Thursday, March 26, 2015

Alamo Montclair Reverb

  Had a rare old amp on the bench today, this little single 12" Alamo Montclair Reverb. Nothing special about the job, just a power switch replacement. But the amp itself is really cool. It's an early hybrid amp, 1/2 tube and 1/2 transistorized. The power amp is loaded with a pair of 6V6 tubes with a single 12AX7 phase inverter. It's about 15 watts and packs a mean lil' punch! The preamp is all transistor and has a nice reverb and decent tremolo. This one was loaded with a Celestion Vintage 30, one of the finest speakers out there in my opinion. Great live speaker. I'd love to hear this with a trashy old Jensen though. That's more my taste....

Friday, March 13, 2015

1998 Fender Hot Rod Deville 3/13/15

Need a good, well made amp that is LOUD for cheap? You still can't beat these. This is an earlier version. Easy to work on, mod, bias and make music with. Tonally? Kinda harsh for my taste but I have had success with changing signal caps and resistors in the signal path. Heck. I once changed every signal cap and resistor plus the harsh, terrible modern Jensen speaker for a customer out west at his request. I thought he was nuts as it was a $350+ job. In the end though it sounded like an old amp. I was quite pleased with the results and so was he!

  This amp just needed tome new tubes and routine maintenance. Every few years a bunch of little solder joints inside need to be touched up, they simply come un-done and cause noise and dropouts. This was no exception. Also, I've replaced more load resistors on the phase inverter in these amps than any other. If yours sounds particularly harsh and lacks volume, there is a 50% chance that is the problem. Easy fix for the experienced tech. Don't try it if you don't know what you are doing!

  Great amps overall. They get my thumbs up. One of the only modern amps I enjoy working one. Many modern amps I simply won't look at cause the construction is so poor and they are not made to be worked on at all. These are no problem!


All Test Devices Wah/volume pedal. 3/13/15

Here is a rare bird. An All Test Devices Wah Volume pedal. Yeah, it's really just a Maestro Boomerang in disguise. Nice wah, very nice indeed, but these pedals aren't my favorite. Why not? I'm just not a fan of the volume wah arrangement to begin with. And these really eat your dry signal alive. This one was purchased at a junk shop for $10 last week. The pot was broken, or at least the housing had come undone. I found the perfect replacement for it but still, these have a nice lil' flaw. When you adjust the volume for maximum sound (which also gives you the brightest top end for the wah) it has a 'bump'. In other words a pop happens. The old pot did this and so does the replacement. I needed to back it off a bit to get it to behave. Sounds like a parasite of some sort to me. I'll mess with it to find a solution but I think anything that will help may rob even more tone.

I wish this were mine cause the wah is really good. I would gut that stupid volume part and throw in a true bypass switch. Yup. That would make me happy.


Alamo Fiesta! 3/13/15

 Today we have an Alamo Fiesta. I re-capped this amp last year and also modified the tremolo to play slower. Today it was in for a simple re-tube. Output tube was making horrible howling sounds and the main preamp tube was microphonic. These use a 50L6 tetrode for power yielding about 4 watts. Easy to find NOS examples on the cheap. Nobody makes them any more. For the preamp tube I installed an RCA 12AU6. I'm usually not a fan of amps with these tubes, they have a cheap arrangement for the filaments. They really are kinda crappy when you put them up next to a Fender but, this little amp kicks. Plenty of volume.

  I recommended the customer buy my personal favorite 8" speaker, an old Jensen C8R, one of the brown ones you see pulled from an old organ where they were usually used as midrange drivers. I find these on a regular basis in great condition since they weren't being abused in a guitar amp. And they are usually obtained at a good price. And of course, they just have a lovely sound. Better than anything being made today.

This amp also boast a lovely tremolo. Very rich sounding amp overall, more of a darker sound which I like. Warm like a tube amp should be.

It's always helpful to have a schematic handy. Thanks to whoever drew this one and I hope it's okay to feature it here!

To slow the tremolo down I simply increased the value of the 3 in series tremolo capacitors. The bigger the caps, the slower the trem. Experiment! Start with the one on the plate of the 12AV6 first. Try a .047 or a .1 and proceed from there.


Thursday, March 5, 2015

1959 Fender Champ, signal cuts out. 3/6/15

Quite a beauty this amp. This is the kind of project I really enjoy, it's small and simple with a beautiful voice. These amps are so well made, Fender really raised the bar higher than anyone else did.

This one belongs to a really fine jazz player I know. He uses it for solo gigs. Yes, it can happen. A 5 watt tube amp for jazz! A little breakup and warmth makes music sexy. An Ibanez Ts-9 with a Roland Jazz Chorus? Um, not sexy.

So what was the trouble? The amp would work for about 20 minutes then crackle out and die. He would plug into the other input and it would die after a few more minutes. The client was frustrated as this is his favorite amp and it's been to another tech who couldn't find the problem. Truth be told, I couldn't either till tonight and it took me a week. Oh, I did everything: the ol' chopstick test, tested the caps, resistors, cleaned and tightened everything, checked the sockets. I even changed the cathode caps only because on the 6V6 tube there is 23 volts sitting on a 25 volt cap. I don't like that. I prefer a 50 volt or better cap there. I've seen those lil' Sprague Atoms pop like a firecracker.

I saw this baby was loaded with a JJ 12AX7 and 6V6. Their preamp tubes in my experience have all sorts of reliability issues. So I put that tube in my tester and let it cook overnight just to see if the heat caused any shorts. Nope. Not even tapping on it caused any trouble. This one was made on a good day.

So I could not get this amp to not behave like a champ! (Yes, stupid pun intended!). I did find one disconnected ground wire flopping about which could reach the input wire by the 12ax7 tube. This wire once was connected to the pin 9. The heaters were improved in this amp, lifting that side from ground and 2 100 ohm hum balance resistors were installed. Well done but why leave that wire?

This brings me to my point. I spent a lot of time I can't justify billing for on this amp due to another techs sloppiness. I replaced the cheap signal caps and the ones what were in there were barely soldered. So I figured maybe this was the problem. But once I soldered the new caps in it finally quit on me! YES!!!! If it ain't broke I can't fix it. Now I had something to fix! I hate turning a project in that I don't feel 100% right about.


Yup. A washer. Flopping about like that drunk and annoying hobo asking for a sandwich. Right under the solder joint where the first .022 cap and wire connect. When the amp was taken apart it must have come loose and gotten lost in there.

And here is is back in it's proper place:

Man this kind of thing....well, yeah, job done.

This is a great little amp. The power transformer was replaced some time ago with an early 70's part so the B+ voltage is a bit higher which I like. Also the speaker is replaced with a Kendrick. I don't really dig his speakers but in this amp it's a great choice. I installed a NOS GE 5751 tube so it has a nice darker and warmer voice to it. This is a terrific amp. Sad to see it go home tomorrow but happy to get paid and have another satisfied customer!