From: [email protected] <[email protected]> On Behalf Of thoyer via groups.io
Sent: Saturday, February 15, 2025 8:07 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-28A Hum?
Ok, tried two different 6V6¡¯s, no change.
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On the plates of the 6V6¡¯s there is 6.8Vrms of 120hz ripple. If I remove the 6v6¡¯s it drops to 4.7Vrms and the hum is no longer audible (as expected).
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With the 6V6¡¯s back in (Russian tubes BTW), switching the bass ¡°IN¡±, which shorts CH2 and C43, the hum goes away but has no impact on the measured ripple.
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These measurements are made with my o¡¯scope.
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I did some poking through my ¡°inventory¡± of parts and do not have a suitable choke to swap in for CH2 ¨C still thinking there may be some leakage going on there¡¡?
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Fun stuff huh?
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Tom
W3TA
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Hi Jacques, I just received 1.5 cents from you.
Your proposal may well be, but how do you explain the difference ?the switch setting makes?
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My two cents:
If the 120Hz ¡°hum¡± is still heard when the 6SC7 tube is removed, that could be that the output stage is not balanced current wise.
Meaning: if one of the 6V6 is way less polarized (more weak) than the other, that could be the cause.
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73, Jacques, VE2JFE in Montreal ?
--
don??? va3drl
