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Ampeg B2R

Drummer1120

Drummer1120

Dec 3, 2018
12
2
#1
Hi. A friend brought me this amp. Ampeg B2R. I replaced all the corroded jacks and all the pots. i am getting very distorted signal. I was doing some research and all the pics and amp I found online the FET's are placed differently as in the back side (metal part of FET's) are facing up. (the board is flipped). This one left side has 2 that are placed differently than all I looked at. I just found a schematic so im taking a look. But has anyone seen this. the solder joints are very good so either it was done at factory or someone was pretty good at soldering. Thanks for any info
20191126_093356.jpg
 
#2
The metal backs of the MOSFETs should be against the heatsink. Via the schematic the gate on Q10,11,12 should be connected to the 47 ohm resistors R36,38,40. This is only correct on Q12 in this picture.
Also the source should connect to the 5W .47 ohm cement resistors R37,39,41. This is only correct on Q12 in this picture.

Schematic
[Invalid or Expired Link Removed]

IFRP9240 Datasheet
https://global.oup.com/us/companion...s/pdf/microcircuits/students/mos/IRFP9240.pdf
 
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#3
OneWayPunk said:
The metal backs of the MOSFETs should be against the heatsink. Via the schematic the gate on Q10,11,12 should be connected to the 47 ohm resistors R36,38,40. This is only correct on Q12 in this picture.
Also the source should connect to the 5W .47 ohm cement resistors R37,39,41. This is only correct on Q12 in this picture.

Schematic
[Invalid or Expired Link Removed]

IFRP9240 Datasheet
https://global.oup.com/us/companion...s/pdf/microcircuits/students/mos/IRFP9240.pdf
Click to expand...
 
#4
Thank you. Thats what i was thinking and read also on the schematic. Wasnt sure if there was a revised unit or got changed. Just wanted a second opinion on it. I have a feeling someone worked on it before.
Thanks again
 

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