API 550 schematic needed
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Tekay
Well-known member
Call me!
martthie_08
Well-known member
sorry to bring this thread back from the dead, but has an actual schematic of the 550 popped up someplace?
All the schematics I've seen around are not correct. I am specifically interested in the buffer amp section, as this differs from the 550A
If anyone has something to share, please post in the API technical documents section, thanks!!
All the schematics I've seen around are not correct. I am specifically interested in the buffer amp section, as this differs from the 550A
If anyone has something to share, please post in the API technical documents section, thanks!!
martthie_08
Well-known member
a little light in the dark, I have two old 550 (non-A) and found some time to draw up a little schematic of the three filter section voltage followers, each with two transistors. This part is different from the later 550A model, I hope I got it right.
One of my two units was making troubles and I decided to replace this whole section. The old (original?) transistors were TIS 97 and something else, I replaced them with 2N5088 and 2N5087. I will add a "circuit board layout" once I get better at KiCAD.
The very old rev A circuit board doesn't have the gain trim resistor on pin 11 of the edge connector and was missing one of the 1k base resistors for the mid band vf.
both of my units had 2M2 resistors added underneath the pcb on the base of each NPN to ground. (3 altogether)
One of my two units was making troubles and I decided to replace this whole section. The old (original?) transistors were TIS 97 and something else, I replaced them with 2N5088 and 2N5087. I will add a "circuit board layout" once I get better at KiCAD.
The very old rev A circuit board doesn't have the gain trim resistor on pin 11 of the edge connector and was missing one of the 1k base resistors for the mid band vf.
both of my units had 2M2 resistors added underneath the pcb on the base of each NPN to ground. (3 altogether)
