$1 AMP find

[adamamp]

Originally posted by Eli Duttman


I agree. Still, that trafo isolates the amp from whatever is driving it. That's good for both safety and ground loop control.

In addition to the polarized plug, a wiring tweak in the voltage doubler B+ supply can increase safety. A full wave doubler connects 1 leg of the AC being rectified to the center of the filter cap. stack. Make that leg the "hot" side of the AC mains. That way, both the signal ground and B+ in the unit are associated with the "neutral" leg of the AC mains.

Thanks again Eli for all your input.

Yes keeping the input isolation transformer is a must with this amps ACDC power supply. Also great input on the voltage doubler. Have several possibilities here in my old(1953) RIAA manual. I am sure your suggestion was noted for the best alturnitive.
Now that AC is polarized at the wall I was thinking about deleting the need for a B+ trafo and the cost associated. This way you could focus the major cost where it should be IMO, the sound trafo. The A & C voltage being cheap due to their low potentail. IYO Eli or anyone FTM, could such power supply if designed just right ever pass UL or CEA?

[adamamp]

Originally posted by dougv
Adamamp, my dad will have no problem reading and following the schematic. I only see him on the weekends since he lives over an hour away so there is no hurry. If it ends up being a very involved or risky project the amp will goto ebay, but if it can end up like a champ clone that would be worth it. And again no hurry this would just be a weekend project doing alittle at time.

Real cool with your Dad!
Check this out,
http://www.geocities.co.jp/HeartLand...radio/100f.jpg

Site owners addy is,
http://www.rrsignal.com/railroad/
ask him about schematics

Why? because look here,
http://www.rrsignal.com/railroad/ctc/niagara.htm

and thank!
[] Layberinthius []
if you see him here.

Maybe we could fix it, then sell it and buy you a real Champ
Your Dad know anything about striping the un-stock paint?

[Eli Duttman]

IYO Eli or anyone FTM, could such power supply if designed just right ever pass UL or CEA?

I suppose a voltage doubler directly connected to the mains could be made legal under today's code. The I/P signal isolation trafo would be necessary and you would have to double insulate EVERYTHING except the I/P jack. Everything exposed, except for the jack, would have to be plastic. Nylon bolts and nuts would be required and you would have to use plastic shaft extensions on the "buried" controls.

BTW, that old WE amp is AC only. An AC/DC unit has only a simple half wave rectifier in it. FWIW, it's well within my adult lifetime that parts of NYC's Greenwich Village were still being serviced by Tom Edison's DC generators.

[Eli Duttman]

If part of the rebuild of the amp includes the addition of a 6.3 VAC filament trafo, you have options to chose from. If you insist on tube rectified B+, change the 25Z6 to a 117Z6; that way you will not need to allow for rectifier heater power in the filament trafo. OTOH, if you SS rectify the B+ with 2X UF4007s, you gain a socket for another signal tube, say a 2nd 6SL7. With SS B+ rectification, be sure to put a NTC thermistor in the line connecting the mains "hot" lead to the doubler stack. The NTC device will protect the SS diodes from an inrush surge at turn on and slow the B+ rise a little too. Peak surge limiting into SS diodes directly connected to the AC mains is necessary. I learned that lesson the hard way as a youngster.

Consider adding a 1.5 H. choke and additional capacitance after the doubler stack, as you squash ripple and increase energy storage.

[dougv]

"Site owners addy is,
http://www.rrsignal.com/railroad/
ask him about schematics"

NO schematic, but he said it should be able to use the signal right from the pickups.

[adamamp]

Originally posted by Eli Duttman


I suppose a voltage doubler directly connected to the mains could be made legal under today's code. The I/P signal isolation trafo would be necessary and you would have to double insulate EVERYTHING except the I/P jack. Everything exposed, except for the jack, would have to be plastic. Nylon bolts and nuts would be required and you would have to use plastic shaft extensions on the "buried" controls.

Wow thanks EliSounds like the old adage"The more things change, the more they stay the same

[adamamp]

Originally posted by Eli Duttman
BTW, that old WE amp is AC only. An AC/DC unit has only a simple half wave rectifier in it. FWIW, it's well within my adult lifetime that parts of NYC's Greenwich Village were still being serviced by Tom Edison's DC generators.

If part of the rebuild of the amp includes the addition of a 6.3 VAC filament trafo, you have options to chose from. If you insist on tube rectified B+, change the 25Z6 to a 117Z6; that way you will not need to allow for rectifier heater power in the filament trafo. OTOH, if you SS rectify the B+ with 2X UF4007s, you gain a socket for another signal tube, say a 2nd 6SL7. With SS B+ rectification, be sure to put a NTC thermistor in the line connecting the mains "hot" lead to the doubler stack. The NTC device will protect the SS diodes from an inrush surge at turn on and slow the B+ rise a little too. Peak surge limiting into SS diodes directly connected to the AC mains is necessary. I learned that lesson the hard way as a youngster.Consider adding a 1.5 H. choke and additional capacitance after the doubler stack, as you squash ripple and increase energy storage.

Ahh silly me, as if the voltage doubler would work from DC. It does however say sometheing on the back lable about DC current drain? Wow, you remember Tom Edison's DC generators, thank goodness for Tesla and the AC generator!

Good stuff also! Don't know at this point what might be best for Doug. Maybe getting it stock and selling it so he can buy a real guitar amp might be best for him. I do not mind SS recs. I use 5408s in my amps unless someone asks for tube rec. Then I have a box full of 5U4s, mostly made in the good old USA
That thermister is one of a few things I am hoping I can use to fly through CEA, UL and CSA in my new amp line. As you know in rush current is a concern with Cap/R/Cap pie filters. I assume NTC is the brand?

