Fisher 1210X

[dbanner]

My brothers, I build fisher 1210x as per shematic, can you tell me if I can use zener diode instead of lm336, .47uf instead of 1uf?

[waltr]

My brothers, I build fisher 1210x as per shematic, can you tell me if I can use zener diode instead of lm336, .47uf instead of 1uf?

A 2.5V Zener should work for D5. This sets a Reference Voltage. Just Measure that you do get 2.50V.

0.47uF should be ok since these are AC coupling to the next stage.
Of course you could parallel two 0.47uF caps to get 0.94uF which is close enough to 1uF as AC couplers.

[dbanner]

Yes, thank you very much. Always good to ask questions, even though the answer might seem obvious. But why did designer use special lm336 instead of ordinary zener. I'm just curious to know if their is some benefit.

[Qiaozhi]

I have moved the above posts to their own thread, as this subject has nothing to do with the Rimatron 7MX.

[dbanner]

My brother administrator, I am sorry for using your thread, but rimatron 7x and fisher 1210 is same schematic(except for power supply), so was hoping to get advice from you. My apologies.

[Qiaozhi]

My brother administrator, I am sorry for using your thread, but rimatron 7x and fisher 1210 is same schematic(except for power supply), so was hoping to get advice from you. My apologies.

Yes, there are some similarities between the schematics. I did state this (over 10 years ago) when I posted the Rimatron threads, and referred to the Fisher 1212X.
However, I still think this topic is better to have its own thread.

For reference, the original Rimatron threads are here ->
http://www.geotech1.com/forums/showt...light=Rimatron
http://www.geotech1.com/forums/showt...light=Rimatron

[dbanner]

I fully understand. Thank you. I used this very compact layout that I corrected, now it is good, the pin connections for op-amp chip are re-arranged to suit layout, but opamp- for op-amp are good, if you get my meaning.

[Davor]

A good substitute of a 2.5V zener can be produced using a pair of transistors and a red LED. It is even temperature compensated, and has superior noise to a zener.

[dbanner]

Thank you very much, here I was digging through old box looking for 2.5 volt zener, guess what, I have a million zener diodes, but not a single one around 2.5volts! Its probably the only one I DON'T have! What rotten luck. Now I can use your circuit as substitute, thanks again.

[Davor]

There are red LEDs with different barrier voltages, but you'll get voltage close enough.

[dbanner]

Yes of course, I have a bunch, will see how it works out and post results. I have a feeling that this little 1210 circuit has been under-estimated by many as good project for simple turn on and go detector.

[Davor]

E.g. a housewife's choice

[dbanner]

What the #$%^&^? HA HA , very funny. https://www.youtube.com/watch?v=EHBXZFCv3aE

[Koala]

I have an original 1260 of a similar age.

Keeps up with modern detectors most of the time.

Light fluffy soil it beats most machines.

But useless on waterlogged ground around here

Headphones are a must. If it's a light beep with a slow sweep and still there with a fast sweep it's a good target.

It's better than my 1265 if that's due to a problem with the 1265 I don't know. 1265 is slightly deeper but doesn't discriminate as good

Love these older machines. Wonder how the 1210 compares to the 1260

[dbanner]

I've watched a number of videos with test of all of fisher m- scope detectors. I think 1265/66 is best, but 1225/35 and 1220/60 is good too. The 1210/12 and the 1220/60 both use the lm13700 chip which I happen to have quite a few original. So I thought I build a circuit just to see for myself how it will work on soil here.