TGSL Tuning & troubleshooting

[Farside]

I pulled the transistors and both are OK. I rechecked the resistors for tolerance and OK, diodes and caps are OK too.

I scoped the circuit and the transistors are being driven correctly...

I noticed that the current draw on the -5v line is doubled when U4 is in place so I am coming to the conclusion that the -5v generator is working correctly and there is something wrong in a circuit connected to U4.

I put an IC socket onto some veroboard and connected U4 via 14 wires to the main board U4 socket. Now I can isolate the various circuits asociated with U4 by removing the wires to see which one is the culprit.

The circuits are:
U4(a) which are pins 2, 4 and 5.
U4(b) which are pins 1, 6 and 7.
U4(c) which are pins 8, 9 and 14.
U4(d) which are pins 10, 11 and 13.
Power circuit which are pins 3 and 12.

[simonbaker]

I pulled the transistors and both are OK. I rechecked the resistors for tolerance and OK, diodes and caps are OK too.

I scoped the circuit and the transistors are being driven correctly...

I noticed that the current draw on the -5v line is doubled when U4 is in place so I am coming to the conclusion that the -5v generator is working correctly and there is something wrong in a circuit connected to U4.

I put an IC socket onto some veroboard and connected U4 via 14 wires to the main board U4 socket. Now I can isolate the various circuits asociated with U4 by removing the wires to see which one is the culprit.

The circuits are:
U4(a) which are pins 2, 4 and 5.
U4(b) which are pins 1, 6 and 7.
U4(c) which are pins 8, 9 and 14.
U4(d) which are pins 10, 11 and 13.
Power circuit which are pins 3 and 12.

Good troubleshooting, sounds like you'll find it soon.

Can you put an ammeter just on the V- rail and see how much is being drawn? It still seems that 100 mA is not out of range, but maybe it is.

-SB

[satdaveuk]

Hi all, I just put together a SilverDog kit IGSL TGSL and while running some initial checks I found that my -5v rail was only -3.2V.

I desoldered the anode of D4 and it measured -6.2v.

I resoldered it and started looking for shorts - found none.

I measured the resistance to gnd and other rails and there was nothing that indicates a short or semi-short.

I then started lifting IC's to see if one of them was dud and found that when I removed U4, the supply rail changed to -6.2V so I figured it was the IC.

To confirm this, I swapped U4 with U7 (they're the same) and the supply rail went back to -3.2V which proves that the IC is fine and there is some other reason.

So my question is this... Is this behavior normal? I'm suspecting that the -ve voltage generator that is supplied by the 7.3 kHz signal isn't capable of providing the necessary current, which may or may not be a fault.

Is -3.2V while the board is operating normal?

I'm working off this schematic FWIW:
http://silverdog.co.uk/shop/image/da...LTGSLcoils.JPG

Thanks

p.s. The board is drawing about 100ma from the 12V supply which I figure is normal.

Before you go any further check the prefexs numbers of your 4066 because there are 5v supply versions and 15v versions, I bet a pound to a pinch of **** you have the 5v version.... is it getting warm?... does the ID start with 74hc, if any of those thats your fault.
It will work up to a point but the symptoms you gave are what will happen with the wrong IC installed
Any doubt google your part number for a spec sheet, 5v is a no no

Regards

[simonbaker]

Before you go any further check the prefexs numbers of your 4066 because there are 5v supply versions and 15v versions, I bet a pound to a pinch of **** you have the 5v version.... is it getting warm?... does the ID start with 74hc, if any of those thats your fault.
It will work up to a point but the simptoms you gave are what will happen with the wrong IC installed
Any doubt google your part number for a spec sheet, 5v is a no no

Regards

Good call, this is a well-documented issue in another thread.

-SB

[satdaveuk]

Good call, this is a well-documented issue in another thread.

-SB

Yes Simon im sure you agree its got all the hall marks of yesturday, started reading the symptoms and the coin sure did drop.
On another level though Simon its another instance that proves people doing these projects must read and read these threads over and over again otherwise they will get caught out, as could of quite easlily of happened to me.
By the way got email from farnell stateing that although they couldnt add or subtract on the order that had been sent in, they were willing to send me as many Hef4066bp ICs as I liked with no delivery charge and offered to take the two 74HC4066 back, so all turned out ok will keep the two because they were cheap anyway not worth the hasle of posting, and ive ordered six of what we need, maybe over the top but who knows, fucture projects maybe.

