I'm tired of anemic guitar amps!

[toobfreak]

The amp is back in the case! Boy, that was a pain and a half. Speed nuts suck, they lift the chassis off the case so you end up with the entire weight of the amp on 4 screws point-wise. Which is not a problem, it's well within the capability of the screws - however the amp doesn't sit flush against the case and the weight isn't distributed like it's supposed to be. In real life the amp gets jostled, so I used 1/4" bolts to minimize the chances of anything bending. However the thread on those speed nuts is not the best, the bigger danger is the amp lifts off the case vertically because a thread got stripped. Have to tell the roadies to be careful

Ugg. Speed nuts. Hate the things. I've seen and know every kind. Designed as a cost-saving feature, there is always a compromise in strength just so one can easily attached a threaded nut of sorts to sheet metal for easier production. Sounds like you are using the u-type (they clip or slide over the edge of something), at least this type can have more/better threads than the flat type.

If you are committed to the things now, one thing you might be able to do when you have the time later is to file a depression, inset or detent along the edge just enough to move the nut inward an 1/8th inch or whatever is needed so that the case goes over it.

Another possibility (I'm working blind here) is to replace the speed nuts with standard full hex nuts with a smooth side so that you have two clean, smooth surfaces (wipe the surfaces with a solvent to remove any vestigial oil) contacting each other and apply a drop of Loctite RC-60 to the nut (I think it has been replaced now with RC-603) then fasten it down in place tight. If you see any green liquid oozing out, just touch it lightly for a split second with a Q-tip to wick up the visible excess so there is none free. Then just let it sit for a day in a warm place if you can. After 1-2 hours, if you can, you can even heat the area warm with a little torch to speed the cure, but not hotter than you can touch comfortably. Too hot will damage the compound.

Don't underestimate this stuff! If you do it right, this stuff has incredible holding/bonding strength and that nut will be glued in place. Then you can screw and unscrew the case at will with a full thread nut that will not move and you won't have any of the issues as with speed nuts.

 

[scruffy]

Heads up!

There's another one of these AIMS chassis for sale on Reverb, 700 bucks shipped. Here's the link:

https://reverb.com/item/6929150-aims-vt-100-6550-vintage-tube-amplifier-head-serviced-ready-video

It's a very good deal just for the chassis and case alone. The equivalent from MojoTone would cost you more. Plus you get the transformers, tubes, and a vintage Gibbs reverb tank that sounds infinitely better than the modern ones.

This one works, there's a video so you can hear how it originally sounded. It's from 1971 so it has a PC board (which you can throw away, then you'll have to punch six 3/4" holes for the tube sockets). The reverb tank is under the chassis in this one, so maybe a little repositioning there too, you can fit a new Accutronics tank upside down on the top of the case.

I need another tube amp like I need a hole in the head, but if none of you want it and it's still around in a week I might buy it, it could be a project for a rainy day.

There's enough room on this chassis for a full 200 watt monster amp. You can get a suitable power transformer from Antek for less than a hundred bucks, and you can get a 200 watt Hiwatt output transformer from Pacific Magnetics for about 250. The existing iron on the AIMS is maxed out (else you could put KT-90's in it), the heaters are only spec'd for 6 preamp tubes and you'll probably want to add a couple.

200 watts is like an Ampeg V-9, it's plenty for bass or any other application. Two things I learned from the last build: use locking jacks for all 1/4" connections, and put an XLR DI in there (with ground lift). To build the 200-watter, move the OT to the middle of the chassis and put filter caps where it used to be. A single 12at7 is enough to drive four KT-88's. If you're ambitious you can use a pair of 12au7's instead, I tried it and it works great (especially the presence control is spectacular in this arrangement).

If you're a bass player and you want to build one of these, I'll share my secrets with you. I know basses and bass amps like the back of my hand, I know how to isolate and emphasize all the essential frequencies. If you're a fretless player you'll love this design, it makes a fretless respond like it's supposed to and sound better than it's supposed to.

 

[elektra]

This is what I'm going to start with.

View attachment 1148124

This company AIMS was in Arizona from '67 till about 72 or so, it was started by some ex Fender employees who left after the CBS sale.

It's not going to look anything like this when it's done, gonna rebuild it from the ground up.

This is the back:

View attachment 1148123

You can see the reverb spring hiding in the back there, that's the only part I'm going to keep. (Because it's an original Accutronics tank, sounds great). Plus it has the right number of tube sockets, save me some drilling work.

But y'know... anemic... that's a pair of 6550's but they're running at 450 volts, non ultralinear, there's no way they're getting 100 watts out of that. Maybe 70, tops. So I'm gonna put KT-88's at 560 volts with an ultralinear OT to get an honest 100 tube watts, which is very loud. Giant 350 uF filter caps to prevent sagging.

