Let's made a PC-base metal detector with usb interface !!!

[WM6]

Hi all,

I finally repaired my oscilloscope . I am very glad.

Aziz

Congratulation Aziz.

Now you can open old scope repair service. I have one Tektronix 475 suddenly stop working for repair.

[Tinkerer]

At least you had a good mechanic at hand!!!!!!

I wish you ALL a happy new year.

Tinkerer

[Mechanic]

G'day Aziz,

Good news! I'm very glad you were able to get it going again. I knew you could do that

I find when that sort of thing happens that you go through an initial stage of not being very happy about it and after that I just accept it and start to work through it! On Christmas eve my car broke down in the bush. One of my solenoids for the gas system had gone open cct. I had an 8mm spanner and a flat screwdriver, my pick ad some wire from one of my detector chargers. After about an hour of just trying to start it and getting really p!ssed off I ended up pulling the solenoid off, unwinding it as the wire that went to the middle had broken. So I then set about rewinding it with a new tail out from the middle. But all was not over yet! My gas convertor had filled with coolant So I had to get to town to buy some spanners and sealant as I was expecting to have to do some bush surgery on the converter! Luckily once I was able to drain the gas compartments in the converter the car started, so I just put some coolant stop leak in and all is now good!



Cheers Mick

[Aziz]

Good News

Hi all,

I finally repaired my oscilloscope . I am very glad. Yes, it was the high voltage full bridge rectifier (200V/1.5A). I took four UF5404 (400V/3A) and made a discrete bridge rectifier. However, these diodes were the only nearest ones I have found in my box.

Thank you all in encouraging me not to give up.
Cheers,

Aziz

[Aziz]

Before final new bridge connection, check circuit after bridge on shorts to avoid fault repetition.

Yes, sure. Two diodes of the bridge rectifier seems to be damaged. It's shorting the AC input line. That's the reason, why the transformator get's hot too. And there is no +/-5V regulation without the +32 V line.

I can't get the damaged bridge rectifier. I have to build my own with four power diodes. (200V/1.5A specs)

I hope, the power transistor's are not damaged too. They are difficult to get.

Aziz

[WM6]

Good news:

The fault is localised: The 32 V bridge rectifier so far (smoking and getting really hot, I have burnt my finger). That should be repaired really easy. I hope.

Aziz

Before final new bridge connection, check circuit after bridge on shorts to avoid fault repetition.

[Aziz]

Good news:

The fault is localised: The 32 V bridge rectifier so far (smoking and getting really hot, I have burnt my finger). That should be repaired really easy. I hope.

Aziz

[WM6]

Hi all,

yes it seems, the fault is in the power supply section. +/-5V and +32V not present actually (mV range). A very hot getting bridge rectifier is one of the suspected candidates. I'll check the transformer and the linear regulator power NPN transistors tomorrow.

Fortunatelly, I have the schematics of the device. This will definitely help to repair it.
Cheers,
Aziz

Good luck with repair Aziz.

[Aziz]

Hi all,

yes it seems, the fault is in the power supply section. +/-5V and +32V not present actually (mV range). A very hot getting bridge rectifier is one of the suspected candidates. I'll check the transformer and the linear regulator power NPN transistors tomorrow.

Fortunatelly, I have the schematics of the device. This will definitely help to repair it.
Cheers,
Aziz

[WM6]

Well,

I have changed the fuse and it break again. The transformer is getting very hot and is not looking good too (after shorting the fuse). Seems to be a serious power supply problem.

That's not good. I'll have to look for another one on ebay soon.
Anyway, for some dumb measurements, I can still use my sound card scope.

Aziz

Bad, but you can still use it as coffee heater.

[Aziz]

Well,

I have changed the fuse and it break again. The transformer is getting very hot and is not looking good too (after shorting the fuse). Seems to be a serious power supply problem.

That's not good. I'll have to look for another one on ebay soon.
Anyway, for some dumb measurements, I can still use my sound card scope.

Aziz

[WM6]

Hi,

my oscilloscope died today (obviously died due to transportation) . Sadly, I couldn't check the latest ideas. Well, another big challenge to get a working device. I don't think, I can repair it. So everything will be delayed.

Aziz

Which scope Aziz? Your Tektronix? Was it memory type?

As Mechanic say, if CRT tube is not broken, then if it was due transportation, usually only some lose contact happen.

Worth to open it, clean it and fix again all mowing parts (slots, IC in sockets, CRT socket, valves) and probably it will start like new. Look at Car spare parts for Electrical components cleaner spray of Sonax or something like this: http://www.amazon.de/KONTAKT-CHEMIE-.../dp/B001H0XLVC

[Mechanic]

.....

I don't think, I can repair it.

Aziz

Unless the tube is broken, I'm sure you can

Good luck

Cheers Mick

[Aziz]

Sad News

Hi,

my oscilloscope died today (obviously died due to transportation) . Sadly, I couldn't check the latest ideas. Well, another big challenge to get a working device. I don't think, I can repair it. So everything will be delayed.

Aziz

[Aziz]

Warning

Hi all,

I do not want to miss to give you a warning. With the high power VLF, you are getting in the region of harmful to one's health. With high coil voltages (>100V) and the low source impedance, please don't touch the hot connections carrying a high voltage.
These voltages are as dangerous as the power lines.

Fortunatelly, the coil power can easily be adjusted. The coupling capacitors to the mixer coil must be changed: low cap -> low output power, high cap -> high output power. This power regulation is very efficient (low power-> low battery drain). It is also possible to make a weighted power spectrum adjustments. Just increase or reduce the coupling capacitor of the specific frequency input pin.

Of course, a low/high power switch could easily be made too.
Take care,
Aziz