Repaired an old $5 worth 'boom box' from a person that deserved help. The rubber pinch roller in the cassette unit cracked split.
Did not find one among my bins and junk. Made it with a piece of rubber hose and two layers of shrink tubing on top. Lots of effort, but the thing worked. Happy.

 

Someone gave me a Yamaha music sequencer machine to repair. It was dead with no signs of life. List price is about $300.
All it needed was a new 7805 voltage regulator.

 

Finally replaced my inner tubes today.

 

Someone gave me a Yamaha music sequencer machine to repair.

What model?

 

What model?

Yamaha QY300 music sequencer.

 

Yamaha QY300 music sequencer.

It's amazing that this tech was available 30 years ago -- in such a small package -- and that musicians (not engineers/programmers) could figure out how to use it.

 

Yes. I looks so complicated that I didn’t know what to do with it. I just returned it to the owner without trying it. I use Band-in-a-Box on my computer.

 

Yesterday I was a friend's hero for a day because I repaired his refrigerator. As a matter of fact, I saved him well over two thousand bucks since he was already planning on buying a new one.

His fridge's controller broke down and was only showing a bunch of garbled lines and dots on its display. So he removed the control board and brought it to my shop. I told him there was only a 5% chance that maybe I could possibly fix it. This because I was not the circuit's designer, and figuring how it worked would probably take me a long, long time.

Anyway, the first thing I did was inspect its underside to see if there were any burned or overheated spots. There were none. So next I began to look at each individual part and noticed that the thing had a glass fuse (soldered) and that it looked a little smoky on the inside. I then tested for continuity, and got inconsistent results. That is, sometimes my MM beeped and sometimes not. So I changed the fuse (for one with a little more capacity) and re-installed the board to test it on the fridge ... and NOPE ... it didn't make a difference.

But then I remembered I saw three electrolytic capacitors that were a little swollen at their tops, and I didn't like the look of that. I mean, I'm used to seeing leaking capacitors, or burnt out or with their plastic coverings a bit opaque due to overheating. But I hadn't payed attention to puffed tops before. Those capacitors had values of 470 and 220 µF @ 25 volts, respectively. So I replaced them with equal valued parts, but this time rated at 50V, see if that not only fixes things but also makes them last longer.

Lo and behold! ... the device became operational and worked flawlessly as soon as it was plugged in! ...

I now realize that the caps must've been filters for its electronic DC power supply. It wasn't until after I took this pic that I noticed they were right next to a 7805 regulator. That explains the screwed up display. The controller must have been fed unfiltered DC and it was probably trying to start up but was continuously resetting itself.

​

My theory now goes that a fair amount of controller boards fail after ageing a bit primarily because of badly rated electrolytic caps... what do you guys think?

 

My theory now goes that a fair amount of controller boards fail after ageing a bit primarily because of badly rated electrolytic caps... what do you guys think?

Ripple kills caps—I’ve always wondered if caps in switchers were more prone to failure because of it.

 

Ripple kills caps—I’ve always wondered if caps in switchers were more prone to failure because of it.

Yebut caps are supposed to kill ripples too, aren't they? ...

And yeah, I'm sure that the caps in an SPS are being subject to harsh conditions 100% of the time.

 

Yebut caps are supposed to kill ripples too, aren't they? ...

And yeah, I'm sure that the caps in an SPS are being subject to harsh conditions 100% of the time.

Yes, but I suspect the design of consumer switchers is heavy on the BoM reduction so sub-optimal use of the caps could increase the heating effects that kill them.

 

Yes, but I suspect the design of consumer switchers is heavy on the BoM reduction so sub-optimal use of the caps could increase the heating effects that kill them.

And also, they're probably part of the nefarious "programmed obsolescence" policy most companies practice nowadays ...

 

And also, they're probably part of the nefarious "programmed obsolescence" policy most companies practice nowadays ...

An ugly prospect.

 

Yes. Caps are the weakest components in electronics.
I have fixed many items by replacing bad capacitors. Tantalum capacitors will often short across supply rails. Apple Macintosh was famous for having failed non-polar capacitor in the horizontal drive circuit. I fixed a display monitor with a bad cap (not in the supply section) and a laptop with a shorted cap across one of many in parallel in the power supply (hard to locate which one).

 

I was told poor electrolyte and construction, cheap caps made in china. I purchased Panasonic to replace them in the secondary side of the board.

I fixed maybe 40 or 50 that were slated for surplus sale.

TIL: The Capacitor Plague, where capacitors had much higher failure rates between 1999 and 2007, as the formula was miscopied when a scientist stole it through corporate espionage in Japan. They returned to China and gave it to their previous employer, who put the faulty formula into production.

kv

 

Fixed the music holder on my Yamaha DX7 synth. It was held by little brackets with a cylindrical hole the holder slots into. The cylinder broke off on both brackets long ago.

After dabbling with playing for 40 years, I am taking my fist lesson Monday, and the teacher asked if I had a music stand. Emergency measures were required. Found replacement brackets listed on two sites, both out of stock, and I expect will never be in stock again given the age of it.

So I 3D printed new ones with a more robust design, and, on the fourth try to get the hole diameter and angle right, they work beautifully. I love ABS.

 

On another front, this is what I repaired today. It is not electrical nor mechanical. My girlfriend is epic at sussing out a bargain. She was at a department store and ran across a sickly Christmas decoration. It was a pink velour reindeer with silver glittered antlers, gold glitter on its back and forehead, and a white fur shoulder piece.

Gail’s bargain had antlers falling off, glitter experiencing dandruff and shedding antlers. It was marked 50% off of $55. She asked for a manager who marked it down to $26. But when Gail got to the cashier, she told her that the manager had marked it down to $11. Since everything in the store was supposed to be marked doen 50%, Gail got it for $5 (the cashier was math-challenged).

I did the following:

• Glued down the velour everywhere it was loose
• Mounted the ears in a hot glue base where the styrofoam body had deteriorated
• Touched up scratches on ears with silver pant
• Glued nose on solidly
• Pointed joints pink where velour had pulled away
• Put a coat of lacquer on loose glitter
• …and antlers
• Added highlights to eyes

It looked beautiful! But I wondered if it was gay, because female reindeer don’t have antlers. My girlfriend said it was transgendeer!

 

I was told poor electrolyte and construction, cheap caps made in china.

The start & run caps used in Chinese originating motors are notorious for early failure.

 

My 14 year old 7 inch portable TV with its 8V prismatic internal lithium dead battery at a replacement price higher than the TV forced it dormant for years. Decided to attach 2 'canteen' battery holders for 18650 on its back. Works perfect again. Hundreds of 18650s spares in my bins, and individual cell chargers.

 

I "fixed" my BK501 curve tracer. I got tired of the banana jacks for vertical and horizontal outputs, so I replaced them with BNC connectors. Also got tired of the limited transistor socket options, so I added sockets for TO-18, TO-39, TO-220, and BC/2SC in TO-92.

The NPN/PNP select switch is flakey, so that's next. It's 4PDT and I'm waiting on parts and it's going to be a PITA to replace.