Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Who in there right Mind?




 
The AM Forum
November 25, 2020, 02:39:42 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Who in there right Mind?  (Read 3917 times)
0 Members and 1 Guest are viewing this topic.
N8ETQ
Member

Offline Offline

Posts: 788


Mort


« on: September 18, 2013, 12:40:41 PM »



     Found this on the primary side of power
xfmr in an AL-80A..  Amazing!  The guy even
strapped another 10 ohm 10 w across it after
this one melted!  One Dam tough "R"...

     I  found a bunch of bad diodes..

  Never saw one melt like that.

/Dan


* AL80A 001.jpg (20.22 KB, 752x416 - viewed 649 times.)
Logged
KL7OF
Member

Offline Offline

Posts: 2152



« Reply #1 on: September 18, 2013, 01:13:17 PM »

Looks like it melted because of  RF......not current overload..Huh
Logged
N8ETQ
Member

Offline Offline

Posts: 788


Mort


« Reply #2 on: September 18, 2013, 03:42:26 PM »


 after a little more "pokin'" around it looks like
part of a Harbach Soft Start install gone Wild...

   I think you need to get a diff. R for 110VAC on those.
Nice clean little amp. Hope the guy didn't ruin it.

    God never intended for a medium power amp
to run off 110 VAC.  Can I get an "Harrumph"?

/Dan
Logged
KA9EGW
Member

Offline Offline

Posts: 79


« Reply #3 on: September 18, 2013, 04:23:37 PM »

Harrumph!
Logged
WQ9E
Member

Offline Offline

Posts: 3225



« Reply #4 on: September 18, 2013, 04:55:08 PM »

When anyone installs one of these mods there needs to be a fuse that will open if the relay fails to short across the resistor after the "soft start" period.  I have seen a couple of cases where damage was done from resistor shrapnel with this style of modification. 
Logged

Rodger WQ9E
N8ETQ
Member

Offline Offline

Posts: 788


Mort


« Reply #5 on: September 18, 2013, 10:10:03 PM »


Good Idea Rodger,

   An appropriate SLO-BLOW in series with the "R" that
also gets jumped out by the relay should do it easily.
This could be the first time I've used my Tektronics
current probe!

Thanks,

/Dan

When anyone installs one of these mods there needs to be a fuse that will open if the relay fails to short across the resistor after the "soft start" period.  I have seen a couple of cases where damage was done from resistor shrapnel with this style of modification. 
Logged
WQ9E
Member

Offline Offline

Posts: 3225



« Reply #6 on: September 19, 2013, 11:59:41 AM »

Dan,

You are welcome.  If you are rebuilding the circuit you might also consider using a relay with an extra set of contacts for the step start circuit and use one set  of contacts in series with the T/R line so that the amp cannot go into transmit mode until the step start relay closes.  I set up my homebrew amplifiers this way.

Logged

Rodger WQ9E
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.09 seconds with 18 queries.