Title: [solved] V6 Behavior
Post by: WD8BXS on 05. November 2018, 17:03:47
I have a head scratcher here. This is a new build Version 6. it is not receiving correctly.
Here is a screen shot.
There are identical signals on both sides of center.
It seems like it hears the whole band at once.
I have replaced U2, U3, Q1, U15, U16 and T1
No Joy.
Normally when testing, you can touch a wire to R1, R4, Q1 collector, output of T1 etc.. and hear the noise floor come up.
On this one I lose it at the collector of Q1, I hear a click when I touch there but no noise floor.
This is why I replaced T1, U15, and U16, but again , no joy.
Any ideas whould be helpful.
Thanks,
Chuck WD8BXS |
Title: Re:V6 Behavior
Post by: WD8BXS on 05. November 2018, 17:04:45
I forgot to mention, It is the RF board, as it does the same thing with another UI board.
Chuck |
Title: Re:V6 Behavior
Post by: DF8OE on 05. November 2018, 17:36:58
There seems something wrong in I/Q-path. Missing LO signal (one) ??
vy 73
Andreas |
Title: Re:V6 Behavior
Post by: WD8BXS on 05. November 2018, 18:48:29
I have good signals with a scope and frequency counter at R22 and R23
Chuck |
Title: Re:V6 Behavior
Post by: WD8BXS on 06. November 2018, 13:46:48
Any chance someone could post pics of scope waveform from R22 and R23, T1 output, U16 input and outputs I and Q ??
Thanks,
Chuck |
Title: Re:V6 Behavior
Post by: WD8BXS on 07. November 2018, 15:10:36
Title: Re:V6 Behavior
Post by: DF8OE on 07. November 2018, 16:58:07
I do not have time to take such pictures and additionally I am not sure you can see measureable signals except the two LO inputs.
You can cut I and Q traces to opamp and see if both are working. Normally you should see identical signals (with mirrors) when cut cut ONE of the two and mirrors are eliminated when both are connected.
vy 73
Andreas |
Title: Re:V6 Behavior
Post by: WD8BXS on 08. November 2018, 13:32:55
I think I understand, do you mean lifting R43 or R43 one at a time, then measuring pins 2 or 3 respectively on U16?
Thank,
Chuck |
Title: Re:V6 Behavior
Post by: DF8OE on 09. November 2018, 11:50:22
The chains are from the secondary winding of T1 via resistor via U15 via resistor via U16 via resistor to header. There are TWO symmetrical chains (I and Q). The signals on the chains must be IDENTICAL at identical places. You can compare DC *AND* AC measurements. If you cut a chain it should be without changing WHERE you cut it (regarded to the behaviour of UI PCB - not for comparing measurements). If you compare measurements both chains must be connected identically (e.g. both resistors behind T1 fitted or BOTH not fitted).
I hope this helps.
vy 73
Andreas |
Title: RE:[solved] V6 Behavior
Post by: WD8BXS on 09. November 2018, 20:10:18
I found a bad R49
Causing too much bias on T1
Thanks for all your help!
de Chuck
73 |
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