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Old 19th Jul 2017, 10:11 am   #50
crestavega
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Join Date: Apr 2014
Location: Kirkwall, Orkney, UK.
Posts: 165
Default Re: Sailor T128 Marine Transmitter.

Yes, I do appreciate that the "brains" of this radio is in the small signal department. However, I am pretty sure that is all working. I can hear decent SSB, carrier, and the two-tone signal (not all at the same time!) on a nearby receiver, pretty well on the advertised frequencies. so I think I can safely say that it is working all the way through to the balanced modulator and probably beyond that.

as I understand it: the built-in test meter, in pre-drive position, sniffs the half-wave recitifed (D602) voltage from the QRP signal being applied to the PA valves.

P.8 of the original manual (Tunin-up main channels procedure), step 10, says to adjust the drive level for a peak on the pre-drive meter. Now I cannot get the meter to even twitch in this position so either there is no signal at all getting to the PA grids or there is something amiss with the sniffing line leading to the pre-drive meter.

I have put a small dc voltage on the anode of D602 and the meter moves so it's ok to there. Beyond that is 8.2pF C605. to test that properly I need to get out the sig gen and scope etc as you say.

I think it probably is pointing in the direction of a problem around the driver tube V501 as you hint, which I have not even investigated up to now (other than replacing a toasted resistor R515 I think it was.)
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