Fisher 1266 PART 2

[zoomtronic]

Ivoncic,
Did You managed to finalize detector?
kind regards

[Davor]

I looked at the Fisher 1266 schematics, and it seem to me there is a part that can be omitted which would make this design somewhat more desirable to replicate.
It is the 8:800 transformer. The LM339-s have PNP input transistors, and the common mode voltage includes negative rail. That means that the comparators can be hooked directly to the 1 ohm resistor, and work happily ever after.

[Sean_Goddard]

SOMEWHERE I have a schematic of a 1266 with oscillograms of ALL important points. It may help those of you attempting to build your own. I'll have a dig around and if I find it I will Zip it up and post it.

[Funfinder]

try to get a chinese MD3030 and use the coil of this MD for your Fisher.

Fisher 1266 PART 2 - Page 3 - Geotech Forums
7 Jan 2009 ... Page 3- Fisher 1266 PART 2 Schematics. ... For coil i am planning to use CC coil from MD3030. ... Much better than original Fisher coil. ...

[Gyur666]

Nobody made a good DD coil for 1265/66? I use fisher spider coil, but it has destroyed. Our country the 10,5 spider 190 euro

[Gyur666]

I’m going to build a 10,5” DD coil for 1265. Can somebody help me about it with parameters of coil?

[Mikes]

Ivconic!







Best regards!

[Funfinder]

Thanks for your answer, I'm happy that you like it.

This Forum really makes new appetite built your own
detectors - which I've done already 15 years ago.

Found an IC LM324M op-amp, perhaps i can invent something.

[Merc]

Thank you very much. I'll add that one to my collection.

Merc

[Funfinder]

http://www.sendspace.com/file/poce13

Fisher 1266-X Schematic 10-5-1993 (Rev. I) 300dpi scan
I hope you can need it!

@ ivconic
Good Luck with your work and keep us informed about your progress - it's really interresting!

Do you or anyone else know how to adjust the GEB pot @ 1266-X or a other little tuning to make it go deeper?

[Mikes]

Also..what opamps you put there instead 27M...? Or if you put originals than what should be closest substitutions?
Can you recheck differences on both versions on schematics and draw accurate and proper version of schematic finally?
Regrads!

I use TLC27M4. It is possible to use TS274, LMC6484. It is possible to use and simple TL064.
Corrected scheme F1265 I will publish little bit later.

[ivconic]

Thanks much! That's helpfull!
Best Regards!

[Mikes]

Greetings, ivconic!
Good work and correct discrimination F1265 depends on correct adjustment of synchronous detectors. We leave a payment the first (where RX and TX), and the second payment while it is disconnected. Further, we disconnect resistors R220, R222. One channel of an oscillograph is connected to U101/14, and the second channel is connected U202/14 and received:



If the picture it is arranged R205 is impossible.
If the picture is impossible, is added in RX – 33-39 nF and again arranged R205.
If the picture turns out from a negative impulse of the channel of synchronisation we change exits U101/1, U101/14.



Similarly we look the second channel – U101/1 and U202/8.



After that we put to the place of R220, R222. All! The first payment is finished!!!!
Yours faithfully, Michael.

[ivconic]

"...So i didn't knew from where to start with troubleshooting!?.."

I had many issues at those pcb's, not only one!
Most dramatical was strange phase behavior!
I simply could not adjust phase properly.
Right now i also have one original 1265 on service and it is acting the same; can not adjust phase, no way! Everything seems to be alright and still it is working very bad. Seems that geb trimmer has no influence at all when turned. Coil is right, OP27 seems right, all caps arround seems right...???
I don't have much luck with those 1265 lately?
...
Not so good detection and bad phase - that's what i gained at my handmade and also on this original one i have at service...

[ivconic]

Mikes i put that handmade aside long time ago.
I had bad luck with it; most of the components i put on pcb's were scraped from other scraped pcb's. So i didn't knew from where to start with troubleshooting!?
Also there were some mistakes on original schematic.
So i lost enthusiasm about it.
But now with your news i am again gaining some enthusiasm and since it is tough winter i might be start it all over again.
So...
confirm me please if those pcb's are alright now? What corrections should be made?
Also..what opamps you put there instead 27M...? Or if you put originals than what should be closest substitutions?
Can you recheck differences on both versions on schematics and draw accurate and proper version of schematic finally?
...
Right now i do have original 20cm ("spider") coil for 1265/66, so there is much sence to me to make again 1265!
I was also thinking to try to merge those two pcb's and make one smaller and compact.
...
Regrads!