Crawls Backward (When Alarmed)

IconProjects, musings about guitar builds, guitar repairs, vintage tube amplifiers, old radios, travel, home renovation, and other stuff.

Callaham and Reverend Bigsby B11 Upgrades on the ES-225

Back in March of 2015, I put a Bigsby B11 vibrato on my 1958 Gibson ES-225.

I've been playing the guitar a fair amount since then and decided to make a few changes/upgrades to the Bigsby, and also to the type of strings I've been using.

I spotted Bill Callaham's Bigsby upgrade parts and decided to give a couple of them a spin. I've also been less-than happy with the super-stiff spring on the Bigsby - I tried both 7/8 and 1 inch springs and neither made me happy. So I found a new spring to try as well.

And I wanted to try out a longer arm on it tool. Finally, I was itching to try some Thomastik-Infeld flatwound strings on the guitar.

Sounds like a lot of stuff but it got done in a couple hours. And I have a boatload of pictures.

Here's the Bigsby before the operation. You can see the length of the arm. That's a stock 6.5 inch arm, and I'm going to put on a long (9 inch) bar.

I felt like the current bar is a bit short so I'm giving the long one a spin.  Don't know until you try.
We need to take the strings off first, and since the bridge isn't attached to the top, I made some tape marks to aid in relocating the bridge when it goes back together.

One of the new Callaham parts I'm putting on is a main string bar which is countersunk for the string ball ends. As opposed to the infamous Bigsby string pins you see on the old bar here.

Removed the strings. And posed the new goodies on top of the guitar for this picture.

From the left we have the new longer arm, a Callaham 360 degree arm mount, the Callaham main string bar, and a 'soft touch' Bigsby spring from Reverend Guitars.

Removing the Bigsby is easy...undo the three screws on the bottom of the hinge.

To replace the arm mount, and to remove the string bar, undo the 1/4 inch allen screw holding the mount onto the main shaft.

I thought the string bar would just slide out after I took one of the nylon bushings off the end where the arm mount was attached. I was sort of right.

It looked like there was enough clearance between the pins and the hole for the bushing to tap the bar down to get it to drop out without damaging the pins.

There was, but in the process, I still managed to shear one of the string pins off after all. Not a big thing, since I won't be reusing the bar. And if I ever did, I could maybe just put a new pin in, I thought.

Note the missing pin near the bushing. All of the pins have to be removed to get the bushing off the one end, since the bushing is held on with a spring clip.

Seems that the suggested method of disassembly is to take the pins out while the bar is still in the body of the thing. (Or remove the clip, but I don't have a spring clip tool).

As it transpires, if I had tried removing the pins with the bar in place, I would have failed. Because I was totally unable to remove the pins!

If you look closely at the picture of the pins, you'll what they are - just a rolled piece of metal. You can see the seam on the one on the end.

So it seemed like squeezing them to reduce the diameter and then pulling them with pliers would do it. (As is mentioned on the interwebs).

Nope. Not for me. I soaked them in PB Blaster, tried 3 different types of pliers, tried heating them with a soldering iron...they refused to budge.

You can see where two more pins snapped off in the process.

I stopped to think. (A rarity).

I'm not going to reuse this bar, right? If I ever needed it, I could just get a replacement, right? Yes to both questions.

Ok, now to remove those stupid pins.

Sometimes brute force is required.

Sixty seconds with the Dremel and a reinforced cutting wheel, and our pins are gone!

I also had to grind down the stubble that remained of the pins after cutting them off. Doesn't look pretty.

BUT.

I got the bushing off!

Here's the Callaham string bar. Stainless steel, and countersunk so you don't have to hassle with putting the string ball ends over those insipid pins!

Is that beautiful or what?

Here it is installed in the B11 body. It turns much easier than the old bar did, to boot.

This is getting exciting.

Now we take the old handle off the mount.

You might be able to tell the arm bolts were not the 'official' Bigsby nut with a nylon insert - they were generic nuts. I procured the proper nut and will use that for the new arm.

The old mount is on the left, and the new Callaham 360 mount is on the right.

And the old 10-32 (I think) nuts, which will wind up in my 10-32 nuts drawer (I kid you not).

Now we put the new mount on the string bar. The new mount has a lovely stainless allen screw on it.

The new soft touch spring is on the right and the old spring on the left. The new one is definitely softer - note it has less coils.  The height is part of how it is less stiff, I think.

Here's the B11 reassembled and back on the guitar.

I'm going to try these Thomastik-Infeld George Benson flatwounds this time. I was using DR Pure Blues nickel roundwounds, but I have flatwounds on my Rickenbacker 12 string and my Breedlove bass and they're fantastic, so I figured, why not on this one too?

All back together.

