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 |
![]() Antique Electronics Supply |
![]() WD Music |
![]() Guitar Center |
![]() Amplified Parts |
![]() Apex Tube Matching |
![]() Sweetwater |
![]() MOD KITS DIY |
![]() Advertise here |
![]() Musician's Friend |
![]() Jensen Loudspeakers |
* 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 / Fender Blues Deluxe Channel Switching Issue
FDP Forum / Amp Mods, Repairs, and Projects / Fender Blues Deluxe Channel Switching Issue
Hammond101
Contributing Member
**********
*
So. Cal. USAOct 26th, 2017 09:49 AM Edit Profile
I replaced the switch (S1) and relay (R1) however the amp has a mind of its own and will cycle between clean and drive at random. Looking at the schem, this is an original Blues Deluxe, it could be an IC however I'm unsure as to which one.
Anybody have any experience with this? BTW plugging in a foot switch seems to stop the problem.
Peegoo
Contributing Member
**********
**********
******
Enjoying
the downtimeOct 26th, 2017 12:02 PM Edit Profile
Many amps use a 4049 hex inverter IC for channel switching. It's a fifty-cent jellybean part.
Look for one (or similar) in your schematic.
If it's in a socket, pull it and re-insert it to see if it's simply dirty contacts that are the problem.
Peegoo
Contributing Member
**********
**********
******
Enjoying
the downtimeOct 26th, 2017 12:06 PM Edit Profile
Also: if plugging in a footswitch stops the problem, that indicates the poor connection causing the intermittent issue could be a switch inside the footswitch jack.
Sticking a plug into the jack clears the problem because it opens the 'normally closed' switch that allows channel switching to be operated from the front panel when no footswitch is plugged in.
willie
Contributing Member
********
Too Near Atlanta GA
Amp Tech EmeritusOct 26th, 2017 12:31 PM Edit Profile
I recall that problem being commonly caused by a defective JFET...I think it was Q1 in the earlier model which is a J111.
w
Hammond101
Contributing Member
**********
*
So. Cal. USAOct 26th, 2017 01:21 PM Edit Profile
Thanks guy! I will apply this new knowledge and see where it leads me.
Peegoo
Contributing Member
**********
**********
******
Enjoying
the downtimeOct 26th, 2017 01:57 PM Edit Profile
There ya go.
Peegoo: guessing.
willie: definitive answer!
Hammond101
Contributing Member
**********
*
So. Cal. USAOct 26th, 2017 01:59 PM Edit Profile
I figured willie would chime in and sure enough he did! Awesome.
willie
Contributing Member
********
Too Near Atlanta GA
Amp Tech EmeritusOct 26th, 2017 02:49 PM Edit Profile
Hope that is the fix,...I found it to be quite common so I kept a large supply of J111, J112, J176 etc JFETs in stock. They are sometimes hard to check so I would usually just change them out and more often than not it would be the fix.
w
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.
Copyright © 1999-2019
Fender Discussion Page, LLC All Rights Reserved