Wagner Amp Repair

Do you like small, compact, lightweight, powerful vintage amps? If so, this one’s got your ticket punched. Doing a little research on this first generation Walter Woods MI-100 amp, I learned that it was designed to compete with the much larger and heavier Ampeg SVT amps. This certainly lives up to that.

Owner requested a new power switch and power cord, plus cleaning of the controls. To access the power switch does require a fair bit of disassembly, but as long as you’re paying attention, it isn’t difficult to do. I will caution that there’s a hidden toggle switch in the heat sink fins that I didn’t catch initially when removing the rear. More on that later.

Cleaning the pots and jacks was straightforward. The owner asked for a toggle instead of the pushbutton for the power switch. I was able to find a mini toggle that fit in the space and had sufficient ratings for the duty it was to handle. I also swapped out the power cord for a new one. In doing so, I also rewired the fuse to be on the hot side of the incoming power and adjusted the filter module input wiring to accommodate the brown/blue international color scheme for the hot and neutral wires.

Once those were done, the unit was powered on and voltage rails were checked. They were reading about half of what I was expecting. After studying the circuit traces, I flipped that hidden toggle and was able to confirm that the voltages are back to where they should be. Seems that toggle switch was a 120/240 power switch. The amp was reassembled and tested again. Overall, this was a very interesting amp that impressed me with the design, features, sound and package.

Here’s another fun vintage amp where the owner requested a fairly significant conversion. He requested implementing something similar to what the guitologist video did. One thing you’ll find on a lot of these old amps is that the amp in front of you doesn’t always match (even closely) the schematic for the amp. That required tracing out the existing circuits to understand what the components were doing.

The amp had some prior work done to it, but wasn’t in great shape. Significant rework was performed. All new electrolytic caps, updated heater wiring, single input jack, add bright switch, change tone stack to Marshall style, add a mid pot, new OT with multi-taps and impedance switch. The original footswitch has the buttons too close so a new footswitch control jack for typical 2 button footswitch was added to rear panel. The reverb transformer was shot so we went with the option to convert both the transformer and the reverb tank (and RCA jacks) to the more common Fender style for less than the replacement transformer for the original. The power switch was replaced; a new purple jewel lamp was installed along with a 3-prong power cord. Add in some new matched EL84 tubes, clean the pots and jacks and she’s now able to sing in many tones. The owner is ecstatic with the transformation.

This cool little vintage looking, old school TV shaped Ibanez amp came in with complaints that it stopped working. The power light also wasn’t working. It should be two channels of fun, with one having the tube screamer sound added to it.

All of the tubes tested strong so that wasn’t it. Pulling the board revealed several bad solder joints, especially on the pots and jacks. This is a common failure mode of many amps that come across the bench. Reflowed those bad joints, cleaned all the pots and jacks. Power on bulb just needed to be screwed in as it had worked itself loose. Amp is back to rocking out.