Fault on Garrett Master hunter7

[hepta]

Hi to you all,

First of all, best wishes for the new year 2014 to all fellow Treasure Hunters

I am new to this forum,

My name is George,Situated in South Africa.
I have my master Hunter 7 for many years, and I am very fond of it. After all the years, +/-25 t0 30years, it is still spic and span.

Recently I lend it to a friend for some prospecting, and it come back, with fault. No audio, and meter does not register both battery's
when you switch on the machine.
Since I am in Electronic field for decades, I decided to open the unit, and find out what is wrong. But to my surprise, and great annoyance, all the IC Numbers is grinded off from factory.

What I need, is circuit diagram of the " Master Hunter 7 "
There is no known agent anywhere nearby to my best knowledge in this country.

Can anybody help please. My Email is <hepta.surf@gmail.com>

Thank you - George

 

[John-Edmonton]

The numbers are filed off to protect Garrett from some countries (who specialize in cheap reproductions) producing cheap knockoffs. You could call Garrett and make arrangements to send it in for repair, or advertise that you are looking for this specific Garrett model. Because it has been around for a long time and was a favorite for many, there should be a lot of them lying around at a real good price.

Good luck!

http://www.garrett.com/

 

[hepta]

Hello John,
Thank you for your prompt reply. usually when one inquiere on some other web sites, it take long time to get any respnse.

It is bit to far for me to send it to Garrett Factory,and cost of sending and insurance would be prohibitive for me, from South Africa.
As I stated, I am electronic tech, so I take it as a chalenge, to repair my own equipment.

So, after sending the post in today, I attack the old MH7 again, stripped it apart andstart testing it all in detail.
Find fault on OutputAudio Drive Transistor, NSDU45. Being Darlington pair transistor, is not easy to test in circuit. After extracting it, found faulty. Replaced it with "TIP122" .
MH7 come to live again.
It is true, that some manufacturers do disguise the Ic numbers, but from my point of wiev. as repair technician, I consider it very anoing.
If someone brings me equipment to repair, and I am not be able to help him with simple task of changing 1 IC, or transistor that has gone faulty, it is bad for my business.
That tells me, that manufacturer is to secretive, with his design.
Today, even if numbers are filed off, there is the way to find out what is inside of the IC's. So that is old-fashion, old-timers practice.

Even in this case, if I put my mind to it, and spend some time, I can determine what IC's are used there, as long I can fing where the supply voltages are on the IC. It is not rocket science no more. It is mostly Cmos,logics, some opamps and maybe one 555 timer.
Besides, with todays designs, when PC boards are produced by Pick&place automatic asembling machines, and components are so minute that some you cant even see with out magnifyer. That is totaly outdadet practice.

But I am happy that my MH7 is well and healthy again, with out major surgery, and looking forwar to go hunting in the field again.
Will post, if find somthing interesting,
Regards - George (hepta)

 

[John-Edmonton]

All the best in 2014!