More Judybox Revival

Sometimes you stumble over something, and as you follow the trail, an entire new world is revealed. People who dig quirky guitar amps are no different, and that led me to the Judybox-partially because it's named after my wife. I decided I had to have one.

The story's quirky. The amps were developed by Al Nelson down in Austin, Texas about six years ago or so, and that's where you'll find most of them. A pretty big splash was made at the 2006 NAMM show which was held in Austin that year, and from what I read on TGP and other forums, the wheels started to come off the project soon after. Deposits were taken and whether they were returned or anyone got amps is anyone's guess.

Suffice it to say there were and are a lot of unhappy people in the Austin area who'd ordered amps and didn't get them.

There are stories of illness and mismanagement, a transfer to shadowy investors, some or all of the assembly being done in China, and that's pretty much where the story ends, in 2007.

The registered address of the business, 8804 Chisholm Lane, looks a lot like a residence with a stable out back. It's owned by a gentleman named Stanley Phillips and has been in his hands since 1972 according to the Travis County Assessor.



Entity Information: JUDYBOX, INC.
8804 CHISHOLM LN
AUSTIN, TX 78748-6378
Status: NOT IN GOOD STANDING
Registered Agent: AL NELSON
8804 CHISHOLM LANE
AUSTIN, TX 78748
Registered Agent Resignation Date:
State of Formation: TX
File Number: 0800639464
SOS Registration Date: April 10, 2006
Taxpayer Number: 32019547028

Well. What's the story on this orphan?

It's cathode biased, two channels each with its own volume, bass and treble, and reasonably well equipped although looking like it was done in a bit of a hurry. There are no identifying marks on the transformers which look a bit Asian. There are extra taps on the power transformer that could prove interesting.

The tube layout is conventional: 5AR4, 6L6GC, 6L6GC, 12AX7, 12AX7, 12AX7. The voltages are relatively low, with a B+ of only 369v and 309vAC on the legs of the power transformer. Some of the fitments are a little cheesy-the pilot light and power inlet socket are pretty much low grade schmutz plastic, and shot, but overall it looks pretty decent.

Sound wise, this amp does clean in a big way, and it's got a nice deep bass tone that's right for single coil pickups, particularly P90s. The original speaker's been replaced with a Celestion Super 65 that gets the job done well.

Where the story ends, I don't know. If you've got some information feel free to post a comment.

UPDATE 4-7-11
Since I wrote this piece I've been doing the work required to get this amp in serviceable condition and here's what's been done so far..

I replaced the pilot lamp assembly with a military surplus item that the original looked like it had been copied from, got rid of all the ceramic resistors except the cathode resistor, replaced the electrolytics with suitable replacement values, and went up to the hardware store for enough hardware to cook up proper standoffs. This required modifying a few holes and drilling others, but now the board is level, well supported and not preloaded at all.

When you think about it, the screen resistors and grid stoppers do not need to be 5w ceramics, and the dropping resistors do not need to be 10w. 7w and 5w ceramics. Fender did just fine for the last sixty years without that stuff. Plus, smaller resistors make for a cleaner installation and that's the look I'm going for.

Even as we speak the UPS man is supposed to be bringing me a new power socket to complete the job. Then, I can reassemble it and survey the grounding.

One interesting thing I found was the control pots-they're all linear, made by Cosmos Tokyo and very nice looking stuff. I shall try and find a source.

Judybox Revival

I finished up the Judybox Revival amp and powered it up today. It got topped off with a nice set of vintage Dakaware chicken head knobs I'd been saving for a special occasion.

Here's what I did to it.

Replaced all the ceramic dropping resistors with a 3w metal film, a 2w metal film, and a 2w carbon comp.
Replaced the ceramic 5w screen and grid resistors with 2w Dale metal film and the grid resistors with 1/2 w carbon film from Rat Shack.
Replaced the pilot lamp assembly with a Fender item. This was broken
Replaced the power receptacle. This was broken as well.
Replaced the 40-22-10 e'lytics with 47-22-22 450v items
Replaced the three ceramic octal sockets with bakelite.
Installed 5 standoffs of the proper length to support the board level and not preloaded.
Revised the ground scheme to a star ground setup
Replaced the chassis screws with new stuff from the hardware store.
Installed a smooth plate Tele in the first position.

How's it sound? About the same-bright and sparkly with a lot of depth on the bottom end. Sounds a lot like an AB165 with the bass and treble dimed and the switch on bright.

The builder used Tocos (Tokyo Cosmos) pots-very good stuff-but they're all linear. I may change them out for audio taper, at least the volume controls. All the connects from the pots to the board are shielded wire. I didn't see a nfb resistor but maybe it's there somewhere. I'm thinking that the first two preamp tubes share a common filter capacitor, because if they did not there would be four and there are only three e-lytics. Both preamp tubes have small electrolytics on both cathodes.

I don't know whether I'm qualified as an expert-I'm in the middle of doing a schematic layout and a bill of materials and when I'm done I may be an expert in which case if you find this drop me a line.

