Fisher 1266 PART 2

[aft_72005]

Hi ivconic
Very good work .thank you. Are you built it?
Best regards.

[ivconic]

Not yet. I just finished drawing these pcb's. Waitng first to make pcb's than i will solder components and test it. First pcb is error free, just checked it. Second is about to be checked tomorrow. For coil i am planning to use CC coil from MD3030. Already tested on original 1266 and it is working splendid! Much better than original Fisher coil.
At this very moment i am finishing eldorado1265. Last component was just soldered. Tomorrow i will perform tests...if snatch some spare time..
Cheers!

[ivconic]

Just finished 1265. Workable but with certain problems...
In nonmotion mode it is working by the book - excellent. But in Disc mode it is working very bad. Disc seems to be out of range. Can't get it right after 2 hours of searching for problem. I managed to find some small quartz without label and with it i gain exact 4.8xx kHz at pin 1. of 4024. Good!
Not only that Disc works wrong, but also audio is not so loud as on original. Turning trimmers do make some changes. But turning Disc pots doesn't make any changes. Also turning Sens pot does make small change almost bairly noticeable. I am using original 1265 coil (8").
What is the problem here? Damn!
I must recheck all over again. Oh yes...i cant obtain 27M4 so i checked 27M9 and TL084's instead. Seems (pretty subjective) that TL084's works a bit better than 27M9's...
Damn... i wanted so badly to success with this!
Also i noticed some components differences beetwen this schematic and previous one posted long time ago...
Instead fet at pow. supply stage i put only one diode (4002) beetwen D and S. All the voltages are proper, just like i measured on original 1265...something arround +6.35V and -3.89V ... so this not suppose to be a problem...
The role of this rare (at local shops) fet is very simple; when something goes wrong at power lines it simply "close" (disconnect) the power path and prevents some major damage. (Also when battery drains under range).
So in testing purposes we can use simple diode to provide all the functional voltages.

[KingJL]

The role of this rare (at local shops) fet is very simple; when something goes wrong at power lines it simply "close" (disconnect) the power path and prevents some major damage. (Also when battery drains under range).
So in testing purposes we can use simple diode to provide all the functional voltages.

Actually, this PMOS (VP0104N3) provides regulation. My 1265 provides +3.92 -3.87. I have substituted a FDV304P with good results. Any PMOS with similar specs should work (watch out for the pins when substituting this as some pins are different sequence). If the source/drain is reversed you will get voltages similar to what you are experiencing also (ask me how I know).

Regards,
J. L. King

[KingJL]

Oh yes...i cant obtain 27M4 so i checked 27M9 and TL084's instead. Seems (pretty subjective) that TL084's works a bit better than 27M9's...
s.

Main advantage of 27Mx is the exceptionally low supply current drain.
Regards,
J. L. King

[ivconic]

Actually, this PMOS (VP0104N3) provides regulation. My 1265 provides +3.92 -3.87. I have substituted a FDV304P with good results. Any PMOS with similar specs should work (watch out for the pins when substituting this as some pins are different sequence). If the source/drain is reversed you will get voltages similar to what you are experiencing also (ask me how I know).

Regards,
J. L. King

That's new for me? I measured voltages on one "accurate" device which works well and voltages were in ranges +6.xx and -3.8xx volts...?!
So...considering this, what you are saying, i start to think that my problems with Disc are maybe tied to inproper voltages? Right?
For sure i can not find that or simillar fet here in local shops. So i should make quite different supply stage with available components.
I am asking you now; are the symetrical voltages so important for this design? Cose those are NOT in TGS case at all...Maybe this fooled me?
If not than i will search for some other cause of problem, but if yes than i will make another supply stage instead.
I am not quite sure about 1265. I had 2 devices so far but never had any problems working with those, so logically i never performed deatiled measurements and checks. Also had few on service, but almost by the rule i had to replace LM339 and MPSU51 and nothing else (reversed battery poles...ha,ha,ha...quite a "hobby" among local prospectros here!!!)...and damn VPOxxx always survived such piffle with batteries!?

... "...These enhancement-mode (normally-off) transistors..."


"Normally-Off" says....yes you are right, i understood it wrong! Not only that switches but also can regulate voltage....sheeshh!
But...how the heck device (the other one) works with voltages such far from being symetrical??? Like i told here, i measured pretty close voltages as on my handmade and still device worked correct. Usually i do keep papers with schematics and later added comments on those. So in this case i found out old paper with 1265 schematic and my old remarks and measuring results from that time. At the time i measured voltages and few other points...cleary do remember that device...

Ok..whatever...i just need to know your opinion on how important is to achieve symetrical supply here..? Thanks in advance!

[KingJL]

Ok..whatever...i just need to know your opinion on how important is to achieve symetrical supply here..? Thanks in advance!

I can't say with complete confidence. Although, considerig the methodology that the 1265 uses to discriminate, I would be biased toward the balance between +/- to be faily important. It uses a comparison between the resitive motion channel and the discriminate motion channel. The discriminate level potentiometers(s) bias the disc motion channel between the I & Q (they are actually 208 degrees apart) phase detector channels. The output of the Q channel phase detector is a negative voltage that goes more negative and then to slightly positve for maximum signal phase change. The resistive channel goes from 0 to positive back to 0 for maximum signal phase shift. If the +4v & -4v are not somewhat close, you will not be able to adjust the comparison point (which flips the comparitor) to achieve proper discrimination.

I would vote for important that they be reasonably close.

Regards,
J. L. King

[KingJL]

Ivconic,
I have the 1266 PS modeled in LTSpice. The 1266 PS uses the same methodology as the 1265 (uses the same VP0104) . The model uses a FDV304 in place of the VP0104. The 1266 schem is slightly different. If you want the model, let me know.

Regards,
J. L. King

[ivconic]

Thank you, i will make symetrical supply on another, small pcb.
Yes i would like to see 1266 model. I have LTSpice installation somewhere on hd.
Thank you very much for your comments.

[KingJL]

Thank you, i will make symetrical supply on another, small pcb.
Yes i would like to see 1266 model. I have LTSpice installation somewhere on hd.
Thank you very much for your comments.

I included all of my models for the 1265/1266. They have helped me understand what is going on in the circuitry. They also help in troubleshooting problems. I may be using some device models that are not included in the LTspice release. These usually can be found on the internet. If not, yank my chain and I will try to get them for you.

Regards,
J. L. King

[ivconic]

Thank You very much!
Just logged in... ok, now i will see this .


....
ooh yes...many of them missing... mpsa20, ne5534...and many more...
i will search on the internet...although..dont know where to start!?

[KingJL]

ooh yes...many of them missing... mpsa20, ne5534...and many more...
i will search on the internet...although..dont know where to start!?

Try here for a start.
http://tech.groups.yahoo.com/group/LTspice/

Join the group and then you can search there files for models. They have most of what is needed.

Regards,
J. L. King

[KingJL]

Ivconic,
Also, make sure you have the latest version of LTSpice!

Regards,
J. L. King

[KingJL]

ooh yes...many of them missing... mpsa20, ne5534...and many more...

Here are most of them. Have fun!
Regards,
J. L. King

[ivconic]

What to say? Thanks again! Thanks much!
Best Regards!