Fisher 1265 Revival

[ivconic]

Please do not be in awe. It's not rocket science.

Analog detectors such as those from Whites, Tesoro, Fisher, Viking, Cscope, etc., etc., are all using the same basic idea, although the topologies do differ in subtle ways. Newer digital technologies can provide much better discrimination and (of course) target ID, but surprisingly it's not what you might call a step-function change. At an MD rally I've seen people using the latest and greatest detectors completely upstaged by a little old lady with an ancient Cscope. Most detectorists were complaining bitterly about the lack of finds, but there she was with a handful of roman coins and a couple of gold staters. You just have to be in the right place at the right time ... and sometimes it pays to hunt more carefully.

Ehhhh Cscope! Sweet memories! Was it beacuse in the past my terrains were not so exhausted or was it because of something special in Cscope 1220B - yet my sweetest memories are tied exactly to that model!
If you adjust it properly and a bit hot, walking slowly and moving very slowly coil over soil surface - no chance to miss a thing in soil! And no chance disc at it to be confused even for a moment! Those times will never back again!
Metadec and 1220B are unrepeatable! That's for sure.

[Qiaozhi]

I bow down to your superior knowledge and understanding.

I have revived my fisher 1260X with replacement of long lost battery holders and my grand daughter (13) is now learning it's language (soon to become the girl who fisher talks to). She delights finding treasures of zinc cents...
She got five yesterday!!! The ground was so hard that today we are coming armed with hammer and big screw driver...

I am delighted at the reputation this machine has and surprised that technology has not made it completely obsolete.

Please do not be in awe. It's not rocket science.

Analog detectors such as those from Whites, Tesoro, Fisher, Viking, Cscope, etc., etc., are all using the same basic idea, although the topologies do differ in subtle ways. Newer digital technologies can provide much better discrimination and (of course) target ID, but surprisingly it's not what you might call a step-function change. At an MD rally I've seen people using the latest and greatest detectors completely upstaged by a little old lady with an ancient Cscope. Most detectorists were complaining bitterly about the lack of finds, but there she was with a handful of roman coins and a couple of gold staters. You just have to be in the right place at the right time ... and sometimes it pays to hunt more carefully.

[Dustyr]

I stand in awe..

I bow down to your superior knowledge and understanding.

I have revived my fisher 1260X with replacement of long lost battery holders and my grand daughter (13) is now learning it's language (soon to become the girl who fisher talks to). She delights finding treasures of zinc cents...
She got five yesterday!!! The ground was so hard that today we are coming armed with hammer and big screw driver...

I am delighted at the reputation this machine has and surprised that technology has not made it completely obsolete.

[Qiaozhi]

it samples in phase and 90 degrees out of phase received signals
and other places it combines different signals into one.?

One thing for sure, I clearly do not understand how this circuit works.
Is there any documentation which explains the circuit function or do you have the experience which enables you to understand the circuitry by examining it?

I do not know of any documentation that explains the operation of this circuit, but by examination of this design, I can determine that it uses a classic approach of sampling at the zero-crossing point of the received signal to achieve ground exclusion, and then 90 degrees later (adjustable by the two DISC pots) to perform target discrimination. Other analog switches are used to switch in or out certain sections of circuitry related to discrimination or battery check.

[Dustyr]

as I understand it--

it samples in phase and 90 degrees out of phase received signals
and other places it combines different signals into one.?

One thing for sure, I clearly do not understand how this circuit works.
Is there any documentation which explains the circuit function or do you have the experience which enables you to understand the circuitry by examining it?

[Qiaozhi]

What is the 4066 symbol represent and what does the device do(how does it act in the circuit)

Thanks...

The 4066 is a quad analog switch. In one part of the circuit it is used to sample the in-phase and quadrature portions of the received signal. Elsewhere it is simply used as a multiplexer.

[Dustyr]

Can you tell me, please?

What is the 4066 symbol represent and what does the device do(how does it act in the circuit)

Thanks...

[kt315]

oops! noted mistakes. revised again.

[kt315]

1266

fixed 'bulgarian' 1266 schematic. delete old revision one in your archives. i hope now it is correct. enjoy

[ivconic]

You're welcome!

[getsa]

Thank`s a lot!!!

[ivconic]

...

[getsa]

1265

Would you please post the 1265 shematic here?

[ivconic]

Remember to be carefull what op-amps you use or you will overload the PS analog gnd. If you use 3 TL074's (or TL084) you'll be drawing 30ma through the analog gnd vs 3 ma for a TLE2024 and 2 27M9's.
Also disregard all 1265/1266 schematic other that the official Fisher schematics posted on the forum. The 1266 reworked schematic has TOO many errors!
Regards,
J. L. King

I think i have TLE2024 here.
About schematic..yes i noticed also some differences between original Fisher schematic and other.

[KingJL]

That's why my handmade 1265 never worked properly! Now is time to fix it and try all over again to put some life in it!

Remember to be carefull what op-amps you use or you will overload the PS analog gnd. If you use 3 TL074's (or TL084) you'll be drawing 30ma through the analog gnd vs 3 ma for a TLE2024 and 2 27M9's.
Also disregard all 1265/1266 schematic other that the official Fisher schematics posted on the forum. The 1266 reworked schematic has TOO many errors!
Regards,
J. L. King