Franchesca Schematic

Trainwreck schematics, designs, pictures. Only members may post files here.

Moderators: pompeiisneaks, Colossal

User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Franchesca Schematic

Post by UR12 »

Here is a copy of the Kelly 90 schematic that I changed to match Franchesca. If your building an Express and want it to match the Franchesca pics this is what you need to use. If anyone sees any corrections needed just let me know.

[img:1625:1260]http://users.zoominternet.net/~jdhall/a ... evised.JPG[/img]
User avatar
rockstah
Posts: 197
Joined: Fri May 19, 2006 4:37 am
Location: Austin Texas
Contact:

Re: Franchesca Schematic

Post by rockstah »

Thanks UR12!
User avatar
Allynmey
Site Admin
Posts: 1406
Joined: Sun Mar 06, 2005 12:38 am
Location: Dighton, MA

Re: Franchesca Schematic

Post by Allynmey »

That is right on to Francesca as we saw it!

Allyn
Luke Duke
Posts: 22
Joined: Mon Oct 02, 2006 4:52 pm
Location: Arkansas
Contact:

Re: Franchesca Schematic

Post by Luke Duke »

NICE!

Thanks man!
User avatar
stoo
Posts: 156
Joined: Thu May 25, 2006 3:46 pm

Re: Franchesca Schematic

Post by stoo »

Is the shield of the i/p cable connected to the plate instead of ground?
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: Franchesca Schematic

Post by UR12 »

stoo wrote:Is the shield of the i/p cable connected to the plate instead of ground?
Good point!!!! The shield on Franchesca is grounded at the input jack. I'll change the schematic. (Thanks!) The shield does go to b+ on the Liverpool but not the Express.


update

Schematic changed!! Thanks again! Stoo
User avatar
stoo
Posts: 156
Joined: Thu May 25, 2006 3:46 pm

Re: Franchesca Schematic

Post by stoo »

You're very welcome. One more thing..those two 100K 3watt resistors in seies in the power supply....I think there was once two caps in series with a resistor across each one to balance the drop across each one. So couldn't a single resistor suffice now?
Stoo
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: Franchesca Schematic

Post by UR12 »

stoo wrote:You're very welcome. One more thing..those two 100K 3watt resistors in seies in the power supply....I think there was once two caps in series with a resistor across each one to balance the drop across each one. So couldn't a single resistor suffice now?
Stoo
Actually Franchesca doesn't use the two series caps in the power supply. It runs two 40uf caps wired in parallel for a total of 80uf. The two 100k resistors are actually bleeder resistors that bleed off the high voltage to ground after you turn the amp off.
User avatar
skyboltone
Posts: 2287
Joined: Wed May 10, 2006 7:02 pm
Location: Sparks, NV, where nowhere looks like home.

Re: Franchesca Schematic

Post by skyboltone »

Hi Dana, I'm pretty new to the express lanes here. What are the diodes at the output plates for? Do they affect tone?

Thanks in advance

Dan
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: Franchesca Schematic

Post by UR12 »

The diodes and the MOV are both used to protect the amp from Transient Spikes. Basically, Ken included these mods in his "Trainwreck pages" and he used them both in all of his Express amps. (I guess he didn't think the lowly EL84 was important enough to protect) If you were to get some high level spikes on you AC power line, this would also be passed through your power tranny and into your amp. The diodes protect mainly your tubes from being hit with these spikes and taking out your tubes. When you think about it most power in clubs and other venues have a lot of equipment connected to it that produces noise on a power line. Most older light dimmers are horrible and produce a lot of noise that sounds like a buzzing sound coming through your PA or amp. While these aren't considered Transient Spikes, I bring it up just as an example of how nasty with noise and spikes your AC power can be. Other things that produce spikes are light switches and and motors. They have nothing to do with tone.


Will the amp run without them? Yes It's just cheap insurance that you will probably never be needed but, if that 50 cents worth of diodes saves you one high dollar NOS EL34 being shorted out because of transient spikes then you come out ahead.
kyoungsteadt
Posts: 13
Joined: Tue Apr 17, 2007 8:27 pm

Re: Franchesca Schematic

Post by kyoungsteadt »

Thanks UR12.
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: Franchesca Schematic

Post by UR12 »

Seems a lot of people are confused regarding the varistor. I have redrawn the power switch to show it as being DPST and added the 130v varistor. Hope that helps.
guitbanger
Posts: 2
Joined: Wed Nov 21, 2007 4:20 am

transient spikes

Post by guitbanger »

MOV on the AC are to protect transients on the AC. The diodes on the tubes are to protect from transient spikes due to the inductance collapsing on the output tranny, usually occurs at high power output and hard attack I believe.
Rick
Posts: 151
Joined: Sat Mar 24, 2007 11:46 pm

Re: transient spikes

Post by Rick »

guitbanger wrote:MOV on the AC are to protect transients on the AC. The diodes on the tubes are to protect from transient spikes due to the inductance collapsing on the output tranny, usually occurs at high power output and hard attack I believe.
This makes sense as to the diode usage. What would cause such a collapse? A broken voice coil? Blown preamp tube? Inadvertent speaker cable removal? Staccato? Abrupt drop of input signal? Open in speaker wiring? All of the above?
User avatar
skyboltone
Posts: 2287
Joined: Wed May 10, 2006 7:02 pm
Location: Sparks, NV, where nowhere looks like home.

Re: transient spikes

Post by skyboltone »

guitbanger wrote:MOV on the AC are to protect transients on the AC. The diodes on the tubes are to protect from transient spikes due to the inductance collapsing on the output tranny, usually occurs at high power output and hard attack I believe.
I left them both out. Just a rebel I guess.
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Post Reply