Triumph Model 830 Oscillograph-Wobbulator (1943)

Say, Wobbu-what? Yes, folks, that's the real name. This instrument looks a lot like an old oscilloscope—which it is, in fact—but it also combines a type of sweep generator known as a wobbulator.

I saw this item at a local shop, very dirty and forlorn. I was intrigued by the odd name and the reasonable pricetag, but passed it by. A couple of days later, Curt Schreiber posted a restoration question about the very same device in the rec.antiques.radio+phono newsgroup. Here is Curt's description of this device:

A wobbulator is basically a sweep generator so that 
I.F. transformers can be "flat-topped" rather than peaked.
This alignment technique was called for with the "high 
fidelity" sets that sported broad-band I.F. strips. (Whether
this provided for a better listening experience might be a
topic for debate.) A plain wobbulator is a device that 
would be hooked up to a scope in conjunction with an R.F.
(really an I.F.) signal generator. The Oscillograph-Wobbulator
is a scope with a built in wobbulator.

Armed with a little more knowledge, I revisited the shop and decided to take a chance on it. The 'scope was loose in its case and terribly dirty, but all of the knobs were present and it showed no obvious signs of abuse.

The next photo shows the front of the oscillograph-wobbulator after I cleaned it up.

Again cribbing from Curt Schreiber's message, here is his description of the tube lineup and controls.

Picture tube is a 3AP1 (I presume electrostatic deflection?)
Other tubes: 1V, 6K8, 884, 6SJ7 (2 of them), 6J5, and 6X5.
The power transformer has 115VAC primary, and an 800V CT
secondary (also filament voltages).

There are 4 controls around the screen: Vertical Beam, Horizontal
Beam, Intensity, and Focus. On the left side of the lower panel 
are three contacts (R.F. In, Vert., and Ground) and three controls
(Vert. Gain, Locking, and Sweep Vernier).

On the right side of the lower panel are three contacts (R.F. Out, 
Hor., and Ground) and three controls (Hor. Gain, Band Width, 
and Sweep Frequency). At the very bottom there is a jack for
Ext. Sync. 

The Vertical Gain control is calibrated with "Direct" and then
"0-10". The Horizontal Gain control has the same calibrations.
The Locking control has a switch that locks in at 60 cycles. After 
the switch is turned it is then a variable control calibrated "0-10".

The Band Width control has a switch with "R.F. Off" and then K.C.
calibrated "0-50". The Sweep Vernier control is calibrated "0-10".
The Sweep Frequency control is a 6 position switch "Off, 7-70, 
60-600, 500-5000, 3M-30M, and R.F."

Restoration Notes

I have gotten pretty confident about my ability to restore old radios, but restoring old test equipment is a different proposition. The ills that afflict old radios—leaky capacitors, bad tubes, and so on—are often shared by test instruments. However, fixing a test device may introduce a chicken-and-egg problem. How do you calibrate the calibrator? An incorrectly-calibrated measurement instrument is useless.

I don't have any special expertise in fixing test gear, but this device piqued my curiosity, and I had very little invested in it. I decided to crack it open and see what happened.

The first step, as always, was to clean up the device and shoot some contact cleaner into its controls. The next photo shows the oscillograph-wobbulator on my workbench, partially disassembled.

Internally, the device showed good build quality. Everything was nicely laid out and the construction was robust. That's consistent with this unit's military role. Riveted to the top of the case is a metal plate stating that it was manufactured for the Navy under a contract dated November, 1943. This instrument must have gotten a lot of use and regular maintenance. Inside the chassis (not visible in these photos), I saw about half a dozen different brands of replacement capacitors.

After spiffing things up, I put the device back into its case and cautiously powered it up on my variac. I also connected the audio output from a small radio to its vertical and horizontal inputs, to see whether it would display any kind of trace.

To my delight, it started up without any problems and seemed to work just fine! The green trace was bright and it looked exactly as you would expect from an oscilloscope.

That's as far as I have gotten at this writing in June, 1999. In a radio restoration, even if the radio nominally works, I would normally go on to replace all of the paper capacitors and the filter capacitors in the power supply. I haven't yet decided whether to do that. If it ain't broke, why fix it? I already have a modern solid-state oscilloscope for everyday work. As things stand now, I could just power this one up every once in a while to enjoy that funky little 3-inch CRT display.

Sooner or later, though, I probably won't be able to resist finishing the restoration. With a known-good oscilloscope and other test gear on hand, I can probably calibrate this one "well enough for government work"—just what it was originally designed for!