Vox Beatle Super Reverb V1143 Restoration Project

[nevetslab]

There are two holes on the bottom of the head cabinet. One is for the original shipping reverb lock bolt that secured the tank during shipment from the factory, which was to be removed by the dealer during inspection/setup. The second one located in the center of the bottom panel is for the thumbscrew that held the metal bracket that secured the head to the roller speaker stand. There are probably photos of the stand clamp out there on line.

I see where it should be, but on this cabinet, there never has been the one centered to engage the pan of the reverb tank. I'll have to locate that position, drill and install the 1/4-20 T-nut. I don't have any inserts as Vox used on the outside surface as they added to the storage hole for the thumbscrew. The cabinet is not in the greatest condition. All but one of the corner guards are broken, and I ordered a replacement set of those. On the rear panel, where the original round XLR speaker connector was located, someone really did a botch job with a jig saw to enlarge the area for two XLR's. That cheezy metal plate that's screwed onto the back panel covers that botch job, though only three of four screw holes engage wood.

While removing the wires from the top panel pots (one pot at a time), I saw that odd-ball insulated phone jack that someone installed below where the Vox emblem is normally located. It snakes its' way out to the added XLR male connector, next to the XLR Speaker connector. No longer round connectors, but D3M style. This added connector has a poorly formed L-pad attenuator off of the speaker connector, wired on the XLR as a Line Level Output, then also shows up on the top panel as a Line Level output (in parallel with the XLR connector). I'll have to deal with that clap-trap kluge later.

[nevetslab]

I'm just about thru with the top panel controls.....removing the wiring carefully, as so much of it is in the 26-28AWG, some stranded (including tiny single-conductor shielded cable wires), most are solid core. And, inserted, wrapped around the solder lug, sometimes several on a given terminal, that are stranded, and leaving the challenge of desoldering all of that without having the insulation of the wires shrivel up. I don't have a set of those anti-wicking tweezers to aid in that. I may have one size tucked away someplace, but not being used on this project. Each pot's removal is an adventure. Once I get the pot unsoldered and removed, I disassemble it for cleaning and lubrication:



I've found these Erem 71AE 45-deg flush-cutting diagonal cutters work excellent for slipping in and prying open the cover of potentiometers, as seen with the four tabs pried open.



The silver-plated wiper contact ring, which is removable from the resistance wafer on these CTS 24mm size pots have shown a lot more oxidation than this particular pot. Applying some Brasso metal polish with a Q-tip does a good job cleaning them up....rinsed with water, then re-seated onto the resistance wafer. I clean the resistance track with alcohol and then dry them. Check them with an ohmmeter for verifying there's no break in the track. Sometimes I'll lightly tap on the rivet with a small drive pin punch on my small anvil or heavy steel plate. These have thus far been well seated and tight.



After applying Red Grease to the resistance track, wiper contact ring, brass wiper fingers of the Rotor, as well as onto the plastic shaft (in this case plastic, often aluminum shaft), I reassemble the it, placing the cover back on,then, using a Optima 505J-US (that was a 16-pin IC insertion/removal tool that I cut down to 8-pin use), I close the flaps down firm and the pot is now reassembled, cleaned and lubricated. P/N on this control is 24-5201-3 137 6715. It's a 10k Linear taper. 6715 is the date code....15th week of 1967, so another series of parts that have 1967 date codes on them to date this amp, probably built in late 1967 or 1968.

Tim Conniff taught me the tricks of using the Metal Cleaning compound on the silver-plated contact rings, as well as the use of the red grease. I had apprenticed for Tim in his vintage keyboard shop in Encino for a couple years....brilliant engineer, fabulous Trumpet/Flute player and one of the highly gifted technicians on classic synthesizers like the Prophet 5, Arp synths, all the gear built in the 80's using 'glue-logic', as well as Hammond and Vintage Yamaha organs.

Now, back to finishing up the top panel...one more to go, then I get to lift up the circuit board assembly for the first time on this V1143 Beatle.

