Title: [solved]Another V6 service question
Post by: WD8BXS on 20. November 2018, 00:03:58
just finished a V6 board set, all works well, but i am getting full output on 80/160 meters with no drive levels.
Receiving just fine, putting out a signal there as per my 7610 scope, no spurs.
Any ideas where to look for this bug??
Thanks,
Chuck |
Title: Re:Another V6 service question
Post by: DB4PLE on 20. November 2018, 11:20:32
Hi Chuck,
check bias voltage and current consumption change when going from SSB rx to transmitting SSB without audio signal.
Have you tried to actively set the bias and does the current consumption change when changing bias?
If current changes, bias voltage is applied when transmitting as it should. However, it may be much higher than expected -> something around the bias ciruit is faulty or of wrong value and provides higher bias than expected.
If rx current is much higher than normal and does not change when going to tx, bias voltage is applied all the time, potentially a fault in he bias hardware.
73
Danilo
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Title: Re:Another V6 service question
Post by: WD8BXS on 20. November 2018, 20:54:59
Yes that is true, but only on 80/160 meters.
works fine on all other bands.
I will do some voltage checks at a later date.
Thanks
Chuck |
Title: Re:Another V6 service question
Post by: DB4PLE on 20. November 2018, 21:00:02
Hi Chuck,
yes, you're right. Can't be a general failure of the bias unit, otherwise it would occur on all bands.
73
Danilo |
Title: Re:Another V6 service question
Post by: DF8OE on 21. November 2018, 04:46:14
Because there are no band specific behaviours in firmware the only possibility is that it changes because of self oscillating of the PA at those bands... Self oscillation can have the following reasons:
- missing or bad rf blocking an BIAS , PA or driver circuit
- badly working BPF or LPF on those bands (terribly mismatching)
- T5 miswound or pkaced unhappily so that it is coupling to PA output transformers
Good luck
vy 73
Andreas
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Title: Re:Another V6 service question
Post by: WD8BXS on 22. November 2018, 21:24:43
I Installed the PTT relay and that fixed the issue.
I don't understand, but it worked.
Chuck |
Title: Re:[solved]Another V6 service question
Post by: DF8OE on 23. November 2018, 14:52:18
That is the known issue (since ~2 years) about self oscillation when using pin diodes ::)
vy 73
Andreas |
Title: Re:[solved]Another V6 service question
Post by: WD8BXS on 24. November 2018, 13:44:50
Yes, I thought that involved more than one band when that happened.
Chuck |
Title: Re:[solved]Another V6 service question
Post by: DF8OE on 24. November 2018, 14:04:51
Mostly it involves the lower bands < 14MHz. I cannot tell you what parameters are the ones which leads to self-oscillation - but with replacement of pin diodes with relay the issue is always gone.
vy 73
Andreas |
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