Potentially insteresting amp - '77 SF Super Reverb

[mike9]

I have a '77 SF Super Reverb head here. It has the push/pull master volume and the balance and bias tube matching pots. And it has the UL OT tranny. All considered negative aspects of the amp from many sources. Still I think there might hope for it to be remade into an interesting amp.

For instance the B+ is 500v - that would drive an EL34, or KT88. Rewiring the master volume could be done, or it could be gotten rid of altogether. The UL OT can be replaced with a regular 50 watt Fender, or a 50 watt Plexi for a more interesting twist. If I had to loose the vibrato I could live with that, but keeping it would be a bonus.

I like the idea of Plexi OT and KT88's. Whatcha all think hmmmm? Any ideas floating around that might pique your interest? I mean this amp is pure loud clean headroom. It's like HiFi, or something - it's brutal in a good way, but it's not good in a brutal way. I'd like to open it up and let it sing from its soul.


Any ideas are really appreciated - a layout sketch is a total bonus. If some one were interested in such a project I might be game if it's affordable. Talk to me peeps - here's some pics.

[img:600:800]http://gallery.me.com/motone9/100026/SF ... _1/web.jpg[/img]

[img:800:600]http://gallery.me.com/motone9/100026/IS ... V2/web.jpg[/img]

[img:800:600]http://gallery.me.com/motone9/100026/IS ... V3/web.jpg[/img]

[img]http:800:600]http://gallery.me.com/motone9/100026/SF%20SPRV4/web.jpg[/img]

[img:800:600]http://gallery.me.com/motone9/100026/SF%20SPRV6/web.jpg[/img]

[Andy Le Blanc]

sounds like you already have a notion...... look over on the trainwreck side
at the info about VVR....... as a replacement for the master volume....
and double check the available ma. from power side before you choose a
tube type....

[Tubetwang]

i pick up one of those a few years ago for 350.

It sat in a club for all those years and smelled like it to.

I took the Master off. Replaced the bulging caps.

Speakers were pretty well gone... put the Master back on and sold it.

Major Twang

[Wayne]

Every time I see Fender guts, the same thought comes to mind - looks like a plate of spaghetti!

You've got enough 9 pin sockets there to build 2 completely separate preamps, one for each side of the PI, and A/B/Y the inputs. The left over socket (assuming 2 for each pre + 1 for the PI) could be reverb drive and recovery with a 12DW7.

I wonder what would happen if you just disconnected the UL taps & created a more conventional screen grid arrangement - would the impedance be right?

Errr, wait a minute - this is supposed to be your project, right? Sometimes I get carried away...

W

[CaseyJones]

I'd blackface it. Rip out all that modern crap and build yerself a time machine back to '65 or '66.

The amp has some value as a retro-converted genuine Fender. Hell, it has value stock as a Super just waitin' to be retro-converted.

EL34s are cool, a lot of modders goin that direction.

I'm a big fan of inexpensive transformers but if it were mine I'd pony up the dough for Mercury Magnetic's repro Super OT. Get it mulitapped, that way your speaker options are wide open.

Any time I mod something I never lose sight of what it's gonna be worth if I have to hock it. If you want a Marshall buy a low buck JTM45 chassis or better yet Allyn's nice Trainwreck chassis and go that way. I hacked up more vintage Fenders than I care to admit to "back in the day". Surely I'll go to Bad Amp Tech Hell when I die!

[FUCHSAUDIO]

Add a choke. That power supply is a good one, once you add a choke.
That output iron is not bad. You can simply tape off the UL taps and run it like a conventional Fender output stage, and it will work fine, once you add the choke.

[mike9]

Thanks for the replies - I don't have an agenda just yet. The UL thing threw me at first, but different folks have been lendging ideas and advice so the thing is to sift through and see what I'm capable of performing.

For instance I don't know where to add a choke - I could do the work, but I'd have to follow a layout, or drawing. I'm learning amp theory, but I couldn't design a circuit myself. I'm a guitar builder looking to broaden my horizens and have a great sounding amp when I'm done.

[jelle]

In response to FUCHSAUDIO Andy's post:

B+ is 500V with that PT

http://www.schematicheaven.com/fenderam ... tr_rev.pdf

The screens will be at about 500V as well. I would not recommend doing that since 6L6 is rated for 450v max screen voltage. I suppose he could drop some B+ for the screens using a voltage divider and big ass resistors but that is a bit more tricky.

