SD2000 increasing the gain.

[Woody.au]

This is not my mod, it comes via Ismael from Minelabmods.com
I carried out the mod to my SD2000 and it accounts for between 15% and 20% increase in sensitivity. You need to locate 2 X 100K surface mount resistors and change these to 220K. Ismaels mod is to connect a pot of 500K accross the connections and have variable gain. I thought that 220K gave a real good boost without going over the top.

I attach pictures of the 2 X SD2000 boards with the position of the resistors.

In these pictures both surface mount resistors have been removed.

[gef12]

I gather these are the opamp feedback resistors... should make sure they are metal oxide low noise types
cheers
gef

[Woody.au]

Johnson noise could be a factor using a large value of resistance so metal film would be a good choice. Another thing that increases the detectors performance is changing the IRF710 output FET to a IRF840 will make it go a bit harder on depth.

[eclipse]

Are those the 2 resistors connected to the inverting input of TLC27M7?

[ZED]

Err nop !

One is a 100k in the feed back loop of the LT1057 on channel two, the other is a 100k in the feed back loop of the TLC074 on channel one.

Zed

[eclipse]

OOps yes I found them now, thanks ZED!