The Callaham arm mount doesn't have that 'stop' machined into it like a stock Bigsy, so you can swivel it anywhere you want. Very cool.

I'm getting used to the arm -it's really long!  But it's right under my picking hand, and easy to use.

And you can see how the ball ends just snug right up into the bar now. Easy to string - just run the string though the hole, over the bar and up to the tuners. Nice. And looks clean too, especially compared to the alternative - the ugly Vibramate. Bleh!

And the view from the top.

Couple of notes: first, the Reverend spring is amazing! The vibrato is now super touch sensitive and responsive. Now I can get gentle or dramatic pitch changes with it. Most highly recommended.

Second, the T-I strings are fantastic. Smooth touch, zero finger noise, and a great balanced tone. Plenty of treble, unlike a lot of flatwounds. Expensive, but very much worth it.

 
 

Testing Electrolytic Capacitors for Electronic Leakage

I saved 22 electrolytic capacitors I had changed during the recent Altec Extravaganza.  You may have read me writing that virtually all old capacitors - especially can-type electrolytics have a life expectancy of about 25 years maximum.  Here we will prove that fact.

Periodically I test them for leakage just for the heck of it.  It's really an academic exercise, but it gives me a chance to look at the cool eye tube on my Heathkit capacitor checker.

Here we are testing one of the blue Mallory/no name caps that came out of one of the Altecs.  Testing with the checker is easy.  Connect the leads up to the cap - observing polarity, set the rated voltage on the checker and throw the 'leakage' switch.

And...the eye tube on the IT-11 closes and never opens.

That cap is leaky.

Note that all of those caps physically look good.  In fact, they look really cool with their blue coloring.

But they're leaky - which I knew going in and that's why they were all changed.

Here's a photo illustrating the bad and good caps.

All of the caps I tested were those aluminum cans, except for 3 sealed some-sort-of-plastic caps used in the Altec microphone transformers as input caps.

Overall, almost 82% of the capacitors total were bad.  The three plastic caps tested good, as did one newer (maybe from the late 80s) Mallory cap.

If you calculate the percentage of bad can caps only, the percentage of bad ones goes up to about 95%. 

And this is on a small sample. You still want to leave those caps in your gear?

I have a couple dozen old (as in 1930s-50s) paper caps I've been wanting to test, again, just as an exercise.  One day I'll do that.  Those are legendary for going leaky.

This is why restorers replace old capacitors wholesale.  They have a finite life. Sure, your XYZ tube radio/amp is "working fine" now with its original caps.  But if you continue to use it, the caps will expire.  Guaranteed.  And possibly take something expensive like a power transformer with them.

The original power supply caps on my Hacker RP-38A failed while I was listening to it!  Made a terrible racket and hum.

What makes the caps go bad is that they absorb moisture from the air, and the dielectric goes bad.  Capacitor manufacturers realized this since the begininng of radio - they've made caps that will be more moisture resistant - early radios used capacitors placed in a tar-filled can or block (RCA and Philco come to mind).  Later, paper capacitors were dipped in wax to ward off moisture.  Larger electrolytics were placed in sealed cans.  And finally plastic types were developed.  Those tend to have a longer lifespan, but they also fail eventually.

Here's what I do with bad caps: to the trash can.

Older types with PCBs or other hazardous waste get taken to the hazardous materials dump run by my local gummint.

 
 

Altec 1588B Microphone Transfomer Rebuild and Modification

I mentioned previously that I have 5 Altec 1588B microphone transformers that came with my 1592B.  I wanted to rebuild them and run them in with the mixer after I rebuilt that.  So here we go!

Here's one of the transformers with the can removed, on the 'helping hands' stand.  The cans are easy to remove - there are small tabs on the can that are bent down to hold the chassis in place.  Just bend them back and use a small screwdriver to prise the can off.

I'm going to simply rebuild 3 of my 1588B modules to the stock values with new caps. And I'm going to modify a fourth one. (Keeping the fifth one stock for now to compare tonal/noise differences).

If you search the interwebs for anything related to 'Altec 1588B,' you'll find the famous Ned Clayton modification schematic.  His mod is to enable the use of a 1588B as a standalone preamp by raising the output gain by decreasing negative feedback.

A stock 1588B has a gain of about 33.5 dB.  His mod puts it up to about 52 dB, making it viable as a preamp for condenser mics without using the rest of a 1592B's output circuitry (if that's the Altec mixer you're using).  A 1592B has a gain of 87 dB (!) with a stock 1588B.  I wanted to try the standalone mod, but I also figured it might be interesting to try a ribbon mic with the extra gain - theoretically 107 dB - yikes!

The 1588B works in virtually any older Altec mixer/preamp, not just the 1592B.  For example, it works in the 1589B. The 1589B has an output gain of 66 dB I believe, so the high gain module would make that one suited to ribbons as well.  I'm speaking in the theoretical at this moment; I haven't tested any of this.  In fact, I don't own a ribbon mic yet!

