Amp Techs - What are the useful tools that you've built?

[waspclothes]

So repair guys and girls, what is the most useful tool that you've built?

- I have an 8ohm 200W dummy load that has a 2x BNC tap for the scope that gets used often.
- I also have a simple capacitor drainer connected to a small multimeter that comes in handy, lets me verify the voltage before sticking my grubby hands into the chassis.

[Enzo]

I have made countless test fixtures, from simple to complex. Some are very specific - like the jukebox amplifiers that have a volume control located elsewhere through a connector. SO I made a volume control with connector for the bench. Control boards for coin hoppers in dollar bill changers? Little system to apply power and switches and LEDs to test function. Some things come in modules, like SVT has main chasis and preamp chassis. I make specific cables up either es extensions or in some cases to sub in test signals.

Got the XLR4 speaker connector for Ampeg flip top amps? I made a speaker cord to take its place so I could run the amp on the bench.

My dummy loads are 250w Dales, mounted to an aluminum plate under the bench. I brought them up to my speaker/load patch panel on my bench riser. ALso on the patch are bench speakers, and output from a cheap stereo. (Something to drive speakers and crossovers) The panel has 1/4" jacks and banana posts for each. Those are wired parallel. I have short banana to banana jumpers so I can parallel any or connect the amp to a speaker. On the second channel of my scope I use a BNC to BNC cable to a BNC-banana plug whwich can be plugged into any of the pacthes. They stack.

I have a large ceramic resistor 5000 ohms, must be like 100 watts (not that it needs to be) got clip leads on it so I can clip it in a circuit in place of a field coil. I used to work on power supplies a lot (SMPS) and have a variety of load resistors with clip wires. 1 ohm, 5 ohm, 12 ohm. Those particular ones for pulling 5A from 5v, and 1 amp from 5v or 12v.

Those old style circuit breakers with the red post sticking out? Got a selection of those with clip wires. I can clip them to a fuse holder instead of using a fuse during test.

[xtian]

My workstation! I designed it in Illustrator and had it laser cut from 1/8" plywood. Has felt feet so I can slide it closer to my work area when I've got an amp to work on.

[eschertron]

I also have a simple capacitor drainer connected to a small multimeter that comes in handy, lets me verify the voltage before sticking my grubby hands into the chassis.

A resistor with a built-in voltmeter, probably a good idea for an old, forgetful person such as myself

I'll throw a jumper between the plate of a preamp tube and ground. May take a few seconds-to-minutes to drain, but that's OK with me. Worst-case scenario is I leave it in place on power up, and I get no sound through that stage.

[Mick Bailey]

Most used item is probably my dummy load along with a simple fixed-frequency 1khz oscillator. I also get plenty of use out of a ring tester to test transformers for shorted turns. Something I use a lot is an audio probe - I find it makes quick work of tracing a signal through an FX pedal and I prefer it to a scope for a lot of jobs.

[nevetslab]

This is my AC mains & Dummy Load cart. It consists of a Magtrol 4614B 100A/3-phase Power Analyzer, with a Superior Electric 0-140V/30A Powerstat sitting atop it. It's sourced thru a Topaz 5KVA Isolation transformer, set up with a 240V primary and 120V secondary. Plugged into a 240V/30A outlet from the shop power panel, so I have enough AC mains power to handle large power amps. Next to the Power Analyzer is an 8-Ch 4 ohm/500W Load bank, built up from non-inductive 2 ohm 250W Dale Power Resistors, mounted onto the Aluminum Extrusion that BGW Systems used on so many of their earlier power amps. I was one of the design engineers for them for years. Fan cooled with a pair of 120mm AC fans, controlled with thermal switches as well as having manual fan switch.



What gets used the most is a simple service cradle that was built to hold Marshall chassis' like JCM 2000's, which may be what's sitting in it at the moment. Fender Twin Reverb and other similar Fender chassis' sit on it ok.

In the background is a stack of Bruel & Kjaer instruments...a 1027 Sine-Random Generator, a 1617 Band Pass Filter and a 1023 Sine Generator, Sitting atop those is a Symetrix SX-202 Mic Preamp, a Symetrix SX-204 Headphone Amp and an HP 353A Transformer/Step Attenuator Patch Panel. That's a great piece of gear, while little known and usually found cheap. Then an Amber 3501 Audio Analyzer sitting atop a Hameg curve tracer, and above it I have an HP 3467A 4-Ch Multimeter, a Krohn-Hite 3550 Filter, a Genrad 1396B Tone Burst Generator and a GenRad 1382 Pink Noise Generator. Next to that is a Tetronix 7633 storage scope a Wavetek 185 Log Sweep Generator and a Tek TM502 mainframe for a variety TM500 series plug-ins.



Salvaaged from my old Dark Room black-out/Ventilating windows is one of the dual Fan boxes I have for cooling down power tubes during sorting and matching duties

At an associate's Keyboard shop, I had set up a small bench and made use of a Tektronics scope cart, loaded with two shelves to hold a 7834 Storage Scope, an array of time base, vertical amps, curve tracer and universal counter plug-ins, then a TM504 mainframe with Tek's AA501 distortion Analyzer and a pair of the SG505 oscillators, a DMM, and a power supply. Below that is a fiber optic headlight source for my surgeon's headlight. Atop the scope is a GenRad 1382 Pink Noise generator and a Symetrix headphone amp. I think I also have a current probe amp attached to the side of the scope.