Regards

[golfnut]

Hi Farside

Pull U11 and see if ok

[Merc]

p.s. The board is drawing about 100ma from the 12V supply which I figure is normal.

100mA sounds awfully high to me. Maybe if the speaker is sounding loudly, but if just sitting quietly, I would think 10-20mA or so.

Merc

[Farside]

Before you go any further check the prefexs numbers of your 4066 because there are 5v supply versions and 15v versions, I bet a pound to a pinch of **** you have the 5v version.... is it getting warm?... does the ID start with 74hc, if any of those thats your fault.
It will work up to a point but the symptoms you gave are what will happen with the wrong IC installed
Any doubt google your part number for a spec sheet, 5v is a no no

Regards

Right on! My IC is SN74HC4066N which is indeed a 5V version. I'll need to order the CD4066BE
http://search.digikey.com/scripts/Dk...56951559561508

Now that's frustrating! I tried searching the forum for a -5V supply problem but nothing turned up. Hopefully now others will find this as there are likely others who'll have the same issue.

I've gotta say, there are a few niggly things with that kitset. component sizes not fitting the board pitch and now this.

[der_fisherman]

Yes Simon im sure you agree its got all the hall marks of yesturday, started reading the symptoms and the coin sure did drop.
On another level though Simon its another instance that proves people doing these projects must read and read these threads over and over again otherwise they will get caught out, as could of quite easlily of happened to me.
By the way got email from farnell stateing that although they couldnt add or subtract on the order that had been sent in, they were willing to send me as many Hef4066bp ICs as I liked with no delivery charge and offered to take the two 74HC4066 back, so all turned out ok will keep the two because they were cheap anyway not worth the hasle of posting, and ive ordered six of what we need, maybe over the top but who knows, fucture projects maybe.

Regards

The chips we all usually use in our MDs (actually most of the components we use!!) are relatively cheap, cheaper than paying postage for a replacement, therefore always order multiples.

I always order 100 resistors of each value I ever need, they cost about €1,50 for each packet!!! Really cheap. That is the only downside of kits, you only get what you need!!

So what you are saying is a good idea for all of us.

regards

Andy

[satdaveuk]

The chips we all usually use in our MDs (actually most of the components we use!!) are relatively cheap, cheaper than paying postage for a replacement, therefore always order multiples.

I always order 100 resistors of each value I ever need, they cost about €1,50 for each packet!!! Really cheap. That is the only downside of kits, you only get what you need!!

So what you are saying is a good idea for all of us.

regards

Andy

Hi Andy
Your correct and far as capacitors to get the specifactions correct you need to buy at least 50 of each value, and out of those 50 you may find 2-3 that are actually in spec which is needed with these projects. good quality LCR capacitors are the thing to use but even buying in bulk your looking at £2-£3 per cap which is way to exspensive.
Resistors always buy metal film1% otherwise you could go through a whole bag and not find the spec required and there not that much more exspensive.
Far as semi conductors try and get known brands such as texas instruments etc checking data sheets to compare of at least 2-3, it also tells you pin outs which is required anyway.
Im in the middle of building a second TGSL with spot on specifacations as per Ivonics circuit and PCB design, with the 100k preset in the TX tank circuit incl Don Flowers recent mods. Once Hugho has given me the black and white PCB outlay will incl 2 tone soldered directly onto main mother board.
Doing it to see how much difference there is in performance to my first build which was out of the bag components, because im pretty convinced this is why theres been so many good and not so good builds between people on here.
Once all thats done and dusted will try your mods with the 2, 1.5megs and the 2,100k resistors to see the difference.
Im still trying to design simple pinpoint mode for the TGSL, need to look at other similar designes for ideas.

