Skipp, I appreciate your suggestions. I will follow your advice to see whether input level is causing the erratic behavior. Many thanks for your analysis and advice. John
>-----Original Message----- >From: [email protected] [mailto:Repeater- >[email protected]] On Behalf Of skipp025 >Sent: Saturday, November 07, 2009 9:52 PM >To: [email protected] >Subject: [Repeater-Builder] Re: LDG Voter RVS-8 Mystery > > >With a constant test tone into the Voter, you should be able >to adjust the pots while watching the proper voter input >metering point with an AC Volt Meter or even better a scope. > >I doubt the pots are bad out of the starting gate, but >who knows with maybe the use of low cost parts, with >the corresponding lower quality. > >My first guess is you might have way too much input signal >or if there are adjustable gain stages, they are set (maybe >with a gain set resistor strapped) for max gain. If >you don't already have one, a Spray Can of Caig Labs DeOxit >is a must have for anyone working in electronics. A very >small shot of DeOxit or ProGold G5 Spray to the pot should >be a big help to most any cranky control pot. > >If it is a case of junk pots... the Caig Labs Spray would >help resolve the issue... or at least hopefully tell you >yes/no if the pots are the real problem. > >> So my question is, "Is there any way something external >> to the voter could cause the voter POTs to behave this >> way?" > >Yeah, really excessive input levels and op amps with improper >gain set resistor values. > >Test time: > >Get a 100K Linear Taper Pot, you can use an Audio Taper if >you can't find a linear taper version. Connect the receiver >output to the high side of the pot (one end of the pot becomes >the "high side", the other end is grounded and becomes the >ground side). Ground the other end of the pot as mentioned >above "ground side". > >Solder a wire from the center tap of the 100K pot to the >input of the LDG Voter. Be sure the common ground from the >receiver audio to the ground side of the pot is also connected >to the audio input ground on the voter. > >Set the Voters internal Audio Input Level Pot to 1/4 best or >1/2 rotation. Set the external pot about 1/4 rotation from >the ground (totally off) position. > >Apply the receiver audio test tone input... measure and/or >look at the value of the tone inside the voter input at the >test point. > >Rotate the test pot up and down to reduce the inside voter >test tone down to almost off. Then rotate the LDG Voter Audio >Input Gain Pot up and down to see if the tone still jumps >in large block (amount) values. > >Yes - The same big audio value jumps... Then I would next >try the Caig Labs Spray and test again. > >No - The audio seems to rise and fall in a more controlled >ramp... Then you're hitting the input with way too much >signal. > >Miller Time... >s. >
