I got IFR510 from someplace. I can't track the order history. But using a simple set of DVM-based tests they check out for on/off state. I know that says nothing about the actual performance on the circuit.?
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All:
The BITX40 is sold. Thanks for your interest.
Jack, W8TEE
-- Jack, W8TEE
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The fact that you could do the bias adjustment implies that K1 is working.? It also implies that both of the IRF510s are OK.? Either could be false, but not likely.
That leaves the drivers from Q90 on.?
To progress from here it would be best to know what test equipment you have on hand.? We will need to trace the signal from the base of Q90 to the gates of the finals.? I find that an oscilloscope works best for me (assuming it can measure the frequencies to be used.
I use the CW mode to test the drivers, as the signal is constant, and easier than doing the single or two tone for SSB. (getting input levels correct can be a hassle)?
I will assume that you have the schematic from HFSignals.
In another thread I posted the waveforms that I measured on the test points up to the finals.? I will look them up if youi have a scope.
73
Evan
AC9TU
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Let me try to help you OM with my limited knowledge which I have gained after building my homebrew ubitx based on V5. Disclaimer: I don't own any version of ready made build ubitx :)
My first question will be where you have sourced your replacement IRF510. If it's from reputed source like Digikey or mouser then you can start the troubleshooting or else check if those IRF510 are genuine one.
Since you have replaced both the K1 relay and the MOSFETS at the same time. Check if there is any contact issue with the replaced K1 relay. Since your receiver is working, are you still able to listen to the receiver when to press the CW key ?
As the receiver is working fine I would focus on things located beyond C80.
73
Anthony
VU3JVX
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Check the connection between the traces and the 510s. Check continuity between the 510 pins and the trace not just at the hole.?
73
Aa4pg
On Dec 12, 2019, at 11:47 AM, Don - KM4UDX < dontAy155@...> wrote:
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Hello all!? I failed to pay attention and left my beloved V4 uBIX on TX into a high SWR situation with too many watts for too long while and things got sort of too hot. Like Africa hot.
After I got Chernobyl cooled off, every time I hit TX the rig went to ground, so I figured the 510s had gone to heaven.?
And K1 had been sticking randomly for a while. So removed the old K1 relay and put in a new guy. I don't know how to test the new K1 beyond hitting TX and seeing what happens?
I then removed the old 510s, and watched a bunch of uTuber on MOSFET DVM testing.? After testing, one of the two olds were clearly " totally dead".?
So I replaced both - a first for me!? Then adjusted bias to get to 100mA delta on each. So all good.? When I now hit TX with the CW key (I think this is full audio drive into the TX section), the amp draw increase by about 1 amp -- which I think (?) is fine.
Only problem is I get no RF out. When I use the mic input I get the same behavior. No RF. Ditto when I use WSJT-X tune function which triggers the TX and send a big audio tone into the rig.? No RF.
RX is perfect.
What can I check, or what is the likely issue?? I could have messed up the PA repair, or the K1 repair, or something else got whacked in the Chernobyl event that I haven't figured out?
Or am I doing something moronically stupid (which is an actual possibility..just saying...).
And thanks for all for all the help.
<IMG_20191209_215240_01.jpg>
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Hello all!? I failed to pay attention and left my beloved V4 uBIX on TX into a high SWR situation with too many watts for too long while and things got sort of too hot. Like Africa hot. After I got Chernobyl cooled off, every time I hit TX the rig went to ground, so I figured the 510s had gone to heaven.? And K1 had been sticking randomly for a while. So removed the old K1 relay and put in a new guy. I don't know how to test the new K1 beyond hitting TX and seeing what happens? I then removed the old 510s, and watched a bunch of uTuber on MOSFET DVM testing.? After testing, one of the two olds were clearly " totally dead".? So I replaced both - a first for me!? Then adjusted bias to get to 100mA delta on each. So all good.? When I now hit TX with the CW key (I think this is full audio drive into the TX section), the amp draw increase by about 1 amp -- which I think (?) is fine. Only problem is I get no RF out. When I use the mic input I get the same behavior. No RF. Ditto when I use WSJT-X tune function which triggers the TX and send a big audio tone into the rig.? No RF. RX is perfect. What can I check, or what is the likely issue?? I could have messed up the PA repair, or the K1 repair, or something else got whacked in the Chernobyl event that I haven't figured out? Or am I doing something moronically stupid (which is an actual possibility..just saying...). And thanks for all for all the help. 
