VLF Gold master repairs needed help

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AtomRat

AtomRat

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It seems my VLF just doesn't want to keep a signal anymore. Every time I use it on tr disc. the tone drops away within 3 seconds. Is this a capacitor issue?

It seems the dual pot G.E.B knob is a bit out of date too. Also seems some problems with the battery terminals or contacts to the main board.

Any help on how to do a general circuit board check with a detector? Ill just be checking for dry solders, connections or breaks, checking components for burn, and cleaning the board with alcohol. I'll spray the knobs with silicone when I go to jaycar next week.

I have an oscilloscope if signal testing needs to be carried out. And considering to elimate the battery issue by soldering a new battery bank connector.
 
Also will add, how can I test the coil? Just a multimeter continuity test?

Forgot to add image:

1436919981_img_20150715_082704.jpg
 
You can get a frequency meter from jay car it will only be a circuit board for about $20-$30 to test the coil is running at the correct frequency as they do wonder a bit... Don't ask me how to adjust it if it's out' but there is a way.

Post up the details of the machine and I'll see what I can find out'
 
Gday zuke_lynzy, its a bit of a problem finding info on this detector. Theres some more pics down the bottom of this thread:
https://www.prospectingaustralia.com/forum/viewtopic.php?id=8353

I just want to check that theres no broken wires along the coil wire or coil itself as the detector seems to be loose and sensitive somewhere?! on it. Moving the detector, knocking it, wet grass anything makes it turn on and off, drops the signal out, becomes very noisy

When I turn it off onto G.E.B NORM which is like its all metal mode, it works sort of ok. But disc. just drops out so no more beach n coin hunting for me at the moment :(

Is a frequency counter the same thing? Ive been going to get one off gumtree for ages. Would I then need a freq. generator to send a signal down the line too?

I know the basics of electronics, but have not been shown too much from there on so do ask a few wrong things about the subject.
 
Ahh' yeah I remember that post, I think your going to struggle with that machine as I'd say that no one at whites now will have ever seen one so my only suggestion would be join the Geo tech forum and make a new post about "Vintage goldmaster machine" and hope someone there knows something or has a schematics for that machine.

The other thing is where do you stop with an older machine before its easyier to upgrade? It might be worth just as much to a collector without getting it running.
 
It looks like a 5100D goldmaster keep your eyes open for a old coil on eBay, I've seen them for $10' just to try might be cheeper than test equipment at least then you can measure the pins and inductance between the two coils.
 
Bumped a tree root today and that was it. Ol goldmaster turned into a noisy crunchy signal that dropped in and out constantly not holding any clear signal. I've opened her up yo take a closer peek. Thankfully no visible damaged components from burn outs, at the same time I can't diagnose by eye the error.

I'm starting to think mabey the pots are a little bit dodgy so ill replace what I can. First off are disc, sens and tone pots. 50k, 5k and 100k. The 50k discriminator pot makes a crunch, mabey its shorting out the whole circuit and this detector hasn't had discriminator working for a while..

I've never seen the power on off type switches, they look a bit rusty inside..don't know if I can replace them though and some silicone spray may have to suffice. I've given the board a brief metho clean.

The contacts to the battery supply is a bit dodgy so I'm going to hardwire a new caddy and see if this helps. Well, off to jarcar for me tomorrow..if anyone else can suggest what I might need to replace it would be very very useful.

Ill re-wire the whole lot as well. All components by eye though..seem ok. Don't think I can see a rom or eprom ic in here..might be able to copy the whole board if I get desperate

1447559846_14475597839880.jpg
 
Awesome grubstake, ill replace them too while I'm at it :D when shebfirst started to play up.. the signal faded lots like it was a transistor or cap issue straight away.

Bit of soldering tomorrow after i return from the hour drive to get the components..ill write down a list when I return home. That reminds me.. I even gotta buy some wire
 
*sigh*

Replaced all bits and its still doing the strange jittery thing :mad: after todays effort.. I think I might just give it a rest. The coinmaster doesn't work ny the way either :( just cuts in and out abruptly for no reason like a shirt I can't see. I'm starting to think its in the main switches which ill have to try and replace mabey. I dunno.. after finishing the soldering and its still not workin, im pretty upset and not really keen to touch it anymore today...next subject. :mad: :mad: also $20 down after buying the components to attempt to fix it. I dunno. Re wired the whole thing nearly too. Damn damn damn damn... :(
 
But now that you know a few things that are not the cause of the problem,... you are narrowing down what it could be ! ;)
 
Lol thanks for keeping me positive silver.. whatever it is is like a loose copper track..cracked solder join or a short. Something very minute and I'm having trouble spotting it anywhere. Changed new capacitors, potentiometers and hard wired a battery pack ( at least I certainly know its not to do with any of them yes )

Being the majority of the main components.. I don't understand why its not working. It really should b
 
AtomRat said:
Ok hmm..I just turned it OFF and the speaker kept ringing. Certainly a short somewhere
Click to expand...

Wont be sending my detector to you for repairs :p , hope you get it sorted mate ;)
 

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