Cscope 1220B Schematic

[Davor]

Ah! Thanks. Now it is obvious, silly me

[mohandes]

hello ivconic
do you have shematic cscope metadec1 ?
i need the help
thanks

[Peter Jones]

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...) !?

Sorry to resurrect an ancient thread, but has anyone experimented with the value of R28 ? I'm guessing 6K8 would make a noticeable difference (whether good or bad) and still be safely within the op-amp parameters ?
I'm in lockdown (Furlough) and have just rediscovered my 1220B when tidying the garage, so might experiment this afternoon

(Not been involved in detecting for several years, as life has gotten in the way)

[dbanner]

Sorry to resurrect an ancient thread, but has anyone experimented with the value of R28 ? I'm guessing 6K8 would make a noticeable difference (whether good or bad) and still be safely within the op-amp parameters ?
I'm in lockdown (Furlough) and have just rediscovered my 1220B when tidying the garage, so might experiment this afternoon

(Not been involved in detecting for several years, as life has gotten in the way)

Increasing the gain of the preamp? Try it and see what happens. Best to test outdoors in real conditions before and after.

[Peter Jones]

Unfortunately, it now seems I have to get the thing working before I can fiddle with components

[Peter Jones]

Experimented with R28 value today - results not quite as expected.

The audio frequency shift/swing seemed greater, whether in the ferrous or non-ferrous direction, making the detector seem more "exciteable" (if that makes sense) in meter/audio disc mode.
Sadly, it had a negative effect on the in-air depth of all targets.

I have replaced the original resistor (13K), but it was worth a try.

A factory set-up manual showing waveforms, dc voltages at test points would be very useful, however I reckon C-Scope will sadly never let one of these go, even for obsolete models.

[dbanner]

Experimented with R28 value today - results not quite as expected.

The audio frequency shift/swing seemed greater, whether in the ferrous or non-ferrous direction, making the detector seem more "exciteable" (if that makes sense) in meter/audio disc mode.
Sadly, it had a negative effect on the in-air depth of all targets.

I have replaced the original resistor (13K), but it was worth a try.

A factory set-up manual showing waveforms, dc voltages at test points would be very useful, however I reckon C-Scope will sadly never let one of these go, even for obsolete models.

Haven't you seen the service manual or setup manual? It's here on this thread, you can download it. Last page has some waveforms. It has a detailed explanation of every stage of the circuit.

[Peter Jones]

Cheers, spotted those after meddling and after my last post

[sinclairuser]

i know earlier in the thread there was some dismay about the resistor only being 13k and that the gain is only 9 times but it is built that way for a reason increasing gain just makes the machine unstable.

[Peter Jones]

i know earlier in the thread there was some dismay about the resistor only being 13k and that the gain is only 9 times but it is built that way for a reason increasing gain just makes the machine unstable.

It certainly does.

I love how this detector works, in "Meter Audio Disc"; a version of this with purely that mode (and preferably ground balance), but more modern depth capabilities and a range of coils, would be somewhere near top of my list. (When I had an XLT I had it set for multi tone, bit the effect on busy ground was like listening to a Sinclair Spectrum loading )

[sinclairuser]

i still love older cscope machines, allthough i sold my collection a few years ago in disgust.
its all in this forum, but in a nut shell years ago cscope licenced some cx2m versions to be sold as parkinson pro's, but these were kits when built they looked just like the old white and green cx2m but were white and blue and had parkinson pro livery, the point is THEY CAME WITH FULL BENCH SCHEMATICS, my granddad bought a kit but never built it the schematic got lost during his house clearance after his death(i was offshore) at the time.
i contacted cscope asking for and being prepared to pay for the plans that came with the machine, so i could build it.
they not just refused but actually denied that the "parkinson pro" ever existed, treating me like a "muggle".
so in disgust i got rid of all my cscope stuff, only keeping the "kit" and grandads old" daily driver" unit.
so the question is if the parkinson pro never existed why do they turn up on ebay every now and then?.
cscope are way too over protective of old obsolete tech, they want you to send it to them so they will look at it say its buggered but here's this years catalogue, its corrupt.
sorry rant over.

[Guzzi]

The only CScope kit i know is the K5000. I own a kit manual ( In Dutch) K5000.pdf

Regards

Leendert

[goldie]

What is the ic1/ic13 marking? Does anyone have a photo of the board in normal quality?