[Heathkit] HW-16 Warble

[Rodger Singley]

Mark,



That is a pretty bad chirp in the recorded audio you uploaded.  Coupled with your finding that it shows up on the receive side with the audio output increased it certainly sounds like a B+ issue and is sufficiently bad that the VR tube in the HG-10 cannot compensate for it.  If the problem was only on transmit I would suspect an issue with an aging VR tube in the HG-10 but since it shows up on both either the power supply itself or something creating an unusual load on it is at fault and the problem on both transmit and receive (at higher audio loading) points to the problem being in the supply itself.



Although power supply regulation issues are usually fairly easy to find this isn’t always the case and a standard scope setup will sometimes fail to catch little variations.  Since this is likely a voltage change/regulation issue you will need to set the scope input to DC coupled but then most scopes aren’t sensitive to a small change because the base DC level “swamps” the variation.  I use a Tektronix 7A13 differential comparator plug-in with my 7854 mainframe and this plug-in has built-in adjustable DC offset so that you can cancel out the main DC input voltage and leave the plug-in set for high sensitivity to display minor variations in voltage.



Rodger WQ9E



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From: Mark K3MSB<mailto:mark.k3msb at gmail.com>
Sent: Wednesday, August 17, 2016 7:31 AM
Cc: Heathkit List<mailto:heathkit at mailman.qth.net>
Subject: Re: [Heathkit] HW-16 Warble



Good Morning.

I should mentioned in my initial post that I monitored the voltage at “C”
with both a scope (through a divider network) as well as with at VTVM.   I
observed no correlation with voltage variations (very, very small) with the
warble.

A few times the voltage dropped by 5 volts or so (could have been power
line fluctuation) but this did not cause the warble.

I did not monitor the heater voltage as some of you have suggested.   I
should have thought of that as I’ve run into heater related issues in the
past.

73 Mark K3MSB
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