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Re: ?BITX & QRP labs 50W PA
Like all of the stuff Hans sells, the manual is exceptional.
Lots of notes in there about design tradeoffs made.
And a bunch about what it would take to make it linear.
Should have a way to evaluate IMD if you give linear operation a try.
Price is right.
Has a very nice solution for QSK TR switching.
Jerry
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Re: ?BITX & QRP labs 50W PA
Ah ok¡. ? Well if it¡¯s ¡°Class C¡± it¡¯s not gonna work for SSB.? The only way to change that is to bring it to at least ¡°Class AB2¡±¡ by reducing the bias and allowing the device more resting current.? That generates a lot more heat (because the devices are conducting more of the time) so the cooling needs to be increased.?? You can make it happen but it¡¯s gonna take some work. ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of iz oos
Sent: Thursday, December 12, 2019 11:24 AM
To: [email protected]
Subject: Re: [BITX20] ?BITX & QRP labs 50W PA ? Nice to know. I don't think it can be used for SSB as it is a class C amp unless some mods are done. Looking forward to seeing Allison's reply ? Il 12/dic/2019 17:49, "Arvo W0VRA via Groups.Io" <arvopl=[email protected]> ha scritto: Anybody considering using a QRP Labs 50W PA with their ?BITX?
There's no band switching yet.
-- ¡_. _._
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BITX40 for sale...again...
I have a BITX40 for sale in its original shipping box for $50, with free shipping to CONUS.Write to me privately if you are interested using my email address on QRZ.com. PayPal only please!
Jack, W8TEE
-- Jack, W8TEE
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Re: ?BITX & QRP labs 50W PA
Nice to know. I don't think it can be used for SSB as it is a class C amp unless some mods are done. Looking forward to seeing Allison's reply
Il 12/dic/2019 17:49, "Arvo W0VRA via Groups.Io" <arvopl= [email protected]> ha scritto: Anybody considering using a QRP Labs 50W PA with their ?BITX?
There's no band switching yet.
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Re: ?BITX & QRP labs 50W PA
Ok, I sort of take that back. The webpage also says: ######################################
2. Can it be used as a Linear for SSB and other modes??
NOT SSB as it is - it is designed as a Class-C amplifier, for CW operation (or FSK modes). Single Sideband (SSB) requires a Linear. If you want to experiment using this amplifier as a Linear, you can try setting the bias trimmer potentiometer to achieve a higher "idle" current during transmit, of around 250mA. This will dissipate some watts of heat even when there is no signal, and is normal for Linears. The efficiency will also be lower. Accordingly, heat dissipation may be higher too (depending on the average power output and other factors). So proceed with caution if you want to modify the amplifier for LINEAR operation - you will be in experimental territory.?
.......
6. Could it be modified for multi-band operation??
?
Certainly. Just bypass the Low Pass Filter section of the design, and use an external switched Low Pass Filter for the bands of interest. There are no other band-specific components except for the Low Pass Filter components and it will work across all HF. As usual... everything gets harder at higher frequencies so expect the power output to start to fall off (see also the measurements section of the manual).?
##################################################
So multiband should be possible with just an appropriate LPF as a lump in your antenna feed line.
I would guess you will have to adjust the drive into the amp whenever you switch bands, the upper bands will require more drive.
As he says, linear operation for SSB might be possible but is not designed in.
You're on your own.
Jerry
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Re: ?BITX & QRP labs 50W PA
That's a class C amp.
