[Hammarlund] HQ-150 Question

[jthorusen at centcoast.com]

Greetings to Dan and the Hammarlund list:

   It sounds as though you have a real puzzler.   If the problem is 
definitely mechanical, then you have to be pretty close to it.   I note from 
the schematic that I have downloaded that both C1 (Main Tuning) and C2 
(Bandspread) affect the L.O.   Have you also carefully cleaned up C2?  I 
would also inspect both C1 and C2 for foreign matter between the plates. 
You might also take an insulated stick and poke around the vicinity of the 
L.O. tube and circuit.   See if you can force the noise without moving the 
tuning capacitors.   Don't forget to wiggle the 6C4 in its socket.... bad 
socket connections can cause noise.   Basically, you are looking for 
problems in C1 or C2, or some area of the receiver that is mechanically 
coupled to the tuning mechanism.   By mechanical coupling, I mean chassis 
flexing, component lead movement or some such.

Good Luck,
Jim T.
KB6GM
Palus delenda est.


----- Original Message ----- 
From: "Dan Martin via Hammarlund" <hammarlund at mailman.qth.net>
To: <hammarlund at mailman.qth.net>
Sent: Monday, July 29, 2024 17:57
Subject: [Hammarlund] HQ-150 Question


Have an HQ-150 here with a very noisy high band, 18-31 mHz.  Only the 
highest frequency band. No others. Lots of loud pops, snaps, and crackles 
while rapidly tuning up and down the band. LO signal on scope shows sharp 
variations and spikes in amplitude up and down corresponding to the snaps 
and crackles. Noise is main tuning cap movement driven. Radio sits quiet on 
a fixed frequency. Try tuning around and it gets real noisy fast.  I could 
post a video w/audio if this system could take the bandwidth.

I have rotated in several 6C4’s (oscillator) and 6BE6’s (mixer) without 
change. I’ve put in place the 6C4 and 6BE6 from my excellent performing 
HQ-140, to no avail.  I’ve cleaned, Deoxited, and even used metal polish to 
a shiny mirror gleam the C1 cap wipers and contact disks. No change. I’ve 
preemptively replaced C89, C6, and C29 caps without change. All associated 
resistors in and around osc. grid circuit check OK. Pin voltages of mixer 
and osc. OK. I’ve checked and tightened the screws mounting the cap 
sub-assembly to the chassis.

Have simply run out of ideas and need help and comments.

I have worked on HQ-140’s/150’s extensively and currently have one of each. 
These are excellent radios and among my very favorites. Treated right and 
aligned well the single conversion HQ’s are wonderful.

Comments? I’m dead-ended. Need more ideas.

Thanks in advance.

Dan
WB4GRA

Sent from my iPhone
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