I've had a couple of LOR 1602's fail this year (no blinking LED but fuses are good, etc), and want to dive in fixing the units, but either I'm an idiot or the schematics for these boards is nowhere to be found on the LOR website.
Will LOR give these out, or do they come with the CTB-16D kit? (I bought mine preassembled).
I'm curious why the schematics aren't published. If a potential competitor wanted to copy your design, it'd be fairly simple to derive from the circuit board itself. Im in no way wanting to do that myself, but if they're kept private for trade secret purposes, then I think that's a false sense of security.
It would definitely help troubleshooting if the schematic was available.
chuckd wrote: I'm curious why the schematics aren't published.
It's probably because it would take work to get them in a format suitable to publish, few customers would benefit, and the design occasionally changes, meaning it would be tough to keep the multiple versions straight.
The troubleshooting guide is very comprehensive. I have used it several times and works well. In the event you cannot pin point the problem there is always support.
Anyway based on your description of the problem I would 1. check/verify the LED is in deed working. 2 sounds like the porcessor may have had something to it.
In the past I was careful and swapped suspected parts between a known good board and my non functioning board. In my case I could not communicate and it was the 485 driver chip. Then when i contacted support I knew what I needed.
Chuck
Last edited on Mon Nov 2nd, 2009 10:18 pm by cmoore60
Steven wrote: chuckd wrote: I'm curious why the schematics aren't published.
It's probably because it would take work to get them in a format suitable to publish, few customers would benefit, and the design occasionally changes, meaning it would be tough to keep the multiple versions straight.
Steven is correct. Others have already copied the controllers.
eldoradoboy wrote: even if someone copied the controller they arent goingto have the the code for the PIC.. as im sure the fuses are burned in the chip....
-Christopher
It's a sure bet it will not be published by LOR as John stated.
It's just odd that an electronic product that can be purchased in kit form doesn't include schematics. The Ramsey transmitters all do, as did every Heathkit (dating myself here) I ever built as a kid. It's fairly simple to take your schematic capture package and simply 'print to PDF'. Probably takes a whole 2 minutes to do.
My particular problem involves a dead unit (no blinking LED at all). The fuses are fine, and nosing around a bit with my scope, I notice that the left side of my diodes (Anodes) that I 'think' are involved in the power supply (D1 and D2), have an extremely clipped waveform. The 5 volt regulator runs about 4.55 volts, and is extremely hot, while the 9V regulator outputs nothing at all (let's just call it noise).
Taking out the few chips that I can easily remove (my unit is prebuilt, so that's only the EEPROM, CPU and RS485 transceiver), the 5V regulator output goes nuts.
So, not knowing what the configuration of the transformer is (center tapped, two secondary windings, both, etc), it's a bit harder to tell what the output should be. I'm assuming that at least the 5V section is a center tapped winding with two diodes for rectification (since I can't see four diodes together), but I can't really know for sure without reverse engineering the whole thing. Frankly, I don't have time for that this time of year.
That result seems odd. My recollection is that the 5V regulator is fed from the output of the 10V regulator, so as to not drop all the voltage from the transformer secondary in a single spot. Is it possible that with everything installed, the 10V regulator is putting out the 4.55, and that the 5V regulator is putting out noise?
While the kit build troubleshooting guide is aimed a bit more towards uncovering where soldering issues are likely, it still has some good suggestions on where to check. Also, the most common failure is likely the RS-485 chip. Testing with the microcontroller and eprom in place is a reasonable step as well.
There were never any schematics for the controllers. They were so simple that we went directly to the PCB layout. Everything we design and build now is first laid out as a schematic and then goes to the board layout and routing.
