[Amps] Basic Question Finding Passive Component Up in Smoke

[Carl]

You cant really test many of the components with just an Ohmeter, they need 
to be under stress.
Try a 1A fuse with the tubes removed and if OK just the 6CL6 and see if it 
oscillates. Finally add the 6146 and go to a 3A fuse. The best way is with a 
Variac.

Possibly the short just momentarily overheated some component and didnt 
cause permanent damage.

Carl
KM1H
Currently refurbing a DX-100


----- Original Message ----- 
From: "john starr001" <jstarr001 at hotmail.com>
To: <amps at contesting.com>
Sent: Tuesday, April 09, 2013 11:41 PM
Subject: [Amps] Basic Question Finding Passive Component Up in Smoke


>I am a beginner learning amplifier basics and decided to build a simple 
>6146 class C final CW rig with a 6CL6 driven crystal oscillator much like 
>the Eico 720 or Globe Scout.  The power supply is a full bridge 600v B+ and 
>300v non-regulated screen supply.  I did something stupid and accidentally 
>grounded the B+ supply.  So I blew the 3A AC line fuse but just before one 
>of the components in the 6CL6 or 6146 circuitry went up in a cloud of 
>smoke. I have visualized every cap, resistor and inductor and find no 
>damage.  I have measured every resistor, directly or indirectly, in-circuit 
>and all are to spec.  No open inductors and no shorted ceramic caps (all 
>in -circuit).  I tested the power supply disconnected from the RF circuit 
>and the supply, without load seems fine.  The 6146 and 6CL6 test fine as 
>well.  I want to put it all back together again and test the voltages with 
>the 6146 and 6CL6 removed but I am a chicken worrying about blowing up 
>something else (like my transfomer t
> he next time).   There was a obvious puff of smoke so something was lost. 
> I figure approaching this kind of problem must be routine for you guys 
> working on amps so would appreciate learning what would be your next steps 
> to find the bad part while minimizing further damage.  I thought the 6146 
> screen would burn up if the plate B+ were suddenly lost but it tests fine 
> on my Hickock. tnx and 73john
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