New 3rd gen build

[sergio]

Hi ,It's a really good cab , I like that cover also!! beautiful color!

Have you not thought to a Vox Brown grillcloth?

Bye Sergio

[stelligan]

Cool looking build. Very well done logo as well. All this suede around here is really growing on me. Look forward to following this one.

[sonicmojo]

I do like the brown cloth and I also really like the even rarer blue cloth. But after polling a few family members on their opinions, I decided on the black which was also a little easier (and cheaper) to actually find. Maybe next one....

[sonicmojo]

Here's a little more progress. It's time to motor through to the fire up....
Boards completed
[img982]http://www.sonicmojo.com/3rdgen/buildpr ... oards2.JPG[/img]
Pots, grommets, stackpoles, and ground lugs added to chassis
[img730]http://www.sonicmojo.com/3rdgen/buildpr ... assis1.JPG[/img]
Inputs wired and tested
[img956]http://www.sonicmojo.com/3rdgen/buildpr ... nputs1.JPG[/img]
[img742]http://www.sonicmojo.com/3rdgen/buildpr ... nputs2.JPG[/img]
Ready to wire in the transformers
[img683]http://www.sonicmojo.com/3rdgen/buildpr ... oards1.JPG[/img]
[img815]http://www.sonicmojo.com/3rdgen/buildpr ... oards1.JPG[/img]

[dcribbs1412]

Looks great sonicmojo


Darin

[sonicmojo]

Looks great sonicmojo

Thanks Darin! I am in the home stretch now. I've been wiring in the last board tonight and I've got my newly built current limiter at the ready. Along the way I tested the input power and confirmed my old school Radio Shack relay is working. Now to just power through the final connections and get testing.

[img545]http://www.sonicmojo.com/3rdgen/buildpr ... tthere.JPG[/img]
[img1063]http://www.sonicmojo.com/3rdgen/buildpr ... imiter.JPG[/img]

[David Root]

Sergio, +1 on the brown Vox cloth! Looks great with smooth blonde Tolex.

[sergio]

Thanks David! , I like a lot the brown tolex , seems to me more vintage style.
I think to build a #124 on brown , #102 blond and #183 in black cab.

[sonicmojo]

It works! Mostly.....

I've got everything working except the FET input and/or FET board. I hear a loud click when plugging in the cord but no sound.

I need some help debugging this area since I am a little hazy on the FET circuit. With no guitar cord plugged in, I've got about 280V coming into the board and my reading at the 10k/150k junction is around 20V which I've read is where it should typically be. When I plug in a cord, the value jumps to about 55V. I doubt this should behave like this but maybe someone can shed some light.

Any thoughts on how I can further troubleshoot the FET are appreciated.

Thanks,

Bryan

[img590]http://www.sonicmojo.com/3rdgen/buildpr ... rking1.JPG[/img]

[ToneMerc]

With no guitar cord plugged in, I've got about 280V coming into the board and my reading at the 10k/150k junction is around 20V which I've read is where it should typically be. When I plug in a cord, the value jumps to about 55V.

What type of jack did you use for the FET input? With 55v there you have most likely killed the FET too.

TM

[sonicmojo]

What type of jack did you use for the FET input? With 55v there you have most likely killed the FET too.
TM

You're probably right about the FET. I've got a couple others but I want to sort out my issue before trying one. For now I've removed the transistor. I'm using a Switchcraft 3 conductor for the FET and a 2 conductor for the NOR. I wired like the layout and triple checked things. It looks messy now since I was messing around with the jack but I tried to clarify my wires. I probably do still have some sort of bad wire loop happening.

http://www.switchcraft.com/Drawings/14b_cd.pdf

[img:968:1296]http://www.sonicmojo.com/3rdgen/buildpr ... etjack.JPG[/img]

[ToneMerc]

Wiring scheme

[sonicmojo]

Thanks for the diagram. It looks like I have the Switchcraft 14B and have things wired that way. Just to confirm, the FET Out on the diagram feeds to the 10k trimmer, right?

UPDATE: I think I see my jack wiring problem. Tearing down all the inputs and starting over clean......

UPDATE#2: After rewiring my jacks according to the diagram, I got it working with a different FET board that I had. It's back to the drawing board to figure out the problem with my 3rd gen style FET board but I plan to plop it back in eventually once I sort it out. I was still getting high voltages and probably had fried my FET.

Thanks again TM for pointing me down this path.

[Structo]

That diagram is kind of confusing to me.

What I did was just follow the #102 layout which shows the 14b FET jack and the Normal 12a jack.

Look at the connections carefully, especially the short little jumper on the FET jack on the right side.

I put both the 14b and 12a jacks in a piece of cardboard with the holes the same as the chassis and wired them up as much as I could then installed them into the chassis, then connected the FET and normal shielded cables.

[sonicmojo]

+1 on Tom's 102 wiring suggestion for the Switchcrafts. I was close but now have the proper grounding on the FET input when unplugged. It all makes sense to me now now so next time it will be easier. Everything is looking good now. Plate voltages were right in range and biasing was no problem. It's got new tubes in it and the PI trimmer was easy to get where I wanted it. Now to play and burn it in!

[img:767:1216]http://www.sonicmojo.com/3rdgen/buildpr ... ished2.JPG[/img]
[img606]http://www.sonicmojo.com/3rdgen/buildpr ... ished3.JPG[/img]
I'm particularly fond of my cool looking relay. It's replaceable from the outside.
[img879]http://www.sonicmojo.com/3rdgen/buildpr ... utside.JPG[/img]