Title: V6 new issue
Post by: WD8BXS on 04. June 2018, 21:49:21
Just finished a V6 build, all works well, but, getting high current on 40 meters only. Almost 3 amps for 9 watts.
Other bands are about 1.9 amps for 10 watts.
Any ideas ?
I removed C78 and no change.
Thanks,
Chuck |
Title: Re:V6 new issue
Post by: DF8OE on 05. June 2018, 05:32:18
Misalignment (hardware) in PA or oscillating of PA I think...
vy 73
Andreas |
Title: Re:V6 new issue
Post by: DF5LI on 05. June 2018, 08:44:49
| You have removed C78, then the only remaining components for 40 m are in the 40 m LPF. You should carefully check those L's and C's. Also listen to the "Click"" of the relays, when you switch to 40 m. And have a look on RFC 5 and 6. Maybe the drivers are oscillating on 40 m. I always change these chokes to a lower value with a higher self-resonating frequency. |
Title: Re:V6 new issue
Post by: WD8BXS on 05. June 2018, 14:35:57
Interesting note about RFC5 and RFC6, what would be a solution for a replacement?
Thank,
Chuck |
Title: Re:V6 new issue
Post by: DF8OE on 05. June 2018, 15:41:54
I always take self-wound on small binos. Gives more output on hihjer bands, too.
But this are all "shots in the dark". Best is to connect 50R load directly after PA output transformer and take a look at the utput signal via scope.
vy 73
Andreas |
Title: Re:V6 new issue
Post by: WD8BXS on 05. June 2018, 19:30:19
By signal scope do you mean spektrum analyzer?
I do not have one of those, sadly
If I use "O" scope it looks clean. |
Title: Re:V6 new issue
Post by: WD8BXS on 05. June 2018, 19:56:49
Changed RFC5 and RFC6--No Change
Changes LPF coils--No Change
Changed the Finals--No Change
Changed R81 and R82 to 100 Ohms -- No Change.
Still drawing almost 3 amps on ONLY 40 meters.
Scratching my Head hihi
|
Title: Re:V6 new issue
Post by: DF8OE on 05. June 2018, 20:06:26
If power gets in it 100% gets out somewhere ::)
I mean oscilloscope.
It is impossible that signal is clean AND there is not an output which is adequate to input power. It must be frequency dependent - otherwise it would be present at all bands.
vy 73
Andreas |
Title: Re:V6 new issue
Post by: WD8BXS on 05. June 2018, 21:59:37
I do not understand.
Do you mean that I should see the same amplitude before the LFP and after the LPF ? |
Title: Re:V6 new issue
Post by: DF8OE on 06. June 2018, 05:29:17
No.
As I understood you have correspondent power in / power out combinations on every band except 40m. Right?
If so you have to look where your power goes.
First is to cut PA from LPFs because they are frequency dependent and it may be you have a LPF or LPF switching problem. Of course you have to add a load to PA output transformer!
If now both powers are corresponding as on other bands you are ready (problem in LPF or switching).
If not you must take a look at the signal coming out of PA. Is there something oscillating e.g. You have to look at the signal with an oscilloscope. May be you have overdriven your PA by power settings in PA menu? You quickly see that by oscilloscope.
vy 73
Andreas |
Title: Re:V6 new issue
Post by: WD8BXS on 06. June 2018, 10:47:17
"As I understood you have correspondent power in / power out combinations on every band except 40m. Right?"
NO, I do have power out on 40 meters!, The drive levels in the PA menu for 5 watts look very similar on all lower bands, BUT on full power, the 40 meter setting has to be 2 TIMES the value of the others and it will not go above 8.5 watts!
"If not you must take a look at the signal coming out of PA. Is there something oscillating e.g. You have to look at the signal with an oscilloscope."
I did touch the scope to R26 and to C58, signals look clean.
Thank you for your patience with me, I am still learning hihi |
Title: Re:V6 new issue
Post by: DF5LI on 06. June 2018, 11:35:07
Very strange! You have changed L14, L18 and L22? Did you have checked the caps in the LPF? Try to make a bridge over the entire LPF for 40m. Remove C46 and C58, L14 and L22. Then solder a wire from the left pad of L14 to the right pad of L22.
So there is no LPF for 40m. If the problem persists, we have to look at T6 and T7....
(a friend of mine has managed it to solder 100nF instead of 470 pF for C57. The results are similar to your problem ;-)) |
Title: Re:V6 new issue
Post by: WD8BXS on 06. June 2018, 12:49:43
Hello Harald,
I put the jumper in across the LFP as per your suggestion, and that fixed it!!
I put NEW caps in and re-made the coils, re-installed, and back to the same issue!!
VERY strange!! This is my 23rd build, not a novice to the coil winding etc... hihi
Thanks for your suggestions, keep them coming!!
de Chuck WD8BXS |
Title: Re:V6 new issue
Post by: WD8BXS on 06. June 2018, 15:53:38
I just changed C58 to 100pf, that made everything look good!
What do you think??
Chuck |
Title: Re:V6 new issue
Post by: DF5LI on 07. June 2018, 11:40:09
I think, you have made the cut-off frequency (and perhaps the output impedance) of the LPF a little bit higher, and now the 7 mc-signal will pass the filter. I always measure the inductivity of the coils with my L-meter and sometimes i have to reduce the number of windings a little bit (1 winding less). The T37-2 cores sometimes have different AL-specifications (+- 20%).
|
Title: Re:V6 new issue
Post by: WD8BXS on 07. June 2018, 15:38:15
Harri, what is the meter you use to measure the coils??
Chuck |
Title: Re:V6 new issue
Post by: WD8BXS on 07. June 2018, 15:48:41
| I just discovered that I DO have an LC meter, I measured the coils and I am seeing 1.08 - 1.09 Uh on the coils,looks like I may need a bit more windings hihi |
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