Ramsey Electronics UAM4SYS Assembly And Instruction Manual page 32

all circuit foil runs on both the main board and front panel board.
If you can't find anything wrong it is possible that U3 is defective
but first let's check one more thing. Turn all the controls fully
clockwise and check the voltage again. If you find it is correct
go to step 4, otherwise go to step 3.
3. Because the voltage changed with the setting of the controls
there appears to be a problem with one or more or more of the
wiper, or center pin connections, on one or more of the controls.
While measuring the voltage turn each of the controls to the
fully counter clockwise position. If the voltage on U3 pin 17
changes the problem is somewhere in the circuit path between
that control's wiper and it's associated resistor (R5, R6, R8 or
R13). There could also be a short on any of the circuit paths
connected to U6 pins 1, 2, 3, or 4. Check all these paths for
shorts.
4. If you still can't find the problem it is possible U3 is defective.
You may want to contact our technical support department.
Problem:
Checks:
1. Measure the voltage on U3 pin 17, [READING = 5.4VDC] If
correct go to step 2, otherwise go to the "Improper operation of
bass, treble, balance, loudness and volume controls"
troubleshooting section.
2. Measure the voltage on the actual terminal from the front of the
front panel board, not at the circuit board of R18. [READING =
5.4VDC] If not correct go to step 3 otherwise re-solder the
connection on R18.
3. While adjusting R18 measure the voltage on the center
connection of R18. [READING varies between 0 and 5.4VDC]
If correct measure the voltage on U3 pin 14 while adjusting R18.
[READING varies between 0 and 5.4VDC] If correct U3 may be
defective. Otherwise check for opens, shorts and incorrect
component installation of C7, C19, C20, R6 and R18 and
connected circuit paths or U3 may be defective.
Problem:
Checks:
1. Measure the voltage on U3 pin 17, [READING = 5.4VDC] If
correct go to step 2, otherwise go to the "Improper operation of
bass, treble, balance, loudness and volume controls"
troubleshooting section.
Bass control only not functioning properly
Treble control only not functioning properly
UAM4SYS • 32