[ARC5] T-19 first run issues.

[J Mcvey]

 The installation is on a metal framework. The prior inhabitant, an SCR274, was connected to the shelf and frame better than the ARC5 is at present, But I make use of the ground clips on the rack. I used some clip leads to connect  the boxes as test to see if that helped. Unfortunately, it didn't.I pulled the MD7 oscillator tube as well, no joy on that either. 
The carrier hum sounds just like a 120 cycle hum from an AC supply .The power supply I'm using is an old industrial SMPS , so no 120 Hz from that!

    On Monday, April 20, 2020, 5:46:52 PM EDT, Michael Hanz <aaf-radio-1 at aafradio.org> wrote:  
 
  Amen.  It's one of the reasons I use aluminum liberally for the support racks in my rig.  Reproduce the environment that they had in the aircraft, and you'll head off a lot of strange problems you sometimes get with grounding/bonding/shielding inadequacies.
 
 https://aafradio.org/flightdeck/layout.htm has some construction thoughts on the bottom half of the page.
 
 - Mike  KC4TOS
 
 On 4/20/2020 12:22 PM, Mark K3MSB wrote:
  
 
 Ground all your "boxes" together directly;  don't rely on the connectors.   
  
  Mark K3MSB
   
  On Sun, Apr 19, 2020 at 1:26 PM J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:
  
   Just got this ARC-5 system wired up and going. Even the rack had hacked/dry wires that needed rewiring. The T-19 was recapped, cleaned, etc.  
  
  I have this strange problem with a hum in the carrier.  It sounds like a rig with a bad filter cap. I rechecked my wiring, etc, but everything is OK. The only other "symptom" is low output, about 2  Amps in CW mode . ( It's not the meter because I use the the same one with the SCR274 which will go 3+ amps). I'm using an A-27 dummy load
  
  I'm thinking that it may be an alignment issue where the finals are off-resonance and drawing too much current compared to the carrier amplitude and inducing a ripple modulation? 
  It's real subtle when looking at it on a scope, but obvious on a radio.
  The Dynamotor is almost ripple free , putting out around 590V under load. 
  
  Any thoughts?
  
    
  
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