Bad Selector Switch?

crgolfer · 2835

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Offline crgolfer

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on: June 01, 2012, 09:09:53 AM
I am having a problem with the selector switch in my Foreplay III.  Two input selections work properly but for the third it acts like the padding resistor is not in the circuit.  When taking a resistor reading for this selector position I get a very low result, a couple of ohms across the selector outputs. This happens with both chanels and it appears that there is a short in the selector at this one position.

Am I right in concluding that there is a fault internally with the selector for this one input?  Is this something that is common?




Offline Paul Joppa

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Reply #1 on: June 01, 2012, 09:38:10 AM
The padding resistor is external to the switch and should be easy to measure.

I don't understand what you mean by "a couple of ohms across the selector outputs" - there are four terminal on the switch that I would call outputs, labeled A-B-C-D. what exactly are you measuring?

Paul Joppa


Offline crgolfer

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Reply #2 on: June 01, 2012, 09:51:11 AM
If I measure the padding resistor for both chanels while in the circuit I get just a couple of ohms.  Measuring at the selector switch terminals I get a reading corresponding to the appropriate padding resistor at two selector positions but for the third selector position I only get a couple of ohms.



Offline Paul Joppa

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Reply #3 on: June 01, 2012, 11:20:20 AM
Apparently either the resistor itself is the wrong value or it is shorted by another path. You can disconnect one end of the resistor to measure it by itself and determine which is the problem.

Paul Joppa


Offline crgolfer

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Reply #4 on: June 02, 2012, 12:44:36 AM
I discovered the problem and it was me. I thought/planned to install 360K resistors but installed 360r instead.  Thanks for yourr help.



Offline Paul Joppa

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Reply #5 on: June 02, 2012, 06:06:23 AM
Excellent! Thanks for posting - it's almost always something like that, isn't it? Anyhow, looks like you are now set.

Paul Joppa


Offline bobster

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Reply #6 on: June 03, 2012, 12:47:42 AM
pun intended? ;D

Bob Musson
Seduction (extended), Foreplay, Paramours, Klipsch Heresys, Orcas, Crack plus HD 600s
Lovin the Bottlehead sound in Maryland


Offline Paul Joppa

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Reply #7 on: June 03, 2012, 06:27:43 AM
Sadly, no, it was completely unconscious. Wish I HAD thought of it though!

Paul Joppa