Anyway, I took Ned's original schematic and added in the original component values for those seeking to restore an original. That new version is shown on the left.  Hopefully this will help anyone contemplating work on one of these.

I included the transistor types as well - there might be some advantage to be had by changing these to more modern transistors.  My head is still spinning a bit from the rebuilds, so changing transistors is something I can't contemplate right now.

On the right is a photo illustrating what I did with three of my 1588Bs.  I changed out the three electrolytics, and changed the 27K collector resistor on the first stage transistor to a metal film to reduce noise.  The electrolytics are Elna Silmic IIs.

I also changed the 390pf ceramic cap across the output of the input transformer to a silver mica.  In the process of removing that cap, I managed to break the original 22K emitter resistor in half (!), so I changed that to a metal film also.  I hadn't planned that as part of the rebuild.  


The high gain mod calls for a 100 uF cap to replace the stock 47 uF cap on the pad line.  I found that the Silmic 100 uF/35v cap I had on hand was simply too tall to fit.  So I wound up using a Nichicon FG 100/25 instead.

You can see the size difference on the left.  I honestly don't think there will be much tonal difference - the FG is a quality cap.

A 25 volt rated cap is all that's needed here, by the way.  I just didn't have any 25 volt Silmics (Silmi?) on hand - they may be smaller than the 35 volt cap I had, and they may fit in this application.

The picture on the right is a 1588B with the high gain mod.

I changed the input and output caps for Silmics, and changed the 27K carbon for a metal film as in the 'stock' rebuild.

The high gain mod calls for replacing the 47 uF pad cap with a 100 uF and the 3.3K carbon resistor on that part of the circuit with a 499 ohm metal film.  I only had a 470 ohm resistor on hand and used that.  I wouldn't think the 29 ohm difference will matter that much.

I burned in in my rebuilt 1592B mixer with the newly rebuilt mic transformers installed.  I couldn't judge the gain difference in the modded transformer all that much - there is more gain for sure.  But I won't be able to do any critical listening tests until I can record with it.

 
 

Altec 1592B Mixer Amplifier Rebuild, Pt. 5: Reassembly

With the amplifier board and tone control board rebuilt, and the filter caps replaced, we can reassemble the Altec 1592B and test it.

First we resolder the tone control board - those 8 connections to the pins at the bottom of the board.

Recall the board is held to the front panel via the tone control pots. Reinstall the nuts and tighten them.

There's a short brass strip that connects the ground from the main/amplifier pc board to the ground buss for the inputs.

When I took the board out originally, I undid the screw that attaches to the board (green arrow). It has a lockwasher and nut under it. I realized after the fact that the way to attach or remove the strip is to undo the screw at the buss end (blue arrow). That end is just a screw, with no nut to attach from the underside.

So this time, I undid that screw on the left, and then attached the right side screw along with the strip to the board. That way you can attach the nut from underneath with the pcb out of the mixer.

I left it a bit loose, since it will have to be adjusted to line up with the buss.

I magnetized the screwdriver so it would hang on to that little screw that goes to the main buss. Not fun to drop those things inside a piece of gear.

Now we put in the four screws holding the main board to the chassis.

And reconnect those big multi-pin connectors back to the board.

I'm not sure why Altec didn't use connectors on the tone board also.

Everything's back in place.

I fired it up and used a microphone to test all of the inputs...it works!

On these projects where you're removing several boards at once and replacing a number of components all at once, you don't have the luxury of replacing a few things and then testing, as you would on a point-to-point wired radio or amplifier.

However, if you're careful and methodical as you go, you'll usually have success. If the gear in question doesn't work after putting it back together, it's usually something not connected or not grounded.

I took off all of the channel input knobs so I could clean the front panel with Simple Green. I just put a small amount on a clean painter's rag and wipe it down and then dry it.

The tone control knob screws take a flat blade, while the big knobs are allen screws.

Now we put all the knobs back on.

I connected the output of a small radio tuned to a local classical music station to the inputs using jumper cables. Looks a mess but works :-)

I didn't have enough XLR plugs to hook it up through the back panel!

I left it on for a couple days to burn it in* and make sure nothing went up in smoke.

*Following that supposed 100 hour break-in for the Silmic caps.

Here's the rebuilt Altec 1592B ready to go into the rack.  I also rebuilt 5 1588B microphone input transformers and will post about that next.

Altec 1592B Rebuild Project
Part 1: Overview and Initial Dissassembly
Part 2: Power Amplifier/Main Board
Part 3: Tone Control Board
Part 4: Filter Capacitor Replacement
Part 5: Reassembly (This page)

 
 

Altec 1592B Mixer Amplifier Rebuild, Pt. 4: Filter Capacitor Replacement

The main amplifier board and the tone control board have been recapped. Now we just need to replace the filter caps and a handful of resistors on the chassis. In other words, almost done.

