Vintage Parts Excursion Crashes and Burns

I went to an auction Saturday and bought four cabinets full of vintage capacitors-Mallory Gems and Sprague Black Beauties, so I thought it would be nice to outfit the Redhead with a suite of cool old vintage capacitors and see how it sounded.

Well. It barely worked at all. No volume until about half way up and then it let out a strangled squawk-or maybe it was a burp.

I removed the chassis from Brownie and laid them out side by side on the workbench and proceeded to retrofit the Redhead with exactly the same values in the same places, adding and removing nice new parts-yellow polys as required.

In doing so I also took the opportunity to validate my board layout and bring the Redhead back to Brownie configuration. At that point I also found that what voiced the second channel in the original Redhead configuration was a 150k resistor in series with the first grid on the second preamp tube, and a small silver mica capacitor bridging the channels. Both items were noted and removed. One .1 uf capacitor was added in the same place it exists on Brownie.

The result? It sounds just like Brownie, only a little heftier because of the bigger output iron.
The Bad Betty speaker sounds pretty good as well.

So the board layout is complete, noted and checked for accuracy, and I can now concentrate on the connections to the tubes and controls. At that point I can proceed to start a schematic.

I guess what I learned is to check stuff carefully before installation, especially if it's old stock.

Custom Guitar Gear

Custom Guitar Gear's website is still offering Judybox amps, but I do not know whether their offerings are current. If they are, these amps are at least three or four years old, but it's useful for the price information.

Crates Are Good For Something After All

The Judybox output transformer on the Redhead was acting a little strange, so I decided to change it out. What was happening was in measuring plate voltage one side was OK but the other would make my multimeter go crazy and drop off line. It also made a lot of audio noise at the same time.

After looking around the place and interviewing several likely prospects I settled on the output transformer from a Crate TV6212 amp that I bought for some reason that escapes me, and that has become something of a parts bank.

You can see from the picture that it's got a bit more metal than the unmarked Judybox iron alongside of it, and it is an American made as well, from before SLM got bought out and the new owners got the yen for Viet Nam and other mesne places. Once the extra holes were drilled and it was secure and wired up, the voltages started acting normal again.

It's about the same piece of iron as a Bassman output, so I'm calling this a stage II mod-upgrading the output iron.

Transitional Year Website Shots

Here's the transitional webpage and it's interesting for the detail it provides even though the pictures are missing.

More Screenshots From The Judybox Site

Here are the last three iterations of the Judybox website I found-prior to the announcement of the Revival project in 2006, dating from 2004, 2003 and 2002.

It seems that at this point the company was still something of a one-off, craft industry, custom building house.

The transition page is interesting even though the pictures are down.

Enjoy. I think I may start trolling the web for interesting discussion threads and other items.

Judybox Website Archive

Here's a screenshot from the old Judybox website served up by the Wayback Machine. I'll do some more prospecting as time permits.

Looks like the Redhead, doesn't it?

Redhead Power Supply

Here's a look at the Redhead with the Stage 1 power supply mods completed, the tube sockets replaced, the diode protection mod on the rectifier tube and the Fender style pilot light assembly installed.

I've yet to remediate the grounding scheme and replace the power receptacle.

I did remove a number of slabs of ....hard to describe-aluminum foil backed with very sticky, thick rubbery asphalt that had been attached to the inside of the chassis. There is some other schmutz in the corners of the chassis that has to go. Interestingly this amp came from Corpus Christi, Texas and its life in a shore environment showed up in the surface corrosion I found.

I've noticed that the output transformer is a bit odd-one side shows vP as it should but the other side is lower by about 15 volts and it makes my multimeter go crazy at the same time. I do have a nice old Thordarson 25w output transformer that I may swap into place for fun, or maybe I'll shop around for something interesting-I do have a nifty 30w transformer from an organ....but if the idea is to develop a series of product improvement mods maybe I'd better stick to commercial items.

I've also noticed that there are some differences between Brownie and the Redhead on the circuit board component choices. As the goal is to make the Redhead sound like Brownie, I'm likely to bring this amp back to that build standard. At this point I've nearly completed a circuit board map.