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When Farhan released the new V4 boards, one of the advertised changes from V3 was a better distribution of output power across the bands,
realized by changing C81 near Q90 to 470pF.

I tried to replicate this change on my V3 board but the net result is about 1W out across all the bands with a supply voltage of just over 12V.
I noticed that in the V4 schematic R83 changed from 10 ohms to 2.2 Ohms so I made that change as well and it made little to no difference.

I also tried adjusting RV1 and it does make a slight difference but there is very little room for adjustment on this pot so the change is insignifcant.?

What am I missing ??

I reverted back to the original components and I am back to about 5w out on 40m and 1W out on 10m with 12+V supply.

Cheers?

Michael VE3WMB

At what operating voltage?? At 12V or less its not going to produce.

Most I've seen on 40M can do 7 to 10w easy.? Except one that had a 40M filter with mis-wound coils
but that one still did 5W on 20M and over 15 on 80M.

Allison

Two things did you get decent power on 80 and 40 before the mod?? Decent is more than 8- to 10W on 80.
Is it possible while making the cahges you could have broken a trace or caused a short or the extreme?
burnt out Q90?

Allison

Allison :

I am running off of a 12v SLA so I am seeing an input voltage of maybe 12.3 V DC.

I get about 7+ Watts out on 80m, around 5 watts out on 40m and about 1 watt out on 10m with this DC voltage in and the stock components.

I made the mods twice, the first time without changing R83 and the second time with both R83 and C81 using the V4 board values.
In both cases I doubled checked the component values (and measured them) before installation and the soldering looked fine.
What I saw was ?< 1 W out on 40m through 10m (didn't check 80m). Increasing RV1 improves that but I only have a few?
degrees of rotation before I hit max so it tops out at a little above one watt.?

Everything is back to normal when I restored the original components at C81 and R83, so Q90 is fine.?
I am seeing the original power out values but I am at a loss to explain why this didn't work if this is stock
on the V4 boards ??

I don't see any other related changes in the V4 schematic, which is why I asked if anyone else has done this mod
to a V3 board.?

Cheers

Michael VE3WMB

You have one that is like mine not every happy.

The mod worked but something else is not working well further down stream.

Check R84 (10 ohms) and R89 (2.2 ohms) to see if they got cooked somehow.

failing that...
The only solution is replace those six 2n3904s with 2n2222A (the ones in the can)
or something else.

Allison

Allison :

Thanks for your comments. ?I will consider them for a future round of mods (I do have a pile of 2n2222a's).?
I am actually pretty much OK with the power out that I have at the moment, I was just hoping to?even it out a bit with a?
couple of simple component changes.?

I think I am getting about 3w out on 20m with 12+v in and the difference between that and 5W?is 40m not worth worrying about.
Also?1W out on 10m is not something I am going to have to be very concerned about until propagation significantly?improves on that band,
with an upswing in the sunspot cycle. Realistically 1 W and a wet noodle for an antenna?is all you need to work the world on
10m anyway, when it is open.?

I think that it is time to start thinking about the logistics of getting my rig into a permanent enclosure.??

Cheers

Michael VE3WMB?

It seems like every time I try to bridge a surface mount resisitor, like I did in my search for more power, the resistor dies. ?I replaced R941, 942 and 96 last night with leaded resistors soldered to the pads, since my efforts to increase power caused a loss. ?Now I get 10W out on 80, 40 and 20, 5W on 30, 17 and 15 and 2W on 10 with a few 2n2222a's and 270pf caps added. ?If your results are poor, suspect those sneaky resistors.

73,

Tom ?W1EAT