Sheldon Amps TrueTone schematics/info?

[tubeswell]

I have acquired a 'blank'* Sheldon Amps TrueTone head chassis with front and back panel markings (in white) screened onto a blue background. I am curious to know what amp this comes from (if anyone can help with this please?).

The control panel markings are Input, Vol, Compass, High, Middle, Low, Special Sauce, Freeze, Master and some on-off/stdby switch holes and a lamp hole, and the back panel has holes for a Mains voltage selector, mains and HT fuses, Triode/pentode (switch?), Impedance selector, 2 x speaker jack holes and Bias TPs and "Range" and (Hum?)"Balance" TPs and a footswitch jack hole.

On top, there are holes for what looks like 4 x octal and 3 x noval sockets as well as PT and OT mounting holes for upright (X mount) xformers.

Anyone got any idea what True Tone head chassis this comes from? and where I might get a schematic or some info on it please?

* there is no serial # stamped on the back panel (altho' there is evidently a space for such when the time comes)

TIA

[tubeswell]

Happy ending to this story. I emailed Mark @ Sheldon amps and he sent me the schematic for TT1 as well as layout drawings, gut shots and TF specs.

[Willabe]

That was nice of him. Glad you got what you needed.

I've got to say I was in N.Z. once for a week, people were great, so was the country/island. I'd love to go back some day.


         Brad            

[tubeswell]

Well if you do get back, then feel free to look me up. I will show you my collection of home-brew amps (including the planned TT1 clone if I still have it)

[Willabe]

Thanks tubeswell, I'll do just that if I ever get back down under again. Like I said, great people in N.Z. If I had'nt had seen it with my own eyes, how beautiful your nation/land is, those green, (the greenest grass you'ld ever what to see) rolling hills dotted with sheep, the beautiful lakes and rivers (with world class fishing no less) and Mts. and got the chance to experence the earthy, warm and friendly personality of your people, I never would have belived it, but I'm not sayin anything you don't, your a lucky man. Yeah, I'm butter'in your bread on both sides, but what I say is true, IMO anyway. Being there was absolutly one of the best times in my life. I had the best lamb I've ever had in my life in N.Z. loved it! It was better than steak by far IMHO. If the US goes belly up, and it's not lookin good sad to say, it's gonna be Kiwi's and Ozzi's, for my wife and I, the Apple Isle/Tasz. is wonderful too.    

I still hope to go back down someday, promised my wife if we ever get a chance I would take her there, and she realy wants to see it for herself too. Wont be till the kids leave leave the nest, only 3 more years (or so ).
  
I'd love to see your builds up close and hear them too, heck we'll have to do some playin. I'm sure Kiwi's get the blues too.        Hard to take the blues out of a Chicago boy, even after a good days fishin with Kiwi friends and he's got a belly full of N.Z. lamb, fresh trout/salmon and a pint or two of the local beer or ale! Still gonna play and sing the blues, at least a little.        



         Brad        

[tubeswell]

Well then, when you do show up, make sure its on a blues club jam night - last Thursday of each month at The Bristol in Cuba St. That's usually when my amps get a good workout these days

[Willabe]

Well alright then, a blues club, with a jam night? I should have known.       You know I'm not gonna miss that if I go that far from home, hangin with "blues cats" in N.Z. no, noway I'm missin that.   Gotta get those kids out of the nest. The blues clubs are dyin off in Chgo. Glad some ones still keepin the torch burnin.   

Like I said great people in N.Z.


         Brad      

[shane]

Hi Tubeswell
Lemme know if you get stuck with the TT1. I'll see if I can help. I actually designed it!
There were two versions, a hot and a cool version. one had a little more gain than a plexi and the other was more hot 2204 type gain territory.

I may be a bit vague as it was several years ago and I aint seen a schematic for a while!
Cheers
Shane

[tubeswell]

Thanks Shane

I think I have deciphered the (low-res) schematic that Mark sent me (although the component values were hard to read on the pic I got).  Can I say it was pretty much as I had expected, except the 1st tone stack (between V1a and v1b) seems a bit odd. Did you intend to have a couple of smallish caps with a mixing pot as a vol control bypass? (or was that only a prototype drawing? - only I wondered about the actual effectiveness of that). I'm curious to know what you ended up doing in the end on that

Otherwise I can see that I will possibly go with Merlin's variation of the James tone stack (that has the mid scoop-shift control) for the 2nd tone stack (instead of the version I saw on the schematic Mark sent me).

Also the version that mark sent me had what look like a couple of PNP for the tone stack raw/lift switching circuit, but when I worked through this with a buddy of mine we decided that they probably should've been NPN transistors they way they are shown to be wired in on the schematic, because with a grounded emitter, NPN transistors work on positive supplies, while PNP uses a negative rail. (I think I have that right? I'm only a beginner on SS stuff). Also the zener used to clamp the bias supply for the transistors is probably a 12V 1/2W zener, and I guess that the value of the little supply resistor in the bias filter is 1k - Does that sound about right to you (for supplying the current to the zener?)?

Lastly - I gather that the LEDs which have a supply that is bridge-rectified from the heater winding, are only there as pretty lights?

TIA

Cheers

Pete

[shane]

Hi Pete

That 1st tone stack was called compass. and I think was a sort of selectable bright function come pre tone control I'll see if I can dig up a schematic to remind myself of how it worked! I may have an express pcb file of it somewhere.

Merlins james stack with shift control works very well I've used it with the tone stack values used on the sheldon with a 470K pot for the shift and its very good probably more use than the standard mid control  on the Sheldon.

The transistors should be NPN something like 2n3904. MPSA02 or similar you could equally use ldr's. And your right i think about the zener though we used 3W. Though before I left I had planned to run that stuff from the heaters rather than the bias tap.
And yes the LED's powered from the heaters were just pretty lights!

Which version he sent you I dont know. The cool one had a normal gain stage with a 220K anode load and 2k7//.68 cathode into a 22nF cap in series with 220K res compass control and 1M gain pot followed by another gain stage with 220K anode and 1k5//.68 cathode. Tone stack then PI

The hot version used a cascode 1st stage into same second stage as cool version but then a CF into the tone stack. This was the one I used personally. With hind sight I'd tame the cascode a bit!

Output tubes were 4X 6V6 as standard but you could use any octals I liked two KT88'S in mine.Though the four 6V6 output stage has always been one of my favorites!
If you get stuck I'll see if I can draw up a schem from memory!

Cheers
Shane

[tubeswell]

Thanks Shane. I drew up a schematic based on what Mark gave me, but the 'compass' control sounds different to what you described. Can I PM you for your email addy?

Cheers

Pete