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Johnson Ranger Problems




 
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N6WDR
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N6WDR World Domination Radio


« on: March 04, 2019, 10:42:28 AM »

Hello All,

A friend of mine bought a Ranger off of Epay and asked if I would go through it for him.  He brought it over and of course it was non-working.  Low Voltage rectifier was cold so I put a working rectifier in it and it proceeded to blow it the minute I turned the power on.  So I stopped right there and decided to replace all caps as they were original.

After replacing all the high and low voltage caps I powered it up with no rectifiers in it and checked the voltages on the pins for the rectifiers.  I am baffled as it came up with the following.

Low Voltage:

pin 5-3 900V? suppose to be 300-400v

pin 2-7 6.5V which is good

High Voltage:

pin 4-6 reading 0

pin 2-8 700V suppose to be 5V

This is my first time trying to do a rebuild and I am limited knowledge on circuits so please dumb it down for me so I can understand what you reply with.  All help is appreciated

Richard N6WDR

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WD8KDG
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« Reply #1 on: March 04, 2019, 11:19:16 AM »

Richard,

Some techniques which have save me countless $$ and time. If the previous owner can demonstrate all is working to spec, then and only then bring it home and plug it in.

Lacking that, do research: Get a schematic, from BAMA if necessary. Enlarge said schematic where values can be read. Check for modifications, are they well documented? Old electrolytic caps got to go. Check wiring for mistakes, use schematic! Read the trouble shooting section for resistance values of transformer windings. Sometimes tube voltage values are given, check them! All of the above can and will find issues that need to be repaired first "before plugging in" and letting magic smoke escape.

Your data supplied is a little hazy. pin 5-3 of what? etc. and so on.

Rangers are well documented and many of the common failures are known to those that post here. It can be repaired.

Craig,
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N6WDR
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N6WDR World Domination Radio


« Reply #2 on: March 04, 2019, 12:51:14 PM »

Craig

The voltages I checked were at the sockets for the low voltage and high voltage rectifiers per the manual and wiring schematic. 

This is my first attempt to figuring out a radio issue, so it is a big learning curve for me.  My Ranger that I own has not given me any trouble in the 13yrs I have owned it so I am learning how to diagnose and repair on this one. 

I will check all the wiring and see if the sockets were wired right and also check the transformers for the resistant values as per the manual to make sure they are good to go. 

Any other things to check would be helpful

Richard
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WD8KDG
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« Reply #3 on: March 04, 2019, 02:08:24 PM »

Richard,

There were at least 3 versions of the Ranger. I have the first version, no grid block keying. Ranger I has the grid block keying, Ranger 2 later color scheme and 6 meters vs 11 meters on the earlier versions.

Short version: I think your power transform T1 lost some magic smoke. Your description of the high voltage pin 2-8 has 700 volts rather 5volts (filament voltage) is the big clue. T1 has lots of wire leads. To get good resistance reading you most likely will have to unsolder all. Then measure resistance. Also please check for shorts to ground on each set, check for shorts from each set to other windings.

Trusting old electrolytic caps is one cause of failed transformers. Cap shorts out and too much current does a number on rectifier tube and transformers.

Craig,
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N6WDR
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« Reply #4 on: March 04, 2019, 02:57:12 PM »

Craig

I agree that they may have taken out the transformer and I will verify that by taking all the leads loose as you stated.  Thank You for the reply back.

Richard
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WD8KDG
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« Reply #5 on: March 04, 2019, 03:38:46 PM »

Richard,

Try removing tubes, then check resistance from winding to winding, and winding to ground first. That might prove a failed T1 and then unsolder all leads and check again. Pain in the back side.....use schematic along with testing while looking for grounds/shorts. Chances are you will see hints before warming up the iron.

Keep us updated here on the forum. Others might have better ideas. If T1 went south, gotta get things fixed.

Regards,
Craig
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N1BCG
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« Reply #6 on: March 04, 2019, 10:33:43 PM »

Some things to check:

1) As mentioned above, be sure the transformer is providing the right voltages to the right pins on the rectifier sockets and tube heaters.

2) Check the resistance across the various power supply filter caps for shorts.