As it says on the web page you pointed to:
>? ??This amplifier is not intended to be a Linear (for SSB use) - it is designed for single-band CW operation only.?
Jerry
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On Thu, Dec 12, 2019 at 08:49 AM, Arvo W0VRA wrote:
Anybody considering using a QRP Labs 50W PA with their ?BITX?
There's no band switching yet.
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Anybody considering using a QRP Labs 50W PA with their ?BITX?
There's no band switching yet.
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And solved issue for me, thanks for posting
--
PE3ES - F4VTQ - Erwin
73
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Erwin I was meaning the power adapter for the active antenna not the uBITX.?
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On Dec 12, 2019, at 06:17, Erwin Serl¨¦ via Groups.Io <waterwin2@...> wrote:
?Reversing the power would not make my uBITx work I think.
And it is working (still ;-)
--
PE3ES - F4VTQ - Erwin
73
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Re: My #ubitx build from scratch
#ubitx
Anthony,
Thanks for letting us know about the spot weld cutter drill bit.
Looks ideal, perhaps the easiest way to prototype a circuit.?
The almost solid ground plane on the top side is good enough in most cases.
For a radio, especially in critical sections, I might drill a bunch of holes through the board,
then solder wire into those holes to connect the top and bottom ground planes.
Can't have too good of a ground when dealing with large gains and several watts of RF.
Jerry, KE7ER
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On Wed, Dec 11, 2019 at 11:15 PM, Anthony Gomes wrote:
What you said " I'd first try taking an angle grinder with a cutoff disk to an old drill bit, leaving the center and a "wing" on each side " this does work but I found a better tool which does the work very easy and clean way.?
as you can see they are quite cheap and available on amazon.com also, you don't need to get the best as we are not going to use it for spot welding so even the cheap one will cut like butter on copper board, good thing is that you can change the side of the cutter which you will hardly require.
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Re: Audio isolation w/ digital modes
#ubitx
Hi Erwin,
Did You perhaps use a linear potentiometer instead of a logarithmic ?? ?That can cause the effect of the volume id very sensitive at one end of the scale.
Best Regards, Jonas - SM4VEY
Den tors 12 dec. 2019 kl 12:31 skrev Erwin Serl¨¦ via Groups.Io <waterwin2= [email protected]>:
Hi Arvo,
I have something like it on a ugly build uBITx V5. It is very difficult to control the volume of Audio Out. Very sensitive at the beginning of the volume knob. Did you (or somebody else) think of making gears for that knob 1 : 10 or so for better handling. Or install an extra resistor in series or so?
The volume should be very low as to not overdriving the pc soundcard/external sound card.
--
PE3ES - F4VTQ - Erwin
73
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Re: My #ubitx build from scratch
#ubitx
QRPme style pads created using the bits as shown in the picture (attached incorrect picture in my previous post). I would recommend using the 3/8 inch bit to cut the pads and using the 5/16 inch to cut the island with a hand drill (if you have a cordless even better). Usually they sell it as set of 2 bits (3/8 inch & 5/16 inch) easy to get in your local shop/online. Hope then don't run out of stock after the discussion on this forum :)  From my personal experience I can say with this tool you can lay down any schematic in matter of no time. I have even build a FT8 digital interface in no time for my Yeasu FT-450D. I was even able to fix the relay in correct orientation after bending the pins side ways but I won't recommend doing so with IC's and hence you can see the vero board build in the in the middle of my ubitx build as I have used TDA2822 for audio and the circuit was simple one.
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Re: Audio isolation w/ digital modes
#ubitx
The potentiometers provided with the case kits and maybe even for the board kits are both linear. ? For audio volume control purposes, an audio taper will provide the logarithmic progression necessary for the human ear's response curve. ?Sounds like this could be your problem with sensitivity at the beginning of the control.? Try replacing the control with an audio taper control.??
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MadRadioModder
Arvo W0VRA
Skip Davis