2000gtl freq.cntr. prob. nomad? DTB? help!

[loosecannon]

hi all,

just replaced the FETs in my counter module, as it was getting erratic.
switching to 11.xxxx for a second and then switching back.

i replaced all the electrolytics in it about 2-3 months ago, and it worked the same afterwards.

i am now getting the dreaded 92.2000 readout in AM, and 0.0000 on SSB.
replaced D528 with NTE136A.
i tried replacing the two transistors and the SCR mounted on the rear panel with NTE replacements. no change.
put stock ones back in. old FETs could not be salvaged.
old ones too haggered to go back into chassis.

i also found one tantalum cap (.47uF) on the board that the schematic says is supposed to be an electrolytic, so i replaced it with one.

when putting my RF voltmeter (dont own a scope) on TP504 (IC512 pin 5), i get no reading and adjusting L501 does nothing.
similar result when on TP502 and adjusting L502.
no reading on RF voltmeter.

so, no RF output?

did i somehow blow IC512? i was very cautious about static electricity.

the stock FETs in my counter were:2SK192a
i replaced them with NTE312.

should i have used the NTE133?

yes, i know about NTE parts being relabeled parts, but assumed they would work in this app.

any help is appreciated.
loosecannon

 

[bigred222]

looseCannon I cant really help you, however I have a similar problem with my Dx2547. its not really a problem but the last 1-2 digits of my freq counter like to change a little even though i have an unlocked clarifier. its not really bothering me its just odd.

 

[DTB Radio]

The 2000GTL counter is one circuit that I haven't got any real experience with. I've just never encountered any that had trhe usual problems, so I've never had the opportunity to go into one in-depth.

Id check for some kind of signal at the gate of FET501 to see if its at least receiving the signal from the PLL circuit. If it is, and you dont see it at IC512, then the breakdown is in that FET circuit somewhere.

 

[loosecannon]

well, i feel foolish.

the one good thing about stupid mistakes is that they are usually easy to fix.

i didnt check my datasheets well enough before putting in the NTE FETs.

the lead configuration is exactly backwards from the original part.

took them out, turned them around, replaced them.
voila!
counter works great!

im very relieved.

hey DTB, even though you havent worked on these too much, your instincts were right on the money.
the FETs!

nice to know your guesses are on track eh?

thanks for the replies,
loosecannon

 

[DTB Radio]

I can relate to the very relieved feeling, AND the dumb mistake, lol!