FDP Home Page / FDP Forum / FAQ's

The FDP is made possible by the following companies and individual members like you.
Please use the links below to show them we value their sponsorship.

Yellowjackets Tube Converters

Musician's Friend

Amplified Parts

MOD KITS DIY

Apex Tube Matching

Antique Electronics Supply

Amazon

Guitar Center

WD Music

Jensen Loudspeakers

Sweetwater


* God bless America and our men and women in uniform *

* Illegitimi non carborundum! *

If you benefit and learn from the FDP and enjoy our site, please help support us and become a Contributing Member or make a Donation today! The FDP counts on YOU to help keep the site going with an annual contribution. It's quick and easy with PayPal. Please do it TODAY!

Chris Greene, Host & Founder

LOST YOUR PASSWORD?

......................................................................

   
FDP Jam
Calendar
Find musicians
in your area!
  Search the Forums  

FDP Forum / Fender Amps: Vintage (before 1985) / Repeated loss of bass response on B/F Showmans?

kart24
Contributing Member
**********
********

Vacaville CA

Runs with scissors !!
Feb 28th, 2017 10:07 PM   Edit   Profile   Print Topic   Search Topic


(This message was last edited by kart24 at 10:07 PM, Nov 20th, 2017)

ECS-3
Contributing Member
**********
*

USA / Virginia

Mar 1st, 2017 06:58 AM   Edit   Profile   Print Topic   Search Topic

I would find out from your amp tech what he did to fix them before, as the beginning step in understanding what is happening.

Hammond101
Contributing Member
**********

So. Cal. USA

Mar 1st, 2017 03:42 PM   Edit   Profile   Print Topic   Search Topic

Does the bass control not respond? See if the mid control is not working on those channels so equipped as well.

kart24
Contributing Member
**********
********

Vacaville CA

Runs with scissors !!
Mar 1st, 2017 06:41 PM   Edit   Profile   Print Topic   Search Topic

The mid range on both amps are working at this time.
Just poor tone response from the bass pot. There is some variance in tone. Just very little.

The amps I'm comparing in this post are '65 single and my '67 dual showmans. The newer Showman 500 "PR 2809"is at our practice space across town. With same issue.

(This message was last edited by kart24 at 08:42 PM, Mar 1st, 2017)

Hammond101
Contributing Member
**********

So. Cal. USA

Mar 2nd, 2017 09:41 AM   Edit   Profile   Print Topic   Search Topic

Clean all the pots with DeOxit D5. I've seem many Fender blackface style tone stacks where the treble pot gets shorted with some crud, dendrite or who knows what and that takes out the rest of the tone stack.

You should be able to test for this with a VOM. The wire that connects the treble pot to the wiper (middle terminal) of the bass pot on both channels in your case would show shorted to chassis.

If cleaning doesn't fix it and the short is evident you will have to replace the tone pot. I've always been successful with a good cleaning and to best of my knowledge the problem has not re-occurred when using DeOxit D5 cleaner w/lube.

It could be other things but try this first if you are comfortable with pulling the chassis, discharging the filter caps and cleaning the pots.

kart24
Contributing Member
**********
********

Vacaville CA

Runs with scissors !!
Mar 3rd, 2017 04:43 PM   Edit   Profile   Print Topic   Search Topic

Will do. thank you.


kart24
Contributing Member
**********
********

Vacaville CA

Runs with scissors !!
Mar 8th, 2017 10:56 PM   Edit   Profile   Print Topic   Search Topic

My amp tech will be picking up both of my old B/F Showmans as well as my almost new Bassman 500.

He does excellent work and can do the warranty repair on my Bassman 500.

Meanwhile its back to my PF500 Ampeg for awhile.

Hammond101
Contributing Member
**********

So. Cal. USA

Mar 9th, 2017 10:22 AM   Edit   Profile   Print Topic   Search Topic

I'd be interested to know what your tech finds and what he does to correct it.

1958Bassman

USA

Mar 13th, 2017 02:19 PM   Edit   Profile   Print Topic   Search Topic

Does a loss of gain accompany the loss of bass? If so, I would have him check the cathode bypass cap on V1 and V2.

Hammond101
Contributing Member
**********

So. Cal. USA

Mar 13th, 2017 03:39 PM   Edit   Profile   Print Topic   Search Topic

There would be an inherent loss of gain in that the bass signal would not be contributing to the overall output of the stage. Agreed that bypass caps could be the issue but usually not cause a total loss of bass response at the control.

Interesting re-failure here.

amphead4

Cincinnati, USA

Mar 14th, 2017 07:23 AM   Edit   Profile   Print Topic   Search Topic

A mystery. I'm also interested in the outcome of this.

kart24
Contributing Member
**********
********

Vacaville CA

Runs with scissors !!
Mar 17th, 2017 11:21 PM   Edit   Profile   Print Topic   Search Topic

The "single" Showman is now out for repair.

kart24
Contributing Member
**********
********

Vacaville CA

Runs with scissors !!
Oct 5th, 2017 10:28 PM   Edit   Profile   Print Topic   Search Topic

Well sorry this took so long. I forgot about this post.

My amp tech cleaned and tightened all the tube sockets on all the amps. He replaced all of the power tubes, and a few of the pre-amp tubes. The 6L6GC's were really old , dating back to the 70's. A couple were old RCA blackplates, and an old Amperex 12AX7. They had a good life. I'm good to go on all my old Fenders at this time. I do have a sick SVT7Pro that needs attention...

s

kart24
Contributing Member
**********
**********
*

Vacaville CA

Runs with scissors !!
Nov 20th, 2017 08:09 PM   Edit   Profile   Print Topic   Search Topic

All 3 amps are bad again. Same problem This is the 3rd time on the old Showmans. And the 2nd time on the Showman 500.


Hammond101
Contributing Member
**********
*

So. Cal. USA

Nov 21st, 2017 10:28 AM   Edit   Profile   Print Topic   Search Topic

Dang, this is getting old eh? This is a sign of your tech not being thorough I'm afraid. Less than 8 months and you are down again. Were those pots cleaned and lubed?

I just don't see a tube issue causing a bass pot not to respond in a Fender Showman. Loss of volume, noises, yes, but to just loose the bass, not in my opinion.

If you have dirty pots transporting the amp(s) may cause them to respond. It could possibly not fail in the tech's presence giving him the benefit of the doubt here.

Could be a wacked out bypass cap. If you still have the loss of bass issue does it do this on the vibrato and normal channels? Maybe a bad coupling cap in the phase inverter or beyond?

Maybe a funky solder joint somewhere?



FDP Forum / Fender Amps: Vintage (before 1985) / Repeated loss of bass response on B/F Showmans?




Reply to this Topic
Display my email address             Lost your password?
Your Message:
Link Address (URL):
Link Title:




Moderators: Chris Greene  Iron Man  reverendrob  

FDP, LLC Privacy Policy: Your real name, username, and email
are held in confidence and not disclosed to any third parties, sold, or
used for anything other than FDP Forum registration unless you specifically authorize disclosure.

Furtkamp.com 
Internet Application Development

Copyright © 1999-2017 Fender Discussion Page, LLC   All Rights Reserved