I am in a position to make some recommendations in order of importance.
Ditch the power receptacle and pilot light for something good.
Install proper standoffs to support the board and level it out.
Dump all the ceramic resistors except the power tube cathode resistor. They look stupid.
Revise the grounding to a star grounding common-it was strictly from hunger.
Replace the octal sockets with bakelite, Beltons, or military Amphenols

If you've got any questions about this amp, drop me a line.

Sherwood 84-22

I acquired a Sherwood 84-22 a few years ago in a state of disrepair-deshabille might be more like it-and some stinkiness about which more anon, mostly because I liked its looks.

The Sherwood dates from the late forties and was probably sold by Montgomery Wards. It was clear from the beginning that it had been made by Danelectro back when they were in Red Bank and before they'd discovered the uses of Homasote as cabinet material.

The circuit is interesting, as it uses the filament of the first preamp tube as a cathode resistor, in conjunction with a resistance on the ground side-which keeps the filament above ground and dumps the detritus into the center tap of the filament winding. It also runs the 12SJ7 pentode pretty hot which makes for some crunchy sounds-not the typical late forties thing.

Along with the Rola field coil speaker, with modest voltages provided by the iron from the House of Freed, it's got its own groove that owes little to anything else of the era.

The overhaul resulted in some head scratching because the stinkiness got worse and finished up with a cloud of evil smelling smoke and lots of distortion. After puzzling over it I realized I had a similar amp in the collection and on opening it up, it was easy to see where the last owner had bodged the circuit which accounted for the stinkiness and lousy vibrato.

Of course, experimenting with odd circuit ideas was something that happened a lot in the House of Nat Daniel. I've seen several variations on this theme, including one which uses a power tube to modulate the field coil current for a Leslie type vibrato effect, and one that uses a potentiometer to adjust the preamp tube filament voltage for yet more cool Danelectro edginess.

The circuit is the same as the Silvertone 1303, and I've seen it in amps from Wabash, Noble, and Danelectro. As part of a cooperative project I dug up an original copy of the schematic and it was redrawn by Sean Weatherford of Bean Amplifiers, so that was probably the last one the seller got five bucks for.

It is now the world's property, and it would make a great home brew project. Why make yet another tweed Deluxe? This'll get you there in style, plus vibrato to boot.

I've got an 84-23 which is the same amp with an extra 8 inch PM speaker, and it's undergoing a refit as we speak.

How's it sound? Sharp, edgy, and full of fight. It's not smooth at all like a Deluxe but edgy and in your face like you'd expect a guy from Jersey to be.

Vox AC30CC2 Normal Channel Shutdown Hissy Fit

I've got a Vox AC30CC2 named Sophia Loren that is presently up for sale. This may be a cautionary tale about Resistentialism-which is the philosophical notion that things are out to get us. It also supports the notion that things have feelings and ways of punishing us.

I mean, you have to know that this amp has never been abused or scorned-it has never left my non smoking house either. It has, in a word, been spoiled rotten.

So a guy came to look at the amp and the normal channel quit working right in the middle of my sales pitch. Of course he more or less figured out at that point he was a Fender guy at heart, and so am I, which is why Sophia Loren was up for sale anyway. She was acting more like Roseann Barr at that point.

I got a little time today to dig into things and schlepped the chassis out and down to the laboratory. I started checking voltages and the preamp voltages seemed OK. Then a little grid disturbance testing led me to the first preamp tube's normal channel grid which produced no noise. Then, as if by magic the normal channel sprung to life. So, I tightened up the tube socket pins and retested and things were still on again, off again.

Looking through the holes in the vertical preamp chassis I could see that not only was pin seven-the one at issue-on the first preamp tube a lousy solder job, but pin seven on the second preamp tube was equally dodgy. I was able to reach through the holes and resolder the connections, and things are back to normal.

I know now that it's not right to threaten eviction when a needy and dependent lover is on the receiving end.

Repurposing A Courtesy Outlet

When installing a grounded three prong power cord on a Fender amplifier the question always arises "What in heck am I going to do with the courtesy outlet, which is itself ungrounded?"

It occurred to me a while ago that the courtesy outlet occupies the same footprint that a garden variety octal socket does. As I was in the process of replacing the two conductor cord on an AC568 Bassman, I also found that the power tube sockets needed replacement. It was a good opportunity to remove the hybrid cathode bias setup that Fender briefly used, and convert the bias balance to a simple bias level adjust system.

The only reason I can see that the hybrid system was used would be to ensure that if you lost your bias supply the amp wouldn't go into power tube melt down mode. It didn't last at Fender.

Checking the bias on a Bassman or similar amp configured as a head is impossible without removing the chassis, which can be problematic if changing tubes on the fly or between sets at a gig.

I took a replacement socket and installed two 1 0hm 1w 5 per cent resistors as shown. I wired each to the cathodes of the power tubes, and downstream I grounded the cathodes.