3) The 9 pin accessory jack on the back of the chassis is a notorious place for shorts. Check that the coils and capacitors on each terminal aren't shorting to the chassis.

4) I've found it beneficial to use a series bulb in the A.C. supply for initial testing. Find a three conductor extension cord you don't mind sacrificing and carefully cut it open to expose the white, green, and black wires. The black (hot) wire gets cut and each lead is then connected to a porcelain lamp socket.

Plug the Ranger into the cord, insert a 60 Watt bulb into the socket, and plug the cord into an outlet. Basically, you're creating a safety load so even if the equipment plugged into the cord has a direct short, the worst that will happen is that the bulb will light to full brilliance.

Turn on the Ranger and note the brilliance of the bulb. You can now test the various transformer outputs. They'll be low of course, but zero volts will indicate a short. Add the rectifiers and see if you get LVB+ and HVB+. Again, they'll be low but not zero.

A high resolution schematic:

https://faculty.frostburg.edu/phys/latta/ee/ranger/schematic/rangerschematicfullres.jpg
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MikeKE0ZUinkcmo
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« Reply #7 on: March 05, 2019, 01:14:03 AM »

Pins 4-6 of High Voltage rectifier, you should be reading AC Volts, measuring from each pin, to ground.  When reading pins 2 and/or 8 to ground, should be reading DC volts, and about 700 VDC is OK.
---------------
Pins 5-3 of Low Voltage rectifier, should be reading AC Volts, again measuring from each pin to ground.   When reading pins 2 and/or 7 to ground, should be reading DC Volts and about 300 VDC is in the ball park.
-------------
To measure AC Filament Voltages, remove rectifiers and then measure across Filament pins.
-------------
To measure overall AC power drain, buy yourself a "Kill-A-Watt" meter at your home center or hardware.  Plug it in your AC source, and plug the radio into the K-A-W meter and set it for Watts.  This gives you a real "number" not some nebulous interpretation of a "glowing" light bulb.

Read the manual and memorize what the "NORMAL" power drain is, and hopefully they will indicate if that is stand-by or "transmit" power drain.   It is +/- 10% or so but don't let the drain go above those limits.   Keep in mind, the power drain during transmit is MUCH larger, often 2 to 3 times, than the standby power consumption.

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N1BCG
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« Reply #8 on: March 05, 2019, 08:59:08 AM »

Does this Ranger have tube sockets held in place with rivets or screws? Rivets were used on factory assembled units while the kits were sold with screws for this purpose.

I've heard, twice, cases of kit Rangers being assembled incorrectly and put away in a box to be fixed "some day". Decades later they were sold with condition unknown.

It's possible, remotely, that the transformer is wired incorrectly.
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N6WDR
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N6WDR World Domination Radio


« Reply #9 on: March 05, 2019, 03:25:19 PM »

Thank you all for the input, I will be checking it out again this weekend when I have more time to play with it again.

This Ranger is a Factory unit that from what I can tell is all original and zero mods done to it. 

Richard
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WD8KDG
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« Reply #10 on: March 05, 2019, 03:34:50 PM »

Richard,

All the Rangers also have a resistor in the VFO that fails, known as the Chernobyl resistor. From the factory it does not have a high enough wattage rating. Lots of info pertaining to that rig to be found on the web. While you are under the hood of the transmitter, fix everything.

Craig,
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N6WDR
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N6WDR World Domination Radio


« Reply #11 on: March 08, 2019, 05:56:24 AM »

Craig,

Yes the Chernobyl resistor is on my list of things to swap out, but until I can get this to play right with voltages I don't want to proceed any further.  I will also be doing all the audio mods as well once it is up and running.

Richard
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W2PHL
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Phil


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« Reply #12 on: March 11, 2019, 07:39:31 AM »

Check the .002uF and .005uF (usually Sprauge) bypass caps.
I had one (C84) become a dead short. The Ranger went from working FB when I went to bed to arcing the function switch and blowing the 4A fuse the next morning. The PS was already solid state otherwise the rectifier tube might have blown first. Amazingly, the cap did not explode, so diagnosing the problem was a pain.

See the the offender in action here: https://youtu.be/dgho6692Cl8

Phil
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