2475 RD-130 Amp

Joe_D

I have this amp, replaced components on the driver board, and cannot get the bias to adjust correctly. Replaced the 100
Ohm pot, two diodes, and the 16V zener diode. I have gone through the circuits, and replace the two transistors with the 2N6488. Has someone experienced this problem? also the amp sizzles when connected to the speaker cabinet. Replaced the 1458 with an RC4558 op amp. I appreciate all comments. Thank You in advanced.

Full Name
Lars Verholt
Music Man Equipment
HD-130 head, 210X cab, 210RH cab, RD-50 110 combo, Sixty-Five 112 combo, RP65-112

Member for

11 years 2 months

lmv Wed, 05/27/2020 - 18:44

Hello Joe,

please confirm amp model: Is it 2475-130?

The bias can be adjusted with the phase splitter op-amp removed. Is the amp quiet with the phase splitter out?
What does it mean when you say bias will not adjust correctly? What are the actual voltages you are getting?

Sincerely,
Lars Verholt