Re: ubitx troubleshooting help - low power after irf510 replacement
On Thu, Aug 16, 2018 at 11:17 PM, Sean W7SKD wrote:
First time I have replaced with ¡°international rectifier¡± marked parts from asia, which is why I was wondering if that may be it.
I'll put $10 on that :-\ 73, Mark.
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Re: ubitx troubleshooting help - low power after irf510 replacement
Look like you are ended to fake IRF510 from china
On Fri, Aug 17, 2018 at 8:47 AM, Sean W7SKD <sean.jrdalys@...> wrote: I replaced both, yes. First time I have replaced with ¡°international rectifier¡± marked parts from asia, which is why I was wondering if that may be it.
Have been looking for visibly cooked bits in the amplifier section, but so far no joy...will continue though ?
thanks
Sean
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Re: ubitx troubleshooting help - low power after irf510 replacement
I replaced both, yes. First time I have replaced with ¡°international rectifier¡± marked parts from asia, which is why I was wondering if that may be it.
Have been looking for visibly cooked bits in the amplifier section, but so far no joy...will continue though ?
thanks
Sean
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Clarification Please: I have version 4 uBitx Board. My primary mode is SSB. What bands, if any, are currently tested passable for SSB mode?
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Re: Ubitx - Increased voltage to finals thru middle wire on power plug...no effect
Correction Kevin, no need to key the rig. I forgot that the finals are always connected to the power supply.
73, John
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Re: Ubitx - Increased voltage to finals thru middle wire on power plug...no effect
Kevin,
Increasing the voltage to the finals only helps if there is RF drive enough to?
take advantage of it.
Its true for the IRF510, RD16HHF, MRF150.? They all have so much gain
and more voltage does not significantly increase that.
Likely if you were not limited by the TD2822 and you increase the 12V to
say 14V you would see a corresponding increase output power.
Most all of the uBitx I've encountered had a mod to keep teh voltage to the tda2822
and tuning up the voltage from 12 to to 13.8 made a noticeable difference on any band.
Like John said also make sure you actually are delivering increased voltage.
Your power supply could be fading under the current draw.
Allison
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Re: Ubitx - Increased voltage to finals thru middle wire on power plug...no effect
Hi Kevin,
The finals (IRF510s in particular) are sensitive to supply voltage. Even when going from 12 to 13.8V the increase is visible.
The first thing that comes to mind is current limitation although it would be quite a coincidence that it results in the same power output.
Easy first test is key the rig in ssb, no modulation, and check the voltage on the cooling tab/heat sinks of the finals to verify that you get the higher voltage on the drains of the finals.
73, John
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Re: Modular uBitx - "Ex: Harmonics"
Arv,
I have a laptop using a Rpi3b and a 10inch screen (not touch) with a real
keyboard and mouse with a steampunk sorta look.? With a stereo usb
dongle IT runs Fldigi, gsdr and a few other useful things like Xlog under
Raspian (linux).? Noise has not been an issue.? Its mostly all wood so
its not shielded.? Power drain is pretty low with the display backlight down.
The asus Tinker board is faster and uses more power, heck 1.8GHZ,
2gb ram and all that. No Noticeable noise
Android tablets work, the smaller ones with quad cores are ok for this too
and it could be the whole front panel for a radio at cheap prices.? I have
two for that.?
Allison
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Ubitx - Increased voltage to finals thru middle wire on power plug...no effect
hi guys, I thought i would try a little experiment. I was running 12 volts on the dot to the middle wire on the power plug on my v4 ubitx and the output is about 16 watts on 20 meters cw. I then increased it to 23 volts, and the output was the same, about 16 watts on 20 meters cw. I thought there was going to be some increase ? Here are a couple shots.. kevin rea lancaster, calif. k6rea  
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Re: Modular uBitx - "Ex: Harmonics"
Allison
Agreed.? Some readers have an aversion to installing a PC level board inside a radio.
I can understand, but also see the need to try it with one of the tiny but full featured PC
cards like the Raspberry Pi or Pi-Zero.? That could allow any of the Linux applications
(fldigi, etc.) to exist and run inside something like the Ubitx or one of the QRP-Labs
creations.? Using I2C and a Nextion display could provide bus-level interfaces for
many plug-in functions.? USB could host the mouse and keyboard to make a very
compact rig for field-day activities.? Shielding for such a small PC board becomes
less of a problem with these small boards.? I don't have the time, but maybe someone
will take on the challenge.
Arv
_._
On Thu, Aug 16, 2018 at 7:03 PM ajparent1/KB1GMX < kb1gmx@...> wrote: Arv,
All the best radios I've built shielding was most time consuming and worth it.
Confining signals to the place needed only has been a known cure.? Often?
its the difference.
