Hi Neil
I'm very pleased with the initial results having done the parallel resistor part of the fan modification by Richard PA7FA.? ? The fan comes on a lot more now, but will stop reliably once the internal temperature drops.? ?
When doing the mod, Richard is quite right that the plated through hole surfaces need to be cleaned to expose the copper in order to solder to them.? It's a tricky process.? Great care is required.? I happened to have some conventional 33 k resistors with unusually thin leads.? This enabled me to poke the leads through the PTHs from the other side of the board, thereby providing some support for the resistor, and reduce the force on the PTH 'pads'.? ?I sleeved the resistor leads using insulation removed from some thin 7/0.2 hook-up wire.??
It's unlikely that the PTH pads are strong enough to support a leaded resistor 'surface mount' style.? Personally, I would not attempt to even solder a SMD resistor to the PTHs either, because of the small surface area of each PTH pad.? ?
I did wonder about putting heatsink compound under the FET.? But, to be honest, I already had enough to deal with to solder the darn thing in place? :-)? ?The last thing I wanted was to contaminate my soldered joint with foreign stuff!? ?
I'm not entirely convinced that the drive level would affect Q102 much.? ?According to the , once the rig is on 'TX', the Q102 FET (with about 3 volts on its Gate) appears to be biased in Class A.? If this is the case, the drive level probably won't affect the operating conditions of the device significantly.
It's nice to have the rig working again.? It's still very new to me, so I'm still learning my way around the menus, features and functions.? Another incredible box of magic from Icom.? The TX fault was a bit of a distraction.?
The only other modification I've done is the super-brilliant mod by SM6VFZ to significantly improve frequency stability of the TCXO.? ?But this is probably only of use to CW/SSB operators who use 2m and 70cm.? ?See:
I implemented the modification differently, but the improvement was truly amazing for such a simple idea.
72/73
Steve G4ALG
Steve G4ALG