Early Ampeg B-2R

[MstrB]

Hi, I am working on a Ampeg B2-R and it does not match the schematic I have. I am working on problems in the fan circuit and mine has afferent resister values and the current schem even has R54A and B and no R57? Any one have a early schematic?

[nosaj]

Call Ampeg they will give you the correct one based on your serial number.

jason

[Jazz P Bass]

Ampeg had a fan circuit change.
The original circuit came on a little too late.
The schematic is for the newer version.
It is a pretty simple circuit.
The LM39 output pin turns on a transistor, which enables the fan.
Check the transistor for a shorted condition.
If that is o/k, then monitor the LM39 output pin.
The output level of the ic raises a certain voltage as the ic gets hotter.
Link: Ampeg B-2 Fan Trouble

[MstrB]

Thank you. The mod worked great. I only made 1 change from 2 270/5watt series to 2 1k/5w parallel. This fit better and it is what I had in stock.