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.

Apex Tube Matching

WD Music

Jensen Loudspeakers

Musician's Friend

Amazon

MOD KITS DIY

Yellowjackets Tube Converters

Antique Electronics Supply

Guitar Center

Sweetwater

Amplified Parts


* 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 / Amp Mods, Repairs, and Projects / DRRI - what is a "tone stack ground issue" ?? how to repair?

Aftermidnight

Australia

Aftermidnight
Nov 1st, 2016 12:50 AM   Edit   Profile   Print Topic   Search Topic

Following this description on the Amps part of the forum - it was suggested - tone stack ground issue - any assistance appreciated - "I dismantled the amp and found that C8,C9,C11 or R21 had no disconnection visable. I'm not a tech so i didn't measure anything with a multimetter or anything like that, I just had a look to see if I could see any obvious breaks. I can't tell if all the valves are ok - but I pulled them all out and they looked ok. I reassembled the amp. Here's what it's doing. Normal channel - no problem. Vibrato channel - (vibrato and reverb not engaged - foot switch not inserted) loss of volume and bass control not working - when the treble control is turned up the volume increases - its like the volume and the treble control are linked and interactive - if the volume is turned up not much increase - when the treble is increased the volume increases dramatically. Connecting the foot switch and selecting reverb / vibrato works - but the volume is still choked. Can anyone advise if this could be the V2 or is it something else?? Thanks - much appreciated"
Brad

pdf64

UK

Nov 1st, 2016 04:58 AM   Edit   Profile   Print Topic   Search Topic

Does the bass control of the reverb channel work ok?
Do any of the reverb channel tone/vol controls cause a rustling noise through the speaker when they are turned?

Set both channels vol and tone controls to max.
Turn the guitar's volume control down to keep the sound level reasonable.
Plug into the #1 input of one channel then the other and play a bit through each channel.
Which channel is louder?


willie
Contributing Member
*******

Too Near Atlanta GA

Amp Tech Emeritus
Nov 1st, 2016 10:48 AM   Edit   Profile   Print Topic   Search Topic

Not sure exactly how you examined the connections for R20 (bass pot vibrato channel) or any of the associated components, but I can tell you it is often difficult to see a fractured solder joint on a PCB. You really need to totally remove the PCB from the chassis and inspect each connection with a lighted magnifier and if possible to gently manipulate the component from the other side to look for movement at the solder joint.

The symptoms sound like either the bass control has connection flaws, or their is some failure for the tone stack to find its ground through the 6.8K midrange resistor (R21).

w

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

So. Cal. USA

Nov 1st, 2016 11:40 AM   Edit   Profile   Print Topic   Search Topic

Before you begin replacing components, clean all the pots with DeOxit D5. You will need to remove the daughter (pot) board for proper access.

I've seen these pots short and sending folks in a long search for an answer when it's just some crud in a treble pot shutting down the tone stack.

Most times the problem is in the treble pot. When shorted it prevents the signal from getting to the bass pot. Start there then test but clean them all.

With no bass control working and the treble turned down the amp will have low output. It will get louder as you turn up the treble, hence the name tone "stack". The bass works the same way but now seems to be non-op.

If you have a DVOM you will most likely find the leg of the treble pot that supplies the bass pot signal(the one closest to the bass pot) shorted to ground. DeOxit has cured every one of these I've run across.

Best of luck!

willie
Contributing Member
*******

Too Near Atlanta GA

Amp Tech Emeritus
Nov 1st, 2016 12:54 PM   Edit   Profile   Print Topic   Search Topic

Can't hurt for sure...good suggestion. ;)

w

Aftermidnight

Australia

Aftermidnight
Nov 9th, 2016 06:45 PM   Edit   Profile   Print Topic   Search Topic

My thanks to the all the respondents. Although I was unable to source DeOxit D5 readily in Australia - I used isopropyl alcohol which fixed the problem. The amp now sounds perfect. Thank you again everyone. I am very grateful.

Brad

pdf64

UK

Nov 10th, 2016 06:25 AM   Edit   Profile   Print Topic   Search Topic

Good result but IPA will tend to remove all the lube from the pot, so it may not last for long.
To avoid that, a squirt of lubricating pot cleaner would be a good idea.

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

So. Cal. USA

Nov 10th, 2016 09:42 AM   Edit   Profile   Print Topic   Search Topic

Well great! I'm glad that did the trick for you Brad.

Yes, you definitely want the pots lubed. Without the lube their life will be shortened, binding may occur and then you are looking at replacement.

The local (hopefully) electronic supply house should be able to help you out. Look for a product marked "safe on/for plastics".

Peegoo
Contributing Member
**********
**********
******

Onward

Christian Slater
Nov 13th, 2016 03:36 PM   Edit   Profile   Print Topic   Search Topic

An auto parts place will have it too.

FDP Forum / Amp Mods, Repairs, and Projects / DRRI - what is a "tone stack ground issue" ?? how to repair?




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