Tweed Super On The Cheap

While trolling my usual places on fleabay (the "Why pay more?" store), I ran across a trio of partially built tweed amps that consisted of Weber chasses, pots, knobs, and Mercury Magnetics iron but not much else. There were a 5E7 Pro, a 5F6A Bassman, and a high power tweed twin.

Since I'd already built a couple of 5E7 Bandmaster kits I opted to snag the 5E5 Pro and build it as a 5F4 Super. All three of these amps are pretty much the same with some very minor differences.

Once the partially constructed chassis arrived I made an eyelet board for it and loaded it with F&T electrolytics, Mojo Dijon capacitors and mostly metal film resistors. At about the same time I bargained with Dirk Newton for a pair of Weber Ferromax 10 inch speakers and contracted with J.D. Newell for a lacquered tweed cabinet.

Looking through my stash I came up with a trio of new old stock Cinch shielded 9 pin sockets for the preamp tubes and a trio of new-ish Chinese ceramic top loading sockets. For glassware I used new old stock RCA preamp tubes, blackplate power tubes, and a Mullard 5AR4 rectifier tube.

The chassis went together easily as this was my third one, and everything else went together when the cabinet arrived, and it is a beauty. I mostly wired it with 22 gauge pre tinned cloth pushback wire from Stewart MacDonald.

There's a lot of controversy about  what sort of wire and gauge to use for general hookup and filament service but I think it is a relatively simple matter to determine what the current load is and wire accordingly. For instance the total current draw for the preamp and power tubes is about three amps total once the initial inrush is over. At that point we see that 21 awg chassis mounted wire maximum load is 9 amps so that should be well above the margin of safety. Some folks think that they have to use 18 gauge single strand for the filament wiring and there's simply no need for anything that heavy.



Here's the breakdown on prices which includes shipping:

$375.00 chassis
$260.00 cabinet
$  75.00 speakers

Glassware and other components were from stock

Peavey weirdness now morphing into Blunt Instruments

UPDATE: I think I've found an appropriate name for the amps I build, I checked TESS and nobody's sitting on the trademark, so henceforth and forevermore, anything I build will be yclept a "Blunt Instrument". You heard it here first.



Last week as I considered the state my monster amp project was in I decided to plunge for power and output  transformers for the Super Bee.

There are two potential sources for this class of iron, and a possibility of a third. There is, of course, the ubiquitous offerings from Mercury Magnetics about which more anon, or the offerings from Mojotone which are manufactured by Heyboer. If Classic Tone made these transformers I would have shopped there but alas! they do not.

The net total was $117.42 for the Mojo 753 power transformer, and $109.70 for the Mojo 756 output transformer-which came with multiple taps by the way. Shipping was another $20 or so. Mercury would have run me $425 plus shipping so it was a no brainer.  I suppose I could have used a Twin Reverb power transformer which I have as well as a Twin Reverb output transformer and then had to come up with a 5v filament transformer to run a rectifier tube which would have saved some dough but would not be close to the original setup. This amp has to look and sound like something Fender built. If I wanted to hunt til I'm old and gray I could possibly have turned up an original p/n 7993 Triad power transformer and a 45268 output transformer but that is not a likely proposition. I could die waiting.

The transformers were installed with blue Loctite on the screws. I've seen too many get loosened up with age.

I've selected a new old stock Mullard GZ34  for rectifier duties and RCA black plate 6L6GCs for power section duties. I think Uncle Boris over at Sovtek can do the  rest. There is also a Dynaco socket mod for protecting the rectifier tube which I plan on incorporating- to power 4 6L6GCs is asking a lot of a 5AR4.

With the board built, all I have to do now is build a bias board and a cap board, install some controls and start stitching. The biggest unknown is fitment and speaker selection. That will come later.



On the top you can see my layout. This was possible only because a friend owns a high power tweed twin and I was able to lay out the components in the original way. By comparison there is a shot of a recently built tweed twin replica and the output transformer and cake pan are reversed.

 

Peavey Weirdness, Redux part 2.

After having spent the last couple of months fruitlessly looking for a Peavey all-tube Vintage, a voice in my head said, "Hey you! Yeah you. Glassy eyed lounge lizard. That's right. If you want one of these, why not build it yourself?"

After a little thought and study I realized I could build a 5F8A high powered tweed twin and shoehorn it into an only slightly larger Bassman cabinet and accomplish the objective of creating a ridiculously powerful guitar amp in a 4x10 package. I mean, they're the same as an uprated 5F6A Bassman, right down to the components and eyelet board-which I had already built some time ago. There is only one minor difference between the circuit boards which is a smallish resistor.

Of course this project has to be funded on a pay as you go basis, which means that the iron, the cabinet, and the speakers will have to be ordered and paid for out of the sales of my Vox AC30CC2 and my Bogner Alchemist 2x12. and the amps I already have for sale on craigslist. The chassis arrived here from Mojo, and I have the circuit board, new old stock tube sockets (Amphenol military and Cinch shielded) plenty of fine glassware, small parts, jacks and capacitors so I have some work to do.

The proprietor of the shop where I buy cabinets is working on a similar idea and he says that one of his customers, Sligo amps, has built these in the past but they're very expensive and  do not enjoy a great following. I may sound them out for their opinions.

I haven't thought of a name for it yet and Super Bassman is already taken, so that is also going to need some thought.I've added some snaps from the preliminary buildup.

Film at 11, as they say.