However it does not have to be mechanically complicated.
Allison?
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Re: Modular uBitx - "Ex: Harmonics"
Eric,
Why should the PI be any worse than a PC in the shack.? IF anything its?
a small package and easily put in a tin pay attention to heat removal
what there is of it.
Allison
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Re: Modular uBitx - "Ex: Harmonics"
Arv,
All the best radios I've built shielding was most time consuming and worth it.
Confining signals to the place needed only has been a known cure.? Often?
its the difference.
However it does not have to be mechanically complicated.
Allison?
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Re: ubitx troubleshooting help - low power after irf510 replacement
Did you replace both?
Did any traces top side or bottom side heat up or disappear.
Scoping stages has been what I consider the least useful step.
Look for smoked parts.
Allison
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N4ISF DE KG4HLZ. I'm just down in Madison, AL (near Huntsville). Just got mine in the mail as well. If I can get some time to put it together, we might try to set up a QSO. I'm already starting to think if moods.
73s.
Bruce KG4HLZ??
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Re: Does anyone have an AGC/Click kit to sell?
Hi all.
Boards on order.
See:?
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Hi Y'all;? I'm Reuben Titus, N4ISF. Middle TN. ? A friend told me about the uBitx so I ordered one yesterday. Figure I will try it for home/portable/mobile,? maybe tie in a tube amp for home use, maybe build me a solid state amp for portable if the power source is good for it,? or not if it's limited to a small battery. ? I have a Heathkit 80-100 watt all tube transmitter I started with as novice around 1980 if it still works, (it was old then)? it was an AM-CW only unit but could do SSB with external signal input. ? As original it had a drifty tube VFO with crystal option, and the HQ145X receiver that I used was very drifty as well. ? ? Most of my electronics education was early 80's style on back,? the 1982 ARRL amateur handbook was my reference book,? I wore it out and still use it. Spent a lot of time with the QST magazine issues from the 1930's to 80's that I found in a library.? ?? Haven't kept up with modern stuff very well,? but I can try.? And I've been foolin with various things over the years and picked up enough test equipment to play with stuff a little, oscilloscope,? capacitance/inductance meter, signal generators, ? etc.? Mostly doing stuff like weird versions of brushless DC motors, making my own electric fence chargers and electronic ignitions for old vehicles,? etc. ?? So. ? New project to get me a working transceiver again.? The kenwood TS820 I have started having issues a while back so I've been thinking of finding something else, something I can carry around and mess with easier. ? The 820 likes to stay put (heavy) and the interior is so packed it looks like a challenge to fix. And a bigger challenge to figure out why it's doing what it's doing,? throwing in excessive interference on the received signal and kicking the digital readout off at the same time.? ? Think I'll put it on ebay sooner or later,? it might sell for enough to recover the cost of the uBitx. since I see a nonworking one on there now that's bid to over $100.
-- N4ISF
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VK4PP uBitx add-on Boards. (VK4PLN)
Just a note to those interested, I have ordered another set of boards.
Please see here for whats available:
I am still working on others...
73 Nick VK4PP
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ubitx troubleshooting help - low power after irf510 replacement
I have a bit too much experience with cooking the finals on my ubitx...I'm on about my fourth or fifth set of IRF510s.? I think that I'm probably overdriving too much on digital modes...but here's the question
After the last replacement and re-biasing of the PAs using the standard +100 mA per pot technique, I found that I had decent power on 40m, but had virtually no output on 20m or 17m (where I'd previously seen at least a few watts out).
so...here's my question: did I perhaps damage something other than the irf510s, or do I perhaps have bad irf510s (these were from a different batch)?? I have an oscilloscope and a dvm, but not really 100% sure how to proceed.? I had an idea that I might want to put on a dummy load, use the wsjt-x 'tune' function (with a relatively low drive setting) and then measure at different points, but I'm fairly new to electronics and not sure enough what I'd be looking for. I was thinking perhaps checking each amplification stage, but would need some advice on what to look for.
Ideas???
Thanks!
Sean
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I get 7w with a class E NS40 by 4sqrp. Apart from the layout of the board, a real masterpiece, it is amazing that just after key down the final remains that cold (very mild temp). My other twofer qrp by Hendricks with just 1w the final notwithstanding is biased correctly is hot. Thumbs up for class E... a pity there is no commercial class E amplifier as far as I now.
Il 16/ago/2018 18:40, "Daniel Conklin" < danconklin2@...> ha scritto: Jack, I'm getting about 4 watts output with 13.8v the way I have it currently configured. It's driven with a 2n7000 MOSFET. I'm wondering if the uBiTX could benefit from this because it requires lower drive levels from the LO.?
Dan? W2DLC?
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David Posthuma
Nick VK4PP