So much for resale value (TRS Challenger 1400).

[TM86]

Nice work on the Challenger!! I too have sanded and re-sprayed a few cases that had some rust/stains on them. I had a question about the clock. I'm not sure of the best way to troubleshoot one. I have a Teaberry Stalker XX and the clock only flashes all 8's. The clock board has a TM4801P chip. Any tips?

Thanks!!

You've got me at a loss here. I don't have the Sam's for that radio (CB-285), nor can I find a schematic online. I also can't find a datasheet for that chip. I keep getting pointed to a temperature sensor.

Best uneducated guess is that it's missing a signal that it expects to see to be able to count pulses. Less happy guess is that it's already had it's final mental breakdown.

Hopefully someone with the service info or who just knows something about that chip will weigh in with some real advice.

 

[TM86]

So I suddenly find myself in possession of the Sam's for the Stalker XX.
I've also included this crop as a pdf so you can blow it up if you need to.

Pin 37 of the chip should have a little less than 8V AC coming in. The chip uses the line frequency of 60 Hz to count seconds. If that's not there it has nothing to count and can't tell time. Things that could be preventing that from getting through would be the Hold switch not making contact, R603 open, C601 shorted, or D601 shorted. Could also just be a busted wire or a cold solder joint. Slight chance of there being an internal short in IC601.

I'd also take a look and make sure that pins 25, 30, and 39 are grounded like the diagram shows. One or more of these may be used to tell the chip whether to expect a 60 or 50 Hz line frequency. May also have some other function for applications outside of CB radio clocks.

Since the clock is flashing all "8"s you know that the LED driver portion of the chip is good. BTW, the display is common anode. Which I'm sure you probably spotted already.

For the rest of the pins they've laid out what the voltage should be with the switches in the configuration they have them, with the exception of the hold switch. There is a mistake, though. At 12:00 PM pin 8 should be at .22V and pin 9 should be at 1.55V. Otherwise it'll be one weird looking 2 on the display.

At this point I'd walk the pins on the chip and just make sure all 42 of them have the right voltage, at least according to the Sam's info. If not, then it's a process of figuring out if the cause is external or internal.

Good luck. I'm really hoping it's just a cold solder joint.

 

[Lkaskel]

So I suddenly find myself in possession of the Sam's for the Stalker XX.View attachment 75528
I've also included this crop as a pdf so you can blow it up if you need to.

Pin 37 of the chip should have a little less than 8V AC coming in. The chip uses the line frequency of 60 Hz to count seconds. If that's not there it has nothing to count and can't tell time. Things that could be preventing that from getting through would be the Hold switch not making contact, R603 open, C601 shorted, or D601 shorted. Could also just be a busted wire or a cold solder joint. Slight chance of there being an internal short in IC601.

I'd also take a look and make sure that pins 25, 30, and 39 are grounded like the diagram shows. One or more of these may be used to tell the chip whether to expect a 60 or 50 Hz line frequency. May also have some other function for applications outside of CB radio clocks.

Since the clock is flashing all "8"s you know that the LED driver portion of the chip is good. BTW, the display is common anode. Which I'm sure you probably spotted already.

For the rest of the pins they've laid out what the voltage should be with the switches in the configuration they have them, with the exception of the hold switch. There is a mistake, though. At 12:00 PM pin 8 should be at .22V and pin 9 should be at 1.55V. Otherwise it'll be one weird looking 2 on the display.

At this point I'd walk the pins on the chip and just make sure all 42 of them have the right voltage, at least according to the Sam's info. If not, then it's a process of figuring out if the cause is external or internal.

Good luck. I'm really hoping it's just a cold solder joint.

Thanks soo much!! I need to get the Robyn 520 done and then the Stalker goes back on the bench. I'll keep you posted.