Maybe I'll build a practice amp with the leftover parts, but this one has to compete with a loud rock drummer so it has to be correct.

too cool, I wanted to build an amp, I even went as far as to buy the book Fender used, although Fender got his for free from RCA

I got an old first year CBS, I think it is 1967 or 68. The first year CBS is still a great year to have. CBS kept the previous year models, untouched. Mine needs to be rebuilt. I have not had the time, been working too much. I should just send it in. It does have a groove tube in it. I will pull all the tubes if I send it in. I think there is only a problem in the power supply. So I dont want some tech stealing my tubes, telling me they are bad

 

[toobfreak]

I need another tube amp like I need a hole in the head

So I guess it looks like you need another tube amp.

Just remember Scruff, you can never have too many tubes.

Many have tried, no one has ever over-tubed themselves yet.

 

[scruffy]

too cool, I wanted to build an amp, I even went as far as to buy the book Fender used, although Fender got his for free from RCA

I got an old first year CBS, I think it is 1967 or 68. The first year CBS is still a great year to have. CBS kept the previous year models, untouched.

Is it a "drip edge" silver face?

Mine needs to be rebuilt. I have not had the time, been working too much. I should just send it in. It does have a groove tube in it. I will pull all the tubes if I send it in. I think there is only a problem in the power supply. So I dont want some tech stealing my tubes, telling me they are bad

Why do you suspect the power supply?

You may well be right, lots of 40 year old amps need "cap jobs", if the amp hasn't had one yet I'd replace all the electrolytic caps on general principles. Then with good tubes you should be good for another forty years.

Bring it up to Burbank if you wish, I'll look at it for you. A cap job on a Fender is pretty easy, might only take an hour if we have the caps ahead of time. Caps are pretty cheap, they're like 5 bucks each for filter caps and a buck a piece for cathode caps. They take about 3 days to arrive. If you tell me the amp type and model number I can list the caps for you.

I'll say this one additional thing for your consideration: for electrical safety reasons, I would replace the AC line cord on any Fender amp that has a ground switch. I would install a properly grounded 3 wire AC cord and remove the "cap of death" connected to the ground switch. Maybe you're a vintage aficionado and don't want to mod the amp, the switch itself can remain in place for cosmetic reasons. This is an optional procedure but it's better than getting 115 volts on your chassis (and on your guitar strings).

That takes longer than replacing the caps lol - but you do that, do the cap job, put in new tubes and you'll have a brand new amp. Then just check bias on the power tubes and you're good. I have some spare 12ax7's and 12at7's if you need some, but I don't have any 6l6's.

I'm assuming there are no other problems like blown transformers, nothing really ever goes wrong with Fenders unless they're abused. We can find out in 3 minutes, pull all the tubes and measure the supply voltages and if they're where they're supposed to be, and all the tubes light up when you put them back in, it's ready for a speaker.

 

[elektra]

Is it a "drip edge" silver face?



Why do you suspect the power supply?

You may well be right, lots of 40 year old amps need "cap jobs", if the amp hasn't had one yet I'd replace all the electrolytic caps on general principles. Then with good tubes you should be good for another forty years.

Bring it up to Burbank if you wish, I'll look at it for you. A cap job on a Fender is pretty easy, might only take an hour if we have the caps ahead of time. Caps are pretty cheap, they're like 5 bucks each for filter caps and a buck a piece for cathode caps. They take about 3 days to arrive. If you tell me the amp type and model number I can list the caps for you.

I'll say this one additional thing for your consideration: for electrical safety reasons, I would replace the AC line cord on any Fender amp that has a ground switch. I would install a properly grounded 3 wire AC cord and remove the "cap of death" connected to the ground switch. Maybe you're a vintage aficionado and don't want to mod the amp, the switch itself can remain in place for cosmetic reasons. This is an optional procedure but it's better than getting 115 volts on your chassis (and on your guitar strings).

That takes longer than replacing the caps lol - but you do that, do the cap job, put in new tubes and you'll have a brand new amp. Then just check bias on the power tubes and you're good. I have some spare 12ax7's and 12at7's if you need some, but I don't have any 6l6's.

I'm assuming there are no other problems like blown transformers, nothing really ever goes wrong with Fenders unless they're abused. We can find out in 3 minutes, pull all the tubes and measure the supply voltages and if they're where they're supposed to be, and all the tubes light up when you put them back in, it's ready for a speaker.

The amp was modified when I bought it
Drip edge, not sure what that means
I am los angeles, but my amp is in connecticut. I bought the amp in Walnut Creek, a little amp shop, maybe guitars too, I dont remember. I moved to Connecticut in 2016, moved back in 2024.
I most likely will retire in Connecticut, $147k for my house on 1.5 acres overlooking the lake by 100 yards. I can turn it up and nobody will complain. I think, got to get it fixed first
thanks for the info
It worked, and then one day I tried to turn it on and it did not work. I think it is something simple.

 

[scruffy]

Drip edge, not sure what that means

This is drip edge. 1968 or so. You can see the white border around the front grille.

Here's a Bassman 50 from 1971, no drip edge.

I am los angeles, but my amp is in connecticut.