All the best Andy
Regards

[der_fisherman]

Hi Andy
Your correct and far as capacitors to get the specifactions correct you need to buy at least 50 of each value, and out of those 50 you may find 2-3 that are actually in spec which is needed with these projects. good quality LCR capacitors are the thing to use but even buying in bulk your looking at £2-£3 per cap which is way to exspensive.
Resistors always buy metal film1% otherwise you could go through a whole bag and not find the spec required and there not that much more exspensive.
Far as semi conductors try and get known brands such as texas instruments etc checking data sheets to compare of at least 2-3, it also tells you pin outs which is required anyway.
Im in the middle of building a second TGSL with spot on specifacations as per Ivonics circuit and PCB design, with the 100k preset in the TX tank circuit incl Don Flowers recent mods. Once Hugho has given me the black and white PCB outlay will incl 2 tone soldered directly onto main mother board.
Doing it to see how much difference there is in performance to my first build which was out of the bag components, because im pretty convinced this is why theres been so many good and not so good builds between people on here.
Once all thats done and dusted will try your mods with the 2, 1.5megs and the 2,100k resistors to see the difference.
Im still trying to design simple pinpoint mode for the TGSL, need to look at other similar designes for ideas.

All the best Andy
Regards

You are right, I forgot that caps are a problem of their own, which is why I have an accurate cap meter so that I can put ones together to achieve the values required....but I am lucky, I have a large collection already, acquired over the years.....
regards
Andy

[simonbaker]

ashefr10 can't post; needs help TGSL

hello, I'm not a sinusoid wave output of my LF353 but a saturated signal on tgsl. why?

Hi ashefr10:

It depends on which output you mean. Pin 7 output is the RX signal. If that is saturated, then it sounds like your coils are not "balanced". There is a fairly exact region of overlap where the "null" RX signal is small enough to not saturate the LF353. You just have to adjust your coil overlap carefully while watching your oscilloscope.

If pin 1 output is saturated, it depends on how badly. This output is the delayed TX signal for driving the discrimination sync pulse. It is best if it is a sinusoid, but often the MD will work quite well even if the output is somewhat "clipped" and has some "ringing".

However, it may help to put a small capacitor in parallel with the feedback capacitor R17 (for U101b op amp). Use the smallest one that works, as it slightly shifts the sync pulse.

*** It would be best if you could also post this question to the TGSL thread; my mailbox is getting full and I can't answer too many questions here.

Cheers,

-SB

other issues, I have a TX which is 14 khz RX but also when it should be of approximately 16 kHz as provided on the oscillograms. I do not understand what a parameter is on C6? thank you again for your quick answers

14 kHz is OK, it can work with correct RX coil and C6 value. Normal TX freq is 14.5 kHz, not 16 kHz.

What are the inductances of your TX and RX coils?

C6 is .015 uF normally.

Please post this question and future ones on forum so we can answer better.

Regards,

-SB

hello, thank you for the advice, I now have a nice sinusoid at the output of LF353 and I manage to have my nulling of 20 ° between LF353 output and TX. cons by now when I pass a coin, it sounds even to the ends of each coil why?

Hi Nico:

May I have your permission to post your question to a Geotech forum and answer it there? My email box will be full soon.

-SB

ok, I can not post I do not have permission I do not know why

1. Can someone help ashefr10 get his account set up for posting?

2. Nico: I don't understand your last question. Can you describe more fully?

Regards,

-SB

[Qiaozhi]

1. Can someone help ashefr10 get his account set up for posting?

2. Nico: I don't understand your last question. Can you describe more fully?

Regards,

-SB

ashefr10 already has an account, but he needs to reply to the email that was sent when he registered. Currently he is marked as a "User Awaiting Email Confirmation".

[simonbaker]

tgsl frequency 16 khz for RX COIL

hello, I want to know how to change the frequency RX, because I have 14.5 and 14.7 kHz for TX to RX and not 16. So I want to know how to change the frequency of RX 16 khz to do it. THANK YOU
__________________
hello , Nico

Hi Nico:

TX frequency of 14.5 or 14.7 kHz is good!

RX resonant frequency is determined by the RX coil inductance and the parallel capacitor (typically called C6, .015 uF), and is around 16 kHz. You can use a formula to adjust to a different value of C6 if your RX coil inductance is much different.

Look at this link for more information: http://www.geotech1.com/forums/showp...&postcount=494

Post any other questions here. Look at Qiaozhi's message above for advice on getting permission to post messages.

-SB

[Qiaozhi]

Post any other questions here. Look at Qiaozhi's message above for advice on getting permission to post messages.

-SB

I think he's already figured it out, as he's now posting in the Silver Sabre / Bandido / TGSL thread.

Have fun with the questions.