Sunn_300T_Tech_Note_-_Output_Tube_Failure.pdf

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TECH NOTES

Fender Musical Instruments Corp.

7975 North Hayden Road Scottsdale, Arizona 85258

TECH NOTE #

TN 99-4

ISSUE DATE:

ISSUED BY:

PAGE:

Dec., 1999

J. Benson

1 of 1

PRODUCT(S) AFFECTED:

SUNN 300T

(Units built prior to 12-7-99)

SYMPTOMS:

A failure causes output tubes to lose bias, causing the screen resistors to blow, and

causing output tube failure; If there are no outward symptoms, then implementation of

this TN may increase reliability of the unit.

CONDITION:

Ratings on R333 & R353 are borderline, and may allow burnout under some operating

conditions. Increase value from 1/4W to 1/2W. Note: these parts cannot be evaluated

by a visual check, since they may not show outward signs of stress.

PARTS REQUIRED:

0039186001 RES CF 1/2W 330k 5%

REQUIRED ACTION:

1) Visually inspect R333 & R353 to determine that they are 1/4W parts.

2) If so, remove them.

3) Replace parts with 1/2W parts.

WARRANTY CLAIM INSTRUCTIONS:

The above modification should be performed on any

SUNN 300T

that is in warranty,

whether or not exhibiting the above symptoms. For proper labor reimbursement, please

indicate the Tech Note Number TN99-4 in the Authorization Code Box (Box # 12) on

the Warranty Reimbursement Form. Labor reimbursement = 3/4 Hour (U.S. only).