Cscope 1220B Schematic

[ivconic]

Need Cscope 1220B Schematic. Or Metadex schematic can be usefull also.
Beleive me or not, again friend of my need this to service and repair that old,broken unit...
Regards!

[ivconic]

This is also excellent chance to see pretty rare KT315 with brand new face here again!

[kt315]

brand new face here say you Repair Manual on 1220-B have been laid out in forum. try Search.

[walter]

Find attached the schematics for the Cscope 1220B. I've been a passive user for quite a while now, lots of good quality content, so here's my first contribution. Hope that works for you.

Best,
Walter

[kt315]

I am also passive user. some people does not believe that.

[ivconic]

Oh yeah!!?
Where were all of you "active" and contributitive members than, at the time when would be nice to show good will to help?
First silence, than argue and now posting stuff just to show how "great" you exactly are...Bravo!
Too late....1220B schematic already seen and saved...long time ago.
Thanks anyway. No need anything more from you here.

[Qiaozhi]

Oh yeah!!?
Where were all of you "active" and contributitive members than, at the time when would be nice to show good will to help?
First silence, than argue and now posting stuff just to show how "great" you exactly are...Bravo!
Too late....1220B schematic already seen and saved...long time ago.
Thanks anyway. No need anything more from you here.

Better late than never...

[ivconic]

Now, reading my old posts... am a bit ashamed!
To much emotional from time to time.
...
However, yesterday my old wish fulfilled!
I got vintage Cscope 1220B at last!
Got it!
Again!!
Will not part with this one NEVER again!
It is in splendid condition! Like it was made yesterday!
Just checked it; everything is functional with no problems at all!
All original parts are present and all is in excellent shape.
Only battery holders are with a bit rusty connections (springs) and may need to be replaced, not a problem, those are available and very cheap.
Plastic box, knobs, parts; everything is in so good shape, really nice kept all those years.
Opened and inside all shiny and looking brand new. Nothing resoldered and serviced so far.
Not even a dust inside.
I hooked it up on external battery pack and checked it. Working splendid!
Now, after all those years, i am even more convinced in high quality and good knowledge that was present at that time.
By no means this device can not lag by todays machines.
Everything is here.
It is deep. It is pretty accurate. It is stable.
First of all; it is non motion, real one, the right one.
I made several bench testings and it outperforms my expectations (seems i forgot that during last several years, dealing mostly with newer designs).
If you look at it's schematic - you will not see nothing so special , but if you take real device and test - ohh, you may bet that you will experience something very special ... and i mean it.
I am wandering why Cscope not make a jubilee series of those legendary models like 1220b and Metadec?
Ok..they made 1220R and 1220XD, but that's not it. This one, in this kind of enclosure, with this one pcb and parts... that's something which is really wort to be "remake" for jubilee.
It is still very competitive to today's top models.
Only drawback can be very small coil which is common for such series, Isocoon 20cm.
Only 20cm and still outperforms!
I wander what should be the performances with 27cm coil?
Maybe i will try to make one and see.
Ok... that's all for now.
I'll go to enjoy now!
Cheers!

[mikebg]

Ivica, please check if this is true - incompetent design of preamp.
Very low gain of preamp - less than 9 times:

[ivconic]

Ivica, please check if this is true - incompetent design of preamp.
Very low gain of preamp - less than 9 times:

I will, but first i have to decipher that blur schematic to see values noted..

[mikebg]

I will, but first i have to decipher that blur schematic to see values noted..

No need of sharpness. Simly check if the value of R28 inside your machine is 13 kohm. This value generates noise more than opamp and reduces the gain of preamp stage below 9.

[satdaveuk]

i was just about to post that circuit drrrrr missed the window

[mikebg]

i was just about to post that circuit drrrrr missed the window

Dave, if you have more information about Cscope designs, please post it!

[ivconic]

No need of sharpness. Simly check if the value of R28 inside your machine is 13 kohm. This value generates noise more than opamp and reduces the gain of preamp stage below 9.

Just got spare time to open 1220B and check; R28, yes it is 13K, no mistake. R29 is 100K (in case you wander). C7 is trimmer capacitor 65p and C8 is 100nF.
Opamp is CA358 (LM358...) !?

[ivconic]

Yesterday i went outdoor to check this machine.
Have FINDS!
7 silver Turkish coins.
I could miss easily those coins if i were'nt used earphones with 1220B.
Because signal was tiny indeed.
But with earphones 1220B is really mighty.
Smallest coin is 9mm diameter.
Depth was approx 10cm to 12cm in heavy mineralized soil.
Last time i was there, on that spot, i had XP Gold Max Power with me and also detected 19 coins like those.
But it is obvious that use of earphones will give better results.
So 1220B is yet actual, still not for hanging on the wall...