On the right is a picture of the filter caps as they came to me. In a brief test of the mixer before I worked on it, there was a 120 Hz hum, so one or both were bad for sure.

You can see the caps are the big cans that were used on nine zillion pieces of gear. The one on the right is 2000 uF, and the one on the left is 4000 uF, both rated for 50 volts.

I need to disconnect the wiring, drill out the rivets holding the bases to the chassis, and put the new ones in and connect them.

Here's the wiring after I desoldered it. You can see the blue tape labels on the wires - I also made a diagram indicating what goes where.

I don't know how well you can see the ends of the leads, but they're a bit frayed after disconnecting them. Fortunately, they're long enough that I can clip the frayed ends off and strip them again. It's easier to work with clean wire ends :-)

Now we drill out the rivets. I used a 1/8 inch bit for this and it may have been a tad large as you will see.

Use a sharp (new) bit for this, it will go much easier.
Here's the chassis with the filter cans removed.

You can see what I mean about the drill bit being a little too large. On one of the holes, I inadvertently drilled the chassis too, making one of the holes a bit oval-shaped. Not a big deal, but a smaller bit wouldn't have done this.

Need to vacuum that swarf out of the bottom of the chassis. Otherwise it may disperse itself throughout and short stuff out. Not a good thing.

Here are the two old cap cans. I think it's unusual that they are different makes. The blue on is a Sprague and the other one doesn't have a label. I thought the Sprague might be a replacement, but the date codes jive with the codes on the pots (ca. 1980), and the rivets seemed to be original, so who knows.

Aside: this is the sort of removed part that tends to remain on the workbench forever. It's cool looking, so you may hate to throw it away. But what else would you do with it? It's bad. It has no use. You get enough of this junk lying around and pretty soon you have clutter.

TMD and I have discussed this at various times. You have to throw it away or suffer the consequences. Still, I love those blue Sprague cans!

Here are the new filter caps. These are Nichicon FG ("Fine Gold") audio grade. Same ones I used on the 1589B, but these have more capacitance. I love that black and gold finish!

Note that these are "snap" PC board mount, meaning there are two terminals on the bottom designed for a PC board. Naturally, since we're replacing cans with them, we have to cook up a way to mount them.

That's where the chassis clamp on the right comes in. The clamp is a common way to mount capacitors such as these - you'll see them on Marshall guitar amps and a lot of modern hi-fi amps. Pretty simple - the clamp bolts to the chassis and the clamp ring goes around the cap.

Only one small issue in our case. The smallest clamp I could find is 30mm diameter. The 2200uF cap is 25mm in diameter, while the larger 4700uF cap is 30mm.

When I ordered them, I thought to myself, "Self, it's only a 5mm difference on the small cap. How bad can it be?"

Turns out 5mm is enough to cause a headache. After a bit of pondering, I came up with this way of compensating for the size difference. I wrapped a layer of foam insulation - the kind you'd use to seal a door jamb in your house - around the cap.

Hey, guess what? It worked. First time out.

Score one for me.

You can also get a better look at the terminals on the can. I have to connect a few wires on these. Hmmm.

This is what I cooked up to connect the wiring going directly to the capacitor terminals. I took a ring terminal, clipped the end, then squeezed it so it would fit closely around the terminal on the cap.

Check out the fantastic Lisle wire holder I used to solder leads to the terminals. Basically it's a 'helping hands' device, but it's magnetic. The main magnet can attach to something metal, and the two side magnets with clips can pivot or be removed individually. Genius!

Here's everything rewired. The ring terminals worked out well.

I had to replace the old 10 ohm 10 watt resistor with a new one. Not because it was bad, but because its leads were too short to connect to the new caps. Fortunately I had one on hand.

Hard to see in the picture, but I also made two new star grounds. One is under the resistor and one's to the right of the rightmost cap. The old grounds were made to the tabs on the cap cans, and of course the new ones don't have that arrangement.

Here's the view from the back. The mounting worked out well - bolted right on with 6-32 fasteners.

Did I mention how much I like the color combination on the caps? Too bad I'll never see it once the preamp is in my rack.

The last thing I changed were the 1K resistors going from the volume pots to the amplifier board. I was able to reuse the original white plastic insulating tubing.

Now let's put it all back together and fire it up!

Altec 1592B Rebuild Project
Part 1: Overview and Initial Dissassembly
Part 2: Power Amplifier/Main Board
Part 3: Tone Control Board
Part 4: Filter Capacitor Replacement (This page)
Part 5: Reassembly