Deal, or train wreck?

[ivconic]

[Jim in Idaho]

OK, guys. Here's the deal so far. I sent the guy an additional $100 to help defray his shipping expense. I got the units today. Surprisingly, both are powered by a 12v battery pack. The pack in the 900 is actually reading 14.48....8 good, hot Energizer batteries. The pack in the 1200 is more run down...reading 10.84v. So, to answer the question "can the 900 run on 12v?" apparently it can. I really like how "hot" the 1200 seems to be, even with low batteries. Target response is much louder than my TM808 with Cave mode. I have not had time to test either unit in the field, and the weather is rapidly closing in here at 4,500'. The "stem" on the transmit coil on the 900 was repaired, at some point, with what looks like JB Weld epoxy. That repair failed, so the stem is loose, but the wire looks OK. I did not turn that unit on to see if it worked. Other than that coil issue, both units look to be in good condition.
Jim

[Jim in Idaho]

By "stem" I meant the tube that slides over the mounting rod on the main unit. That tube separated from the rest of the antenna.
Jim

[GeoMax]

Hi Jim,

can you share some nice images of your new units? I think many of us want to see the units. Specially the 1200 unit.

Thanks

[Jim in Idaho]

OK here ya go

[kt315]

you have to drill out the rivets. remove a disk with socket from the tube. then delete plastic end cap. you will see torx bolts.

[GeoMax]

Hi Jim,

thanks for the images. The detectors look cool. I compared the pictures with my C-Scope CS 9000 HPX. I cannot see any difference in controls only the labelling is a little bit different text on the casing. Probably the difference is the PCB inside the detector.

[GeoMax]

Here an image of the C-Scope CS 9000 HPX

[Jim in Idaho]

Here an image of the C-Scope CS 9000 HPX

Do you know when yours was made?

[Jim in Idaho]

The 900 works with the transmit coil from the 1200. So both units work fine.
Jim

[Jim in Idaho]

Pictures of the 1200 PCB. Closeup is power supply, I think. One thing I noted from IVConic's link is the 1200 operates at 12.5khz. The TM808's operate at 6.59khz. Apparently the OF for the 900 is the same as the 1200.
Jim

[ivconic]

Check if the scale is original.
This looks like a modification around the sensitivity of the scale, in the picture.

[ivconic]

Although, the lower solder point of the 8k2 resistor looks like it was never soldered.
Which could mean that they did it at the factory, they didn't have the scales of the same sensitivity, so they started a new series with different scales.
Of course this is just an assumption. The way the resistors are soldered with that wire... not very representative!



It's amazing how things coincide in life!
Just these days I had to do something similar.
The scale I installed on the PS2 is of a different sensitivity, so I had to change the resistors on the pcb.
Fortunately, the original resistors were such that they allowed a wide range of adjustments to the given scale.

[ivconic]

Separate "processing" of signals for scale and for sound has its advantages.
This proved to be true with the TF detector, but also with the PS2... and many others!
Both with TF and PS2, the scale literally "announces" the detection with its tiny movements.
It can announce a detection... but more importantly; announce changes in the soil!
Why is it so?
Because the audio stage is imperfect, it is always more inert than the scale.
That is why it is very useful to have a scale with some detectors.
Of course, Minelab seems to have realized this a long time ago, so they were among the first to work on improving the audio stage.
So today we can safely say that Minelab has gone the furthest in terms of audio stage perfection. And they don't need a scale.
I made the story long, and you draw your own conclusions from it.
Useful for this topic is that; indicating the importance of scale in such a detector.
The scale will always react much sooner and faster to changes in the signal.

[ivconic]

And this whole story gives me an idea, to give Carl an idea; to dedicate a separate chapter in his book to the audio stage.
Leaving aside the performance quality of the TX&RX stages; audio stage is the most important stage in the detector.
If the audio stage is bad or mediocre; the super quality performance of the TX&RX stage doesn't mean much.
Because the user loses a large part of useful information about the signal and situation in soil.
And vice versa, if TX&RX is mediocre; and the audio stage is superior; the user always gets better information.
Of course, it is best if TX&RX as well as audio stage are very good.
This is important to know, because here we mainly deal with the processing, reproduction and modification of existing (mostly older) projects.
Additional quality in work can be achieved with such projects; by improving the audio stage.
But also with the addition of a special stage for the scale (either analog or one of the digital types).
Today in the "digital" age, when everything has gone to ADC, lots of samples and lots of filters; this story does not have the same significance.
But "digital" doesn't have that "smell" and "patina" like most of the projects we deal with here.
A good analogy is with audio amplifiers, with tubes. There is no "warmer" sound than that.
It's all for nothing in this digital world. You will never get that sound quality.
Ok, I got a little carried away and wrote an actual essay!
But over the years I've noticed that many "experts" don't really understand the importance of the audio stage in detectors.
And even if they understand, they don't pay too much attention to it.
Mainly, most focus on frontend quality and channel signal processing.
Imagine Joe Satriani playing his guitar, the way he does, but plugging that guitar into an LM386-based amp!



P.S.
Whoever accuses me of scribomania here... let him eat smelly sausage!
Because the activity on the forum has completely died down.
Nothing interesting happens.
Time to give some life to the forum!
Let's go people!