Doug's Electronics

01/17/2026

I thought it might be useful to outline different repair approaches we use as technicians. These are just my own naming conventions, not universal terms, though some of the names are commonly used.

As a technician who has worked in the field for years, I’ve used most of these approaches to solve problems as effectively as possible.

1. Shotgun approach

Process:
Troubleshoot to the general location of the problem and replace a handful of likely parts.

Pros:
• Can save time, money, and aggravation
• Works well with solid general electronics knowledge and some familiarity with the equipment

Cons:
• Slightly higher chance of rework
• Not all issues may be found or addressed correctly

2. Component-level troubleshooting (most satisfying)

Process:
Troubleshoot down to the exact component, components, or process causing the fault.

Pros:
• Much lower rework rate (not zero)
• Fewer components replaced
• Lower parts cost

Cons:
• Requires strong electronics and physics knowledge
• Requires deeper understanding of the equipment’s design
• Can take a lot of time to troubleshoot

3. “I’ve seen this before and it was a pain to find”

Process:
Use firsthand experience with a device and quickly verify that the issue matches a failure you personally encountered and solved before, not general or secondhand knowledge.

Pros:
• Very low rework
• Quick verification
• Lower cost to the customer
• You look like a hero

Cons:
• You must be the technician who personally experienced and resolved the issue
• Secondhand knowledge doesn’t count

4. Secondhand knowledge from a post or forum

Process:
Read a symptom-based post from someone in category #3 and replace the listed parts.

Pros:
• Requires very little electronics knowledge
• Fast repair time

Cons:
• Symptoms don’t always match the same failure
• Results can be inconsistent without verification

Note:
This method can be useful if the original poster explains how they confirmed the failure and the technician understands how to verify the same condition.

5. Board-level repair

Process:
Follow a fault code or flowchart to identify a failing board, then replace the board.

Pros:
• Fast repair
• Requires minimal electronics knowledge

Cons:
• Can be expensive unless parts are sourced cheaply
• Possible to misdiagnose the board
• Dual-board failures do happen
• Replacing only one bad board can damage the new board, resulting in the need to replace both

Note:
This is the preferred method for in-warranty repairs in today’s consumer electronics market.

6. Replace all capacitors

Process:
Replace all capacitors because “they need to be replaced.”

Pros:
• Requires very little electronics knowledge
• Capacitors do fail and can cause many problems
• Based on my experience, roughly 50% of failures can be traced back to a capacitor

Cons:
• Often done incorrectly by inexperienced people
• The root cause is not always verified
• A failed capacitor may have already damaged other components, requiring a higher level of troubleshooting

Note:
This is not an invalid process depending on the equipment, but the need to do this is itself a diagnosis that must be made. For example, paper capacitors in tube radios are almost always bad and should be replaced. However, this is only one part of a proper restoration process and not a fix by itself.

7. Kit repairs

Process:
Fix a failure or known fault using a manufacturer- or supplier-provided repair kit.

Pros:
• Very effective
• Requires a low level of electronics knowledge

Cons:
• The kit must address a very specific, well-known failure
• Limited scope

Note:
Some manufacturers use repair kits to address design flaws or failures caused by those flaws. These kits are typically only installed when the unit comes in for repair.

01/08/2026

Radio Shack is trying for a comeback it looks like.

01/07/2026

Schematic workflow

01/04/2026

I’ve worked on pinball machines for many years, and while groups like this are very helpful, I think there’s something important that needs to be understood.

There is rarely a simple one-to-one cause and effect when it comes to failure symptoms. You can often narrow down a symptom quickly, but finding the exact cause usually requires proper troubleshooting.

For anyone new to EM pinball repair, it should be understood that some basic electrical knowledge is really necessary. That said, one thing I’ve always found a bit ironic is that a multimeter has fairly limited use when troubleshooting electro-mechanical pinball machines.

In my experience, the fastest way to find most problems is relay tracing.

Here’s what I mean. Each function in an EM machine kicks off a series of relays. Most relays have a trigger path and a hold path, and you can see this clearly on the schematic. By reading and understanding the series of relays involved, using the ladder-style schematic, you can follow the exact path required for the function that isn’t working.

