Re: HT-44 Common Problem?
开云体育
Floyd,
I have seen that a couple of times over the years. It boils down to the balance of all triodes in V3 and V4.? The triodes in each tube need to be matched and V3 and V4 need to be matched. If either of the tubes suffers an intermittent short, large loss of
gain or becomes gassy you can lose R16 and 17.?
(You probably already know this, but I thump the tubes in the tube tester while doing the shorts test to check for intermittent shorts.)
If you find it difficult to balance the system, look for drifted resistors or leaky capacitors. The respective components in the V3 circuit need to be very close to equal to those in the V4 circuit.
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Walt Cates, WD0GOF
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From: [email protected] <[email protected]> on behalf of Floyd - K8AC via groups.io <floydsense@...>
Sent: Monday, December 9, 2024 9:32 AM To: [email protected] <[email protected]> Subject: [HallicraftersRadios] HT-44 Common Problem? ?
This is the second HT-44 where I've run into this problem.? I use the HT-44 heavily on CW and my current one has logged hundreds of QSOs in contests.? The other day it suddenly had no output on any band, same symptom observed on another HT-44 I owned.?
In digging into the problem, I found the cause to be the same as on the other HT-44.? Resistors R16 and R17 (22K , 2 watt) were cooked and V3, a 12BH7 associated with those resistors tested weak.? I replaced the resistors and the 12BH7 and now all is well
again.? Had to adjust the pots to null the carrier for SSB.? I wonder if others have experienced that problem?? Not sure if the cause of the failure was the tube, or maybe the two resistors are undersized for the current?
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73, Floyd - K8AC
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waltcates