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Ampeg® SVT-VR View
the
Repair
Won't Balance
Ampeg SVTVR
Ampeg SVTVR Balance and Bias Trimmers
Plate, Screen, and Grid Resistors

The push-pull output stage of this Ampeg SVT-VR bass amp wouldn't balance at any setting of the Balance trimpot.

The two Bias trimmers could be adjusted to light the green LEDs but when the amp was driven to an output of 25VAC at 40Hz the Balance trimmer wouldn't light the yellow LED.

In addition, the amp sounded weak when turned up.  And sometimes it would go into Standby mode by itself, or else not come out of Standby.

Since all the power tubes tested good, we decided to remove the power amp chassis and look for other problems in the output stage.

We ended up replacing four open resistors on the SVT-VR Tube Board.

Balancing an Ampeg SVTVR

These SVT-VR parts are available in our Online Store:

• 6550 Plate Resistors for the Ampeg SVT-VR:
5RW3 Flameproof 5Ω, 3W, 5% Resistors

• 6550 Screen Grid Resistors for the Ampeg SVT-VR:
220RWH Flameproof 220Ω, ½W, 5% Resistors

• 6550 Cathode Resistors for the Ampeg SVT-VR:
1RW2 Flameproof 1Ω, 2W, 5% Resistors


Additional Resources:

Schematics for the Ampeg SVT-VR amp

PDF Folio of Tube Pinouts


Ampeg® is a registered trademark of  LOUD Technologies, Inc.

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