Vox Jaguar with Missing Filter/Switch PCB

Heathkit Vox Jaguar

I don’t usually post about combo organ repairs because I don’t think they’re very interesting, but this was one of the weirdest ones we’ve ever done! The owner of this Vox Jaguar organ told us that he had had it for about 10 years and it had never made sound at all, which didn’t really faze us because that is a common complaint for a piece of equipment this old.  But when he dropped it off, we opened it up and discovered the reason that it wasn’t making sound was far more serious, and far more crazy, than we had expected. The tone filter and selection board, including the switch contacts, was missing ENTIRELY. The rocker switches were all present, but connected to nothing. The signals from the oscillator/divider boards were simply not being sent anywhere at all.

This particular Vox Jaguar was actually a Heathkit once upon a time. Heathkit was an American company that sold DIY electronics kits for hobbyists starting as early as the 1920s, reaching peak popularity in the 1970s. Apparently they just relaunched! Anyway, some of these kits were pretty labor-intensive, putting modern synth-DIYers to shame, including kits for huge theater organs. Somewhere in the mid-range was the Heathkit that allowed the purchaser to build an entire Vox Jaguar at home.
The fact that it was a Heathkit led us to conclude that that part of the kit had just never been built. So most likely, this Jaguar had never made sound, in the entire almost-60 years that it had existed.

We were able to confirm that the oscillators and divider circuits were generally working about as well as we would expect for any organ of this age by listening to the signal on the keyboard’s mix bus with a signal tracer. We knew that there would be work to do on those as well, but we opted to address the mixing filter/switching/output routing circuit before we got into restoring the oscillators, dividers and keyboard.

The Jaguar is a valuable enough combo organ than they are rarely broken down for parts, so we were unsurprised that we could not simply find and install a salvaged replacement for this board. The remaining course of action was to build a replacement from scratch, simply following the schematics.  The circuits are all passive filters using resistors, capacitors and inductors only.  We elected to just build it on pad-per-hole perfboard instead of making a PCB, because we figured there was little to no chance we would ever have to do this again, and because the circuit was so simple that it was not difficult.

new Vox Jaguar filter switch board

The rocker switch mechanisms had to be recreated as well. We are familiar with these rocker switches because they are the same in many different organs. We recreated the mechanism using salvaged springs for the mobile contacts and component leads to create the staple-shaped brackets that they press against on the board.

We then screwed the filter board directly onto the metal L brackets and L channel that form the frame for the switch panel, and it feels quite sturdy.  Some of the wires that had to be connected to the new filter board had already been connected to the other point they needed to connect to; others had never been put in.  While checking over the wiring, we found a few wires that had already been connected between points that had no business being connected at all!

With all the wiring straightened out and the new filter/switch contact board in, the organ was finally able to produce sound through its output!  Testing revealed a handful of the types of issues we always see in combo organs, with bad dividers and oscillators, dirty key contacts, and the like.  We rebuilt the power supply, replaced all of the electrolytic capacitors and identified and replaced the failed transistors that were causing the tone generator issues, and cleaned and aligned the key contacts.  This organ also has a mod that we decided to leave in, despite being awkwardly-placed, because it is so useful– a speed pot for the vibrato. It’s funny that its original owner and builder took the initiative to add a mod but never finished building it.

Finally, it was ready to be sent home and played for the first time in its life!


Leave a Reply

Your email address will not be published. Required fields are marked *