[Boatanchors] HT-37 Low output on 80 and 20 meters

[Al Parker]

Hi Ray,
    The HT-37 & -32 have the same ckt exc. for the SB Generator.  My HT-32 
has always had bandswitch problems occasionally.  It needs some wiggling to 
get decent output, and when I feel strong I open it up & dab some DeOxit 
into appropriate places.  Another thought, it uses the same xtal on 80 & 20 
to heterodyne with the VFO, might ck the oscillator output on the various 
bands.
    I'll see if I can get into the HQ-170 for you tonite or tmw AM.
73,
Al, W8UT
New Bern, NC
www.boatanchors.org
www.hammarlund.info

----- Original Message ----- 
From: "Paul Vasek" <w2ec at bmjsports.com>
To: <boatanchors at mailman.qth.net>; <hallicrafters at mailman.qth.net>
Sent: Monday, September 10, 2007 5:12 PM
Subject: [Boatanchors] HT-37 Low output on 80 and 20 meters


> Has anyopne experienced a situation where they have had very low (30-35 
> watts) output on 80 and 20 meters, but full output (90-100 watts) on 40, 
> 15 and 10 meters?
>
>  I've just started checking out an HT-37 I received several months ago. 
> Pretty clean, replaced the electrolytics right away as the ones installed 
> looked original. Check of all resistances per the manual showed every 
> point well within 10%, most 5% or better.
>
>  Power up went well but a check of actual power output showed only about 
> 35 watts on 80 and 20 meters, while 40 and 15 were near 100 watts and 10 
> meters around 90 watts.
>
>  Checking the circuit shows V7 being used as a straight thru amp on 80 and 
> 20, and as a mixer on 40,15 and 10 meters. Since power is low on only the 
> 80 and 20 meter bands, which share the common operating characteristics of 
> the straight thru amp, it seems that is the obvious place to start. I 
> swapped tubes with no change, and attempted a re-alignment. I was able to 
> peak up all bands by just a small amount, just a couple watts on 80 and 
> 20. At this point I am ready to start some serious trouble shooting. The 
> operation as an amp on 80 and 20 is pretty straight forward, doesn't seem 
> like much to go wrong that would not also affect operation on the 40,15 
> and 10 meter bands which work OK. Major difference is the tuned plate 
> circuits for 40, 15 and 10, and the resistive plate load on 80 and 20. 
> Plate load resistors are 5% tolerance and mine are well within that. Ready 
> now to start with actual voltage and signal checks using a scope to see 
> what is going on.
>
>  Just thought I'd check in the meantime to see if anyone else has had a 
> similar problem to this.
>
>  Thanks & 73, Ray W2EC
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