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Topics - Mikes Radio Repair

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CB Radio Repair Forum / Galaxy DX2517 horrible spurious emissions and low power
« on: January 18, 2016, 02:55:03 AM »
Got a customers Galaxy DX2517 in for repair with a strange problem.  When cold the output power is low but quickly increases.  This radio belongs to a disabled person who is on a tight budget so he can't afford to put a lot of money in it.  When first turned on in AM mode carrier power is 5 watts.  If held keyed for about 45 seconds it goes to full output at 10 watts carrier power.  It has a EPT690010D dual final PCB.  What is strange is the output.  Take a look at the spectrum analyzer views of the output, what the.........  You could use this thing as a noise generator.  Pictured span is 20 MHZ (20-40MHZ) directly hooked up through a 60db attenuator which the amplitude is adjusted for.  Pictured in order: band A, D and F.  Seing as the power problem is operating temp sensitive I figured I would hit it with a shot of freeze spray.  It worked, kind of.  If the pre-driver transistor is sprayed the power drops almost instantly to its low level and goes up as it warms back up.  Well that was easy, or so I thought.  Replaced it with a new one and it does the exact same thing, hmmm.  Thought maybe it cooled a nearby part so I made a shield out of heat shrink tubing to stick on the spray nozzle.  Power definately still changes when only the pre-drivet is sprayef.  It has no effect on the spurious emissions.  Any ideas?  I can't spend much time on it due to customers financial constraints.

Mike

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CB Radio Repair Forum / Dead GE Super Base.
« on: December 26, 2015, 03:09:02 AM »
Got in a customers recent ebay purchased GE Superbase 3-5875A.  He purchased it knowing it had no rec or xmt.  I was hoping the varactor diode in the epoxy sealed vfo box was bad.  I have chipped the epoxy out of more of these than I can shake a stick at and have just gotten to the point that I replace that diode whether it works or not when I restore these radios.  Well, I wasn't that lucky.  Did a quick check for 10.240 on the PLL and it was missing.  Checked the 10.240 oscillator transistor and no voltage.  Checked and had main supply voltage to pin 12 of connector N2 and voltage out of the regulator transistor, hmmmm.  Time to pull the board and sure enough someone had been in it before.  They "tried" to undo a channel mod and didn't get a jumper wire connected and there are also some broken circuit traces that will need repaired.   All that no biggie and easy to fix.  The big problem is the last picture.  A cracked transformer core with a piece of the alignment tool broken off in it, grrrrrrrr.  To make matters worse it is not a standard core.  Its the one for the VFO that has a square hole and is almost impossible to find.  My stockpile of them is getting smaller and smaller.  Keeping my fingers crossed i can get the mangled core out.  The lesson here is if you don't know what your doing and don't have the correct tools don't touch it.  You could turn your what would have been a easily repaired radio into a nice looking brick.

Mike

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Power Supplies / Wayne Kerr AP2080A
« on: December 24, 2015, 03:46:58 PM »
Santa showed up a day early and in a brown UPS truck instead of his sled today.  I stole this puppy for under $100.  These are lab quality switch mode supplies and run in the mid thousands new.  They usually sell for about two grand used.  This one has a adjustment range of up to 20 volts and up to 80 amps.  Perfect for high power mobile radio and amplifier servicing.  I am still kind of dumb struck at how cheap I got it.  It is in excellent condition.  Judging by date codes it was built late in 1998.  They still manufacturer this series of power supply.  Now I just need to find another one so I can run them in master / slave mode.  Internal build quality is superb.  Whoever said only Germans and Americans could build high end test equipment never had the hood up on a Wayne Kerr.  Here are a few pictures of the internals.  Looks like they used UK made parts everywhere possible.

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New member welcome / New member saying hello.
« on: December 20, 2015, 01:51:54 AM »
Just wanted to say hello to everyone.  As you can probably guess from my user name my name is Mike.  I repair radios fulltime for a living.  I guess you could say I am third generation electronics repair.  My grandfather had a electronics store/repair business which was later taken over by my uncle.  The shop closed a year after I was born so you could say I grew up playing in a old repair shop.  Got bitten by my first flyback transformer when I was 10 and have been going ever since.  Work on everything from early 1900's AM / shortwave sets to modern equipment.  Seems here recently I have been getting more and more tube type work.  I think the word got out.  :)  A couple pics of one of my main bench and a few radios I have worked on recently.

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