to figure out why VAB on the bad board is about 3.7v, and about 4.5v on the good board.

The +5v supply voltage is the same on both, right?

Measure the voltage across CR26. On the good board, you'll get around 0.7v; on the bad board, about 1.4v.

Did you ever replace C23? You said you were going to, but never said you actually did so yet.

See if there is a voltage drop across R133. If zero, then OK. If >0, then something in the battery holder is shorting. Removing R133 or lifting one end of it will remove that problem.

If none of that has helped so far, you'll need to either start removing IC's (I'd start with Z2, as you've already replaced it and it's a small IC) or else start cutting traces to find out what's loading VAB down.

 

The +5v supply voltage is the same on both, right?

I tested at CR26 and on both boards +5.08

Measure the voltage across CR26. On the good board, you'll get around 0.7v; on the bad board, about 1.4v.

On both boards I get +0.6v.

Did you ever replace C23? You said you were going to, but never said you actually did so yet.

Yes, I replaced C23 and CR26 and CR37.

See if there is a voltage drop across R133. If zero, then OK. If >0, then something in the battery holder is shorting. Removing R133 or lifting one end of it will remove that problem.

Voltage did drop across R133 to zero.

This morning I went ahead and traced down the VAB -> lines to look for any traces that might be shorted. I marked them on the attached pdf with a circled number. I failed to write down Z22 but I tested it and it ties into the 4081 Pin14 I believe.

After doing that it seems to me that Z2 might be the culprit. Pins 3, 5 and 16 tie together but pins 3 and 5 are +3.67 while Pin16 is +4.49, they should be all the same I think?

 

The schematic shows pins 3, 5 and 16 all connected directly to each other by wire/traces. I missed that before when you reported the voltages; I just looked at the lower voltages and completely glossed over pin 16.

Is there perhaps a jumper that I don't see that connects pins 3 and 5 to 16?
Perhaps bad solder joints? Cracked solder joints? Corroded, cracked or otherwise broken trace? You need to figure out why 3, 5 and 16 are not all the same voltage. If you have to, jumper from pin 16 to pin 3, as it will be a short jump.

 

The schematic shows pins 3, 5 and 16 all connected directly to each other by wire/traces. I missed that before when you reported the voltages; I just looked at the lower voltages and completely glossed over pin 16.

Agreed but on the board its different (see pics) maybe internal in Z2?

Since the schematic shows Pin3, 5 and 16 at the same voltage for a test could I jumper Pin16 to Pin3 on the bottom of the board?

I'm sure you've seen lots of solder jobs I hope mine passes the mustard...

I've ordered another Z2 and a couple of resistors that I didn't have mainly R159 that I had to solder a couple of resistors together to get the correct resistance for.

Thanks,

 

The 3-16 jumper is probably under the IC, on the component side.

 

Agreed but on the board its different (see pics) maybe internal in Z2?

No, it wouldn't have shown the pins wired together then.

Since the schematic shows Pin3, 5 and 16 at the same voltage for a test could I jumper Pin16 to Pin3 on the bottom of the board?

Yes. With the power off, you might measure how many Ohms resistance you get from pin 3 to pin 16 before you solder a jumper in there. Like Gerty wrote, the trace is hidden under Z2's IC socket. Don't try to unsolder the socket; they're kinda tough to get out without messing things up.

I'm sure you've seen lots of solder jobs I hope mine passes the mustard...

A tad "iffy" - but it's hard to tell in a photo. Make certain that you have cleaned the area/components to be soldered with 90% or better isopropyl alcohol and an acid brush (you can get acid brushes at auto parts stores), use rosin flux, 93/37 solder, and a soldering iron of the proper temp that has a clean and well-tinned tip. Be certain to clean residue off afterward.

I've ordered another Z2 and a couple of resistors that I didn't have mainly R159 that I had to solder a couple of resistors together to get the correct resistance for.

What values did you use for R159? Were you careful to clean any flux off of them? Flux has a pretty high resistance, but it isn't infinite.

 

The 3-16 jumper is probably under the IC, on the component side.

Gerty, good point I'll pull the chip and look.

What values did you use for R159? Were you careful to clean any flux off of them? Flux has a pretty high resistance, but it isn't infinite.

I'll post when I get back to the house the values of R159.

Thanks,

 

Gerty, good point I'll pull the chip and look.

I suggest that you DON'T pull Z2 unless you really have to. Those machine sockets tend to tear the legs off your ICs when you try to remove them. You can simply measure the resistance from pin 16 (+ probe) to pin 3 (- probe) and see what it is. If you get anything higher than 1 Ohm, you'll need to solder a jumper from pin 16 to pin 3 on the bottom.

 

Like Sgt said, do not pull chip. Use your meter.

 

Well, pulling the chip revealed a self inflicted wound...!!

When removing Z2 I cut it out with a dremel since I wasn't able to get it desoldered with my desoldering gun, needless to say I cut a bit of the trace, oh man do I feel like an idiot!!!

After repairing the trace and replacing the chip the board boots and the voltages rebounded, obviously.

So while I fall on my sword can I ask alast questionnwith regard to the voltages.

1-.03
2-3.53
3-4.49
4-4.32
5-4.49
6-.19
16-4.49

Pin2 increased a little more than .50v does that appear to you guys to be normal and just my working board might have some weak caps, etc.?

Many, many thanks for all the help, guidance and information. I learned a bit in this exercise and couldn't have succeeded without your help.

Thank you.

 

Funny, I was thinking earlier that you might've nicked the trace inserting a screwdriver under the IC to pry it out.

Don't worry about the Pin 2 increase at the moment.

Is the board working now?

 

Funny, I was thinking earlier that you might've nicked the trace inserting a screwdriver under the IC to pry it out.

Don't worry about the Pin 2 increase at the moment.

Is the board working now?

It is powering up on the bench. I have a feeling I might run into some other in game issues but you've been a great help in tackling the reset issue.

If only I had noticed the Pin3, 5, 16 relationship a bit earlier or not nicked the trace... aaarggh!!

Thanks Sgt,