RG 750 Vista Questions

[Nad]

Deeptek RG 750 Vista. I am here, reading, in awe of what you people take for granted. I can't solder a single wire together without it shorting.. My phone jack is broken, cost to repair would be $35 to $50 in a shop, Postage to Bulgaria about that..I am asking the one turn ground balance pot be replaced with a three turn.. What ever updates they will do, they will do..The sound from the speaker is in my cancel out zone.I can hardly hear it.. I remember an add on amplifier, volume control and speaker assembly was a common item in the 60's....My questions. If powered by an external battery, will the detector batteries last longer than when driving the detector speaker... Can the the present sound be changed in frequency, lowered ,so that I can hear it better with an add on external speaker? Anyone using the Vista 750?..PS while not an electrical type, I can talk wood carving pretty well thank you for any suggestions / ideas.

[N@SKO]

Shematic of rg750
http://detectors.netfreehost.com/vie...orum=detectors
Maybe will help you

[Sean_Goddard]

Will be GREAT when someone draws this up in a proper schematic package .

[porkluvr]

Why is every chip identified except for U8?? Looks like that has a lot to do with your audio and it does not look like a CD4046 would fit there. So, what is it??

You could probably play with the RC component values around that chip and change audio frequency... if you're desperate. But I can't tell you what is happening there.

[N@SKO]

u8=4060

[porkluvr]

There it is, thank you N@SKO.

That would be a 10nF capacitor attached to U8-9. The 4060 main oscillator thereby operates at ~8kHz. Pin-7 is a divide-by-128 output, giving approximately 500Hz.

Nad, you did not say what exactly you would like to do with the audio but you can effect frequency change by adjusting either the 4.7kΩ or the 10nF. (Or both. ) Leave the 47kΩ on pin-10 alone, except that it should -ideally- be about 10x whatever is on pin-10... but that is a guideline and not a rule, ummh, I think.

If you don't want to have to unsolder any parts, you can make parallel additions.

Adding either 1nF (.001uF) or 2.2nF capacitor in parallel with the existing 10nF will lower the audio frequency to either 460cps or 413cps. More capacitance will get you lower freq.

Adding 47kΩ resistor in parallel with 4.7kΩ (parallel value ~4.3kΩ) will raise audio to about 550Hz. Adding 33k in parallel should get you about 575Hz. Adding resistances in parallel lowers the R value, and that will raises freq.
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[porkluvr]

There it is, thank you N@SKO.

That would be a 10nF capacitor attached to U8-9. The 4060 main oscillator thereby operates at ~8kHz. Pin-7 is a divide-by-128 output, giving approximately 500Hz.

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Mistake. U8 Pin-7 is a divide-by 16 output, not divide-by 128. That would be crazy. Sorry about that.

[bernte_one]

who can generate a pcb layout from this shematic above?