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Old 28th Dec 2019, 9:22 pm   #154
Sinewave
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Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default Re: Marconi TF144H/4S

So, there's still a few things to do, however the unit is working fine really, as reported earlier, but I still wanted to go through the whole set up.

So regarding voltages, the valve voltmeter is being specified to measure some of these voltages I'm using a modern DVM for, which may be getting upset with present RF.

For the record with my DVM I'm measuring at the phones socket up to 38V DC with my signal generator connected (pin 1 tag strip) at 1khz 20v pk-pk (manual suggests these are DC voltages, however the rectified probe on a valve volt meter is for AC measurements). The max should be 20v and if not then the manual suggests checking V204, MR206 and C208. All appear to be fine. With carrier off this can be 65-70v.

I don't actually have an audio oscillator, just regular generators, but the sinewave appears pretty clean.

So, to try and be sure what I shall do is come back to this with a working valve voltmeter (hopefully) and see if this can be nailed down. Then hopefully I'll be somewhat satisfied with the Crystal Calibrator section of this set up procedure/performance checks.
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