[nevetslab]

I've now lifted up the preamp board to look at what's beneath in the basement. A pair of 2000uF axial lead caps, a 1000uF and five 500uF caps, all 25V rated. Trying to retrofit the radial lead 2200uF caps and the radial lead 470uF caps I have looked like too much trouble, so found some Epcos/TDK 2200uF/63V and 1000uF/100V, both body sizes the same as is installed. I added some 470uF/63V axials the same size as the 1000uF/35V cap I had installed in the power amp, so that task is done...those will arrive next week.



And, access to the rest of the pots...those on the rear panel. I see a dual-gang pot...that's gotta be the special 40k/100k Speed control of the vibrato. I've never had success in taking apart dual gang pots, so I'll have to be content with cleaning thru the opening at the covers on that one.

I made a simple loop string to hold the board up, hooked around one of the pot shafts and around some terminal pegs at the back end of the PCB. So, tomorrow, I'll start replacing caps on this preamp board.

[nevetslab]

OK, I've made it past component prep work. I hadn't anticipated having to waste a couple hours dealing with tape-and-reel ammo-belt packaged parts from alternate sources besides Nichicon MUSE (unavailable/on-order status), and the stupid tape adhesive residue remaining on the leads, so had to be chemically removed. The first part I removed (attempted to remove) was a 3-leaded dual-cap Non-polar part, one side having a second component lead from a resistor in the same hole that RG had warned about. Working with a mirror to prevent flexing the PCB being held up in place is a lot more tedious than I had planned. So, progress at this stage is frustratingly slow thus far. At least I've gotten all of the tape and reel parts removed from the ammo belts. Sigh....used to be easier than this. Maybe my old age has caught up with me? I was out working with my band in my early 20's when these were being built. Now, can I start making progress, half the day shot already?

[nevetslab]

Saturday morning I came into the shop, armed with a 2" long 1/4-20 FHMS...hex drive screw, having about 1/2" shank w/o threads. I sliced off the head with a cut-off disc loaded into my Foredom hand grinder. Fetched an old Raytheon bar-knob with a skirt, sawed off the skirt and filed the base smooth, as it would serve well for the reverb tank locking bolt.



The new reverb tank came in yesterday, though I haven't looked at it yet. I took a broken Accutronics 17" tank and set it into the floor of the cabinet to have a look. I see the forward mounting holes in the cabinet floor have the tank offset to the left rear side, so I'll offset the mounting hole for the 1/4-20 T-Nut accordingly. I'm looking to install a springy damping plate lined with foam rubber, which this lock-down screw will push on, forcing the suspended tank and it's two tank springs up into the tank chassis, holding all from moving. Just pushing the inner tank chassis up doesn't prevent the two tank springs from moving, so I need to replicate the packing foam we always find in the tank from the vendor. It just needs to be a moving part that has spring retention. I haven't found just what to use as a flexible panel to attach to the chassis of the tank.

I received the new corners from Reverb.com to replace the broken corners of the cabinet. Got those installed, along with the small brads hammered into the front face of each corner guard. All of the broken corners were there, and had all of the original screws, so those got re-used. New rubber feet came in from McMaster-Carr, so those are now mounted.

Then, fired up the soldering iron and headlight, and resumed where I left off. I just finished removing all of the 1967-vintage caps from the PCB, and have re-populated the PCB with fresh caps.





After processing these photo, I discovered I still have two of those original Temple black encased caps left on the board. So, almost done with this phase.

Then, once I have completed that, I have the rest of the pots to remove and clean. Two of those are mounted to the preamp side-wall using twist-tabs as the bias pot was mounted in the power amp. So, another step closer. I haven't ever powered this amp up, so that revealing task is still ahead of me.



I found that terminal strip to which two of the silver colored 500uF axial lead caps are mounted, just above this sentence is very loose...pivoting on the ground mounting terminal, so have that mechanical task to deal with when the caps arrive on Monday.

