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v6 no power


Mitchel Rought
 

new ubitx v6, upon power up received signals are very garbled and off frequency, went through alignment and received signals are now fine, upgraded display to nextion 2.8, new problem is no output power, tried on ssb and on cw into known good power meter, unit was not checked for output before display updated, next step ?

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Mitchel Rought
644 Main street
Chemung, NY 14825
607-742-5426


Evan Hand
 

Michel,
Since there is no power out for both CW and SSB, then the issue starts somewhere with Q90 and later.  The first thing to check would be the current change with SSB.  Does the current go up by approximately 200 milliamps when the PTT is pressed?  If not, then I would start with the finals and verify the voltages there.  If the current does increase, then go back to Q90 and start with static DC voltage checks.  Attached is a file with approximate voltages for the devices.
NOTE:  The file is for a v4, however that part of the rig is the same as the v6 and can be used.

The most common device failure after the finals is Q90.  IF you operated another transmitter with the antenna connected to the uBITX, even with the power off, you can blow Q90.  Look at this thread for more information:
https://groups.io/g/BITX20/message/82029
There are over 50 messages that I would suggest you go through to follow what has been done by others.  Included is a PDF in one of them that has the voltages for the devices.

Good luck in finding and fixing the issue.
73
Evan
AC9TU


 

Evan.,

please share/the original spreadsheet I posted in the group file section. The PDF is slightly messed up.

Raj

At 24/09/2020, you wrote:

There are over 50 messages that I would suggest you go through to follow what has been done by others. Included is a PDF in one of them that has the voltages for the devices.

Good luck in finding and fixing the issue.
73
Evan
AC9TU


Mitchel Rought
 

Evan
thanks for the information, this unit has sat on my bench by itself with only a computer monitor on the same bench, my other radio has not been turned on since this unit arrived, I do realize that this was sold as a "kit" but was not expecting the issues that I am having as it was sold as being pre-tested and aligned, if it was a kit that had to be assembled from the main board up I could understand, but this last issue is definitely a defective part from the manufacturer and I think the advertising needs to be looked at, at this point I am not very happy with this purchase


Evan Hand
 

Raj,

I will from now on.  Thank you. 


73
Evan
AC9TU


Mitchel Rought
 

Evan
current draw
rx  .262ma
tx  .678ma
power on q70 ok
12 vdc on irf510 drains
u2 no power, is this checked in rx or tx
also the pdf you sent lists q70-q73, cannot fin q71-q73 in print or on board,
tghis board is v6.2


Evan Hand
 

Mitchel,
As I had stated before the values were for a v4 board.  I should have made it clearer that I was referring to the transmitter from Q90 on to the finals.  The transistors that are not on the board have been replaced by the LM386 IC.

A 400ma rise is twice what it should be.  Just to verify that was a test with SSB, NOT setup for CW, and no modulation.

Based on this information, and assuming that the test for the final current draw was on SSB, then I would start with Q90 voltage checks.  As I have stated prior, Q90 seems to be the first to give up the ghost most often.

As Raj pointed out, even the voltages for the v4 sheet I gave you may be in error.  Use the following link to the spreadsheet files instead.
https://groups.io/g/BITX20/files/VU2ZAP

All of the Transmit voltages are for when the PTT is pressed in SSB mode without any audio.  That includes U2 (the bias control regulator on the mainboard).

The transistors you want to test are Q90, Q911, Q912, Q96, Q97, Q94, and Q95.  Q92 and Q93 should be the same voltages as Q96 and Q97 (for some reason got left off of the chart).   All when transmitting and no modulation or CW.  A dummy load should be connected when doing the tests.

Hope this helps,
73
Evan
AC9TU


Mitchel Rought
 

Evan,
thanks for the info, it clears up alot, I will double check my notes as to ssb vs cw and will follow up first thing in the morning
again, thanks, I spent the last 45 years doing cnc machine and control maintenance and troubleshooting, slowly getting back into rf
73