Tuesday, October 13, 2015

Restoring a set of Blonder-Tongue Audio Batons

A long-ago project, these two Blonder-Tongue Audio Batons were a complete teardown and refit, as best I could make them with limited parts. These were one of the first active audio EQs, and used 12AX7 vacuum tubes to provide 9 bands of adjustment.

These units were purchased from a seller in Antique Radio Classifieds, as-is, not working. And not working they were. Someone had punched out several of the potentiometers to put more tubes on the chassis. The wiring and components, already old, was hacked up beyond recognition. One of the units was missing it's case, and had only a few of the signature spiral columns for the adjustments.

The only thing I could do was a complete teardown of the chassis. Everything except for the terminal strips and the transformer were removed. The holes in the front were repaired by soldering washers with the correct inner hole size into the chassis, so pots could be remounted. All new components were purchased - Orange Drops, Nichicon, and IC capacitors, metal film resistors, new tube sockets and the best quality pots I could get my hands on were placed into the chassis. Filament wiring was all twisted to reduce noise. I wound up with a layout more compact than the factory one, although not by much.

Since I didn't have a case for the one, I re-purposed a SESCom rack-mount chassis for it. The chassis fit in nicely, and I moved all the potentiometers to the front panel. These were placed in an arc, two VU meters flanking, and a dim green pilot in the middle. The other unit, it's case in moderately good shape, was left alone save the addition of some band labels where the previous owner had attacked the front panel with a scraper.

I added some circuitry to handle the VU meters, and a centralized switch to allow both units to be turned on from the rack chassis. All audio and power routed through the larger unit.

I was really pleased with how they turned out, but I really didn't have room for them and ended up selling them to a studio a few years later.





 I took a number of pictures beforehand, but, being pre-digital, I seem to have lost some of them. These two, a bad shot of the original case and the chassis/VU meter unit, are all I have left. I'm hoping to find the person I sold them to, I'd like to get some more shots.

If you have these, please contact me. I don't want them, just photographs if they are still like this.