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Galaxy DX-88HL weak finals?

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  #1  
Old 11-19-2011, 08:21 AM
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Default Galaxy DX-88HL weak finals?


Since its starting to get to cold to ride my harley I starting looking for a few project radios to keep me busy indoors this winter. I traded a guy another CB for an 88HL. and received it yesterday. Not a bad radio.

The rig has an issue with very low output. 2 watts AM and 2 pep in SSB mode. I did the tx alignment this morning and found the driver bias barely able to make 50ma. Can't get the final bias set correctly. I can get V10 to bring up the bias current but V20 has no effect at all on the driver bias. The collectors of TR51,44, 43 and 56 are only showing 4V and they should read approx 6.5V. Maybe the Voltage regulator is bad??

I also repaired a cracked band board so I'm seeing all frequency bands now which was another issue at first.

I started out seeing about 2 watts AM and 2 watts pep on SSB. After trying the alignment it's doing about 6 watts AM but, still 2 watts SSB. Nice receive though and the frequency counter seems to be spot on.

Anyone else have one of these and had issues with output/finals? Just looking for other ideas before I order the VR and finals for the radio.
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Last edited by RatsoW8; 11-19-2011 at 08:34 AM.


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Old 11-19-2011, 12:05 PM
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Im almost thinking its a Voltage regulator issue I would first look at the solder joints in that particular area to start out. When you were checking voltage did you flex or push around on the board to see if any changes for better or worse??
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Old 11-19-2011, 12:10 PM
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Quote:
Originally Posted by TonyV225 View Post
Im almost thinking its a Voltage regulator issue I would first look at the solder joints in that particular area to start out. When you were checking voltage did you flex or push around on the board to see if any changes for better or worse??
Yep..did all that and I found couple new 2SC817 votage regulators in my drawer so I replaced it. Still seeing 4 volts on the collectors mentioned above.
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Old 11-19-2011, 12:18 PM
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If you are seeing 5 watts; then I do not think it is the final.

Sounds like this radio has received a lot of rough treatment - eg 'the cracked board'.

I would use that reasoning to look for other abuse in the driver/predriver stage.
Or more cracked trace(s).
Look for 'mods' or bad solder joints.

Have/use a DX 99V in my mobile - same board/radio . . .
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Last edited by Robb; 11-19-2011 at 12:28 PM.

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Old 11-19-2011, 05:06 PM
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Those are old radios and most have been bounced around dropped golden screw drivered ETC it sucks but its gonna be a rat race tracking the problem down. Ive seen these with hairline cracks in the boards from age and pi$$poor soldering ontop of it all. maybe BOB85 will stroll in and may have an idea
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Old 11-19-2011, 05:15 PM
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Thanks guys. I'll keep checking things until I find it or someone chimes in.
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Old 12-01-2011, 06:35 AM
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Ha! Took a little time and testing but I discovered the problem is bad final output transistors. the driver was fine. I found one of those RFX 75 final modules on ebay for cheap so I bought it.

Piece of cake installing on a 36XX board. No extra components needed and it only took me about an hour last night to do the work. I haven't done the TX alignment yet but I'm initially seeing about 50 watts AM and 70 pep on SSB (on 10 meters of course).

The receive on this radio tracks right along with my Kenwood TS-140S and doesn't drift at all. I may very well retire my trusty HR-2510 from mobile duty and put the Galaxy in the truck.

Anyway, it was fun to tinker with.
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Old 12-01-2011, 02:46 PM
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That sounds like a good way to fix that old beast up, the RFX-75. That said I would not be in a rush to replace the 2510 unless you talk mostly AM and love trucker echo with talkback. If you are a dedicated sidebander the Galaxy 88 will show it's true colors in the mobile this winter. The word sailboat comes to mind. Cool project though, I like what you did.

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