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Got some e-waste from former employer. Replaced one transistor and now have a perfectly functional QSC PLX-2502.
QSC PLX-1804 requires further diagnosing.

Churning along recapping my DDA DMR12. 13 strips done (except for 220UF/35V caps, should ship from Mouser ~Oct. 6, but only 3 per channel so...) Still 19 more to go on the input side, 24 on the output side, and Master strip and 2 Aux strips. Here's hoping I can keep this pace going and get through it in the next few weeks.

Goddamn that’s a lot of e-caps

You're doing all that on a double-sided board with a soldapult? Braver than I.

Adam P wrote: Thu Sep 23, 2021 11:57 am Goddamn that’s a lot of e-caps

Fucking tell me about it. something like 3400 total in the whole console. 57 on each input channel.

Nate Dort wrote: You're doing all that on a double-sided board with a soldapult? Braver than I.

I dunno about brave...stupider maybe.

Just finished with a 1978 Deluxe Reverb that I picked up about a month ago. It was in pretty good shape, but there were some things that needed addressing, and then some little issues I wanted to run down.

The tubes were a complete grab bag; half a dozen different brands spanning decades of manufacture. I had a problem right away with super low volume and found one of the 12AT7s (PI) was bad. After that was sorted I re-tensioned the power and rectifier tube sockets as they were very loose. The speaker had been replaced with a Vintage 30 and I wanted to get closer to OEM. Thanks to FM Tommy's recommendations, I found a Fender Special Design 1975 Oxford 12L6 for $20 locally. It had a very small tear in the cone which I repaired. Now the DR was sounding pretty damn good but there was noise in the reverb circuit during warmup. It wasn't a big deal, but I ended up replacing both 12AT7 tubes and cleaning all the reverb contacts and the noise was remedied. Also replaced V1 and V2 12AX7s with some nice ones from an old 60s console stereo. Now the only issue was the vibrato, it was ticking loudly when engaged. I performed Fender's 'service bulletin #9' and it totally did the trick.

This was particularly exciting and satisfying. I survived my teens and early 20s of tinkering around in tube amps with only minor shocks and fuck ups, but had been less inclined to attempt repairs over the past decade because I understood the danger and because I guess I finally admitted to myself that I didn't really know what I was doing. In the past year or two I have educated myself in the basic safety precautions and cap discharging, verifying voltages, etc. and picked up a nice soldering station and other tools. It felt so good to competently undertake the repair and have it go successfully. It's the kind of thing I've wanted to be able to do (and sort of pretended I could do) since I was 14 and first fell in love with tube technology.

As a pleasant surprise, it was also recapped somewhat recently, which the seller didn't mention. The circuit looked untouched otherwise.

The amp sounds fantastic.

My Traynor TS-50 died during our gig last weekend. It cut out during soundcheck and I jiggled the speaker cable to get it working again. Then it crapped out 3 songs into the set and I couldn't jiggle it back to life again. We finished the show by plugging the guitar into the other input on the JC40, but that's beside the point.

I opened up the Traynor today noticed a few things:

1) Speaker cable was intermittently shorting and opening as I moved it around with a DMM connected.
2) There was some low-volume output, but it was very distorted.
3) Nasty squeal when reverb was turned up. Went away when I disconnected the tank.
4) One of the reverb tank mounting screws was missing. I found the lock nut in the chassis, and the screw in the bottom of the cabinet.

Solutions:
1) Built a new speaker cable.
2) One of the output transistors was failing, but only when under load. A 100 ohm resistor on the base of the low-side output transistor was burned up. Wasn't getting any negative output at the speaker, only the top half of the waveform. Output looked fine with no load after I replaced the resistor. I shotgunned a few more parts in there (some diodes and the driver transistors) before I settled on on the main output transistor as being bad. I had some old 2N3055s, probably pulled from a Sunn Concert Lead, that I dropped in.
3) There was a very thin ground trace running along the top of the preamp PCB that had opened up, which had isolated the ground on the reverb driver/recovery circuit, hence the squealing oscillation. Jumpered that GND plane back to the main PCB GND with a short wire.
4) Put it back together, this time with some loctite.

