Vox Beatle Super Reverb V1143 Restoration Project

[nevetslab]

So, here I am on a Saturday afternoon, Memorial Day weekend, in the shop at CenterStaging, Burbank, CA,, eating day-old Pepperoni Pizza, with a Vox Beatle amp now disemboweled to give me a first-hand look inside of one of these. All we have in our rental inventory are re-issue Vox AC30-6/TB's, AC30-CC2X, some AC30 HW models, some AC15's of various vintages. This one has date codes on resistors and caps in the 1967 and 1968 era,

I had purchased R.G. Keen's Vox Owner's Safety Net and V1141 Beatle Repair Supplement books, and read thru them once, some sections a few times, as well as read the threads he's posted on these amps over the years. Yesterday afternoon I took this one apart to see what I have to work with. After removing the rear panel of the somewhat modified rear panel, it having a funky galvanized steel plate sporting a Switchcraft D3M and a Cannon equivalent version, which IS the speaker output....the D3M has a resistor attenuator, so must be a line-level output, though coming from someplace else yet to be discovered. The wooden panel was hacked open to allow this to fit into place. The opposite end of the panel shows a crack in the particle board, so there's some mechanical issues already. Every plastic corner guard on the cabinet are broken. No mtg feet. Piping on the bottom of the cabinet is starting to come out. Once I got the rear panel off, I discovered there 's no Reverb tank, so this isn't quite a Super Reverb now, lacking that.

Someone has previously installed a 3-wire AC Mains cord, though they just laid the Hot and Neutral wires of the cord in and tack-soldered them to the 2-wire outlet connector. And soldered the Ground wire to the mounting frame of that AC outlet, so that will have to be addressed. They left the death cap in place, parked below the rotary power switch assembly, so that needs to come out.



While I was taking photos of the large preamp PCB assembly, I found most of the wire terminal pins are still Wirewrap, with many of them soldered over. Most of the small electrolytic caps on the PCB look a lot like the TSI electrolytic caps I had made for me back in 1982, also using those black plastic housings.



Seeing the second layer of pots below this wire-wrapped preamp PCB assembly, I can see how many of these amps would find their way to a dumpster in frustration of the monumental task and patience required to tackle something this fragile and tedious. I haven't yet gotten the real approval to purchase all of the replacement electrolytic caps, along with fresh output power xstrs for the power amp. I'll follow this post with a second one showing the power amp assembly close up. At least I didn't waken any black widow spiders in the process of disassembly. I did find some dead spiders of some type inside the Gibson Lab Series L5 Combo this past week.



I found the two Reverb input/output cables taped off so they wouldn't cause trouble just dangling about inside. There also was no E-Tuner module plugged into it's mating connector.
The Serial Number of the amp....when I first removed the rear panel, I saw a stamped number on the rear panel of the preamp chassis...30-5084-2, and thought maybe that was it. But as I pulled more of it apart, I found similar numbers stamped onto the metal panels and formed parts all over, so now guessing that was an ID number for that particular chassis part, and not the product Serial Number. Usually those are found on a mfgr's label on the outside surface of the product somewhere....though never found one on this amp.

Is there a particular Reverb type used for these amps, and the form factor (mechanical size) to retrofit this amp? I don't yet know if that will be left out, or wanted to be restored yet.

I'll follow up this post with one of the power amp assembly.

[nevetslab]

This post shows the Power Amp section of this Vox Beatle V1143 amp. It was on this section of the amp, as I was processing the photos, that I spotted date codes on the 5W and 10W wirewound square resistor bodies, being from 1967 (6732, 6740, 6720....32nd week of 1967, etc).






I gotta confess this will be the first time I've worked on a solid state amp with a driver transformer feeding the quasi-complimentary output stage. In the early days at BGW Systems, we were using TO-66 driver xstrs to drive the TO-3 output stage of our Model 250 series amps...eventually phasing out that TO-66 package, as well as the TO-3 metal can xstrs.



Did Vox have those 3/8-32 phone jack mounting nuts made special for them? Other than using a pair of round-nose pliers, I can't think of a tool I have that can mate with the two indentations on the sides of those fasteners.

Well, it's now off to start a parts list for capacitors needed on this project.

[g1]

I think you've already done all this, but here is the video I watched that shows how to get these danged things apart. At around 3m45s you can see the size of the tank, typical long style.

[DrGonz78]

I bought a set of really long phillips and straight blade screw drivers years ago. Had one of those newer Yamaha amps and had to buy long screw drivers just to get it apart. I guess I am well equipped if one of these Beatle amps lands on my bench.

[Jon Snell]

These were origionaly made for the UK by The Jennings Organ Company.
Nice whilst working and a total nightmare to test out of the box!
Good luck, I have repaired a few in the past.
There was a tool to remove the jack socket nuts, a wide flat screwdriver with the centre ground out, allowing the remaining edges to fit the slots.
It looks like the capacitors are dated around 1967.
Here is some history from the Vox Showroom.

[drewl]

RG's site (and probably book) also describes disassembly and how to shore up screw holes with sawdust and glue.

Typical repair stuff.

Those black electrolytic a are the ones that cause problems.
Just replace them all.

They seem to hold up as cathode caps in Gibson tube amps, but fail in these amps.

[nevetslab]

RG's site (and probably book) also describes disassembly and how to shore up screw holes with sawdust and glue.

Typical repair stuff.

Those black electrolytic a are the ones that cause problems.
Just replace them all.

They seem to hold up as cathode caps in Gibson tube amps, but fail in these amps.

That was the plan....replacing all of those black caps....just ordered the remainder of the NP ones yesterday, and have stock on Nichicon PW series Radials and Muse series NP's for those parts. Still gotta get the replacements on the two orange-colored electrolytics under the preamp board..

[nevetslab]

I think you've already done all this, but here is the video I watched that shows how to get these danged things apart. At around 3m45s you can see the size of the tank, typical long style.

I watched a similar video on that procedure, and having misplaced my 1/4" universal joint, picked up another...though found I didn't need it with the 10mm socket on a long extension to remove the nuts.

[Mick Bailey]

I think it remarkable that Vox made such an electrically and mechanically complex amp, even back then when labour was relatively cheap. I don't know about Vox specifically, but many electronics assembly industries paid female workers a fraction of what a man would earn, so maybe that figured into the overall build cost. I've had a few SS Vox amps from that era to repair but I always end up embarrassed about the true number of hours I have to put into them and end up charging what I think the customer would expect to pay rather than the real cost. I sometimes think if I got a paper round it would have paid better.

[g1]

end up charging what I think the customer would expect to pay rather than the real cost. I sometimes think if I got a paper round it would have paid better.

Here we call that a paper route and I totally agree.
Now delivering flyers for 1/4 cent per was another thing entirely...gave that one up after the first day and some calculations.

[nevetslab]

Here we call that a paper route and I totally agree.
Now delivering flyers for 1/4 cent per was another thing entirely...gave that one up after the first day and some calculations.

Ah...the paper route. I hadn't yet turned 21, was living at home with my dad and his second wife and beautiful daughter. I had bailed out on school as my band was now working a lot around town, though that was a 'pie in the sky' in his eyes. To appease him, I got one of those telephone book delivery jobs that the phone company gave out every time new books came out, and, having a 3/4 ton small bobtail truck, I figured taking a commercial route would be the thing to do. Little did I know delivering 800 phone books on a commercial route didn't pay any more than delivering small qty residential books. Got the addresses, loaded the truck up, only about half the qty, and drove from downtown LA to San Pedro, where the first address was on San Pedro St. Found the address, only it was an elementary school, and not the business called out on the first location. Looked at the next number of locations, and realized I just drove all the way out of Downtown LA, where there ALSO is a San Pedro St...the correct addresses! Drove back up to downtown LA, now two hrs behind, delivered all those books, back-breaking work, not equipped to deal with the weight of seven books bundled together with cheap cord that cut into your hands, and had to come back the second day to complete the job....which paid $15. I quit that second day, which totally pissed off my dad. I suspect I lost money on that job on gas...though back in 1967, it wasn't yet a dollar a gallon, but that truck only got 8 miles/gallon.

On this Vox amp.....assuming I get the ok to replace all the caps and probably the output xstrs, though I suspect he'll pass on putting a new reverb tank back into it....I'll have to charge what it would normally take on an easy-to-service amp, and not what it takes to deal with the potential horde of breaking wires on this one. This is more of a task to just see one light up, and hope all goes right with the efforts.

[drewl]

It's actually the Thomas engineers who designed those, for good or bad.

Built in fuzz, TMB which was the predecessor to the wah wah, repeat percussion and built in tuner.

Also the compressor/limiter circuit which helped keep these from blowing up.

All that organ building experience.
There is a Gibson head out there that is very similar in construction and sound that I've worked on.

Run one of these preamps into a tube power amp and they sound fantastic, like the Vox built 7- series all over Revolver.

[g1]

Built in fuzz, TMB

I don't like proper 'fuzz' so I'll note that this is called 'distortion' in this amp. I mentioned in another thread that it is the best sounding simple on/off distortion circuit I've ever heard. Maybe it's just the way it works with the rest of the amp that makes it sound so good. Loads of overdrive and tons of sustain. No adjustments.
TMB I think you mean the MRB mid-range boost.

[drewl]

Yes, mrb, mid range boost.
brain fart.
As heard on the end of Back in the USSR with John manually switching the settings.
Of the Vox UK amp.

But if you look at the fuzz circuit, it's pretty much a fuzz face.
Damn! Built in fuzz face!

[nevetslab]

Well, here it is Sunday morning, coffee just made, removed my CA license plate on my beat-up 2001 Honda Accord sedan to clean it, and attach this years License Renewal tag, then remounted that. Set the Vox Beatle preamp on the check-out bench next to my desk, and the power amp section on the test bench, where I'll start the project. I had ordered a pair of Kemet ALCS10 series 10,000uF/63V snap-in power supply caps..35mm dia, 60mm long. I'll have to mount these with brackets, after I unsolder the cap can 5000uF caps. Getting these into that space, sandwiched between the heat sinks, xfmr and shield wall that's fortunately removable, looks like a challenge mechanically. I looked at the data sheet I had downloaded. Looks like a very good part, but.....there's no charge current rating on them! Huh???!!

Kemet ALC10S Series Electrolytic Caps.pdf