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Pair of Johnson transmitters.




 
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Author Topic: Pair of Johnson transmitters.  (Read 3182 times)
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MikeKE0ZUinkcmo
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« Reply #50 on: November 12, 2017, 08:02:22 AM »

Nice work!   It's amazing just how much smaller electrolytics are today, compared to 50-60 years ago.

Mike
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kc4umo
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« Reply #51 on: November 13, 2017, 03:33:52 PM »

Nice work!   It's amazing just how much smaller electrolytics are today, compared to 50-60 years ago.

Mike

Thanks Mike. Yes these new capacitors are so much better today.  Gives a lot if room to free up also.
Got all the caps replaced. I did find both 10 Mf caps in the speech and audio circuit leaky.
Now to check resistors and other components. Then start testing tubes.
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kc4umo
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« Reply #52 on: November 15, 2017, 08:37:25 PM »

Success  !

So here is where we are at on the VII.

All electrolytic and wax caps changed.  Spent Monday and yesterday evening cleaning the tubes, knobs and reinstalling all them.  Nothing belter than working on a clean boat anchor with fresh capacitors installed.

When I first got this rig I know there was two problems the original owner told me about.

Intermitted transmit When transmit dropped out there was plate voltage, no grid, buffer or oscillator.
Second problem was no audio or cw tone when it would transmit.

So tonight I brought the VII up on a variac and all was fine. Went by the book and tuned the rig on 40 meters with no problem. Nice dip of the plate and saw 120 watts on the external meter.  I pressed the cw key and heard a tone in a near by receiver.  The tone would change though from a high pitch to a low pitch tone.

Connected a mic, switched to AM and set it up. Flipped the plate switch, spoke in the mic while turning the audio up.  It sounded great on the 747 receiver sitting on the shelf.  Not bad at all.

So I wanted to start checking voltages, high and low supplies, bias ect.  Now the whole time I am recording this for the video. I fired the rig up. flipped the plate switch and saw the meter rise. Hit the key and nothing. I looked over at the spectrum analyzer and saw no spike in the 7 MHz range.  Flipped the meter to oscillator and nothing.  Pulled the crystal and did an external check and it was fine.  Now during this time I have not checked or replaced any tubes, Wanted to do a trouble shooting walk through video.

Pulled the 6AU6 osc tune and changed it out with a known good tune. Still nothing.  Put original tube in and started getting late on me.  I was probing around under the tube (V6) and then saw the spike rise on the SA. Then it sank as quick and it came.

So no oscillator running. I think I need to check the wiring under the tube, cw / phone switch, and crystal board. I have not yet check the LV supply. What ever is causing the problem seems to be  intermitted.  Really should be something simple.

More to come.
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K1JJ
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"Let's go sailing, Tommy!" - Yaz


« Reply #53 on: November 16, 2017, 12:37:23 AM »

You're a good troubleshooter and restorer, Buddy!  In this day and age of throw-aways and board changers, a person who can troubleshoot down to the component level is getting rare. They are grossly under-appreciated considering the thousands of hours it takes to get really good at it.

It's a science and an art. You have the right attitude; always keeping calm and plugging away. With that combination there's nothing you can't eventually get working right.

Your video documentation will help a lot of hams in the future.

T
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“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

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kc4umo
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« Reply #54 on: November 17, 2017, 09:11:44 PM »

You're a good troubleshooter and restorer, Buddy!  In this day and age of throw-aways and board changers, a person who can troubleshoot down to the component level is getting rare. They are grossly under-appreciated considering the thousands of hours it takes to get really good at it.

It's a science and an art. You have the right attitude; always keeping calm and plugging away. With that combination there's nothing you can't eventually get working right.

Your video documentation will help a lot of hams in the future.

T

Thank you for those very kind words and vote of confidence. 
Repairing electronics is very relaxing to me. I enjoy a good challenge.  I find it like a good murder mystery or detective story.  I hear so many folks say that repairing old radios is a dying art,  I find it as being a lost art.
Since I started the video blog I have had many folks mail me saying how much it has inspired them to get into repair. Speaking of email I get several hundred a week now. Hard to keep up with them.

Thanks why I do this, is to help give others that push they need to get started. Just the comments I see is very rewarding. Thanks again.

Anyway I am off tomorrow and plan to look over the oscillator issue.  The oscillator seems very strong as I can hear it in the near by receiver.  I believe there is a resistor that may be causing the problem I did try the 122 and did not get any signal out.  Have to dig into that deeper. Going to try and upload some video on the VII this week  end.
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kc4umo
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« Reply #55 on: November 18, 2017, 11:00:09 AM »

This morning I have been playing around in the oscillator circuit.  At the moment it will not fail.
Hard to troubleshoot a problem that does not want to rear it's ugly head.
So I grabbed the 122 and connected it to the rig. Nothing! After spending a bit of time looking things over I grabbed a key and plugged it into the rear of the vfo, engaged the shorting bar and bam! Good strong signal. Frequency is way off. Got to do a bit more reading on this thing. But it is working and was able to drive the transmitter with no problem.  BTW the V2 front panel cleaned up pretty good.

More to come.....


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KB2WIG
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« Reply #56 on: November 18, 2017, 08:09:37 PM »



Love your multimeter cradles...   Guess I've another project to start.

klc
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kc4umo
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« Reply #57 on: November 18, 2017, 09:41:41 PM »



Love your multimeter cradles...   Guess I've another project to start.

klc


Thanks.
I never cared much for the installed kick stand they came with.  They fall over and the angle just was not right. When recording video there was always a glare.  Just grabbed some scrap wood and that is what I came up with.

Here is a better picture


* IMG_20171118_213232.jpg (1266.94 KB, 2560x1440 - viewed 37 times.)
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WD4DMZ
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« Reply #58 on: Yesterday at 04:11:44 PM »

Frequency is way off

The 122 is really easy to calibrate. I had mine on the money for all the ranges in minutes. Just wait about 30 minutes for it to warm up first as mine drifts a lot while warming. However, once warm it stays dead on according to reports I have received.

Another issue is the way the dial is calibrated. The marker freqs are to the right of the main hash marks. Initially I was trying to center above the center of the indication. For instance, the 7.25 Mhz is under 7.26 and 7.27 but 7.25 is the long line to the left of the #. Initially I found that odd.

Rich
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