Fisher 1265X

[nalag46]

Eugene, you are slighly wrong in label... VP_zero_104 - VP0104

http://search.datasheetcatalog.net/key/VP0104

http://www.alldatasheet.com/view.jsp?Searchword=VP0104

have a nice day

Hi Eugene,
I was wondering if had seen my last post of 31/5/2011 re. Fisher 1265X discriminator 2 problem and whether you might have any comment on the matter?
Best regards,
Tony

[nalag46]

Fisher 1265x

Got all the parts now and after carrying out all necessary set up and adjustments after the installation of components etc, I got all the correct voltages and everything is working as it should, well everything except for Disc 2, which does not respond when switched on by the Mode Switch.
The 3 way mode switch with its centre tag grounded and in the middle position works Disc 1 fine. Grounding it (switching it) to Pin connector 3 (U303 pin 13) enagages the Static Mode ok too, but grounding it to Pin connector 14 (U303 pin 6) which should engage Disc 2 does not and all it does is bringing on the Static Mode as if on the other position of the switch.
After grounding pin 6, Pin 9 also goes "high" which indicates the chip is switching correctly and there is nothing wrong with it.
The 8v from Pin 9 is fed to the other 2/4 of the switch Pin 12 Disc 2 Select but the ouput at Pin 11 is only 3.9v and the rotating os Disc 2 pot. does not change this voltage which is the same as Disc 1 Select Pin 4 but that does work the variable pot. Disc 1.
Have changed TLC27 (U302) but has made no difference.
Can anyone through a light on what could have gone wrong here?

[Altra]

I missed it earlier. It looks like water or battery juice leaked on the board. I would clean that before doing anything else. If you did not notice look around U12, LM339?, C20 etc. on your first photo. You can use alcohol and gently clean the area. Use a pin or exacto knife and scape the corrosion off. There could be a short in that area which is killing your power supply.

[Altra]

Nice photos, you are right that power supply is different than the analog CZ's.

From what I can see there are 3 LM2951's. These are adjustable voltage regulators.
Maybe one of them is for the display circuit +5v? The other 2 for the analog circuits?
The LM293 could be a low battery detect or virtual ground (see 1280X schematic)

[nalag46]

Fisher CZ5/CZ7

Hi Mark,
I am enclosing a couple of shots of the power supply and main board.
In the past when I had to contact Fisher US about anything to do with technical
stuff relating to any of their detectors, I was always referred to a UK approved
repair shop which I do not trust and are very expensive, specially with anything
like the complexity of these CZs.
I will try them again though but I do not hold my breath.
Anyway, let me know if you can spot anything there. I can see there is an 8 pin LM293
ic. which is of course a voltage regulator but like I said before, nothing is feeding it
at the moment.
Regards
Tony

[Altra]

Tony,
Can you post a photo of the power supply section of the pcb?

Also you might try writing or calling Fisher's repair department, explain your problem and that it would cost too much to send it to the US for repair. You may be suprised.

Mark

[nalag46]

Fisher CZ5

Tony, See post #11 in this thread.

http://www.geotech1.com/forums/showthread.php?t=12364&highlight=cz5

The attached schematic is a CZ5 power supply. As I recall the CZ70 base circuit was similar to a cz5, but with a LCD display.

For the diode use any schottky rated at 20v or greater, 1 amp.

Regards Mark

Hi Mark,
Thanks for the schematic and info. It is much appreciated.
I can see there are similarities but the CZ70 circuit looks quite different. It is the CZ6, 7 and 70 that all share the same pcbs, having said that, I got something to work on but I cannot see any Cmos enhanced transistor in my 70 power supply and cannot work out where the +10v supply (if that is what this one uses) is derived from. Tough cookie this twin board to troubleshoot without a schematic.

Thanks again
Tony

[amtech2005]

Eugene, you are slighly wrong in label... VP_zero_104 - VP0104

http://search.datasheetcatalog.net/key/VP0104

http://www.alldatasheet.com/view.jsp?Searchword=VP0104

have a nice day

Hello KT315 !! It is OK because I am slightly Learning these Fisher screw-ups !!

Best Regards to Everyone ..........Eugene

[Altra]

Tony, See post #11 in this thread.

http://www.geotech1.com/forums/showthread.php?t=12364&highlight=cz5

The attached schematic is a CZ5 power supply. As I recall the CZ70 base circuit was similar to a cz5, but with a LCD display.

