adamjking Posted December 30, 2003 Report Share Posted December 30, 2003 Hi all,I've created the JDM module from scratch (no PCB, on a proto board) and am having problems getting the correct voltages in the hardware test. I have laid out all the component identical to the schematic, and when i run the hardware check the voltages i am measuring (with a battery multimeter) are waaaay too low. The data in/out toggles fine but the voltages are not right.I have checked and rechecked the circuit many times, replaced the transistors, tried different PC's ( win98 ), different cables, adding the two 9v batteries, everything i can think of. Does anyone have any more advice on where the problem could lie?I have looked through all the JDM issue pages but can't find my problem. I'll be getting a more experienced friend to check my circuit, i was just hoping someone might have any pointers or additional tests i can try first?Cheers. Quote Link to comment Share on other sites More sharing options...
Wilba Posted December 30, 2003 Report Share Posted December 30, 2003 I can only suggest my fix for low voltages: try using a 9.1v zener diode instead of an 8.7v (or an 8.2v substitute). That should increase programming voltage. The 9.1v zener is the only thing different in my JDM and what made it work!Make sure you're testing MCLR voltage against the VSS pin, not the GND of the RS232 socket. Quote Link to comment Share on other sites More sharing options...
Steven_C Posted December 30, 2003 Report Share Posted December 30, 2003 Where do you live? maybe someone who uses a JDM could try your one, and see if it works on their system?maybe someone could start selling pre-made JDM's that have been checked, before shipping. I would make them, check them, and swap them for parts for parts if anyone is interested....Steve Quote Link to comment Share on other sites More sharing options...
Wilba Posted December 30, 2003 Report Share Posted December 30, 2003 (Wilba checks Meeshka's profile)Meeshka: You live in Melbourne, Australia. Unbelievable coincidence - so do I! ;) I've sent my email address in a private message, perhaps I can help you out.Wilba Quote Link to comment Share on other sites More sharing options...
adamjking Posted December 30, 2003 Author Report Share Posted December 30, 2003 Thanks Wilba,I've replied to your email - it's good to know there's another midibox'r nearby. Hopefully you can help me figure this out and i'll post the solution back to the forum.Cheers. Quote Link to comment Share on other sites More sharing options...
adamjking Posted December 31, 2003 Author Report Share Posted December 31, 2003 Hi All,The JDM seems to be working now so I'm just posting a follow up. As I thought, the extremely low voltages were caused by a bad connection somewhere - a re-solder of the serial plug brought the voltages right up to a much closer level.Following wilba's advice I upgraded the 8.2V zener to 9.1V. With the addition of the two 9V batteries I was getting close enough to the correct voltages.When I tired to program the 18f452, i was getting a verified failed. Swapping to COM1 and a connection to SGND seemed to fix that problem (not sure which one it was as i did them both at the same time).Now, the programming of the bootstrap loader seems to have worked - is therre any other way to verify that it burned correctly or is the "Verify after programming" enough?Thanks all for your help, now that i've finished the JDM (with all the optional extras ;)) I can begin on the core module. Quote Link to comment Share on other sites More sharing options...
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