--- In Repeater-Builder@yahoogroups.com, Mike Morris WA6ILQ <[EMAIL PROTECTED]> wrote: > > At 09:30 PM 08/19/08, you wrote: > >On the VXR-7000, the RJ45 pins 1 and 2 are the collector and emitter > >respectively of an optoisolator that changes state when the squelch is > >broken and the correct pl/dpl is used. www.jammerdave.com/vertex.html > >says to connect the pin 1 to the pl detect of the repeater controller > >and pin 2 to ground. He also says it is basically an open collector > >circuit. > > > >I tried step 1 and no luck. I then connected a 33k pullup resistor > >between 12v and pin 1. I took pin 2 to ground. I keyed the HT on the > >correct freq and pl and lo and behold, pin 1 dropped to ~1.3 volts. > >Problem is, my controller needs to see more like 0 volts. I looked in > >the service manual and it looks like there is a zener keeping pin 1 at > >1.3 volts or higher. > > > >Any ideas???? > > > >- Jerry K8CMI > > Two series diodes plus a 2.2 K resistor to the base of an NPN transistor. > Emitter grounded. > A 4.7 K resistor from the collector to +5vDC. > > The collector also feeds the input of your repeater controller. > > Then a writeup to repeater-builder > > Mike WA6ILQ >
Well, using Mike's suggestion, a suggestion from the VXR-7000 group, and some playing around, I finally came up with a solution. Both suggestions were to use npn transistors, but I had some FETs laying around and I wanted to try those. Here is what I did... I put the 2 diodes in series and fed the gate a 2n7000 FET with a pullup resistor on the drain and the source to ground. I tied the gate of a second 2n7000 to the drain of the first, the source to ground, and the drain through a pullup resistor to 12v. For the life of me I could not figure out why I wasn't getting the 1.4v drop across the two diodes. Then it came to me, there is no current from the gate to source in a FET. I put a resistor between the gate of the first FET and ground (provided some current to pass through the diodes) and VOILA! It worked like a champ! I haven't played around much with FETs. I just got started with them when a keyer I bought had a bad FET and I had to troubleshoot it. Thanks for all of your help. The voltage at the COR input is 0.00 volts when the correct pl is heard and the repeater controller keys up just like it should. 73, Jerry Steele K8CMI