[nevetslab]

Moving on to the pots in the 'basement' of the preamp, I began by attempting to remove the Bulldog Limiter Control that is mounted to the power switch side of the preamp chassis. Unsoldered the wires, but this time, not having good access to the terminals, that turned into a botch job, so cut them off, stripped and tinned the wires for reassembly. Using a large pair of duck-bill pliers to untwist the two tabs, one was torqued so severely, I couldn't get the little fingers to close again, and ended up breaking that tab off. Sigh.. Got the other one straightened, so removed the pot, pulled it apart and cleaned/lubed it anyway. Tried to re-use it, but that broken upper tab wasn't helping. Thought I'd maybe succeed in soldering the upper end of that pot bracket to the chassis wall, but that turned into a disaster, and now didn't have a 10k linear pot.

Actually I did...had a number of Allen Bradley 10k Linear pots, with short shafts. So,took one apart,removed the shaft, marked the end of the shaft where I wanted to cut it off, so I'd have a recessed screwdriver control slot. Moved the Foredom grinder base to the bench, after moving the preamp chassis off the bench. Mounted the short shaft in my machinist vise, and proceeded to radius the shaft with successive cuts. As I deepened the cuts, rotating it as I went, I ended up breaking three discs, so that wasn't going so well. Finally did get cut thru, but with a jagged cut. Gripped the shaft with pliers, and hand-filed it holding the shaft against the file blade, finally getting a smooth flat surface.

The shaft was now too short to place in the vise, having that molded appendage that engages the mechanics in the Mod Pot in the way. My small Kant-Twist clamps were small enough to grip the shaft, tightened it up, then placed that clamp into the vise, and was able to cut a screwdriver slot across the end of the shaft. Put that back together, mounted that pot into the chassis and tightened it up. Put the two wires back onto it, verifying the rotation vs resistance was the same as it was with the other pot. But, by then, I was coming unhinged with continual mistakes, I pulled the plug before causing more grief.

On the opposite end (Preamp Ch 1 end), there's another side panel screw-driver adjustment that I have NO IDEA what it is. Anybody know what that control is?

[drewl]

Tuner?
Or limiter.
I didn't feel like reading the novel you posted.

I fixed three amps in the time it would have taken to post that.

[52 Bill]

The second chassis mounted control is for the tremolo modulator adjustment.

And if you want to see the stand mounting bracket, North Coast sells a reproduction on their site.

[g1]

if you want to see the stand mounting bracket, North Coast sells a reproduction on their site.

Here it is. You can see where the threaded insert in the headshell would line up: http://www.voxshowroom.com/northcoas...ead_clamp.html

[drewl]

Cool!
I bought one of their stands for my AC30 way back when.

Put wheels on it for easier moving.

[nevetslab]

Thanks for the info on stand mounting.....but....this amp is heading to Reverb.com to be sold. I still have to drill the hole for the 1/4-20 T-nut for the Reverb Lockdown function. I'll post the solution on that after I've modified the tank.

After I looked at the V1143 schematic, I found the other chassis mtg pot....it was indeed for trimming up the Vibrato modulator.

[nevetslab]

This morning I stopped off at my other shop to pick up some materials I had on hand for the Reverb Lock-Down system. Made coffee and set about the task, beginning with opening up the box the new reverb tank came in. Got the model I ordered....P-RMOD-4FB3A1B. I brought back a sheet of 1/16" Acrylic, along with a small piece of 1/16" perforated Aluminum that I had chopped up to make Marshall JCM 2000 Rear Grill Panels (that seem to go missing over time). I chose the perf material, as the size piece I'd need is small. Also brought back some foam rubber blocks, saved from tanks being shipped with them in place to lock the spring assembly during shipping. I selected the size by eyeball, marked the cut lines with tape, cut the piece with a saber saw, then filed the cuts smooth.



Using the sized piece, I eyeballed the holes to mount the plate onto the inside of the tank chassis, center-punched the locations, then drilled those holes thru, and deburred them. Installed #6-32 x 1/2" screws with Keps Nuts to hold the screws. Used shorter screws on the plate. The Silicon Rubber tubing is the same size I use on power tube hold-down clamps on the top hat....3/32" ID, 7/32" OD. I cut 4 pieces of suitable length, and forced them onto the chassis screws. I cut the foam rubber to size, then had to slit the thickness down, as the thinner material I brought was too thin. Glued that piece into place, though I think the White Glue I used isn't going to hold this foam in place long....probably need to change that to something else.

