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Author Topic: ALINCO DR-605T VHF GONE  (Read 1476 times)
AA3MO
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Posts: 5




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« on: March 19, 2007, 09:35:31 AM »

My VHF side just dissappeared off the map.  It still receives.  PA Pwr out is virtually gone....but the UHF is still punching.  Anyone else experience this? Is this possibly a TX diode/resistor problem I've seen in some threads? I have the meters and the tools and perhaps the parts- just need some direction here. Problem is constant from power up.

Tnx
Dave
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K0BG
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« Reply #1 on: March 19, 2007, 09:49:47 AM »

I'm not that familiar with the 605, but I'd bet it is the final. Most (certainly not all) dual banders use separate finals. If not, could be a driver. In any case, I'd look at the schematic and look for something not common in the final.

Alan, KØBG
www.k0bg.com
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KE3HO
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Posts: 235




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« Reply #2 on: March 19, 2007, 11:54:49 AM »

I had the same problem with mine, only it was the UHF that went out. I accidentally dropped the radio. It was in a padded carrying bag and it fell about 2 feet to concrete. It landed edge first on the back of the heatsink. Right after that the UHF only put out about 3 watts on low and 7 watts on high. DC current draw was still up at the typical 11 to 12 Amps then transmitting on high on UHF. To make a long story even longer, I opened it up and inspected it, but did not see anything at first. Then I looked at it under a stereo microscope at work and I found a very small solder ball that was shoring a capacitor to ground in the output filter on the UHF board. I removed the solder ball with some small needle nose tweezers and everything worked fine after that. I also found several other small solder balls stuck here and there on the board, and I picked them off while I had it open.

This was a rather odd failure, but who knows, maybe you will get lucky and find something similar. Other than that, it sounds like the UHF amplifier chip has gone south.

73 - Jim

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AA3MO
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« Reply #3 on: March 19, 2007, 12:36:14 PM »

Wow: Two fast responses. I see an output device in the Main VHF Unit portion of the schematic.  I'll have to open the radio and check it further.  I'd be surprised to see a Final gone when communications are so short and separated. As far as the solder balls go we're cautious in our shop for these animals.  I call them asteroids depending on whether they originate off the solder machine from a bounce, or after the fact during touchup.  That's all you need is to have one roll in the wrong corner.  
I'll take the case apart and do a visual.

Tnx
Dave
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AA3MO
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« Reply #4 on: March 20, 2007, 07:18:12 AM »

Nothing visual noted.  Going to Alinco.  Will post the repair/resolution when it returns.
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KC8ADU
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« Reply #5 on: March 29, 2007, 12:26:00 AM »

sav17 pa has a crack in its ceramic pcb.
very common and the pa is repairable in most cases.
i see and reair a ton of these.
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AA3MO
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« Reply #6 on: March 30, 2007, 07:02:25 AM »

Wish I saw this reply sooner.  I can see where this could be an expansion problem over time and possibly create the NO VHF scenario.  I'll have to wait and see the result.
  Thanks, Dave
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AA3MO
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« Reply #7 on: April 13, 2007, 07:18:05 AM »

UGH! The RF Shop says it's the Final for the VHF.  Too expensive for the part-not worth the fix.  The UHF still punches out so I guess it's a single bander for the time being. Transmissions were extremely brief (less than 10 seconds and far apart) so it's very dissappointing.  Even with a bad SWR the rig shouldn't have popped the output if it never had the chance to heat up.  Must've been bad or not properly mounted in production. Oh well.
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