Twin -65 reissue reverb

81.232.33.131

Posted on November 1, 2009 at 07:35:52

Stewen
Audiophile

Posts: 219
Location: Sweden
Joined: December 25, 2003

Hi ! Have written earlier about my very much changed and modded twin reverb , how good it finally sounds and ...... But now an unwanted sound has occured . Imagine one takes a thin sheet of paper , similar to that kind they wrap flowers in at a flowershop ! And if one press this sheet of paper into a ball rather slowly . That kind of sound . I´m thinking of anoderesistors..... but they are just 5 years old and modern types. Can it be the powercaps ? Have doubled capacity on both sides of the
"filtercoil". Perhaps some leaking couplingcap . Or the tube for the drive of the reverbpan ( parallelled 12AT7 without anoderesistor ) ?
Bad solderingpoint somewhere ? What do you think ? It´s not a humming sound , its an irregular ,slow , paperwrinkling sound .
Thanks for advice . ( the added filtercaps are reformed just in case they might have been sleeping on a shelf for some years )

RE: Twin -65 reissue reverb

Triode_Kingdom

11:26:28 11/01/09

start pulling tubes & Chopstick test,

FenderLover

18:15:07 11/01/09

RE: Twin -65 reissue reverb, posted on November 1, 2009 at 11:26:28
Triode_Kingdom Audiophile Posts: 629 Location: Travelin' Man Joined: September 24, 2006	I've seen coupling caps and tubes cause that symptom.

start pulling tubes & Chopstick test,, posted on November 1, 2009 at 18:15:07

FenderLover
Audiophile

Posts: 3313
Joined: July 31, 2007
Contributor
Since: May 17, 2009

Pull out the tremolo one first, see if noise still happens. If not, replace that one and pull the tube that drives the reverb pan. If neither solve the problem, try replacing the NORMAL gain stage tubes, one-by-one. Repeat tone check & rinse dry. Use known good 12AX7 or 5751 as replacements in each section. Do same with VIBRATO potion of amp.

Finally, swap each 6L6GC with a known good 6L6GC. Rinse & repeat for all four.

This should narrow down the section. It may not be the tube, but a resistor or cap which has gone bad. Try the wooden chopsticks test on all the caps and resistors in the problem area. You should be able to make the problem worse or sometimes alleviate the noise, by tapping the faulty component with the wooden probe. CHECK ALL GROUNDING POINTS!

Hopefully, you will find the problem. For ANY re-issue with circuit boards, replace the cap and resistors on the board with like-rated component. (DO NOT put a 1-watt resistors in where the OEM is 1/4 watt). You risk damage to the circuit board, which is VERY hard to find and replace.

Good luck!

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Twin -65 reissue reverb

81.232.33.131