Most of the time, the problem turns out to be a contact that isn’t making or breaking correctly. Sometimes it’s a coil. There are other causes, of course, but those account for the majority of issues I run into.

Ladder diagrams are actually easy to understand and apply logic to. There are plenty of tutorials available. Modern ladder logic has become much more complex than what’s used in older pinball machines, so you don’t need to understand everything. Just learn how the system is basically organized and how contacts, wires, and designators work.

That knowledge alone will take you a long way.

11/15/2025

A quick word about stepper unit springs.

In every stepper unit I have worked on, no matter the brand, the rule is simple: never shorten or straighten a spring. The balance on these springs is more precise than it looks. If you are having movement issues, the real cause is almost always friction somewhere in the unit. Check contacts, axles, plungers, and one big one that gets missed a lot: the surface finish on the contacts.

If you sand contacts with coarse paper, you create extra drag that can cause the unit to stall when it tries to ratchet up. To test properly, reset by hand, move it only one position above the reset, then trip the reset and make sure it rests squarely on the reset position. That step tells you a lot about whether the tension and friction are right. After that, ratchet it all the way to the top and confirm it reaches the last position without help.

Some stepper units use nickel plating over copper to prevent tarnishing. If the nickel is still intact, clean it gently and avoid harsh abrasives. If you break through to the copper, it can oxidize and lose conductivity over time. Contact grease is the best fix here. Pinball Resource sells a great formula. A Teflon based lubricant also works well to keep dust down.

Units with many individual rivets on a PC board are the most fragile to service. I usually clean those contacts with a Dremel and a buffing wheel to keep friction low.

Hope this helps someone working through a stubborn stepper.

11/14/2025

11/14/2025

Williams System 6 Bench test board.

11/11/2025

It's been a while since I messed with one of these, but this one's been a bit of a saga.

It came in with a power supply issue—which, apparently, is a common failure for this model. That part was easy. Fixed. Done. Victory, right?

Nope.
Tried to boot it up: "No system disk."
Uh oh.

It still had a working internal bootloader, so it wasn’t completely dead—just barely hanging on with whatever little ROM code it had. But the OS? Gone. Nada.

So I did what anyone does in a moment of despair: I asked ChatGPT how to get ISO images onto 5¼" floppies. To my surprise, someone had written a whole server program to connect a modern computer to an Apple IIe just for this purpose.

Sounds easy, right? Ha.
Turns out the AI kept getting the instructions wrong—probably mixing up version features—and after wasting a lot of time, I gave up and just dove straight into the actual program docs.

And THEN it all started coming back to me. The commands, the flow—I wasn't just typing in stuff like a code monkey anymore. I remembered. And I realized how genius this system actually was.

The setup gives your Apple IIe access to a single directory on your modern PC. Boom—direct access to disk images so you can rebuild lost software. It supports multiple connection methods: RS232 serial, RJ45 network, even analog—yes, like old-school cassette-tape-to-PC-speaker analog.

This Apple IIe had no network or serial ports, and neither did my modern computer. So I went with analog. You plug your PC’s speaker out to your Apple’s cassette in, and your mic into its cassette out. As long as you kill any other sound on your PC, it works. Slow—but it works.

So I started building master boot disks: DOS 3.3 and a bootable utility called ADTPro (open source, GNU license, find it on GitHub). After much trial, error, and more than a few bad floppies, I figured out one of the drives is dead. Not sure if they want to fix that yet, so for now we're flying solo on one drive.

It took several disks (and a lot of bad sectors), but I finally found a few that work. We’ve got a stable boot again.

From what I’ve heard, this machine is used to control some kind of robot. I’ll be getting the software tomorrow to test it out. But given the condition of these old floppies, I’m half-expecting them to be toast too. If so, I’ll go hunting for disk images and bring ADTPro to the rescue again.

Moral of the story?

If you've got an Apple IIe that needs some TLC, I'm warmed up and ready.
Bring it on.

10/27/2025

Replacing Coil Connection Wires on a clock motor.

10/26/2025

Leaf Switch Proper adjustment