[Heath] Heath Digest, Vol 77, Issue 5

Tue May 16 13:09:33 EDT 2017

I have a metric crapload of small panel mount variables...

Sent from my iPhone, still learning to use it

> On May 16, 2017, at 11:00, heath-request at puck.nether.net wrote:
> 
> Send Heath mailing list submissions to
>    heath at puck.nether.net
> 
> To subscribe or unsubscribe via the World Wide Web, visit
>    https://puck.nether.net/mailman/listinfo/heath
> or, via email, send a message with subject or body 'help' to
>    heath-request at puck.nether.net
> 
> You can reach the person managing the list at
>    heath-owner at puck.nether.net
> 
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of Heath digest..."
> 
> 
> Today's Topics:
> 
>   1. Re: HW-8 Issue (g3oou)
>   2. Re: HW-8 Issue (Mike Czuhajewski)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 15 May 2017 17:07:24 +0900
> From: g3oou <g3oou at aol.com>
> To: Ron Kramer <kd6edv at gmail.com>, Heathkit List
>    <heath at puck.nether.net>
> Subject: Re: [Heath] HW-8 Issue
> Message-ID: <4h6ywrp14ejojqxesia0sajt.1494835644046 at email.android.com>
> Content-Type: text/plain; charset="utf-8"
> 
> Hi Ron
> Have you checked if a short circuit is happening somewhere in the preselector tuning range?
> 73
> Bob G3OOU
> 
> 
> Sent from Samsung Mobile
> 
> -------- Original message --------
> From: Ron Kramer <kd6edv at gmail.com> 
> Date: 14/05/2017  22:38  (GMT+09:00) 
> To: Heathkit List <heath at puck.nether.net> 
> Subject: [Heath] HW-8 Issue 
> 
> When I adjust the receiver preselector to the left, it blows the fuse. I am using a 2 amp fuse.
> 
> What is causing the issue and what size fuse should I be using?
> _______________________________________________
> Heath mailing list
> Heath at puck.nether.net
> https://puck.nether.net/mailman/listinfo/heath
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: <https://puck.nether.net/pipermail/heath/attachments/20170515/ddcc40f9/attachment-0001.html>
> 
> ------------------------------
> 
> Message: 2
> Date: Tue, 16 May 2017 02:38:37 -0400
> From: "Mike Czuhajewski" <wa8mcq at verizon.net>
> To: "Ron Kramer" <kd6edv at gmail.com>,    "Heathkit List"
>    <heath at puck.nether.net>
> Subject: Re: [Heath] HW-8 Issue
> Message-ID: <92F77E45CEC64464BA8B769AA6691C25 at michael3ecf5c8>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>    reply-type=original
> 
>> When I adjust the receiver preselector to the left, it blows the 
>> fuse. I am using a 2 amp fuse.
> 
> 
> So use a bigger fuse :-)
> 
> This is obviously a bad preselector variable capacitor, with one or 
> more plates bent somewhere. As you rotate it, the rotor (ground) and 
> stator (hot) touch each other, shorting power to ground.
> 
> The stator of the rear section of the capacitor (C301B) is connected 
> to the drain of RF amplifier Q1. Follow the path on the schematic up 
> through the diodes, inductors and bandswitch sections and it ends up 
> at the main power source. There is nothing to limit current except the 
> low resistance of the coil and forward drop of the diode, so the short 
> blows the fuse. A short on the other section (C301A, used on 80M only) 
> would not do that since it has a 1000 ohm resistor in the path. It 
> still wouldn't work right, of course, but it would not blow a fuse.
> 
> Your options are repairing or replacing the capacitor. Repair may or 
> may not turn out well, and replacement can be expensive. Finding a 
> replacement can be a problem but you can always get one from Oren 
> Elliott Products. Located in the northwest corner of Ohio, that is the 
> company that made Heathkit air variable capacitors (although under a 
> different name at the time), and they are still in business. They call 
> themselves "the largest domestic manufacturer of air-dielectric 
> variable capacitors" and have been making them since 1925. While they 
> probably won't have one of these in stock (it's a decades-old design 
> with very limited demand), they can certainly make more although it 
> won't be cheap.
> 
> The company URL is
> 
> http://www.orenelliottproducts.com
> 
> and you can find their catalog at
> 
> http://www.orenelliottproducts.com.//Docs/Catalog.pdf
> 
> To give you some idea of what it might cost, consider the HW-8 VFO 
> cap, which is somewhat similar, and is listed on their web page at
> 
> http://www.orenelliottproducts.com/oep-capacitors/n-50-group/26-152-ns-51-heath-replacement
> 
> For one piece it's $51.00 (!). That drops to $21 each if you order 5 
> or more. That makes sense, since the cost of setting up production and 
> other overhead is the same no matter how many you order. Of course 
> most people won't order 5 or more unless they are a dealer of some 
> sort. I would expect pricing to be similar for the preselector cap.
> 
> (The Heath number for the VFO cap is 26-152 and the preselector cap is 
> 26-151.)
> 
> You might get lucky and find an HW-8 being sold for parts, but make 
> sure it has the capacitor in it. If you're careful you might be able 
> to adjust the plates so they don't touch. It will be tricky and you 
> might ruin the whole thing--one possible outcome is having the plates 
> pop off the shaft, which I have seen happen. (People who have done 
> that  to the VFO cap have carefully pushed them back into place on the 
> shaft and put on a bit of epoxy to help hold them in place and usually 
> get away with it.)
> 
> If you aren't trying to keep the rig in 100% original configuration 
> and just want to keep it working, you could always replace it with 
> another dual section cap which has approximately the same capacitance 
> spread. It might look ugly and probably require drilling some new 
> mounting holes, and definitely rule out it ever being a museum piece, 
> but at least it would work. (I don't know the capacitance range and it 
> doesn't appear to be listed in the manual, but if I get a chance later 
> I'll measure it.)
> 
> Wish I had some answers that are quick and easy and cheap and 
> foolproof, but there aren't any that I know of that meet all 4 
> requirements. Except maybe having someone donate a free HW-8 or 
> capacitor :-) 
> 
> 
> 
> ------------------------------
> 
> Subject: Digest Footer
> 
> _______________________________________________
> Heath mailing list
> Heath at puck.nether.net
> https://puck.nether.net/mailman/listinfo/heath
> 
> 
> ------------------------------
> 
> End of Heath Digest, Vol 77, Issue 5
> ************************************