Juma TRX2A - Voltage supply problem in Main Board

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Re: Juma TRX2A - Voltage supply problem in Main Board

Postby OH2NOS » 20 Jan 2012 07:30

Hi Matti!

Yesterday I made couple of measurements based on Main board voltage table (Appendix E). Now I have checked receive state only (Mode LSB, f = 3.7 MHz, Filter WID, AGC slow, Speechproc OFF, NB OFF, MIC input, dummy load).

Here I present findings which are not according to the table.

OPAMP A11:
Pin 5: 2 to 3 V (5 V default)
Pin 6: 2 to 3V (5 V default)

AMP A12:
Pin 5: 5,7 V (6-8 V default)
Pin 6: 11,5 V (13-14 V default)
Pin 7: 5,8 V (7 V default)

IC IC4:
Pin 1: 3,4 V (5 V default)
Pin 2: 3,4 V (5 V default)

IC IC1 (Filter board):
Pin 10: 0,8 V (10 V default)

Next I check the solders in supply line of each pin above. Is there something special what I should take into account?


73, Saku OH2NOS “JA”
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TRX2 Main Board, RX section

Postby OH2NOS » 26 Feb 2012 20:18

I have been out of hobby last month, but now I have time again. I have still the problem that my Juma TRX2A doesn’t work.

Before when I listened, I heard nothing even I added gain. 1) Then I decided to change TR3 because I assumed it been defected, because nothing happened when I pressed tangent down. Not any improvements. 2) Then I changed D4. Not any improvements. 3) Then I changed TR4. The result was huge noise in earphones and corresponding noise in the display.

Then I changed TR3 and TR4 again with new ones, but result was the same. Next I made couple of measurements.

4) Tangent up

J6-1 5,1 V
J6-6 5,07 V
J6-7 3,4 V
J6-8 5,2 V

5) Tangent down

J6-1 5,1 V
J6-6 5,07 V
J6-7 5,1 V - rises up slowly
J6-8 8,6 V- rises up slowly

6) A4-B

Pin 7 (tangent up): 5,2 V where AC part 0,4 V roughly – can remark regular pulses up in the signal
Pin 7 (tangent down): 9,4 V - rises up slowly


Give me couple of hints what to do and how to go forward for tackling these problems and getting my Juma up and running! :cry:


Saku, OH2NOS
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Re: Juma TRX2A - Voltage supply problem in Main Board

Postby OH7SV » 27 Feb 2012 06:31

Saku,

It seems you are circling around with the problem.
Please contact one of the Juma comminity hams to repair your TRX2A.
www.jumaradio.com/juma/juma-community.html

73 Matti OH7SV
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Re: Juma TRX2A - Voltage supply problem in Main Board

Postby KH2BR » 28 Feb 2012 16:53

Hi Saku,

I took a good look at the photo that you posted of the main board section A-10 and A-11.
Then I enlarged the picture so I could see it better.
Saku, the board is badly contaminated and needs to be carefully cleaned of all solder and flux residue.
I use Alcohol and a tooth brush. Use a magnifying glass or jewelers loop to inspect between all connections.
Lots of problems can be fixed by careful cleaning. Some problems that you cannot see can also be fixed by cleaning.

Robert KH2BR
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Re: Juma TRX2A - Voltage supply problem in Main Board

Postby OH2NOS » 29 Feb 2012 12:13

Hi Robert!

Thank you for your hint! But I suppose that contamination is more optical illusion than truth. The most probably error is contamination between my ears. :D

My Juma is now “in better hands” and let see what he will find for the root cause of my problems.


73, Saku OH2NOS
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Re: Juma TRX2A - Voltage supply problem in Main Board

Postby F6DEX » 29 Feb 2012 13:24

Saku

Not your eyes or contamination but only a "pure malediction" on A10 and A11 !

I am building my Juma (still not powered on) and just checked for the position A10 and A11 by curiosity. Damned : REVERSED !...

Thank you anyway to share your experience. A specific warning should be added in the documentation about A10 and A11 and this malediction.

It was of course a real please to unsolder and put in the right position!...

73, Laurent F6DEX
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Re: Juma TRX2A - Voltage supply problem in Main Board

Postby OH2NOS » 08 Jun 2012 09:09

Hi All!

My problems with Juma are history now or have been history long time already. I have only forgotten inform what has happened. So Juma has been in use couple of months and personally I am more than delighted customer! :D

When I did my last fixing I did an error: I bought new TR3 and 4 but their polarity was wrong. They should be SST112 type but I used 2N7002. Also TR6 in PA board was broken, but I didn’t recognize it. The root cause for my problem was one bad soldering in I/Q Pre Amp. When that was fixed my Juma operated like a dream!

Juma-Guru, Hessu OH2LH, and his helping hands guided me to next level where I am able to concentrate for operating with Juma. Just now I am doing link dipole for field operations!

73, Saku OH2NOS "JA"
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Re: Juma TRX2A - Voltage supply problem in Main Board

Postby OZ7QU » 08 Jun 2012 17:35

:D
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