Peavey Weirdness

I've got an itch for a fairly rare Peavey amp built in the early 1970s. They were the "vintage" and they were all tube. The amps came in 2x12, 4x10 and 6x10 configuration and used a pair of the now rare 6C10 compactrons to do the preamp and reverb recovery duties.

The schematic is a lot like a tweed Twin. If you find me one, I'll buy you lunch.

Blackstar HT100 Barbecue: Replacing The Tube Board.

I'd worked on this Blackstar HT100 head a while ago and it has served its owner well for the last few years. I'm not entirely sure how the story goes but it is said that a beer got spilled on/in it but who knows?

Either way it had a major cookout which lunched the tube board. Lucky for me it is a separate piece of hardware AND there was available a schematic for the tube board.

On the other hand, the tube board is made of unobtainium. My first thought had been to get a new tube board but that was out of the question.

Looking at the diagram it seemed that I could hand wire it ala Marshall and then I'd figure out how to connect it to the main board. So I installed four ceramic sockets and started in on the wiring and resistors and hookup wire.

When I got to connecting the tube board to the main board, removing the molex connectors was going to be problematic because they're glued to the board. I decided to make loops in the ends of the hookup wires, and lucky me, there was enough separation so that I wasn't going to have problems with bridging.

I finished the wiring today and it powered up the first time. So tonight I'll let it have a slow simmer and see how it goes.

Bored With Boards: Repurposing an Ampeg SJ12T, Part 4.

As I've been thinking about this project some more-well, let me back up.

I've suddenly got a lot more time on my hands due to the ending of my teaching gig.

It happened in a way that was proof of the existence of chaos theory if you needed it. There is a meeting somewhere, people sitting at a conference table, and with the scratch of a pen, everyone goes home.

Meanwhile a couple of years down the road and a hundred miles away, people lose their jobs.

But nevermind.  Let me continue-this line of thought leads only to frustration and less money in my bank account.

I sourced out some 50A bridge rectifiers, the kind that are potted in a metal case-it seemed the answer to my problem about building a hybrid circuit board of 6G3 derivation, and also made more room under the hood, thanks to a thread posted by J.R. Frondelli of DBM Audio in the Big Apple concerning the age old question of what to do with a torched Blues Junior.

Being in an optimistic mood, I then decided that I would out source a circuit board for a 6G3 so as to save myself some work.

What I got was a board that was warped and off dimension, and half the eyelets were not installed. The ordinary dimensions of the 6G3 board are approximately 2-3/4 x 10-1/2 and the backing board is the same size. On the other hand, here is what the board should look like, populated. It took me a bit of time to make up a drilling mask, drill the board including larger pass through holes, clean up the burrs with a razor blade, stuff it with eyelets, tape them down and clinch them. Then, clean off the tape residue and stuff the board with components and solder them in.

 It should look like this:

 The red marks were for orientation of the components. The lower shot is the comparison.

Now. How did I do it? It's posted elsewhere on this blog but it consists of obtaining 3 inch vulcanized fiberboard, making a drilling mask from a photograph or screen shot of an existing board, sizing it with a freeware program called Irfanview, printing out a drilling mask on 8-1/2 x 17 inch paper, trimming the board to size, taping and drilling the 1/8 holes. Then you can trim the burrs , install the eyelets and clinch them and stuff the board.

To complete a board like this one, stuffed with the components of your choice once you have paid the one time cost of the tooling and eyelets should cost you less than $20 in parts.

And you'll have exactly what you want, when you want, with no waiting and no shipping or paypal fees. The folks on fleabay will charge you upwards of a C-note plus shipping for something you can knock out all day long for pennies on the dollar.

Haste, in my case, surely did make waste, but as always it's a teaching moment. I'm making all my own boards from now on, thank you.

Thanks again to Jeff Gehring for being so generous in sharing his knowledge.

The Evil Pro

I've been jonesing for a certain Fender Pro that was made for a couple of years. This model is an AB763 circuit without reverb, and a 15 inch speaker and I guess it is pretty rare as I never saw one in the fleisch as the Germans say.

For a while I was thinking seriously of taking my Bantam and revising the circuit to add vibrato. But then a guy calls me and I was on my way to Boone, Iowa to look at a drip edge 1968 Dual Showman.

The Showman was all there but it was in rough shape, I bought it on the spot, head and loaded cabinet for $325, and I knew right away what I was gonna do with it.

The JBLs were both defunct so I'm gonna have to do something with it.

Some opinion sampling later and a few emails and I settled on J.D. Newell to build me a custom cabinet that would accept the Dual Showman chassis and a 15 inch speaker. They seemed to be the only people who knew exactly what I wanted and how to make it. Money was exchanged, a delivery date was quoted, and I proceeded to overhaul the chassis and spiff it up with a new blackface panel. The Fender logo I had already.

The cabinet arrived right on time and it is a stunning piece of work. A number of my friends have seen it and exclaimed "That's better than anything Fender built."

For the time being I installed a 4 ohm CTS speaker but I have a higher power Oxford that I may use.

How's it sound? Loud as hell, clean and bright, and with the channels bridged it gets even better and you can soften the vibrato by adjusting the balance between the channels. After about five minutes one of my brand new Ruby 6L6GCMSTR power tubes grenaded, so I slammed a Sylvania in the vacant slot and carried on. I've got a quad of Sylvanias I matched up, and there are plenty of RCA blackplates in the stash box. Preamp chores are being handled by Uncle Boris over at Sovtek.

It's the Pro that Fender never built, and I've named it the Evil Pro.