HW-16 HUM

[Mark V. Johnson]

Dennis; My thoughts on your problem as I've worked on a few HW-16's. The 
mechanical hum; it's possible but unlikely unless the speaker is actuallyy 
mounted in the radio itself. Years ago I worked on a hum problem on a GR-54 
receiver. That receiver has the speaker mounted inside the radio and it was 
picking up hum from the transformer. I had no hum when I used an external 
speaker.  As you know, try tightening the screws that hold the power 
transformer laminations and shell together, and make sure the transfomer is 
tight to the chassis itself. If its still quite loud, then you may be 
drawing excessive current. If thats the case, then with key down under load, 
it will likely get louder.

I'd replace that 4 part electrolytic. You don't need an exact mechanical 
replacement. I've had good luck at mounting new axial lead electrolytics 
underneath the chassis, leaving the old can type mounted to maintain the 
original look. you may have to mount a terminal strip to accomodate.

One final opinion, and I stress opinion. I don't favor a mass re-cap of any 
boat anchor. Some caps, yes; like the ones feeding Collins mechanical 
filters on a 75A4, but as a general practice I don't advise it. I try and 
troubleshoot problems and get the unit going, one problem at a time, if need 
be. To me a general cap replace is a waste, can cause problems if mistakes 
are made and is not the best technique to trouble shoot. On all the Heath 
gear I've worked on, I've had to replace the odd coupling or bypass cap, but 
its usually only one every so often.  Electrolytics, that's a different 
story. I replace a lot of them.

HW-16's are very cool little rigs. Hope you get yours going.

Mark V. Johnson VE3DJU/VE3DDI


>From: "Dennis Klipa, N8ERF" <klipad at MINDNET.ORG>
>Reply-To: "Dennis Klipa, N8ERF" <klipad at MINDNET.ORG>
>To: HEATH at LISTSERV.TEMPE.GOV
>Subject: [HEATH-TEMPE] HW-16 HUM
>Date: Sun, 4 Mar 2007 22:19:58 -0700
>
>My HW-16 has a hum that is quite noticeable when the volume is set low and
>less so when it is turned up.  I have read all of the previous emails on
>this issue in the Archives for the HW-16 so you don't have to waste your
>time teaching me that again.
>
>I have two questions about the hum in my HW-16, since there are two
>distinct hums.  Hmmm.
>
>1. There is a noticeable hum when the speaker is disconnected from the
>transceiver.  I believe it is coming from the transformer.  Not a good
>sign for the transformer.  The question is; can these mechanical
>vibrations cause an electronic hum to be generated in the audio circuit
>due to vibrations of the elements within the tubes?
>
>2. I have recapped the HW-16 except for the 4-part can.  I skipped that
>one because it had been replaced before I got the transceiver and I
>couldn't find one to buy, so I thought I would try to get by without
>replacing it.  I did like the one suggestion of stuffing individual caps
>inside the original can after removing the original contents, though.
>
>I have measured the AC voltages for the 5 DC supply voltages and would
>like to get the opinion of the "experienced" as to whether these numbers
>are acceptable or whether I should go ahead and recap the can again.  Here
>are the numbers.
>
>Supply   DC Volts    AC
>A         175        33 mV
>B         310        0.84 V
>C         320        30 mV
>D         700        1.4 V
>E        -150        90 mV
>
>I believe that A,C and E are OK, but I am not so sure about B & D.
>
>Thanks for the help.
>
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Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
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Subscription control - http://www.tempe.gov/lists/control.aspx?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
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