Wobbulator

An unusual piece of test equipment found its way into my collection of worn, forlorn anachronous  electronic items.

The Triumph Manufacturing Company of Chicago made this wonderful Model 830 Oscillograph Wobbulator.

An excellent description of this item can be found here... http://richardsears.wordpress.com/2011/09/08/triumph-830-wobbulator-oscillograph/

When I first started to examine it for possible restoration, it was clear that it would require more hacking than I'd hoped, some key parts have been removed. I will simply clean it up and use it as an unusual bookend.

The most beautiful thing I found inside is the CRT - I may display it in a little case. It is a beautiful example of early CRT technology.

Dumont 2501A3 CRT

This is a Dumont 2501A3 CRT, a 3" medium-persistance green fluorescent tube, using electrostatic focus. Inside the glass tube near the base, some hand-painted numbers suggest a manufacture date of January 1941, coinciding with the earliest appearance of data that I have found for this tube.

Decisions to make...

I was unable to find low voltage multi-section capacitors to replace C39 and C105 (dual section 1500uf@16 volts). This forces a restoration decision - gut the old cases and hide the new capacitors inside the can, or leave the new caps exposed.

These two multi-section capacitors have a cardboard shell, and I did not want to attempt gutting the shell, as it seemed much less sturdy than the typical metal cannister. Thus, I decided to abandon a strict cosmetic restoration. For my Atwater Kent and Crosley battery radios, I did take the time to hide new components inside old cans, or discretely underneath the chassis. For this project, I am more interested in function than museum display.

It isn't pretty. It just works. Purists will cringe.

New low voltage filter caps - nowhere to hide...

I was able to find new high-voltage multi-section electrolytics.

New multi-section 20uf@475v, next to the old.

C30 - initial solder removal.

I was able to avoid removing the originally connected components for the most part. This required careful desoldering to preserve the length of the original component lead, saving time in the long-run. The components were tested, and were within expected tolerances. Any component can pass simple tests and fail under power. I suspect that these will be fine.

I did remove two of the original resistors for C1, simplifying installation of the new one.

Original C1

New caps

Original input section paper caps...

New caps.

Chester remains unimpressed

I am waiting for a few more parts.

C39...

I chose the easiest part to remove to get started... C39. First, I documented the original component.

Easiest part to remove...

I also made a little drawing.

Is it art?

There are several ways to do this. Since the connecting wires are of sufficient length, I simply cut them close to the terminals of the capacitor. I did use soldering equipment on one wire. This gave me a sense of the proper temperature setting for those cases where I do not want to clip a lead. The solder used in this beast flows very nicely. Another important consideration is whether the device uses silver solder - which has a higher melting point. You do not want to use lead-based solder in that case. Some of the old Tektronix scopes used a silver formulation, and even included a small length of the stuff mounted inside the chassis.

Choose the proper tip

Since the tabs of the capacitors are flat metal, a chisel-tip was selected - the third one from the left. This will transfer the heat in an efficient manner, promoting complete flow of molten metal in the desired area.

Until the restoration is complete, I mark the component and save it. Sometimes replacements have different dimensional characteristics, so it is handy to have an old one if you don't yet have the replacement. There is one more cap like this one - two sections of 1500uf @ 15 volts. I haven't purchased these yet, so off to a supplier website...

New Project - HP 400L

An HP 400L  VTVM found its way into my collection of amusing, anachronous test equipment.

Click for larger view

It came with the operating and service manual, which was printed in 1963.

This VTVM measures AC voltages in twelve ranges - .001 VAC to 300 VAC, Decibel range -72 to +52, with a frequency range of 10 cps to 4 mc.

It weighs about 18 pounds, or in terms of our cat, 1 Chester Unit.

1 Chester Unit

Unlike a lot of old stuff, this came with the original box. It had been sitting on a shelf, unused, for decades. It is exceptionally clean, so I don't have to deal with rust, dust, or other annoyances.

What's Inside?

The following two images show the jumble of parts.

Left interior jumble...

Tubes!

First up...

Never plug-in and turn on old junk like this. Yikes. Since I dislike refinishing metal and all the cleaning, this is a nice project to work on. To make it operational, I will replace the electrolytic capacitors, a few Bumblebees (another common old capacitor type) and other random components as I check out the circuitry. Unlike the Hallicrafters restoration (see the previous project), I will use modern multi-section electrolytic capacitors.

The Suspects...

Bottom of multisection capacitor C1, with associated resistors

I will take several pictures of each component prior to removal. Each part directly connected to the capacitor will be checked out-of-circuit. There are no tell-tale bulges or evidence of heat stress in this area.

Selenium Rectifier

I will research the need to replace this selenium rectifier - I vaguely recall some post in another restoration forum about these things.

Getting the Stuff Together

Which meter to use...

 I was too lazy to look for the test leads for the tube-based Simpson 303. Is it a shock (so to speak) to imagine I have two of those? Not pictured - the Weston 931...

Solder, desoldering stuff...

The Powerstat - to gently ramp up the voltage for testing - in a few weeks!

Next: Deciding where to start.