Now, setting the multimeter to millivolts will give cathode current in milliamps, and this can be read while the chassis is still installed in the head cabinet. In addition, each individual power tube cathode current can be read. Knowing the plate voltage allows the operator a safe range in which to operate, or alternatively to choose a spare set of power tubes for the road bag before leaving home.

You could bring out plate voltage to one contact but that could be a little hazardous with the number of little kids with sticky fingers that seem to always be underfoot. Better to leave it inside where it's safe.

In case you were wondering those screen resistors are Dale 2w metal film from Mouser Electronics. They meet the need and occupy a lot less real estate.

New Arrivals and A Project

A couple of new amps arrived here at mi ranchito for stays of indeterminate duration. One's a silver face Deluxe Reverb with the volume boost about which little need be said except that nobody ever uses the volume boost. It needs a little love in the form of a cleanup and a new vibrato roach which will be ordered this morning.

It remains to be seen whether I'll form a bond with it, although the Dragon Lady said "Oh. You can keep that if you like." Which was a big surprise, and it raises questions about whether I've got some kinda Stockholm Syndrome thing going on here but whatever-I'll take de job.

The second is far more interesting but enigmatic, and when I heard it had a 15 inch speaker I was hooked.

It's the Maestro M216 RVT pictured at left, and it's some sort of weirdo production from the Gibson works back in 1963 which was when it was made. The tube lineup is 5Y3-6V6-6V6-6EU7-6C4-6EU7-6EU7.

I've acquired it in a trade for a home brew consisting of a Motorola HS621 chassis mounted in an old Masco speaker cabinet with a 70w Eminence topping it off. It sounds surprisingly good and it appealed to the previous owner of the Maestro. The deal's done, and all that is needed to seal the deal is for me to hand over a couple of Franklins.

The circuit is unique and resembles only the GA19RVT Falcon in the Gibson Master Service Manual, but it is voiced differently-allegedly for accordion. It's single channel with swampy reverb and vibrato, but the amp just doesn't have enough volume. I spent most of Sunday afternoon trying different things to see if I could raise the volume level to acceptable levels-changing resistance values in strategic locations, installing a larger output transformer from a Deluxe Reverb, a solid state rectifier module and bypassing certain components to see whether the mystery could be unraveled.

All was in vain-even though I did find a resting place for one of my 1957 vintage Jensen P15R speakers. A general cleanup and chrome polish was had, and I subbed some Dakaware stove knobs because I just don't like those red pointers any. The knobs came from a tube tester I scrapped a while ago.

So, it seems I must study circuit design and topography to unravel this mystery. One clue that I have uncovered is that if the volume control is dimed, there is next to no white noise-which tells me something's rotten in Denmark.

Resuscitating A Silvertone 1396 Twin Twelve

I'm a sucker for projects, so when a friend brought me a Silvertone 1396 combo that had been in a barn for twenty years or so after being stripped of its speakers and grillcloth I was on board.

The owner represented that it had worked at that time but I find that belief problematic. There was no discernible preamp action, which I later discovered was because the cathode resistor upon which all in the preamp department depends had gone open. It fell apart in my hands, actually.

A preliminary power up with some borrowed speakers showed that the audio section and power supply was functional although needing a complete suite of new tubes and a thorough going over.

Down below there are two separate output transformers, each of which feeds its own speaker. It thus satisfies the Daniel penchant for weirdness and complexity coupled with cheapness of build. But nevermind.

Not so the top chassis-and thereby hangs a tale.

The top chassis contains the controls, a smallish phenolic slab that mounts eight capacitors, four resistors, a tube socket, and a single 12AX7 tube.

Looking at the schematic you can see that the filaments are in series with the cathodes of the power tubes-a favorite Nat Daniel Red Bank era feature.

The upper chassis is a nice cozy place, and it looks as if a field mouse or two shacked up in there for a while, using the upper chassis as a latrine and a source for things to gnaw.

Another feature of this amp is the blue green Sangamo capacitors, all of which showed unacceptable leakage and got tossed. I didn't even need to fire up the capacitor tester I built a while ago, as my trusty IRT2 insulation tester showed enough leakage to make that irrelevant.

The upper board required a complete stripout of all the components, a thorough cleaning and a rebuild that included a new shielded Belton tube socket.

After a few fits and starts and a bit of rework, it's as good as it will ever be. The speaker chores are being taken care of by a pair of period vintage Quam Nichols alnico speakers that came out of a PA enclosure I forgot I owned. They looked almost new, and I doped the somewhat light duty cones for good measure.

Finishing up the upper chassis I bridged the channels for more volume.

How's it sound? Bright and articulate, but the vibrato is slow and dreamy and it will take you to Link Wray "Rumble" territory in a short time.

It's not as in your face as the current day run of cheap amps, but it definitely is one to put on Santa's list. They're not the most common amps in the world either, mostly because they weren't built to last fifty years as this one has.