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Dave,
The MAX chip has built-in pull-ups, and a bunch of people have tried adding external pull ups or pull downs with out any clear resolution. The problem is so intermittent, that its very difficult to tell if you have solved the problem with any particular hardware fix. Of the many years of the problem that have gone by ( And the Mfg denying that the problem even exists) No one has a bulletproof fix. There are several known ways you can induce the converter chip to go berserk, and it only rarely kills the chip.?
FYI, for quite some time, any new MTT4BT-40 has an additional bimetallic thermostat that will switch off the power amplifier if the MTT4BT-40 locks-up in transmit mode. Fortunately, this only happens if their is a cataclysmic failure of the antenna. When any MTT4BT-40 comes back for service, check-out or programming, I automatically add the thermostat to the unit, switching off the power amp when it reaches 50C, and with a drop-out period for cool down of several minutes.?
73,
Allen AF6OF -----Original Message-----
From: David Schultz, KC5WSV <david.schultz@...> To: [email protected] Sent: Sun, Oct 17, 2021 6:45 pm Subject: Re: [TinyTrak] MT4BB Halting On 10/17/21 7:26 PM, vhsproducts via groups.io wrote:
> Compton, > > Why not reset the timer more often? (Every day?) Are you finding that > once a week is enough to keep the units running reliably? Our problem is > not being able to replicate the hanging complaint in a TT4 or an MTT4BT. > I recently found that the MAX232 chip has a non-documented problem that > occasionally causes the chip to lock up, overheat, and draw a bunch of > excess power ( Google "MAX232 overheating" and you will see that the > problem with the chip has been going on for years with no satisfactory > explanation) An open input might be asking for trouble. On something where the serial port isn't being used, a connector wired to pull the input to a known state might help. Putting one of the problem systems in a location where it was easier to troubleshoot when it failed would probably help a lot. -- David Schultz |