The UL output transformer's impedance is a bit higher than the normal OT.

I'd just use the UL config or put new transformers in. Mojotone has nice ones too.

Jelle

[CaseyJones]

Thanks for the replies - I don't have an agenda just yet. The UL thing threw me at first, but different folks have been lendging ideas and advice so the thing is to sift through and see what I'm capable of performing.

For instance I don't know where to add a choke - I could do the work, but I'd have to follow a layout, or drawing. I'm learning amp theory, but I couldn't design a circuit myself. I'm a guitar builder looking to broaden my horizens and have a great sounding amp when I'm done.

And there you have it.

Normally I'd refer you to The Fender Field Guide except it seems the FFG has been beamed up by aliens. Use Schematic Heaven's resources instead:

http://www.schematicheaven.com/fenderam ... tr_rev.pdf

http://www.schematicheaven.com/fenderam ... _schem.pdf

Those are schematics for the very early Super and your very late Super. The FFG had layout drawings, anyone have an online resource for those?

The easy steps are A) Make your Super function as-is, stock. Take inventory of the differences between the early circuit and the late circuit. The next step ("B") would be to look at the early layout and make it so. If you wanted to be anal about it you could track down the early blue caps. Everyone uses cloth wire when they go retro.

Another resource you might want to check out would be the FDP.

http://www.fenderforum.com/forum.html

Those guys like to go over the same material again and again so you'll find a dozen or so members at any given time who will happily walk you through this step ty step or direct you to archived posts about the conversion.

[FUCHSAUDIO]

In response to FUCHSAUDIO Andy's post:

B+ is 500V with that PT

http://www.schematicheaven.com/fenderam ... tr_rev.pdf

The screens will be at about 500V as well. I would not recommend doing that since 6L6 is rated for 450v max screen voltage. I suppose he could drop some B+ for the screens using a voltage divider and big ass resistors but that is a bit more tricky.

The UL output transformer's impedance is a bit higher than the normal OT.

I'd just use the UL config or put new transformers in. Mojotone has nice ones too.

Jelle

Jelle: The B+ won't be that much different (not really any more worse than stock), by adding a choke, and getting rid of the UL hookup. I would go for larger screen resistors (680 or 1-K) instead of 470's for sure. Adding a large wattage dropping resistor and a cap for just the screens couldn't hurt.

I agree, a "better" output could be installed, should the customer want to invest the time and money. It sounds like he's technically a little limited, so take it easy on him....

I agree with Casey Jones, that it makes sense to talk to the Fender "gearheads" who have done this stuff regularly. They could certainly talk you through it, and likely know the pros and cons of each specific mod you're considering.

[M Fowler]

You can also check out this website for kits or parts. My SF Super Reverb was done with the Texan mod.


www.torresengineering.com

Mark

[FUCHSAUDIO]

I think the OP should approach anything Torres with caution.

[Tubetwang]

i ordered Fender printed mods from Torres, when i started this tube amp building hobby 8 years ago.

The photocopies they sent me were so bad, i could hardly read the text...

Major Twang

[mike9]

Thanks for all the input - I troubleshoot and repair/rebuild/maintain a variety of equipment at work from high voltage lighting distro to high temp kilns, etc. I'm getting a little old for some of this and want to move to smaller scale work like amps. I do simple repairs on amps now and I build guitars so I figure why not learn to build my own amps?

I agree, a "better" output could be installed, should the customer want to invest the time and money. It sounds like he's technically a little limited, so take it easy on him.... .

Somewhat - amp stuff is smaller scale than what I'm used to, but the diagnostic principals should be similar - nice lead dress.

[img:800:600]http://www.deanguitars.tv/userpics/lib9/kiln1.JPG[/img]

2300 degrees inside - cooks a pizza in . . . no time.

[img:800:600]http://www.deanguitars.tv/userpics/lib9/kiln2.JPG[/img]

Now this is old school - I rebuilt the power system and retrofit a computer controller to it. I was told it couldn't be done - works like a champ.

[img:800:600]http://www.deanguitars.tv/userpics/lib9/kiln3.JPG[/img]

[mike9]

double post