Super TGSL With H Bridge TX Diff RX Quad Sampling

[scrungy_doolittle]

Try this.

Please enlighten me a bit. On U105, what is the purspose of the back to back diodes?

[scrungy_doolittle]

I think the 3rd pulse duplcates the technique from the Whites patent, where they accept and look at a window centered on the sine wave, and about 2/3 the width. I think they refer to this as the "G" signal.

[hoadlies]

nice to see you back barry, told you the coil was the weak link on el cheapo china, a decent coil makes a lot of difference, my china board is good quality too, they really made an effort with it, shame they saw fit to put a standard 5" gold century coil on it, oh well much better now, i thought about putting the board in a dead cscope cs440 case, but i hated the look of it even more than the china, so i have upgraded the shaft to normal size specs(much stronger and no heavier).
ally.
p.s. dont forget to dump the original coil bolt (steel).

HI,, S/USER YES it was a good mod for the China unit [still open on my bench ] I found that by changing the TUNE-POT-from B50k to B10k [linear pot] improved the air test even further???? I tied going up to 100k it was worse the down to 10k & yes better ,The tune pot is supposed to balance the Coils??? to tune you hold button & centre the analog needle???..
'I feel theres a bit more to be gotten from it & it would be nice to have a SCHEMATIC of what it was copied from???

So far the air test is close to my IDX & it has great discrimination & ground balance !!!
CHEERS MATE take it Easy,,,,,,,,,,,,,,,BARRY..

[sinclairuser]

GOODONYA-MATE ,You will get there I am sure These things can frustrate us & all of a sudden we find our mistakes etc & alls well,But I realize you are Shooting in the Dark as its a new developement you are experimenting with..

I am currently building a DD for my ELCHEAPO CHINA M/D [GC1006] & so far its doubled its air-test ,I would like to know what it was copied from as its quite a good Board with lots of chips & transistors 5 pots analog meter etc....

I will keep playing with it for a while trying to tweek it some-where..

S/D did you have the TGSL running in STD mode ????? Prior to this new set-up ..

All the Best with-it MATE,,,,,,,,,,,,,,BARRY..

nice to see you back barry, told you the coil was the weak link on el cheapo china, a decent coil makes a lot of difference, my china board is good quality too, they really made an effort with it, shame they saw fit to put a standard 5" gold century coil on it, oh well much better now, i thought about putting the board in a dead cscope cs440 case, but i hated the look of it even more than the china, so i have upgraded the shaft to normal size specs(much stronger and no heavier).
ally.
p.s. dont forget to dump the original coil bolt (steel).

[Silver Dollar]

Yes I built it to stock settings before moding it. But now I have replaced 1/2 the board so
lots of places for mistakes. I thought of getting one of those Cheapo's and changing the
coil but now the real ones cost about the same as the Chinese ones so we don't bother...

[hoadlies]

Well I disconnected the RX from the board and nulled it today. It now works in Disc mode but only has a range of 2"!
There are a couple of things on the board that are not to the schematic. I'll have to verify them and change them to
match. So a little bit of sucess!

GOODONYA-MATE ,You will get there I am sure These things can frustrate us & all of a sudden we find our mistakes etc & alls well,But I realize you are Shooting in the Dark as its a new developement you are experimenting with..

I am currently building a DD for my ELCHEAPO CHINA M/D [GC1006] & so far its doubled its air-test ,I would like to know what it was copied from as its quite a good Board with lots of chips & transistors 5 pots analog meter etc....

I will keep playing with it for a while trying to tweek it some-where..

S/D did you have the TGSL running in STD mode ????? Prior to this new set-up ..

All the Best with-it MATE,,,,,,,,,,,,,,BARRY..

[Silver Dollar]

Well I disconnected the RX from the board and nulled it today. It now works in Disc mode but only has a range of 2"!
There are a couple of things on the board that are not to the schematic. I'll have to verify them and change them to
match. So a little bit of sucess!

[hoadlies]

HI,, SILVER-DOLLAR,,
I have been away for a while ,,But I see you are moving Onwards to coil connecting -Stage ..

