Sovereign crystal troubles Sean Goddard please help :) :) :)

[plumabob]

Sovereign XS went dead suddenly. Narrowed it down to the crystal. Swapped in 3 others of similar or same frequency only to have it conk out on me again after an hours use. Any ideas? Nothing seems to be getting hot and this Sov even though old has super low hours on it. Have tries the original 3.904 and a 4.000 and also a 3.93

Thanks for any and all help.

Bob

[nakky]

Have you check , Q7 BS 170

Nakky

[plumabob]

What is Q7 BS 170? Not too good with checking parts.

Thanks

Bob

[nakky]

[ATTACH] 29356 [/ ATTACH] C 37 / Q7 Nakky

[golfnut]

Have you tried putting the original 4mhz one back in and seeing if ok?

This xtal fail mode may be a distractor with sommat else the real problem?

[plumabob]

All is fine now. The crystals I tried were used. I located a new 3.93 and she's purring along now for 5 hours just fine. Thanks for the input.

Bob

[Sean_Goddard]

Sorry, ~Plumabob I only just picked this up, I'm not on here much anymore.

The Sov is VERY picky about crystals or should I say about the IMPEDENCE of crystals due to the value of the bypass capacitors chosen, they put the whole thing just "on the edge".

I swapped out the 3.904 for a 4.5 and mine worked well for a month then suddenly died. Changed back to the old 3.904 and all was well. Not an awful lot of room to "overclock" the CPU, so I did a mod which involves a small SM PCB with both crystals on it and a custom oscillator and you could switch between the two. This became ML's "Interference Cancelling Upgrade" in the Elite series (stolen from me I wonder) but IDC.

If you make one of the above, you have to follow the following procedure;

1) Put CPU into RESET

2) Change OSC Frequency

3) Release RESET

If you dont do this the software gets in a muddle and falls over (random targets appear from nowhere or something like it).

[plumabob]

Hi Sean,

Thanks for gettin back. Well the 3.93 failed yesterday...lol so I did as you and swapped another 3.904 back in and so far she's running fine for several hours. Was thinking about removing the crystal and running 2 leads from the circuit board to the center terminals of a dpdt switch, then connect the 3.904 to one side and a 4.094 to the other. Moving the switch back and forth would change frequencies? In your opinion would this set-up work?

Bob

[Sean_Goddard]

Hi Bob, it MIGHT but you may also get erratic results. You need to assert the RESET line after you change frequency as the Sovereign sets up all it's discrimination and timing at this point, changing frequency half way through will confuse the micros timing and the way it processes the signals. You MIGHT get away with it but at best responses to targets will be unpredictable.

[plumabob]

Hi Sean,

Well my GT is also down at the moment and in for repair so I'll leave well enough alone for the time being. If this latest crystal craps out and has to be removed anyway I'll give the switch idea a try.

Thanks for your thoughts,

Bob

[Sean_Goddard]

Try "tweaking" the cap values. look at the Datasheet for the micro to get an idea of the best ones to use. I know B. Candy thinks he knows better than the people who designed the micro so he prob used a different value.

[sdesic]

Hi Sean,

I am sorry for hijacking this thread but I can't send you a private msg.
You might have data on old detector that I have and it is not working.

Metrotech 220 A
Trying to find schematics for it so I can wire it properly.

Regards
Sinisa

[Sean_Goddard]

Hi Sdesic, Sorry, I've never heard of these until now. You could try tracing out the schematic as that might help. I believe that it is a TR (100KHz) type machine, not very deep on coins but a good machine none the less (from what I read on the "web").

Can you photo the pcb and post here, maybe we can help then.

[sdesic]

I think "PCB" is sealed in plastic
here is my old post
http://www.geotech1.com/forums/showt...654#post178654

[Sean_Goddard]

Hmm, if all the wires go to where they should according to the photos and it still doesnt work, time to crack open the Acetone methinks.

Sorry can't help any more that that .