TESORO GOLDEN SABRE

[Max]

I have 4 original Tesoro coils. If you send me one of your PCBs populated with components, I'll investigate the problem for you. As they say, two minds are better than one. I will even pay the postage both ways! How's that for an offer?

Hi Qiaozhi... what's your epoxy ???

I'm doing stuff with a slow epoxy or maybe is just B component slow... really boring. Have two coils under epoxy at now... and seems an infinite work... I think that in the time it takes make that way... I can build another 10 and seal with a fast (and less cheap...) epoxy stuff.

What you suggest ? Anything from Maplin or something ?

Kind regards,
Max

[Qiaozhi]

Hi Qiaozhi... what's your epoxy ???

I'm doing stuff with a slow epoxy or maybe is just B component slow... really boring. Have two coils under epoxy at now... and seems an infinite work... I think that in the time it takes make that way... I can build another 10 and seal with a fast (and less cheap...) epoxy stuff.

What you suggest ? Anything from Maplin or something ?

Kind regards,
Max

Have you tried using fibre glass? You can get this from somewhere like Halfords. Alternatively you can use Araldite Rapid or Araldite Instant, but it may be a tad expensive if you need a lot.
http://www.silmid.com/adhesives/araldite2000/index.asp

[Max]

Have you tried using fibre glass? You can get this from somewhere like Halfords. Alternatively you can use Araldite Rapid or Araldite Instant, but it may be a tad expensive if you need a lot.
http://www.silmid.com/adhesives/araldite2000/index.asp

Hi,
I've used fiber-glass with epoxy... like in boat constructions or surfboards to have a solid but elastic layer of fiber-glass potted. Used also carbonium sheets under pressure with long last epoxy of similar kind... very rigid but can crack as glass.

But maybe you mean fiberglass resin (polyester type?)... no I never used it. I'll try.

When make coils I usually use epoxy compounds A&B components (resin+hardner) but this time I get this cheap 1Kg total and tryed... but last very long (maybe 6-7 days for full hardening still don't know).

Used also polistirene-based-glue but I was not happy with that thing... bad smell etc

I've used araldite just one time for coils on a BFO one some years ago... but a very few quantity; due to costs I think is not good for sealing coils.

Anyway, I'm doing my last 2 coils using sun-light for to accelerate process... cause UV and some heat will get it strong in less time... few days.

Old tricks.

Best regards,
Max

[ApBerg]

Polyester

Hi Max.

Look out : polyester can shrink, so for coils ?? epoxy is OK.

Succes.

Ap

[ivconic]

I have 4 original Tesoro coils. If you send me one of your PCBs populated with components, I'll investigate the problem for you. As they say, two minds are better than one. I will even pay the postage both ways! How's that for an offer?

Oh, if we are closer! Fact that my country is not member of EU means a lot.
That fact keep Serbia to far away from rest of Europe...on Mars!
Every single,small packet (even plain envelope) will cost damn money for me to send abroad! One my friend send me 3cd's from Holland and payed only 3 euros for that!? If i was about to send simillar to him, it would costed me over 30euros!!! I cant even send money via Western Union from Serbia....can only receive from abroad...goodbye E-Bay! So far this is "deep hole"..i cant escape from here at all. Looking forward, next few years, things to be settled and finally to we get chance to live like any normal people..Until that....only this internet left for us...
Best regards!!!

[ivconic]

Hi,
this is a simple test.

Have you 2x TL071CN from STmicro from not more than 5years old production ?

If so you can use them in place of LM308s and ear for differences.

Do that if you can and you'll restrict the field focusing on 308s or comparators.

I've used for test also TL071CN of above from ST and got no bleeping at all, at max sens, with all the coils I have. Only drawback is that you need recent parts from ST (others seem not so good don't know why... maybe input noise optimization on that) and a reduction of about 5% depth.

I'm using at now 2 original LM308s from national but have sometimes bleeping at max sens... so I turn pot at say 95% max.

Performances are really good.

Best regards,
Max

Actuallly all this started when i was about to put TL081a instead LM308 at the first time. All that bleepeing started than. Later when LM308H obtained...bleeping continued on 8 pcb's!? I checked those with 4 different coils - same!
I will look for TL071 and test with those...

[ApBerg]

Originally Posted by Qiaozhi
I have 4 original Tesoro coils. If you send me one of your PCBs populated with components, I'll investigate the problem for you. As they say, two minds are better than one. I will even pay the postage both ways! How's that for an offer?

For Ivica a problem, but Qiaozihi can give me a mail...

Best regards.

Ap

[ivconic]

JRC/NJM2068

I replaced LF353 with NJM2068, claimed to be lowdrop,low noise and high gain op-amp...
When switched ON.....no bleeping at all.In All metal mode and in Disc mode!
Both! Even when Sense is at max.
But i lost that "soft" sound like it was with LF353. Now it is sharp and consistent...strange!?
Depth is same as with LF353...Havent checked on the field yet, only in workshop...

No i dont think that LF353 was bad choice. I think that LF353 is proper choice, but i must have some other problem here and at the moment NJM2068 suits better here than LF353...??? But what???
I have feeling it has something to do with phase...or have great influence on phase. Cose i noticed certain differences on phase shift, between cases when LF353 is on pcb and case when NJM2068 is on pcb???
There should not be any differences theoretically? But there are?
Also i played with 5K1 at RX coil inputs...No differences from 6K8 to 3K3???
Than why the hell 5K1??? From 3K3 to 6K8 is bleeping all the time and depth remains the same....
But without resistors (RX coil directly connected to LF353 inputs) NO BLEEPING...but less depth too..???
It seems that only weak signals producing bleeps...strong signals NOT??
Huh!
I am waiting my friend to bring me much better scope...and later i will continue experiments...

