Sencore SG165 rf problem - Printable Version

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+--- Thread: Sencore SG165 rf problem (/showthread.php?tid=12267)

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Sencore SG165 rf problem - KCMike - 05-14-2015

I have a sencore sg165 analyzer that came with some of the usual problems I have read about online. The am/fm tuning cap shaft was broke. I repaired it and have accurate am freq. readings but no fm readings.
I checked the tr314 tr 315 out of circuit and they test good.
Any help with what to check next is appreciated. Also all the other settings sine, square wave and sweep etc. appear to be working correctly. Thanks for help.

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RE: Sencore SG165 rf problem - morzh - 05-14-2015

Have you looked with a scope? It is fairly small output.

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RE: Sencore SG165 rf problem - KCMike - 05-14-2015

Thanks Mike, I did have it hooked to scope when checking the sine/ square wave ,not the fm frequency. With the tuning shaft broke after fixing , I was using an B&k 1gig frequency counter to test the fm frequency. The am is reading fine. I will have to reinstall the main rf board and transistors to get it back to look at on scope. I would think the fm should read on the frequency counter. The counter reads all the fm frequencies on my leader lsg 215a signal generator.
Before removing the main RF board I did check the volts from ground to base of the tr315. It read -12volts. according to manual oscillator tr314 runs only when there is 12v+ at base of tr315 turning it on and supplying emitter current to tr314. I don't know why it had 12v- at base. Thats why I thought I had a bad tr315 transistor. The molex plug to RF board from the power supply board have both -12v and 12v+. I will try to get the schematic downloaded and put up here.

http://s1336.photobucket.com/user/220kohms/media/Scan_zpsv30emfxc.jpg.html
http://s1336.photobucket.com/user/220kohms/media/scan%202_zps1k9zljob.jpg.html
Here is the rf section of the manual.

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