Problem temporarily solved. While tracing the signals around U1103, I found no Detected Audio coming into pin 8 of J21, however when I pushed on the pin just a bit, the radio would then squelch up and the pot worked like it should, along with the one on the audio board which was also dead. I pulled the audio board but didn't find anything wrong. I resoldered pin 8 and put it back and it worked fine, until I started bending the interconnect board near J21 in the front of the radio. Now it's intermittent, so it looks like I'll have to pull that board and find the fractured foil. Doesn't look like an easy board to pull either, since it's buried behind the front panel of the chassis and has the big control connector on it.
Bob M. ======= --- Milt <[EMAIL PROTECTED]> wrote: > Bob, > > The info you need is contained in FMR-1735A-1 dated > June 1996 > > The Audio squelch board in the radio is replaced > with HLN5342ESP01 > > From Pin 9 on the front connector (the former busy > light line) on the > interconnect board, the signal feeds through JU1510 > to pin 12 of J21 the > audio board connector. JU1509 and 1511 are open, > JU1512 is in. > > J21 pin 12 is the pin 2 input of U1103. JU1202 is > out. > > IIRC busy light is not used on A7 heads with the > remote squelch control > option. > > It's possible that you have a missmatch between the > head and audio squelch > board. > > Milt > N3LTQ > > ----- Original Message ----- > From: "Bob M." <[EMAIL PROTECTED]> > To: <Repeater-Builder@yahoogroups.com> > Sent: Monday, February 04, 2008 6:26 AM > Subject: Re: [Repeater-Builder] Re: Low-band > MaraTrac Squelch Pots > > > > Thanks to the people who posted the link. I had > seen > > that page earlier but didn't follow the signal off > the > > board. > > > > The pot in the control head seems to have its arm > and > > one end connected to ground. The other end goes > > through some resistors before leaving the control > > head. I can see the effect of turning the pot down > at > > pin 9 of the control cable; it varies from about > 3-5 > > kOhms. I thought it was just a DC signal or just a > > varying resistance to ground. > > > > The schematic posted doesn't show the wiring from > the > > audio board out to the pot on the control head. > I'm > > guessing that the signal coming into the squelch > pot > > on the audio board is detected audio, since it > then > > feeds the internal squelch pot which sets the gain > and > > threshold of the squelch circuit. > > > > I'll have to rethink and evaluate this new > > information. > > > > Bob M. > > ====== > > --- sgreact47 <[EMAIL PROTECTED]> wrote: > > > >> Bob, > >> > >> Look here for the modified audio board. > >> > >> http://www.batlabs.com/images/marsqsch.jpg > >> > >> The squelch control circuit is there, uses the > >> Micor, MSF, high > >> speed squelch. > >> > >> "Bob M." <[EMAIL PROTECTED]> wrote: > >> > > >> > I'm working on a 42-50 MHz MaraTrac with the A7 > >> > advanced head that has a squelch pot on it. The > >> > squelch is open all the time, and neither the > >> control > >> > head pot or the pot inside the radio will close > >> the > >> > squelch. ____________________________________________________________________________________ Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping
