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Capacitor on irf510 sbitx

 

I am replacing the irf510 mosfet's on my sbitx v3. At least
It was told this is a v3 when I purchased it used.
I see what I tested as capacitors wired across the 510's like 
they were an afterthought and I don't see them on
the schematic. Although I am not big into electronics and
may not not be seeing them. My question is can I 
just replace them with a standard cap instead of the surface
mount type shown in the photo? If so what type
should I use?
 
 

Those are transient suppressor diodes to protect the gate.    search for that feature on this forum and you’ll find Ashhar  recommendation 

On Dec 29, 2024, at 16:16, bretnemeth via groups.io <bretnemeth@...> wrote:


I am replacing the irf510 mosfet's on my sbitx v3. At least
It was told this is a v3 when I purchased it used.
I see what I tested as capacitors wired across the 510's like 
they were an afterthought and I don't see them on
the schematic. Although I am not big into electronics and
may not not be seeing them. My question is can I 
just replace them with a standard cap instead of the surface
mount type shown in the photo? If so what type
should I use?
 
<PXL_20241229_195312646.jpg>
 

Looked up the parts and wondered if they were only used on v2 updated to 510s or do they use those on v3 too?
 

It was introduced in v3 using 510 as recommended by the forum. v2 did not use this protection.
Just replace the FETs and do the Bias adjustment. The black colored pcb is visible on v3.
--
Gyula HA3HZ
 

I ordered some of the diodes and some 510s from digikey.
I tried testing the diodes and one of the solder tabs broke
off. from what i was reading they should show some continuity
in one direction. I get nothing so i will replace them. i wonder how I
know what direction they should be soldered in? Or does it matter? 
I'm more of a toolmaker and not a electronics guy. 
 

With the IRF510s you dont really need these suppressors. Just skip installing it


On Mon, Dec 30, 2024, 4:40 AM bretnemeth via groups.io <bretnemeth=yahoo.com@groups.io> wrote:
I ordered some of the diodes and some 510s from digikey.
I tried testing the diodes and one of the solder tabs broke
off. from what i was reading they should show some continuity
in one direction. I get nothing so i will replace them. i wonder how I
know what direction they should be soldered in? Or does it matter? 
I'm more of a toolmaker and not a electronics guy. 
 

On Sun, Dec 29, 2024 at 03:10 PM, bretnemeth wrote:
i was reading they should show some continuity
in one direction.
 
For what it's worth, they are right that standard diodes have some continuity measured in one direction and nothing in the other direction. TVS diodes like the ones used in the sBitx V3s don't show any continuity at all unless you apply more than 18.5V then they conduct, so if yours are not showing any continuity they are probably okay. It also doesn't matter what direction you install them, they are not polarity sensitive like a regular diode. If you have them I would install them, we can use all the protection we can get with the final MOSFETs. It wont hurt anything.
 
Joel
N6ALT
 

One of the legs broke on one diode. So I ordered more. Only problem is I put everything back together and set the bias. Still no power out. Starting to think I blew another fet or maybe there is a software problem. I have read about some peoples radios not working due to software.
 

time to break out the oscilloscope or build an "rf probe" if you don't have one, so you can begin to diagnose with a simple $6 digital voltmeter.
Lots of learning opportunities!    There are some charts (Somewhere on all the amassed knowledge base) of typical signal levels and voltages, that will help you.......

Took me MONTHS to solve a thorny problem with one of my units (which I might have been the cause of, so not blaming anyone else)

Gordon KX4Z


On Mon, Dec 30, 2024 at 1:06 PM bretnemeth via groups.io <bretnemeth=yahoo.com@groups.io> wrote:
One of the legs broke on one diode. So I ordered more. Only problem is I put everything back together and set the bias. Still no power out. Starting to think I blew another fet or maybe there is a software problem. I have read about some peoples radios not working due to software.
 

That's a bit over my head. I would rather buy a new board than go that deep. I'll dig around a bit but if it requires equipment I don't have it's over.
 

We all understand!!   

1.  Does it RECEIVE?   If you put an antenna on it, do you HEAR recognizable signals?    
2.  What exactly does it do when you try to transmit (specify mode, and what you see on the screen; for example, if you tell it you are in CW and have a paddle, and press the mic button, you should see a string of dashes or dots flying past.   

Gordon


On Mon, Dec 30, 2024 at 2:41 PM bretnemeth via groups.io <bretnemeth=yahoo.com@groups.io> wrote:
That's a bit over my head. I would rather buy a new board than go that deep. I'll dig around a bit but if it requires equipment I don't have it's over.
 

It receives fine. I can hear everything that it should with an antenna.
 
When I transmit in any mode I see that it looks like it is transmitting on the screen but it shows 0 watts and 1.0 SWR. Doesn't matter what mode I transmit on. 
 

OK 

1.  I’m assuming you were able to adjust the idle current with the bias potentiometer and get expected results. If not, then there could be a DC disconnection somewhere in the power amplifier stage.

2.  Those four metal cans to the left of the power amplifier stage are the driver stage. They should get pretty warm or even hot within 15 seconds if you put the radio into any single side band mode and key the microphone. Even if you don’t say anything. If they don’t, then there is some problem with the DC connections to the driver stage.

3.  Do you have any other means to measure the output of the transmitter? A SWR meter or anything similar? If so, try to get some kind of a read on whether there’s any real power coming out even if it is only 100 Milli Watts or so.   

Do you hear anything in another receiver tune to the same frequency? Usually, you’ll hear something if there’s any real power out put

4.   Do you have a voltmeter?






On Dec 30, 2024, at 15:00, bretnemeth via groups.io <bretnemeth@...> wrote:


It receives fine. I can hear everything that it should with an antenna.
 
When I transmit in any mode I see that it looks like it is transmitting on the screen but it shows 0 watts and 1.0 SWR. Doesn't matter what mode I transmit on. 
 

Great going Gordon , hope these lessons continue to it's logical conclusion.

It'll surely help someone and me offcourse.

de VU2UPX 

On Tue, 31 Dec, 2024, 1:47 am Gordon Gibby KX4Z via groups.io, <docvacuumtubes=gmail.com@groups.io> wrote:
OK 

1.  I’m assuming you were able to adjust the idle current with the bias potentiometer and get expected results. If not, then there could be a DC disconnection somewhere in the power amplifier stage.

2.  Those four metal cans to the left of the power amplifier stage are the driver stage. They should get pretty warm or even hot within 15 seconds if you put the radio into any single side band mode and key the microphone. Even if you don’t say anything. If they don’t, then there is some problem with the DC connections to the driver stage.

3.  Do you have any other means to measure the output of the transmitter? A SWR meter or anything similar? If so, try to get some kind of a read on whether there’s any real power coming out even if it is only 100 Milli Watts or so.   

Do you hear anything in another receiver tune to the same frequency? Usually, you’ll hear something if there’s any real power out put

4.   Do you have a voltmeter?






On Dec 30, 2024, at 15:00, bretnemeth via groups.io <bretnemeth=yahoo.com@groups.io> wrote:


It receives fine. I can hear everything that it should with an antenna.
 
When I transmit in any mode I see that it looks like it is transmitting on the screen but it shows 0 watts and 1.0 SWR. Doesn't matter what mode I transmit on. 
 

I set the bias with my amp meter. That seemed to work. There is no output on the external swr meter. It doesn't show anything it the 2 watt mode.
I have a good volt meter. The cans do get warm. They are about 85F or more. The little circuit board that is close to a big cap and the red power switch wires gets about 100F.
 

OK, so you’ve got some DC connectivity

Do you have another receiver anywhere?

Do you have a capacitor somewhere, anywhere between 100 pF and 0.1 Uf  that is rated for 50 V or more?  If you do, we can wire it in series with your AC voltmeter and start doing some tests.





On Dec 30, 2024, at 15:54, bretnemeth via groups.io <bretnemeth@...> wrote:


I set the bias with my amp meter. That seemed to work. There is no output on the external swr meter. It doesn't show anything it the 2 watt mode.
I have a good volt meter. The cans do get warm. They are about 85F or more. The little circuit board that is close to a big cap and the red power switch wires gets about 100F.
 

I have some other radios. xiegu x6100 good enough. I have some 50v ceramic caps. I have a 100 pf.
 

I kept thinking that the software could also have a problem. So I flashed the 4.2 software and sure enough it works now.
At 50% drive on 20 meters I am getting 10 watts out with the mic set at 50. CW works great. Maybe the memory card had
a glitch. Thanks for your help Gordon but it looks good now. Guess I got lucky.
 

Great!!!

On Dec 30, 2024, at 17:03, bretnemeth via groups.io <bretnemeth@...> wrote:


I kept thinking that the software could also have a problem. So I flashed the 4.2 software and sure enough it works now.
At 50% drive on 20 meters I am getting 10 watts out with the mic set at 50. CW works great. Maybe the memory card had
a glitch. Thanks for your help Gordon but it looks good now. Guess I got lucky.

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