How to fix PCBs - A Beginners Guide

Would you recommend I get a logic prob if I already have an oscope? Is the audio feedback enough to make it necessary?

I would recommend it. I had a Neo Geo board on the bench tonight that had an audio issue. A quick 10 second check with the logic probe w/audio let me hear the difference in tones on the input of the Yamaha DAC chip which told me the digital part of the circuit was working fine.

One quick cap kit later and the board was done.
 
I would, for $20 it's a worthwhile purchase, I only use mine for looking for floating pins as a first pass over a board, but it saves having to look up at the scope everytime.
 
Only a couple options in that thread. How does one determine if a given logic probe has audio? I've looked at a few online and most don't say anything about audio.

The ones that don't mention audio dont have it, the ones that do, errr, do.
 
The ones that don't mention audio dont have it, the ones that do, errr, do.

I figured that was the case. Wasn't sure if it was generally that important of function on a logic probe that they would state it had sound. I guess it seems like many don't then which kind of stinks. I need to find a place that sells nice chip puller (EX-2) and a logic probe with audio. Thanks for the help. Newb to working on boards and just want to get a few simple tools before I go at it.
 
Here's another thing to consider when repairing a board. When you decide it's beyond your capabilities, and you ask for prices to repair your board it's not always cut and dry. I can't tell you if you have these symptoms it will cost you x amount of Dollars.

Here's a quick break down of parts and prices on a recent Tempest repair.

1x Dac312 $10
4x TL082 $4
3x MC1495 $18
5x 2114 $12.50
1x VSM Prom $9
1x Pokey $6
2x 2901 $10
Sockets $3
Total in Parts $72.50
Now ad in 6 hours of labor, and a 72 hour burn in test.
 
Here's another thing to consider when repairing a board. When you decide it's beyond your capabilities, and you ask for prices to repair your board it's not always cut and dry. I can't tell you if you have these symptoms it will cost you x amount of Dollars.

Here's a quick break down of parts and prices on a recent Tempest repair.

1x Dac312 $10
4x TL082 $4
3x MC1495 $18
5x 2114 $12.50
1x VSM Prom $9
1x Pokey $6
2x 2901 $10
Sockets $3
Total in Parts $72.50
Now ad in 6 hours of labor, and a 72 hour burn in test.

Ouch! Not sure what you charge for labor, but that looks like it is approaching the $300 mark. Better just to buy a working Tempest board no? Of course hind sight is 20/20.

Let me ask you this. As a board repairer, do you ever give a max? Like...... not sure what I'll find on this board, but I won't charge any more than $200. Without having some kind of comfort with the repairer, they could tell you just about anything for how long it took. Or is there some way the person who brought the board in for repair can make an informed decision prior to "over spending" on the repair. Just wondering for when I actually try and repair a board. I'm sure I'll get stumped and need to find someone at some point. On your Tempest example was it all diagnosed within an hour or two and then the person can decide from their if they want to go ahead with the additional expense? This is all curiosity. I have no clue, but would appreciate the insight.
 
For a board that has been a cabinet all it's life, its typically pretty easy to diagnose. It's the boards that have been bought that you have no idea where they've been that kill you. You buy a box of boards that have been rubbing on each other, cutting traces, shorting leads etc those can be a time waster.

I typically do flat rate pricing. Which is going up this year due to price increases in parts. Vector boards need some of the highest price parts out there. Again I assume this is why most people don't mess with them much.
So yeah there's a max price.

If I get a board that will go beyond that max price, I offer a replacement board, and use the bad one for parts if at all possible. I've only had to do this a few times.

There are those that either send me a video of the problem, or pictures which can help narrow down the problem before hand. I tend to work out better pricing for those types of customers because I know what I'll be getting into before hand. I'm always happy to try and help you diagnose a problem so you can fix it yourself.

Also for customers that have multiply boards I tend to give discounted repair prices.

I don't advertise my services for the most part, mainly because I get a steady stream of work, and this is after all only a hobby for me. But I do like helping others get their games up and running which is what it's all about.
 
Not for a fair while tho, unless the faulty ones are somehow permanently removed from circulation, either by scrapping or just tossing. I would think the majority of faulty ones would cycle back through "sold as faulty" sales to people who can repair them to sell on. Gradually the numbers will erode tho.
 
Not for a fair while tho, unless the faulty ones are somehow permanently removed from circulation, either by scrapping or just tossing. I would think the majority of faulty ones would cycle back through "sold as faulty" sales to people who can repair them to sell on. Gradually the numbers will erode tho.

Yeah, it's a good question. How many of these actually get tossed vs. sold? I would bet there are a lot sitting on shelves and forgotten about too..
 
thanks for this primer....

like others have said, thanks for the tutorial....just purchased my grail, an Omega Race and is it not working. Currently reading everything I can on it(got full documentation) and get some equipment in next few weeks to begin...sure you will see some posts from me and hope it not too costly or in-depth of a repair( i know some are saying right now, yahhh right!!!) But this the journey all of us must take in this hobby, and mine just happens to be at the start of it......

Stay tuned....
 
Please don't use your grail PCB as the 1st board you try to fix, the chances of making things far far worse are very high. Practice on some old bootlegs before you give a board you really value a try.
 
Many thanks, this helped me fix my Track & Field board!

Hey,
This was a great beginner outline and it worked to help me fix my Track & Field board. I appreciate very much the time you spent outlining this information.

Jeff
 
Just want to emphatically second what Talon2000 and others have said about crappy sockets. I have fixed a handful of boards where either the only issue or the main issue was crappy old sockets. In particular, these sockets:

attachment.php

attachment.php


This is on an Asteroids, but they can be found on many golden era Atari boards. I've also encountered them on Exidy games.

They're easy to recognize by the "horns" on the outside edges, They usually have a thin strip of white plastic on the bottom, though these don't for some reason. They're extremely unreliable and should almost always be replaced. They often crumble to pieces when you extract them.

I suspected the sockets on this board, so I went to pull the ROMs. The whole frame came up with it:

attachment.php


These come in 16-, 24-, and 40-pin varieties. Replace them all.

Some recent repairs:
- Centipede. Came up in game mode with all the mushrooms on the left edge of the screen. Watchdog in test mode. Replaced sockets @C2 (CPU), @C3 (POKEY), @F7, @H/J7, @D1, @E1, @F/H1, and @J1 (all ROMs). Issues gone.
- Battlezone. 3D drawing glitches after warm up, objects drawn all over / in the wrong places. Replaced sockets @D/E2, @F2, @H/J2, @K2, @B/C2, and @B1, @M1, @L1, @K1, @J1, @H1, @F1. Issues gone.
- Asteroids. Watchdog in game mode, intermittent watchdog in test mode, intermittently indicates RAM errors. Different RAM errors at different times. Replaced socket @N/P3. Issues gone.
 

Attachments

  • L08A1681.jpg
    L08A1681.jpg
    68.2 KB · Views: 671
  • L08A1683.jpg
    L08A1683.jpg
    67.9 KB · Views: 668
  • L08A1680.jpg
    L08A1680.jpg
    63.1 KB · Views: 666
Back
Top Bottom