YES -Nulling !!! I have now Built 4x DD coils & have now gotten the hang of the Nulling ,As DAVOR says you need to fix the coils to stop movement ..
What I have found is that after I tune the TX-coil for frequency with cap selection,, !![in the IDX case thats close to 6.6KHZ] this done from the unit fired-up ,I fix the TX in place temporally by Hot-Glue in maybe 6 or so spots .
I then lay the RX over the TX as you well know , & it is usually only about a 3/4'' gap -between the straight d/s leg's ,I then scope the Both for good sinewave , [I have only single scope,But ''STEVE-G/NUT ,showed me a way of using the exturnal feature & that works a treat -You can view each Coil by probing each TX & RX as long as you leave the time alone ]] .Then scope RX only to achieve a nil reading or minimum- reading [I probe the output of the Preamp for this..] .HOT glue the RX in spots but leave the straight D section for further-finer- adjustment , once close I then try fine-tuning the caps on RX . for the offset ,& the redo the Null .. for minimum output on RX [This is when the IDX is fired up]..
IAM-ONLY a Novice at this but have learned a lot from you members & many hours of practical coil building..my last coil came-out very good ..

LOOKIN-GOOD-MATE ,All the best with it ,,,,,,,,,,,,,,BARRY..

[Carl-NC]

Looks like there is way too much overlap.

[Silver Dollar]

"The coil is either completely out of balance, or you have some other problem there."

I'm using the 45T TX and 280T RX that's bifilar wound. This is the first time using those
so they are not nulled but looking at the signals I don't know how to proceed? Moving
them around does not change the output much. Is there too much TX getting to the RX?

I expected a different output! Here's a pic of the coils;



I'm not sure if I changed the caps in the preamp or not... I think we changed the 470pf to 68pf.

[Davor]

@dfbowers, yes, those are diodes. They could most probably be replaced by 6.8V zener in forward direction (!) but using a transistor of the same kind provides a better match, and basically they cost the same.

[Davor]

I'm not sure how to null the coils...

The coil is either completely out of balance, or you have some other problem there. What kind of coil do you have? Is it still open for corrections? In case it is potted there is a possibility to tune it with a piece of ferrite.
Either way, first you need to see voltage on the coil using a scope without any load. By squeezing, moving or otherwise you bring it to some sort of balance. In case it is a DD coil, at this point you should put some extra insulation between the coils where they touch each other, and put a drop of crazy glue on each side.
Now you can connect your coil to a preamp, and check the preamp output voltage instead.
Check the balance. Now when you obtain balance again, drop some crazy glue a centimetre from the touching points towards the centre. Proceed in the same fashion until you reach near the centre and apply some extra glue on each side, but leave some 5cm at the centre without glue so that you may fine tune your coil. At this point the coils are quite rigid, and you are able only to tweak balance a little bit. It is best not to pot the coil immediately, and just let it set overnight, so that the wires are allowed to relax with the glue. Do the final tuning prior to potting and squeeze it just a bit over the balance point so that the wires relax back towards the balance point. Done.

This way of tuning allows you to avoid extra curls of wire for fine tuning. In case you are not happy with the final result of a potted coil, you can either form a curl of a connecting wire or you can use a small piece of ferrite and find a sweet spot on the coil body that provides a perfect balance, and fix the ferrite there. You'll find that there is always some remaining minimum you can't make any deeper with either curl or a ferrite, and you can make it deeper by finding a sweet spot with a small chip made of a milk carton (very thin aluminium foil is in there).

[dfbowers]

In the schematic TR5 and TR6 have nothing connected to the collectors. Is that an error or does it just turn them into diodes?

[Silver Dollar]

Well I found the problem with the minus voltage. A short had crept in. Now it works
but sounds continuously in PP mode and doesn't sound in Disc mode. Here are some
pictures. I'm not sure how to null the coils...

Pins 1 and 2 of the 4053 - Note Channel 2 is 2v the switch pin broke off my probe...


Pin 15


Pin 4

[Silver Dollar]

Well it didn't work. The negative supply didn't come up. I used a 4069 as I didn't have a 40106 and
figured the TX not coming to gnd would make it not work. So I added a 7660 but it didn't work either
maybe there a wiring error. I moved the power connections as they worked better on the other side
of the board and maybe the negative is in the wrong spot I'll have a look tomorrow.

Here's the schematic as it sits today;