With the recent RI visits I have checked all my second hand gear to see what modifications the previous owners had done and found my FT-7800R has resistor R1288 removed to allow wider transmit coverage. I want to put it back. I have consulted the service manual, but guess what.... R1288 is the only resistor which is not in the parts list.
Has anyone un-modded this radio before? Do you know what R1288 is? Got any hints how to fit SMDs without the correct gear?
I have some experience of SMDs but not this tiny
Any help/advice/moral support would be appreciated.
It's probably going to be a zero ohm resistor - nothing more than a link. I've found the mod on the internet and it's hard to see exactly what required but I think there's more "resistors" near by. Can you measure one of those?
The spec sheet for the CPU chip shows that pin 62 is an I/O pin with internal pullups that can source 20mA. R1288 goes straight to ground so it could really be anything from 300 ohms up. Do any of the resistors labeled R1289 to R1295 exist on the board? They all pull down port lines similar to pin 62, I'm sure you could measure those and figure out what you need to replace R1288.
Edit: As has been pointed out in later posts the resistor is zero ohms. If you want to tie a logic input low you just need to ground it. A low value resistor could be used but there is no point. Digital electronics 101.
Last edited by VK3ALB on Mon Dec 13, 2010 12:25 pm, edited 1 time in total.
There are no other resistors on my radio. They program different freq limits, for europe and such.
Its could be a zero ohm link. But I'm not going to try it until I get confirmation of that. I was the radio back to standard, but I want it to keep working even more
