5e3 problems

Fender Amp Discussion

Moderators: pompeiisneaks, Colossal

stretch2011
Posts: 501
Joined: Tue Oct 21, 2014 2:53 am
Location: ohio
Contact:

Re: 5e3 problems

Post by stretch2011 »

You know I put the standby there in place of the ground switch hole. I got the chassis off ebay from china. I have been overlooking that. I kept thinking what the hell is pdf talking about! Then I looked!

yes Ballz that is closer.

Ill take some voltages tomorrow. Heres the guts.

Im thinking it could be the 65 DR PT I have in it. Since the voltages on the DR schematic are about the same on my power tubes.
You do not have the required permissions to view the files attached to this post.
frankdrebin
Posts: 131
Joined: Wed May 14, 2014 11:40 am

Re: 5e3 problems

Post by frankdrebin »

i don't see any resistor between plate and screen filter caps,are you using a choke?
pdf64
Posts: 2932
Joined: Sat Mar 12, 2011 9:23 pm
Location: Staffordshire, UK
Contact:

Re: 5e3 problems

Post by pdf64 »

frankdrebin wrote:i don't see any resistor between plate and screen filter caps,are you using a choke?
The 2 black wires between the reservoir and screen grid nodes, that go out outside the chassis, together with the high screen grid voltage (and likely high plate dissipation), suggest so.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!
stretch2011
Posts: 501
Joined: Tue Oct 21, 2014 2:53 am
Location: ohio
Contact:

Re: 5e3 problems

Post by stretch2011 »

Yes I am using a choke.
pdf64
Posts: 2932
Joined: Sat Mar 12, 2011 9:23 pm
Location: Staffordshire, UK
Contact:

Re: 5e3 problems

Post by pdf64 »

I think the amp may better be described as a 5E3 pre-amp, with a power amp and supply of your own devising.
My guess is that the 6V6 plates are rather above their dissipation limit; a voltage survey / chart would help to confirm that.
A screen grid node B+ dropper with more resistance, eg 4k7, may help to get the screen grid voltages down a bit, but that cooler operating condition may result in the plate voltage rising even higher.
Given the PT used (DRRI type), it may be that the amp is better suited to fixed bias (see 6G3 http://bmamps.com/Schematics/fender/del ... _schem.pdf ) or even 6L6 type tubes?

Thanks for the photos; the wires from the 68k input resistors to the V1 grids looks to be a screened type, but the screening might not be connected to anything. It may be worth checking that to see if it helps with the volume drop out issue.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!
Post Reply