Hi Jim, I might end up trying that sort of fix pretty soon unless I can find some more used or new old stock Comm Spec TS-32 boards around. I'm pretty much out now...
Glad it worked for you and maybe adding a pull up resistor will work on my damaged chip... cheers, skipp ps: I've added comments to each of the 224MHz Repeater Pictures I just added in the Group Photos Section. http://groups.yahoo.com/group/Repeater-Builder/photos/album/1157128983/pic/list > "wa6vpl" <wa6...@...> wrote: > Skipp, > I once fixed the same problem by soldering (on the back > side of the board) a 1/8 Watt resistor of about 47K Ohms > to provide an external pull up. Unless there is something > else wrong inside the chip this should work. I think I > just got lucky with a midnight fix. > Jim > > > > _____ > > From: [email protected] > [mailto:[email protected]] On Behalf Of skipp025 > Sent: Tuesday, June 23, 2009 10:57 PM > To: [email protected] > Subject: [Repeater-Builder] Another War Story (from the front lines) Those > Tricky CTCSS Boards. > > > > > > > > > Re: Another War Story (from the front lines) > Those Tricky CTCSS Boards. > > The Smoking Lamp is now Lit... Smoke'em if you've got'em. > > For the fun of building repeater gear... > > In what little spare time I have (as of late) I had > formed an informal assembly line to manufacture a number > of 224 MHz Repeaters as described in recent group posts. > > These Repeaters are constructed using Hamtronics Exciter > and Receiver Modules mounted in an aluminum box (with a > center divider shield) with an old (now out of production) > Comm Spec TS-32 CTCSS (PL) Board. > > http://groups. > <http://groups.yahoo.com/group/Repeater-Builder/photos/album/1157128983/pic/ > list> yahoo.com/group/Repeater-Builder/photos/album/1157128983/pic/list > > I've just added a fair number of new pictures including > Repeater Number 2 and 3 already out the door. You'll see > very minor differences in each version. Regardless of what > some people might have said about the Hamtronics Boards, > these units do perform really well and are fairly priced. > > I bought a number of used Comm Spec TS-32 CTCSS Encoder Decoder > modules to use, one for each repeater. Since these repeaters > take off and play pretty well right out of the starting gate > > Yes I got a bit lazy in regards to pre-testing of the various > modules before final assembly. Well... I was almost bit by > a glitch from a used TS-32 CTCSS board. > > I do pre-test the boards... figuring they're probably good if > a quick on the bench test sees a CTCSS tone coming out of the > encoder portion/section. One might "assume" all is well among > common parts within the same circuit? > > Finish up the repeater, set the CTCSS tone (via the top mounted > dip switch) and start down the level alignment trail of happy > times after wiring the controller pig tail (connection lead). > > The TS-32 is mounted with double sided tape and RTV Silicon > Glue as the tape eventually hardens and loses its grip on the > board. I route a wire from the TS-32 Encoder output pin, through > a chassis feed-through capacitor (as seen in the pictures) to > the exciter to provide Transmit CTCSS encoding. Transmit CTCSS > is a nice feature and very easy to include when using the > TS-32 Board. > > I set the Tx level about 400 Hz Tx Deviation (because in the > real world it really doesn't need to be more than that) and moved > on to a function check... darn it no CTCSS Decode Logic indicated > on the external controller. > > I was not looking forward to removing the already secured > and wired TS-32 from the chassis. Out with a Scope Probe to > try some initial testing before a board removal is required. > > The TS-32 docs are very good and there are signal wave form > pictures at various stages of the circuit paths. Everything > looked OK with minor difference with the exception of what > appeared in the TS-32 decoder detector section. Quite the > head scratcher... a non matched decode situation. > > Sometimes a change will do you good and in this case trouble > shooting a low frequency audio circuit at a higher frequency > might help ferret out a pesky problem. So I reset the TS-32 > dip switches and the Service Monitor for the highest possible > CTCSS tone frequency. > > Well looky here... > > Now I've got a nice bright LED on the Repeater Controller > indicating a decoded CTCSS tone? Sure enough a few repeated > decode tests toggled with the Service Monitor and I've got > happy times. > > Dip switches can become intermittent so I figured one of them > wasn't making good connection. I reset the desired 127.3 Hz > tone and the logic once again failed to toggle. > > One can place a multimeter set on dc volts upon the main TS-32 > IC Chip (proper pins of... ) to measure the tone selection > logic as you cycle the dip switches on and off. Through a > process of elimination I found the center dip switch logic > was not "rising high" with the corresponding proper switch > movement, but it was slightly changing value. The key point > here is the logic line was not rising enough, which would > lead some to believe the normally expected present logic > pull-up resistor is bad or not at home. > > But there are no pull-up resistors shown on the circuit > diagram. That function is provided internal to the custom > TS-32 logic chip. Can the chip be partially failed on the > center number 3 logic address line? > > Swapping is simple in the right situation... > > So I swapped the IC over from my last known good TS-32 and > the entire range decode function started working. So yes it > appears the original TS-32 chip has a failed internal pull > up logic function on the number 3 address line. > > One could use the chip for any CTCSS tone not in the range > of a/the third required address line. I marked the chip as > such and put it away. > > I'm happy to report the latest 224 MHz Repeater Project works > very well and is already marked for installation. Once again > pictures of a few of these repeaters are available in the > Group Photos Section. > > I will go back to testing the CTCSS modules before I > permanently install them into the chassis. As a sidebar note > I will mention I actually do solder down the original TS-32 > snap on pins as they will often work themselves loose after > a time. > > The no free lunch rule still applies unless you're a > trusting soul or a gambler. > > cheers, > s. > > ps: The Smoking Lamp is now Out. >