I think the length of the Lock-Down screw penetration is suitable, as the tank carriage/springs hang down more than is shown with the tank upside down. The silicon rubber tubing flexes enough when depressed.



I have more foam, so pulling this piece off, cleaning off the white glue residue on the aluminum plate is simple enough. Any suggestions for a better adhesive to use with the foam rubber? I might still have a can of 3M 77 Contact Spray cement down the street.

[nevetslab]

On the way in to the shop this morning, stopped off at DIY Center to see what they had in Contact Cement adhesive....DAP Weldwood, which should be suitable. I also looked around to see if Cinnamon or Daisy were hanging out someplace....both store cats who make themselves right at home, but didn't see either of them this trip.

So, I'll mix up the Weldwood, peel off the foam that I glued with Elmer's Wood Glue, and use this instead, plus there's some flaps of Tolex that are torn and peeled back that could use re-bonding. So I'll see if this cement is a good choice.

[nevetslab]

Today I finished the insides of the Preamp wiring and pot cleaning. I removed the odd-ball Line Output jack that someone placed on the control panel, and was horrified.



Looks like somebody tried to drill it with a regular 3/8" twist drill, and finding a rectangular hole behind the escutcheon, that quickly turned ugly! As it was, it left a jagged piece of metal below the surface, that I had to flatten, after cobbling a compression clamp from a pair of Greenlee chassis punches. Then, returned the output jack to that hole, just to cover up the damage.

The AC Mains termination of the power cord to the back side of this chassis is where I'm currently stuck, pondering a solution. Reading thru RG's Vox Owner's Safety net book, he discussed eliminating the AC mains wiring to the Line Reverse switch, as well as to the 2-wire AC Receptacle, which had been used as termination of the 3-wire Mains cord....though without any protection for it, and the ground lead was just soldered to the outlet frame! He didn't disclose the solution he's used in his rebuilds though.



I've removed the power cable from the outlet jack, unsoldered the wire from the AC mains switch, which was being fed to the AC Line Reverse switch. Cut off the other wires to the line reverse switch, as well as unsoldered the hot lead of the power cord to the lower terminal of the fuse holder. I chopped off the two wires that feed the harness connector to the power amp chassis, so I'm back to square one, now looking for a solid solution to anchoring the AC Mains cord, terminating it mechanically before running the wires to the AC mains switch and to the power amp chassis.



The two Pilot Lights....Power and Standby.....both are operating off of -31VDC, and their low side ties to a ground terminal of the mounting frame of this AC Mains switch. So, I had to tighten up the chassis mounting screws between this small metal shelf attached to the preamp chassis. It had what was left of the Fishpaper insulator between the two hex washer head sheet metal screws, which I've removed.

Now, how to terminate the AC mains cord in a nice safe-and-sane way?

[nevetslab]

I stopped to look at the cabinet, now that there's a reverb tank in the way, so cable storage is an issue.



I think I could cut away a touch of the side cleat, and carefully install an IEC-320 mounted to the rear panel. That rear panel is very dicey from the way it got hacked by the previous owner. I just ordered more of those with 1/4" quick-disconnect terminals on the back side. Then, ordered some 3/8" pitch 3-position barrier strips that I could maybe mount to the side wall of the preamp.



I've already removed the fish paper, which is still shown on this last side-image of the preamp chassis. Looks like there would be enough space for the barrier strip. From there, input comes from the back side of the IEC connector to the three terminals of the barrier strip., Line goes to the fuse holder and AC mains switch for AC Hot, Ground goes to a chassis ground stud that I've already added a Fast-on terminal to receive chassis ground wire from the power amp chassis, and AC Neutral would leave the terminal strip to connect to the other side of the zip cord which feeds thru the 9-position disconnect between the preamp and power amp.

Time to head home for dinner