I love using chokes but cost factors force me to use resistors
So Eli, are you happily retired/rich/employed? Would you consider the option of design consultant with a new multinational corp?
I have a number of intersted parties in many different countries. They are all pros at what they do, HTML, Web hosting, Tolex, Marketing, Recording etc. I am looking for one real good ET. I am just a guitar player that has done repairs on everything from Eico amps to my beer fridge My uncle, who used to guide me in my design work, has come down with a brain disorder related to his old age. A real bummer to see such a great man go that way.
He helped design sonar, was a design consultant for Sherwood and Eico. He also imported the first Sansui SW/AM reciever to North America before starting his own corp. You may have heard of him, Jack Rockwell.
Anyhow, I need someone to go over my latest designs before I submit them for UL. You have been most helpful to myself and others here and have more than demonstated your ability so I thought I might ask if you are at all interested.

[adamamp]

Originally posted by dougv
"Site owners addy is,
http://www.rrsignal.com/railroad/
ask him about schematics"

NO schematic, but he said it should be able to use the signal right from the pickups.

Well we really need a schematic if we are to get it working stock or mod it a bit. The signal right from the pickups would work in the stock unit but the tone may not be what you need and I doubt there would be enough gain for full output power. Any luck testing the tubes?

[Eli Duttman]

I assume NTC is the brand?

No sir, NTC = Negative Temperature Coefficient. The part's resistance drops as its temperature rises. You size the part so the voltage drop under operating conditions is close to zero. When the part is cold (start up time), the voltage drop is considerable. Mouser and Allied both carry the Thermometrics brand of NTC parts.

So Eli, are you happily retired/rich/employed?

No such luck! I'm an unemployed IBM mainframe system programmer. IT has been HARD HIT since the WWW bubble burst.

Would you consider the option of design consultant with a new multinational corp?

I don't know if I am qualified. Electronics has been a life long hobby with me. I'm 59; I built a Galena crystal radio at age 8. My formal educational background is in Chemistry, not EE.

BTW, Tom Edison's DC generators were in service until the 1970s, in "the village".

IMO, there is no substantial value to that WE amp. To heck with its schematic. Use the chassis, the I/P trafo, and the enclosure to make a decent guitar amp. There are 3 Octal sockets available. 2 6SL7s will provide plenty of gain and a tone stack. A 6V6 (EH current production) will be the final. Mount the 6.3 VAC filament trafo in the space currently occupied by the series heater string dropping resistor. If push comes to shove, a 6 VAC "wall wart" could provide the heater power. Use SS diodes in the voltage doubler. B+ will rise courtesy of the lower forward voltage drop. You can use large value capacitors in the doubler stack, which will improve performance. A RC filter following the doubler stack is quite feasable with SS rectification. A 300 V. B+ rail should be easy. Remember the peak surge limiter; leave it out and even high amperage diodes could fry, as you are directly connected to the AC mains. Recycling the speaker and O/P trafo in the unit is a possibility.

[adamamp]

Originally posted by Eli Duttman


No sir, NTC = Negative Temperature Coefficient. The part's resistance drops as its temperature rises. You size the part so the voltage drop under operating conditions is close to zero. When the part is cold (start up time), the voltage drop is considerable. Mouser and Allied both carry the Thermometrics brand of NTC parts.

Thanks for that! I first came across one in a toaster oven Now I see them in the new Fender amps approved for Canadian export

No such luck! I'm an unemployed IBM mainframe system programmer. IT has been HARD HIT since the WWW bubble burst.

Sorry for the luck SO FAR, but good things happen to those worthy of merit

I don't know if I am qualified.

Yes you do have a sense of humor I have partners so far in the states of MA, IL, and FLA but NY would be real cool as well! Our amps will be using tubes for the signal path and SS only in the power supply & relay drivers. I have several openings yet to be filled and would be honored if you would consider being any part of it. Seeing how you did not say no I assume you mean at least maybe Building guitar amps ain't rocket science but the market potentail is almost unlimited. I am gearing up for some large loans to go into full production. UL ain't to bad as long as you do not get turned down the first time. I have faith that anything you are not sure of that you would know how to find out

BTW, Tom Edison's DC generators were in service until the 1970s, in "the village".

Cool I bet they had a glow all to their own!

IMO, there is no substantial value to that WE amp. To heck with its schematic. Use the chassis, the I/P trafo, and the enclosure to make a decent guitar amp. There are 3 Octal sockets available. 2 6SL7s will provide plenty of gain and a tone stack. A 6V6 (EH current production) will be the final. Mount the 6.3 VAC filament trafo in the space currently occupied by the series heater string dropping resistor. If push comes to shove, a 6 VAC "wall wart" could provide the heater power. Use SS diodes in the voltage doubler. B+ will rise courtesy of the lower forward voltage drop. You can use large value capacitors in the doubler stack, which will improve performance. A RC filter following the doubler stack is quite feasable with SS rectification. A 300 V. B+ rail should be easy. Remember the peak surge limiter; leave it out and even high amperage diodes could fry, as you are directly connected to the AC mains. Recycling the speaker and O/P trafo in the unit is a possibility.

Yes I would totally agree(except recycling the speaker unless adding an ext. spk. jack) and would not need a schematic myself especially if we were to scrap it for the chassis etc. It is up to Doug though and if he wants to keep it stock I feel a schematic would be the best way I could help him over the NET.

BTW, Does a MOV(or a network of MOVs) work very well to suppress line surges? Would one be good to use in addition to the thermister?
Thanks again Eli, you're the man in my books. Speaking of books have you ever seen a publication called "The Dope From Hope" All of Paul Klipsh's design and MOD notes, what a find that was