My theory is that the intermittently shorting speaker cable winged the output transistor, which burned up the resistor. The blown GND trace on the preamp circuit probably isn't related, but who knows?

1921 Dort Model 17

Here's the notes I've taken over the last 8 months:

I found an original 1921 Michigan plate on ebay. Cheap, and obviously needed to be refinished, but hey, what’s another project?




I bead-blasted it in the driveway to get the loose rust off, then used some phosphoric acid and a green scouring pad to clean the rest off. Then I primed and painted it with a few coats of semi-gloss black enamel, per the original color scheme. I then hand painted the white letters with satin white enamel.




Carb rebuilt, fuel pressure regulator added, replaced muffler and moved it to the rear of the car, front tire replaced, new spark plugs and one new plug wire, fixed the intermittent headlight.

Replaced the front right tire & tube, repainted the wheel.

I took it for a drive around the block on Halloween before we decorated it. I found out quickly that the brakes need serious work, so I’ve started on that. I also need to practice double clutching.




Brakes are cleaned up. I ended up replacing the friction material on the left side myself. The right one had been replaced by the PO. Cut, drilled, and riveted the new material to the band by hand after cleaning up and painting it. Broke the adjuster rod during removal, so I had to fab a new one with a bolt and new clevis yoke.




Replaced the old grease zerk fittings on the brake linkages with modern ones.

Also got the throttle and spark levers on the steering wheel working.

The original pot-metal mounting bracket on the starter disintegrated during the first few starts. I’ve been hand-cranking it since then, but I still wanted to get the starter fixed.



So, I took a bunch of measurements, drew up a new bracket in CAD, and had it machined out of aluminum for a not-horrible price. Added a self-lubricating bronze bushing to take up some of the slack and reduce wear. Also completely disassembled and cleaned the starter motor and shaft parts, and repainted the body.




Also found an original Boyce Motometer with the DORT logo on it. It was in rough shape, with cracked front glass and significant wear to the brass body. I found another universal motometer with the more ornate design and frankensteined a nice one with the logo. I also found a dogbone cap with the proper 2.2" x 18TPI thread (common with Buicks of the time), as opposed to the more common 2" x 16TPI thread that most other manufacturers used. I had to drill out the brass dogbone to mount the motometer.




I saw that The Henry Ford has an identical one of these in their collection, in slightly worse shape:

https://www.thehenryford.org/collection ... =gs-251262


Removed the generator, since it wasn’t working anyway. Mounting bracket disintegrated just like the starter, but this one has integrated bearings, so I’d need to engineer something new. I found one on ebay from a '20s Dodge Bros. (or maybe a later Willy's CJ) that bolted right up after I put the old gear on there. Same size shaft, same length, same bolt pattern. Just needed a few bushings added so the nut would tighten down against the gear. Used RTV gasket maker to seal it, as I didn’t feel like cutting my own out of gasket material.




This one was intended to be used with an external cut-out switch, or maybe a voltage regulator. I’m going to put a modern solid-state voltage regulator on there, intended for 6V positive ground systems like this.

Changed motor, transmission, and differential oil. Transmission oil was full of metal particles. I’ve grinded the gears a few times, but certainly not enough to cause this amount of loss. Probably hasn’t been changed in years, so most of it is likely from the previous owner.

Changed all pin-lock style grease fittings to modern zerk types, and greased all points. There’s about 25 of them.

Added a brake light switch and brake light. Found a 20’s vintage “Neverout” brake light on ebay.



Removed the wood rails from the back. Still not sure exactly how I’m going to do it, but the goal is to build a new wood body, similar to this:




Replaced the broken speedometer (apparently from a '20s Dodge, didn't actually mate with the speedo cable in the vehicle) with a period-correct Stewart-Warner unit. Speedo cable was surprisingly intact, just needed some lube.




Took it to the DMV this morning, first time driving it outside of my neighborhood. Topped out at about 45 mph. About what I expected for ~19 HP.

Incredible! Hats off.

^ amazing!