Silvertone 4710 to Magnatone 410

[johnnyreece]

No problem! For those interested, here's a link with some more info on the 210/410: http://www.magnatoneamps.com/schematics ... e_210+.pdf

[dano-rator]

John, awesome job! I'd love to see some pics and maybe even hear a clip if you're up to it and able. Did you end up using the 12DW7 or 6V6 that came with the chassis? Also, you're using the varistors that were in there correct?

Too bad the chassis didn't work out, but it was pretty tight in there.

Dan

-edit- oh, and I finally got around to opening the bench, and inside I found some documentation, including the original service data and parts list which includes the schematic... If you're interested. It lists the varistors, but says only "special, no substitute".

[johnnyreece]

John, awesome job! I'd love to see some pics and maybe even hear a clip if you're up to it and able. Did you end up using the 12DW7 or 6V6 that came with the chassis? Also, you're using the varistors that were in there correct?

Too bad the chassis didn't work out, but it was pretty tight in there.

Dan

Yeah, using both tubes. I need to get a couple more 12DW7's soon, as I've not idea how much life is left in this one. Honestly, if I could have stripped it without breaking anything, I think it would have been great (even if a little tight). My build has some pretty long runs because the chassis is so much bigger. Yes on the varistors as well. This is a perfect little source of components, and if one wanted to reuse as many parts as they could, this would be a very inexpensive alternative to buying the parts to build a Maggie.

Photos will be incoming, as soon as I get the gumption to do it.

[dano-rator]

Sounds like you've got a winner! Glad it worked out. Oh, and see my edit above about the schematic, I must've been posting the same time as you.

Dan

[johnnyreece]

That would be awesome! The schematic online I was able to find leaves a lot to be desired. If I could see the original, I could more accurately know what I was screwing up to begin with!

[johnnyreece]

Okay, here are the nuts-and-bolts:

A node: 369
B node: 340
C node: 284

6V6 info:
Plate to cathode voltage: 322
Screen: 284
Cathode: 16.8
Cathode resistor: 355.5 ohm

That calculates to 14 watts...no bueno! May adjust the cathode resistor at some point.

12DW7 info:
Pin 1: 275
Pin 6: Fluctuates?

12AX7 info:

Pin 1: 159
Pin 6: 103

And, here are the promised photos...don't poke too much fun

[IMG768]http://i218.photobucket.com/albums/cc165/moto_xxx199/Amp%20designs/837CD770-7A99-463D-9EA4-B23363898390_zps3uzotxsy.jpg[/img]

[IMG768]http://i218.photobucket.com/albums/cc165/moto_xxx199/Amp%20designs/EDD6B848-EA9D-4788-8356-258A50A685A4_zps45rpnkia.jpg[/img]

[IMG768]http://i218.photobucket.com/albums/cc165/moto_xxx199/Amp%20designs/2C9EBA49-3B99-4C26-BA46-3D8B898EED5B_zpsdku8g1wm.jpg[/img]

[IMG768]http://i218.photobucket.com/albums/cc165/moto_xxx199/Amp%20designs/4AA47F9E-37A0-4DFE-B6D2-891B4F24E5D7_zps5lj5grwg.jpg[/img]

And, some of you may notice I drilled a hole in the back for apparently no good reason...I eventually plan to put a NFB switch in. However, it's a little tricky, since it will involve reversing the polarity of the cap. What I've decided instead is to just use a DPDT switch and a second cap. Anyone see any problems with this idea (other than the crudeness of the drawing)?

[IMG:768:1024]http://i218.photobucket.com/albums/cc165/moto_xxx199/Amp%20designs/4252213E-C1A4-4FAD-B845-97A89054CDFB_zpshcusa3wo.jpg[/img]

[andyfromdenver]

JR,
We have pretty much identical voltages.
I can tell I'm pushing this oldie 6v6 to it's absolute limit.
I was feeling cavalier and went to clip in a 10mfd parallel at the 4.7k and 22k junction to lower the AC hum a bit and damaged the 10mfd in the cap can... Sigh...will have to replace it, but I unhooked it and soldered in another elytic.

I think your amp looks cool in that chassis, way to go!
I've been rocking out on mine for a while, it has such a raw vintage overdrive. Very different from a fender.

[dano-rator]

Heres the original schematic that came with the Silvertone organ amp this evolved out of.
Ugh, sorry looks like the or the parts list is sideway.
Dan

[johnnyreece]

Wow! That's fantastic! I didn't think it'd be in such good shape! Interesting how they do the same kind of stuff, but a little differently.

[johnnyreece]

Update - I've upped Rk to 470. I'm now at 13.28w (assuming 5% screen current). The data sheet for the tube I'm using lists a max of 14w, so I'm at about 95%, which is close enough for me. I think I'm going to call it done for now. I"m waiting for some new 12DW7 tubes to come in. I'm hopeful that a new one will liven the vibrato up a little. It's by no means terrible, but I expected it to be a little deeper. I suppose we'll see...if that doesn't do it, maybe I'll experiment with LED bias for the LFO.

Also, as there doesn't seem to be a ridiculous amount of interest, I probably won't update my layout, as I'm already on to the next project. If anyone wants me to, feel free to send a PM, but I think most folks here could get what they need from the original (mostly correct) layout.