Solved- The 'Operator Malfunction' Incident

CT Jim

AK Subscriber
Subscriber
It's actually been a long time since I did the same stupid mistake while testing a piece on the bench before pulling any boards. I have had this receiver for three years, started to check it out, confirmed one side was dead, did the deoxit program, and put a cover on it and forgot what I thought. In those days I didn't write myself notes, so I could go back and be back up to speed! Then almost two years ago, I bought a rebuild pak from a fellow AKer, and after that I even bought a light kit from the same seller.
Finally, on the bench, ready for the rebuild magic. All hooked up to a dispensable set of speakers, although I did put in-line fuse holders, just in case. Good antenna, reviewed the operating instructions because the faceplate and knobs have been off for so long the only thing I'm sure of is the power switch.
Ready, dimbulb test...OK!
Recheck, and on to try the FM. Meter seems off, but once in awhile I get a stereo light, but...NO SOUND! I do remember, one channel was out, which is why I did the deoxit thing. Again, recheck settings, recheck wiring, try another source....NaDa.
OH, well, that's why I got the rebuild parts!
Let it sit for a couple days, and actually, while in bed, I remembered, DUH! Left the pre-main jumpers on the table. This thing was dead freakin quiet, all sources! Do you think? No interconnect, dumb ass!
Put the jumpers in today, rechecked, and actually the dead channel is in the left preamp, because both output channels work when the right mono button is on!
It's a hobby, right? Otherwise, it's the box wine I keep under the desk to ward off the cold.....

Why couldn't it just be a fuse......:confused:
 
I think we have all done that. For me, a piece doesn't need to sit too long before it can happen.

Rob
 
We've all done it at one stage. I got to the end of a Pioneer SX-1980 complete rebuild, powered it up and for several minutes sat there in disbelief of no sound.

Then I remembered the pre/main jumpers...
 
Yup, I've done that a few times. I usually trace the signal with a scope and get down to the pre-main jacks at about the same time I realize that I should have checked there first.

Here's another trap that a lot of us fall into: The customer brings in an open-reel tape recorder with tape still in place, but the tape is flipped face out and has a back coating so it's not obvious.
 
My biggest mistake was putting a 50 volt electrolytic cap in place of a 450 volt. It made for a great party popper.
 
A few years ago, I had a monster NAD AVR come in the recycle pile.
It had a sticker from the high end installer/integrator place.
I assume it was from the repair department.

IMG_9676.JPG


Tossed it on the bench, powered it up, yup, dead, as in, no sound....at all.

ALL the jumpers were missing on the back (5.1 unit? 7.1?).

Put a handful of jumpers in and it worked perfectly.

Flipped it for about $200 IIRC.

Another reason I fix my own.


After a few thousand "unknown" units across the bench, I'm getting better at watching for missing jumpers.
 
A couple of weeks ago, I was working on my audio PC. It wouldn't initialize the Paul Pang audio card in the PCI express slot. (still have the problem).

I disconnected the USB to the Singxer bridge. I turned off the PC, but forgot to unplug it. I also left the PSU switch on.

I pulled the Paul Pang card and bumped it into the bottom of the ASUS copper top ($250) video card. The PC cooling fans surged into high speed mode, and I saw a spark.

The video card was dead after this for a couple of hours. It finally came back to life, but I see distort lines on my monitor every once in a while. I may have to get a new video card.
 
The other day, I was getting NO sound from my Arcam amp. Opened it up to find blown fuses next to the output transistors. With little hope, I dumped out my can of fuses...and there it was: a little plastic box labeled "For Arcam." I had totally forgot that, and I was so happy!
 
Anybody find a permanent fix for this?...
Yes. Use painters tape or something similar that won’t damage to the finish to attach a sheet of paper to the inside surface of the cover. Write in sharpie in big block letters “Did you reinstall the jumpers?”
Get in the habit of doing this just prior to pulling out jumpers. :beatnik:
 
Or you can do what I usually do which is scrawl notes in pencil onto my workbench and then completely ignore them/forget that they’re there when I get back to that project.
 
I've had my moments. I once hooked up an SUT backwards when reassembling my system after my wife redecorated the room. At first I couldn't figure out why the volume had to be turned up to 11 in order to get any sound out of it at all. Duh! Embarrassing? Well, yeah.

Best thing to do is to own the mistake, hope it's the worst one you'll ever make, and move on.
 
Ever accidentally cut and wire your ground strap into a power supply?
Me neither, but that would be the winner!
 
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