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  #1  
Old 05-19-2017, 06:33 AM
hipacky hipacky is offline
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Frustrated Dragon Power Supply Problem - Please help!

Hi all,

So, my Dragon started acting up yeterday and I found that the Auto Azimuth belt had to be replaced. Replacing the belt wasnt too hard, but after I had the unit back together, I plugged it in and... nothing. The counter lights up and thats all.

So I started investigating if I accidentally disconnected something... and I noticed that I smashed pin 1 of CN-34 a against the chassis, causing a short! Oh no...

I obviously fixed the short, but +12V on CN-34 and -12V on CN-10 are dead.
I measured resistance on the +12V pin of CN-34 and it shows a 70 Ohms resistance to ground, which I also think is too low. Not sure what is causing this.

I tested Q402 and it measures fine. Im not very familiar with the Dragon electronics so I have no idea what to look for and where. All I know is that this accidental short made something fail. Fuses are OK.

Im so sad right now, what was a simple belt change now made my Dragon an expensive paperweight!

I appreciate any input.
  #2  
Old 05-19-2017, 03:16 PM
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Nakdoc Nakdoc is offline
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Open fuse? That is what should happen with an accidental short. Each secondary of the power transformer has its own fuse.
  #3  
Old 05-19-2017, 03:53 PM
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390FE 390FE is offline
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Like Nakdoc said. (see below pics)

100_5979.jpg 100_5980.jpg

You will see the original Fuses are pigtails & soldered in.


I suggest you convert them all to clip in fuse holders like I did. See below.

100_5981.jpg

100_5983.jpg

100_6017.jpg


Note: I did not damage or modify the original board that can be seen. I only had to slightly open the solder holes in the board so the clips could be inserted flush with the board (like a factory job) & soldered in. My fuses were not blown so all I did was fold the pigtails under the fuses & clipped the fuses into the holders.

Note #2: I did NOT need cut the cable ties or unsolder any wires from the Fuse Board to remove the original Fuses & drill a little bigger holes to solder in the Fuse Clips.


Hope this helps.

Last edited by 390FE; 05-19-2017 at 03:56 PM.
  #4  
Old 05-19-2017, 07:04 PM
hipacky hipacky is offline
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Hi guys, thanks for replying.

Fuses were OK, they did not open, not sure why! I guess current never rose high enough and something blew first.

I spent the afternoon reading the schematics and figured some transistor should be bad. After some testing, found Q403 defective, that was the problem.

OK, so now I have it working again but have another question: I noticed one of my level adjustment trimpots to be 'noisy'. After taking it apart, I found it is actually broken. Where am I gonna find a replcament for this? Any ideas?
  #5  
Old 05-19-2017, 07:46 PM
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390FE 390FE is offline
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Can you post some clear pics of it along with it's ohm value?
  #6  
Old 05-20-2017, 01:24 PM
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Nakdoc Nakdoc is offline
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The controls usually show up as a unit on ebay, and they sell for a lot. I would post a request here, and maybe you'll discover someone with one to spare.
  #7  
Old 05-21-2017, 06:47 AM
hipacky hipacky is offline
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I have a attached a pic so everyone knows what Im talking about.

If they run for a lot, that probably means this things break often, as many need them. I didnt even know mine was broken and to be honest I never pushed it hard or anything that could explain the damage. I guess they are not very sturdy. I guess I'll just have to find a fix without replacing it...
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