Tesoro Eldorado on the bench

[aft_72005]

One more Christmass gift to all descent people here!

Thanking so much .
Best regards.

Hello Ivconic, my first visit to this forum, very impressed. I have a laser powermax 2 and the audio chip has broken. have you any advice about what to replace or can you point me in the right direction to someone that can help.
thanks
Adam,derby england

[ApBerg]

Thanks

Hello Ivica,

Thanks for your 'Christmass gift' the eldorado is a good detector !

Regards.

Ap

[ivconic]

Coil for Eldorado is the very same as for Tgsl.... EXCEPT the fact that RX must have center tap connected to gnd in coil. Inductances and resistances are the same...
Omitting center tap and using Tgsl coil without it, will result in pretty shifted received phase - Disc cicuitry will not work in range. Pay attention on this!
Also i am persistent leaving out amplitude stabilizer on these Tesoro designs, so also on this one there is no FET in Tx section - do not be confused on this.... In practical work with these detectors, on real field, i havent met any problems with amplitude jitters..

[ivconic]

One more Christmass gift to all descent people here!
Enjoy!

P.S.
There are some serbian terms on photo; "prekidac" stands for switch, "taster" for push button and "viseobrtni" for multiturn... KS is just short - coated wire connecting 2 spots..
Also i involved original values founded on original Eldorado, recently had on service. There are just few corrections comparing to W.Lahr schematic... now all is right and accurate..

[aft_72005]

Hi ivcoinc
Was alack , we cannot achieve to original ELDORADO. Anyway ,thanking
So much for your valuable information.
Molzar wrote about air test for original tgs , and seem as that record lower
Than our test with homemade tgs with homemade coil .my tgs seem your tgs
Be able detect one 22mm coin in air from 33-36 cm.i saw your tgs movie at
Youtube website.
Best regards.

[ivconic]

AFT 72005 sorry for the delay in my answer. It was to late to perform any detailed checks than, at the time you asked. Device was packed and send back to owner already.
Yet i observed its behavior good than. Reminds mostly on TGS/TGSL except lower "depths" in the air. I checked its coil with my handmade TGSL and it is working just fine.
One thing i forgot to mention; RX coil is center tapped to gnd in coil housing. Other 2 leads were connected to RX inputs on pcb via cable and connectors
So possiblle reason of lower "depths" could be that. When checked coil with TGSL i noticed that and also TGSL lost on some disc accuracy with that coil.
So...center tapped coils must be balanced somehow different than custom coils we are making here.
Also i rearranged wires in original coil (since already was opened) and wired all up as on my custom coil for TGSL. Than checked with Eldoreado and .... it rejected all the coloured metals totally! Ha,ha,ha! Justifying my previous words about different balancing.
In All metal mode "depths" in air were much better than on Eldorado.
So... Eldorado and TGS do have same concept and same behavior. But with original coils those do goes more shallow than with our custom coils.
Maybe this can be answer on "secret" - why our custom coils performs much better than originals...those are not center tapped and than balanced in different manner...and also wired up differently.

[aft_72005]

Hi ivconic
Yes I remember that you upload pcb file for Eldorado .also you didn’t have
Good result with your handmade coil .

It was good, if you:
Setup some measuring with oscilloscope for original search coil, phase differences
Between transmitter And output of first amplifier opamp at receiver and
Also with what amplitude.
How much phase changes when GEB pot. at min. and max. refer to tx osc ?
How much phase changes when discriminate pot. at min. and max. refer to tx osc ?
Best regards.

[ivconic]

I did that and it is working. I found out one mistake on my handmade. Instead 0.022 i put 0.22 capacitor. Corrected and now is working as original.
I already packed it up in enclosure and prepared it to post back to owner. So i can't make more photos. You dont need that, pcb posted here on this forum is accurate so you dont need original pattern at all.
Schematic is also accurate.
I dont like so many "flying" wires on original setup, so intend to draw my own Eld pcb later. To fix all the commands to one side of pcb and later attach very short wires to front panel. Something like on TGSL 1265 or simillar..
Cheers!

[aft_72005]

........Also please upload more pictures from pcb and coil.
Mybe be able redraw pcb with sprint layout .

[aft_72005]

Hi ivconic
It is good that you having original Eldorado.
Also thanking for your technical report.
Another things, please connect your homemade Eldorado
Circuit to original DD coil. And test it regain .
Best regards.

[ivconic]

Recently i got oldie Eldorado on service.
Cable at the very coil surface was "munched" and broken on many places so i had to fix it. I had to dissasemble coil and replace cable.
Coil was not easy to open, yet i did it.
Inside i found DD coil with 19cm outer diammeter.
Faraday cage is formed from blacklead layers sprayed on both covers and connected with steel naked wire inbred in plastic and also good sprayed with blacklead. Ok...so i replaced cable, glued all on its place and closed the coil.
Despite the fact device is very old and used so many times, when switched ON it started to work excellent. No falses, all modes and presets are workable.
Generally i am satisfied with what i got.
"Depths" in air are not so great as achieved with handmade TGSL yet Eldorado is descent detector. Discrimination is just very good.
I like GEB multiturn pot solution - very precise and accurate.
All Metal mode is just fine.
There is certain nonlinearity reffered to treshold in All and Disc modes. When treshold adjusted to best suit Disc mode - not good than when switched in All Metal mode - must be readjusted. This would be my only remark.
At present setup frequency is 9.8kHz. Coil inductances are 6 and 6.5mH...
Resistances are 21.6 and 20.8 ohms...