For the diode use any schottky rated at 20v or greater, 1 amp.

Regards Mark

[kt315]

Hello . It is actually a discontinued VPO104n3 P-channel FET . So NTE326 should work . Look at the pdf data folder and also a nice clear schematic from this forum already !! Other opinions are welcome .

Best Regards...........Eugene

Eugene, you are slighly wrong in label... VP_zero_104 - VP0104

http://search.datasheetcatalog.net/key/VP0104

http://www.alldatasheet.com/view.jsp?Searchword=VP0104

have a nice day

[nalag46]

FISHER 1265X METAL DETECTOR

Hi Eugene,
Yes, that seems to make more sense. I have not come across a late 1266X yet but if this is the transistor Fisher decided to replace the "problematic" Q506 with, I totally endorse it and I will try to source it to keep it in stock. Many thanks for the tip.
On the subject of my other faulty Fisher Cz70, I have now established that the CZ6, CZ7, CZ7 pro and CZ70 pro all share the same twin surfaced mounted pcbs.
I have a power supply problem where no voltage is being fed to the circuits and where you would think it should be easy enough to troubleshoot, but the fact is without a schematic, trying to trace the thin tracks on both layers and under the huge array of ics is not easy task.
I believe someone has connected the two pin power connector (J3 18v) the wrong way round as it fits in both ways unfortunately. So, with two good 9v batteries, the 18v supply is present between battery minus and both the cathode and anode of D1 -which is a type CS400D and cannot find any data on it, but it tests ok out of circuit.
Do you know what kind of diode is this? Also, I get no voltage reading across main electrolytic C1 so it looks like this is the area where the problem may lie??
I have never worked on one of these circuits before and surface mounted components are a nightmare to source, never mind removing and replacing them without the correct tooling.
I do need to establish what exactlly is D1 before I can continue the tedious task of tracing the supply link and other lesser feed voltages to the different stages.
If you have any information, it would be much appreciated.
Best regards
Tony

[amtech2005]

Hello . They may of had problems on the 1265x , could that be why they used IRFD9213 for q-506 on the newer 1266x machine ?

Regards.........Eugene

[nalag46]

FISHER 1265X METAL DETECTOR

Thanks Eugene,
I have a working circuit and will play with it until I can get better substitute DMOS Fet transistors. Not an easy task here in UK and sourcing them from the States is a non starter as no supplier ships these in small quantities and shipping cost make them prohibited.
On a different topic; have a faulty CZ70Pro. Problem seems to be around the audio stages but this is a different beast altogether and a clear schematic is a must. Apart from most of the circuitry being surfaced mounted, I notice it uses several of these Cmos enhanced transistors both N and P channel, so I may be looking for the same susbtitute all over again.
Has anyone have a schematic for this model. It would be greatly appreciated.
Best regards,
Tony

[porkluvr]

I used to think that this 1265 power supply was sucky because LTspice showed poor load regulation. That was my mistake.

I've corrected my errors and repaired the simulation circuit and have to say it looks great. No joke.

You can have near perfectly symmetrical, well regulated 4V outputs even as the battery drops to 8V. After that the rails droop symmetrically.

Of course my version is only a simulation, but it's good. Maybe that's why Fisher went to the trouble of developing such a complicated circuit, and not just because they had extra parts lying around... big boss walks in and says, "we have extra parts lying around. Somebody needs to use them".

BUT
if you don't use the prescribed enhancement MOSFET for Q506 (or a reasonable substitute) and instead use a JFET, although you might have power it will not be the same. For that matter you could use a jumper for Q506 to save trouble and $$$. That's my two cents.


edit: In all honesty I did make some minor adjustments in the power circuit before I got it working 'freakin' good. I did it through empirical means; trial and error. I am hardly qualified to modify the circuit because I do not understand how it works.

I removed the comparator pull-up resistor ( R508 ) and installed another capacitor alongside C501, connected to +4V. I don't know if these mods would be so very great in real life, but they look good on my PC.

edit 2: That's not all. I also relabeled +4V 'ground', and ground became -4V (which wouldn't make it work any better but it does makes it easier for me to detect asymmetry, or operational anomalies).

[amtech2005]

Yes it is an enhancement mode mosfet . VP1008L . Same as used on 1280x [see parts list] . Here is the correct data sheet pdf below . I am still looking for correct substitution . Always a work in progress until it is fixed .

Best Regards........Eugene