No, my strong suspicion is that the old cap has already effectively disconnected itself via a high ESR failure, ie it may as well not be there.
And as mentioned above, insufficient decoupling at a shared, cascaded cathodes opens a pathway for positive feedback; when the reverb control is increased sufficiently then free running oscillation may result.
Fender Deluxe Reverb AB868 Squeal
Moderators: pompeiisneaks, Colossal
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Stevem
- Posts: 4599
- Joined: Fri Jan 24, 2014 3:01 pm
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Re: Fender Deluxe Reverb AB868 Squeal
If you lift the feedback wire off of the speaker Jack does the issue get worse or better?
Does it look like the OT may have been replaced?
Just for kicks swap the brown and blue output tube plate wires, does this change the issue any?
Does it look like the OT may have been replaced?
Just for kicks swap the brown and blue output tube plate wires, does this change the issue any?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Fender Deluxe Reverb AB868 Squeal
Replaced the V4 cathode cap and the squeal went away! The four other 25uF cathode caps were all dry so I replaced those and the amp is sounding good again. Thanks for everyone's help in not only fixing the amp but getting me to understand the whats and whys!pdf64 wrote:No, my strong suspicion is that the old cap has already effectively disconnected itself via a high ESR failure, ie it may as well not be there.
And as mentioned above, insufficient decoupling at a shared, cascaded cathodes opens a pathway for positive feedback; when the reverb control is increased sufficiently then free running oscillation may result.
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Stevem
- Posts: 4599
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Fender Deluxe Reverb AB868 Squeal
Cool deal, glad to hear it!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Fender Deluxe Reverb AB868 Squeal
Yea, good result!
It nice to identify a faulty part before starting a campaign replacement.
It nice to identify a faulty part before starting a campaign replacement.
My band:- http://www.youtube.com/user/RedwingBand