[nakky]

golden

Hi Ivconic,I have original coil 20 cm cc.I will bring it to you,than I can also have a look at you romain site and pick up a lot of romain coins.TGS with original coil and 1M over 4148 is also noisy,10M will reduce it.But with DD coil it is more noisy ,10M will also reduce it a litle.I think DD is very sensitive?Grt Nakky.

[porkluvr]

It's all about power, or and, noise

You go and stick 2 OP27 equivalent in (NJM2068, - by golly they done (as compared to OP27) it at 1/2 the power! a minor miracle!

[Qiaozhi]

Oh, if we are closer! Fact that my country is not member of EU means a lot.
That fact keep Serbia to far away from rest of Europe...on Mars!
Every single,small packet (even plain envelope) will cost damn money for me to send abroad! One my friend send me 3cd's from Holland and payed only 3 euros for that!? If i was about to send simillar to him, it would costed me over 30euros!!! I cant even send money via Western Union from Serbia....can only receive from abroad...goodbye E-Bay! So far this is "deep hole"..i cant escape from here at all. Looking forward, next few years, things to be settled and finally to we get chance to live like any normal people..Until that....only this internet left for us...
Best regards!!!

Hmmm ... 30 euros!
In that case I'll wait until Serbia becomes part of Europe.

Actually I've just checked the postal prices myself between the UK and Serbia, and your absolutely right. I never realised it was so expensive!

[Max]

I replaced LF353 with NJM2068, claimed to be lowdrop,low noise and high gain op-amp...
When switched ON.....no bleeping at all.In All metal mode and in Disc mode!
Both! Even when Sense is at max.
But i lost that "soft" sound like it was with LF353. Now it is sharp and consistent...strange!?
Depth is same as with LF353...Havent checked on the field yet, only in workshop...

No i dont think that LF353 was bad choice. I think that LF353 is proper choice, but i must have some other problem here and at the moment NJM2068 suits better here than LF353...??? But what???
I have feeling it has something to do with phase...or have great influence on phase. Cose i noticed certain differences on phase shift, between cases when LF353 is on pcb and case when NJM2068 is on pcb???
There should not be any differences theoretically? But there are?
Also i played with 5K1 at RX coil inputs...No differences from 6K8 to 3K3???
Than why the hell 5K1??? From 3K3 to 6K8 is bleeping all the time and depth remains the same....
But without resistors (RX coil directly connected to LF353 inputs) NO BLEEPING...but less depth too..???
It seems that only weak signals producing bleeps...strong signals NOT??
Huh!
I am waiting my friend to bring me much better scope...and later i will continue experiments...

Hi,
if you reduce noise somewhere before you reduce noise-amplification along the chain of amplifiers. So you changed the LF353 with a lower noise one and get no bleeping, fine.

LF353 has noise level of 16nV/sqrtHz @1Khz
NJM2068 has a flat 0.56uV over a wide range

It's the same as you change noisy (some could be also fake... like the 2 I posted) LM308s with something better e.g. TL071CN from recent ST production.

Total noise impact is less along the chain and you gain better stability.

I'll try in next few days... (at epoxy setting, damn slow thing!) the use of MC33178 as preamp in TGS.

MC33178 has just 7.5nV/sqrtHz @1Khz and it's used in bandidoII.

About resistances the diff. config. of LF353 preamp set a gain of about 40 with that values... but if you reduce input resistors you increase the gain, fact that with zero resistors you get less depth is related to bad impeadance matching between coil and preamp... so your input stage lose part of signal cause of that bad factor. I suggest you increase the 220k to something more to get greater amplification saving impeadance matching.

[Max]

Hi Max.

Look out : polyester can shrink, so for coils ?? epoxy is OK.

Succes.

Ap

Hi Ap,
yes you are right... it could shrink... I never tested on coils but I'll do some experiments just to see what happens... also with vinylester-resin that is a bit better than poly.

I always use epoxy 2-components... but this time I get a very slow one... and after 3 days and more... much is hardened... but some few is still fluid... bad thing.

At first I thought I've made some mistake in mixing stuff , quantities... but used grad. plastic beker to measure volumes... mixed well... then I start thinking the hardener is old or something... and now I think that take longer in some small parts cause of cold temperatures here that blocked reactions during night.

But this stuff is making me crazy now. Just hope I haven't to rewound these last 2 coils.

What to say... sometimes is better spending some few eur more than getting so long potting time and problems.

Best regards,
Max

[ivconic]

Hi Ivconic,I have original coil 20 cm cc.I will bring it to you,than I can also have a look at you romain site and pick up a lot of romain coins.TGS with original coil and 1M over 4148 is also noisy,10M will reduce it.But with DD coil it is more noisy ,10M will also reduce it a litle.I think DD is very sensitive?Grt Nakky.

With or without coil, you are always welcomed here Nakky!
Regards!

[ivconic]

Thanks Max!

Thanks Max! Good explanations.
According to all my experiments up to now, i can swear that problem occurs somewhere arround LF353 and first kop's - geb&disc stage....It has something to do with phase....almost certainly!
Although i started to think to mod oscillator also...JC1 stated something about inperfectabillity of fet stabilisation at osc. stage...
It will be good to experiment there....