Keith's Electronics Blog

Sometimes you get lucky.

My friend Jeremy has a 1995 Mustang that had the factory premium sound system in it when he bought the car used. The CD player was broken and he had the head unit replaced within a couple of weeks of owning the car. He later added a subwoofer.

I’ve always thought the stereo lacked clarity in the bass, and the head unit and EQ have had some quirks. Recently Jeremy pulled the head unit and found all sorts of interesting techniques used by the aftermarket installer that will be the subject of a later monologue … but one of the things we discovered is that the amplifier for the door woofers wasn’t working at all. Swapping it with the amp for the rear deck woofers caused them to go silent and the (shot) door woofers to work again (after resoldering their cut cables).

Turned out to be a delightfully easy fix.

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Both my Crumar T1 and T2 “portable” organs (the lower two cases in the stack) came to me without swell (volume) pedals. Each has a rotary potentiometer on its control panel for master volume, but I really want to be able to change the volume dynamically while playing. I’ve been using a Dunlop volume pedal (built into a rocker case identical to the CryBaby wah) on the organ’s output; but (at least when used with the organ) all of the pedal’s action is in about the lower quarter of its physical range, so it’s very finicky to use.

I recently bought this original T1 swell pedal on eBay, listed as untested / project. That usually means tested / didn’t work / can get more money if I don’t admit that I already know it doesn’t work; but I figured I could fix whatever was wrong with it. And I have.

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I recently ran across on Craigslist a

Bad horsie 2 that was plugged into the wrong power supply and messed up, and needs some minor electronic work.

I was intrigued by the challenge (I’m such a sucker for broken things, dang it) and bought it. When the seller and I exchanged the pedal for my cash, he remarked that he read on a forum that it probably just needed a resistor changed, and that if I were handy with a soldering gun I could probably do it myself.

Uh huh. Resistor.

Let’s dig in.

The circuit board has a hole in the top for a foam battery “cage” attached to the enclosure, something clever that I haven’t seen before. And it had no obviously damaged components.

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Recently a couple of pieces of audio processing equipment I’ve bought used have had bad left channels. After recognizing the pattern, I finally thought to swap out the patch cord I had left plugged into the “test” channel on my keyboard mixer, and voila! Left channels fixed.

I’ve always been curious about the construction quality of commercial patch cords — just how good are the connections buried under those lovely molded jackets and strain reliefs?

Naturally, the faulty end was the last one I disassembled. (Logic joke!)

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As mentioned previously, I recently bought a Crumar T2 organ manufactured in 1978 and started ascertaining its condition. Here’s what I’ve been able to fix so far and what I’ve been able to determine about the parts I haven’t yet fixed.

Crackly Volume Knobs and Stuck Master Tuning Potentiometer

Several of the volume knobs were pretty crackly.

Most Crumar keyboards are wonderful to service because of how easy it is to get inside. After removing a few screws, the top panel lifts back on its rear hinge, without even having to take the knobs off all the controls.

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