Deal, or train wreck?

[Jim in Idaho]

Here an image of the C-Scope meter...

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Nearly identical to the meter in my TM808.
Jim

[ivconic]

Here an image from that area around U7... maybe it helps. By the way... on the PCB is also stated Discovery Electronics Inc. but sold under C-Scope UK.

[kt315]

thank you. sure obviously they changed the meter on another, with different parameters. IMO they 'lost' primary provider, but found another one.
so they were forced to change the components around the op amp, getting different gain.

[kt315]

https://youtu.be/s-DA96jFjr0

oh mama mia i did not notice your video link. they changed the analog meter on... LCD one!
so that why TF1200... a discovery for me!

[Jim in Idaho]

More changes then one would expect, KT!. I think, the little I tried it, the 1200 is better than my TM808 (800). That TF900 I bought has the same LCD meter.
Jim

[kt315]

look here Jim c.scope cs9000 HPX - Geotech Forums (geotech1.com)

[kt315]

TM 808 White's - Geotech Forums (geotech1.com)

[Jim in Idaho]

The lower right part of the pcb.
Close up around U7 (screenshot).
And check if the zener diode is 5V6 too?




Ah, so it's an LCD scale?!
It's the first time I've seen such a thing!
I have a simple analog scale.
That explains the change of resistors on the pcb, from that other picture.

Here's the pics, IV. My board only shows "D1" for the zener, and I could not identify the markings, even with microscope. So, I got as close as I could.
Jim

[Jim in Idaho]

One more closeup. Last two digits look like '28'.

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[Altra]

In case someone needs a replacement, I think this is the LCD meter?

https://www.digikey.com/en/products/...-1710/10259107

[kt315]

In case someone needs a replacement, I think this is the LCD meter?

https://www.digikey.com/en/products/...-1710/10259107

really V analog meter is current meter, it has some R internal. LCD has also R internal but another, probably significantly more. that's why there is necessity to change the meter driver op amp's setting.

[kt315]

Here's the pics, IV. My board only shows "D1" for the zener, and I could not identify the markings, even with microscope. So, I got as close as I could.
Jim

in the archive (7GB on my GOOGLE disc) you can find my BOM file on TF900. there you can read - D1 zener 1N5232B
i always do my Home Work, Jim.
also, you can read on the schematic that on its cathode is sure 5.6V.
ok, now a view from my window for u Jim.

[Jim in Idaho]

Ha!, KT, my place has snow on the ground, too. But not as much as yours. It is 7.9*f as I type this. I posted the pics at IVconic's request about the zener. I think he was concerned about the power supply using 12v on his 900. From what you posted it looks like it's regulated, and has a a fairly wide range of safe supply voltage. As far as research...I am more of a prospector, and not an engineer. You guys are more into the engineer side of things. It's what you live for. My life is widely split into many areas. I do machine work, welding, building, some electrical and electronics repair, etc. But my main interest is the outdoors....hunting, prospecting, exploring, etc. So I don't go into the engineering like you, IV, Carl, and the rest. But I'm happy to be accepted here, and enjoy all the info, and contribute what I can.
Jim

[ivconic]

[Jim in Idaho]

Well guys, it looks like the deal was very good. Even after sending him $100 more than we agreed on. For $200 I ended up with two very good working detectors. Here's pics of how I repaired the 900's transmit coil. I bought a 12" length of 1 1/4" I.D. aluminum pipe. Put it in the mill and bored 1 1/4" holes in it to make perfect joints. Then sliced the pieces lengthwise so they'd fit over the original tube. Drilled clearance holes so the rivets in the original tube could be accessed when necessary, and MIG welded the sections together. Glued them to the original mast and stub with JB Weld epoxy. I think it turned out pretty good, and a stronger joint than from the factory. I tried the detector and it works great!