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Messages - Mikes Radio Repair

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Electronic Video Blog / Re: #36 "650 plus subscribers" Thanks!!!!!!
« on: March 16, 2016, 11:04:17 PM »
LOL, didn't know I have the radio voice.  Now I just need to get a real camera.  Currently just using the camera on my phone.

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Electronic Video Blog / Re: #36 "650 plus subscribers" Thanks!!!!!!
« on: March 16, 2016, 08:31:35 PM »
You topped 700 today!!!!!!!  At this rate you will be over 1000 this weekwnd.

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Electronic Video Blog / Re: #37 Hewlett Packard 410A VTVM tear down
« on: March 16, 2016, 08:30:22 PM »
Glad I could be of some help.  Hope you are able to get it up and running.

Mike

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Hmm, not sure why the pictures loaded rotated 90º.  Just tilt head to left.  :)

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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 / Re: Dead GE Super Base.
« on: December 27, 2015, 05:51:13 PM »
Up and running.  Noticed several things That did not quite look right on this radio compared to all others I've ever worked on before. I soon realized they were changes made by General Electric when this radio was sent back to them for service at some point. The changes updated this radio to its common configuration. The main difference I noted was the main RF shield that separates the two circuit boards was missing. It only had a small RF shielding plate soldered directly to the underside of the top board. I soon realized Why this radio looked as older they did at least circuit wise. The serial number is 62.  From a collectors standpoint that's one of those oh my god moments.

https://m.youtube.com/watch?v=ianagoOcs_Q&feature=youtu.be



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CB Radio Repair Forum / Re: Dead GE Super Base.
« on: December 26, 2015, 02:04:00 PM »
No hole in the bottom.  Pictured below Is one I worked on about a while ago. It is a separate circuit board potted in epoxy inside of a metal shielding can then covered with the plastic snap on cover.  Luckily if the varactor diode goes bad it is mounted on the edge of the board and the potting epoxy is the hard brittle type and can be chipped away at and it can be replaced if your really careful.   A NTE 612 is a good replacement varactor diode.  Cybernet made two types of these, a small one (this one) and a larger one.  If the transformer/coil goes bad good luck getting it out.  Its mounted in the center.  On the bright side there is a guy in the UK that makes replacement modules for these.  Apparently there were a lot of different radios in the UK that used them unlike here in the US where we only had a handfull of radios with them.

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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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New member welcome / Re: New member saying hello.
« on: December 25, 2015, 05:23:00 PM »
No scope or spectrum analyzer because it was designed mainly for permanent installation use such as manufacturing assembly lines or on a bench.  Many service monitors are designed for mobile service where you want a all in one box device and can sacrifice the advanced features you get in stand alone spectrum analyzers and oscilloscopes.  That's the main reason I don't like service monitors with them built in, limited features and resolution.

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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 / Re: New member saying hello.
« on: December 21, 2015, 08:11:38 PM »
What image size do you prefer for this site?  I uploaded these off of my phone at whatever size I took them.  I will be sure to resize next time.  Is this one a better size?

The Solartron Schlumberger Stabilock 4040 is my all time favorite piece of equipment.   I own several service monitors but I just like the way this works the best.  For me the best feature is the 3 dual readouts, digital and analog.  Digital displays are great for taking readings but when your doing a alignment I find it impossible to peak stages with a digital readout.  Analog meters are the way to go there and make finding peak a lot easier.  The 4040 has 3 analog meters paired with digital displays below them.  Both analog and digital meters autorange together.  This one came fully loaded with every option available.  Bare bones they operate from 0.4 to 960 MHz.  This one had the rare frequency doubler option so it goes all the way to 1.850 GHz.  It also has the SSB stage, broadband FM demodulator, adjacent channel power meter, duplex FM demodulator, IEEE bus interface and control interface options.  Basically the only thing it lacks is a built in spectrum analyzer.  Personally I could never stand the tiny displays in most service monitors anyway.   Its easy to hook a external one up to it, it has a output for that and that's how I use it.  Honestly you don't need one since it does harmonic measurements.  Just punch in what order harmonic you want to read, transmit unmodulated into it and it displays the harmonic level in db on one of the analog/digital displays.  I got this one not working or should I say kind of working.  At power up all the displays read giberish and the auto test tape drive ran non stop.  I discovered that if you let it on for about 10 minutes it straightened itself out and worked fine.  Let it off for several hours and power it on and it would do the same thing.  I ended up tracking the problem down to a bad cap in the power supply.  Figured what the heck and recaped the entire unit.  3 days later (oh my god there are a lot of caps in this thing) with the recap job done and calibration it is now back to like new.  Since these were really designed for assembly line operation where they get turned on and are used 24 hours a day, year after year I figure it should last me the rest of my life.  If I had to say what I did not like about it would not be the 4040 itself but the manuals.  Ugggg, operating and service manuals written by German engineers.  A little reading between the lines and head scratching later and I had it figured out.

Now back to the customers radio currently on the bench, a Browning Mark IV with a wonky PLL unit.  Man these things are a TTL nightmare. :)  Sucks Nomad stopped making the digital VFO kits for these.

Mike

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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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