You're like me. House and family in OK, just in LA to work. I couldn't fix amps at home, it requires... y'know... scope, signal generator, tube tester, dummy load in a can of oil, .... extensive bench space... the wife would have a conniption

thanks for the info
It worked, and then one day I tried to turn it on and it did not work. I think it is something simple.

Maybe a bad tube. Overnight problems are often tubes. If I were you I'd service the amp anyway, do the cap job. After fifty years a little TLC will keep it in good condition.

 

[scruffy]

My amp survived its first field test!

Played at a coffee house in Sherman Oaks at about 40 watts (very quiet for a bass!), for two hours.

Turns out, the amp is a good conversation piece. People come in, stare at it, point at it ... The one guy was really funny, he came in with his wife, took one look at the amp and busted out in a big wide grin. He came over later during the break, he was still smiling. He goes, "you build that?" I go "yep". His smile gets even bigger. He goes "yep", and walks away.

 

[toobfreak]

Played at a coffee house in Sherman Oaks at about 40 watts (very quiet for a bass!), for two hours.

Cool. Maybe you could call yourself something like 'Footprints On The Moon' or something like that similar to the band on the Big Bang Theory. You can be the bassist to lay down some cool, mellow tunes during the set then on the break, can switch off to debating quantum chromo-dynamics and other GUT and other quasi-dimensional subjects with the audience.

Turns out, the amp is a good conversation piece. People come in, stare at it, point at it ...

And a few probably want to steal it, too. Hope you come with an armed friend packing heat.

 

[scruffy]

There's a great new online tone stack calculator, here:

Yet Another Tonestack Calculator

Guitar amp and pedal tonestack (tone stack) calculator web app. Tweak controls and component values and compare frequency responses in real time. Inspired by TSC in the web and Duncan Amps TSC.

tonestack.yuriturov.com

 

[scruffy]

These are some of my toys.

The one on top is a Laney Klipp.

The one right under it is a Marshall Major.

You can see the BC Rich Mockingbird in the corner, and that's a 6 string F bass right behind it.

 

[toobfreak]

These are some of my toys.
The one on top is a Laney Klipp.
The one right under it is a Marshall Major.
You can see the BC Rich Mockingbird in the corner, and that's a 6 string F bass right behind it.

Nice, Scruff, but what I want to see is the finished product this thread was about, this crazy, jumbo, versatile amp you whipped up. I don't need a ton of technical details nor does every last detail in tweaking it need finalized first, I just want to see what the damn thing looks like with a finished cover plate on it.

Last I saw it, it looked like it needed a nice anodized cover, maybe anodized black or dark blue with white lettering and all those knobs grouped into three groups (sections) to represent function by putting a thin rectangle around the knobs in each grouping.

 

[Etymology gaslight]

These are some of my toys.

The one on top is a Laney Klipp.

The one right under it is a Marshall Major.

You can see the BC Rich Mockingbird in the corner, and that's a 6 string F bass right behind it.

View attachment 1205713

This is really great,
I'd die for a studio like that
R& B guy ?

 

[Etymology gaslight]

These are some of my toys.

The one on top is a Laney Klipp.

The one right under it is a Marshall Major.

You can see the BC Rich Mockingbird in the corner, and that's a 6 string F bass right behind it.

View attachment 1205713

Are they all tubi ?

 

[scruffy]

Nice, Scruff, but what I want to see is the finished product this thread was about,

Ha ha - me too! I got sidetracked over the holidays.

 

[scruffy]

Are they all tubi ?

Yes, and all modified except for the Laney.

 

[scruffy]

This is really great,
I'd die for a studio like that
R& B guy ?

I began life as a heavy metal guy, then moved to jazz/rock fusion in the 70's. In the 80's I actually studied music (with Jimmy Cheatham) and got into Motown and R&B. In the 90's it was alternative like everything else, and somewhere around 2000 I became a touring professional. Then when the kids came I couldn't live that crazy life anymore, so started a production company and a studio and here we are.

 

[Chuz Life]

These are some of my toys.

The one on top is a Laney Klipp.

The one right under it is a Marshall Major.

You can see the BC Rich Mockingbird in the corner, and that's a 6 string F bass right behind it.

View attachment 1205713

I'm just an under achiever. That's all there is to it.

Awesome collection.

 

[Etymology gaslight]

Ha ha - me too! I got sidetracked over the holidays.

Yes, and all modified except for the Laney.

I loke it all

 

[Chuz Life]

Partially inspired by your project in this thread scruffy, I'm clearing my (too small) bench area, and I'm building a larger workspace for amp rebuilds, mods, repairs, etc.

I'll have to invest in some bias adapters, but I think I have everything else I might need.

I decent ESR / LCR bench meter would be a nice addition.

I might even do the YouTube thing.

For repairs and refurbishing, I have two Twin Reverbs, (70's silverface with push pull volumes), a Roland Jazz Chorus, A monster Crate amp, a guitar (strat) build, minor repairs on a Guild Starfire IV, test equipment repairs, lots of good stuff for a channel.

Give us an update on your build, when you can.