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

[Paul Vasek]

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