Date   
Re: V4 TX selective failure #ubitx-help #cat

Don - KM4UDX
 

So that means when connected to your antenna you are not receiving the other FT8 stations on the common frequencies that you use?  

Right, signal levels appear too low to decode now.

What lead up to the issue?  what was the radio attempting to do?  Did you take it apart and reassemble or install a mod just before the failure?

a:  I was using the ubitx in digital mode, adjusting the computer, and just the normal stuff....It has no mods and I learned long ago to leave well enough alone (but I frequently don't head that advice..hahah...tinker till it's broke is my normal moto...but in this case I promise that I didn't touch anything I shouldn't have...

  Do you have access to another receiver that could possibly tune to the 32 Mhz or 12Mhz IF and BFO frequencies to see if the Raduino clocks are working?

a: i do have a SDR (SDRuno) that I could use...

With both receive and transmit being affected, it would point to one of the mixers or clocks, both are hard to troubleshoot with only a DMM.

a: based on the block diagram, the SW sidetone works works, the CW Key works with RF. .. so the fault could be anything on the lower right...CLK#0 or #2, audio (de)mod, 2nd RF Mixer, the IF amps


Hopefully others can chime in here and give you better options.

Sorry can not be of more help.

Re: V4 TX selective failure #ubitx-help #cat

Evan Hand
 

So that means when connected to your antenna you are not receiving the other FT8 stations on the common frequencies that you use?  

What lead up to the issue?  what was the radio attempting to do?  Did you take it apart and reassemble or install a mod just before the failure?

Do you have access to another receiver that could possibly tune to the 32 Mhz or 12Mhz IF and BFO frequencies to see if the Raduino clocks are working?

With both receive and transmit being affected, it would point to one of the mixers or clocks, both are hard to troubleshoot with only a DMM.

Hopefully others can chime in here and give you better options.

Sorry can not be of more help.

73
Evan
AC9TU

Re: V4 TX selective failure #ubitx-help #cat

Don - KM4UDX
 

Evan & Co.

When I turn spkr volume full up, and I tap the top of the capacitors C52/62/64 near the beige jack (audio), I can hear each tap/scratch in the output. 

And on 14.073 I can hear the faintest tone signal at max volume.... Previously it blew me out of the room. (Minor hyperbole.) 

Don
km4udx

Re: V4 TX selective failure #ubitx-help #cat

Don - KM4UDX
 

First off, does it still receive as before?  That helps from the standpoint that the same clocks, mixers and filters are used for both receive and transmit.

Well that is interesting you asked that.  No.  Receive volume is way down.
 
The second question is how are the mic and audio from the digital interface connected?

Mic is wired per kit instructions with little PPT switch and plugs into std mic jack.  Digital interface is from external USB sound card and uses mini male/male plugs from the sound card into the ubitx mic/spk jacks. 
To switch from voice to digital, I pull out the mini plugs from the sound card and plug in the mic and speaker. Sort of primitive, but I do digital 80% of the time, so the jacks don't get a lot of in/out use. 

Nevertheless, I did buy some nice switchcraft mini jacks to replace the "value" jacks included with the kit at some point when I was either bored, or the "value" jacks gave up the ghost.
 
Last question is what test equipment do you have? 

Just a humble multimeter...

For tests beyond static bias measurements, a scope or rf probe is required.   I have traced the signal through the TP's on the board using a 100 MHz scope and the power to the finals removed.  This would help in isolating the stage that is not amplifying, again IF the receiver still works as before.
 

Re: Unexpected Blowing of Fuses on Transmit

harryoliver196410@...
 

Thanks Jerry & MVS Sarma,
That is comprehensive help - really appreciated.  It will have to wait 3 days as I need to prep' for working away from tomorrow but should be back on it Wednesday/Thursday.
Thanks again - I will report back!
Regards
Harry

Re: KD8CEC ‘s SWR senser

Gordon Gibby
 

If you build a reflectometer or other system reasonably  well the losses should be extraordinarily low.  Otherwise they would burn up when used with higher power rigs!



On Dec 1, 2019, at 13:15, Joel Caulkins/N6ALT <caulktel@...> wrote:

Thanks for the info Joel

Joel
N6ALT

Re: KD8CEC ‘s SWR senser

 

Thanks for the info Joel

Joel
N6ALT

Re: KD8CEC ‘s SWR senser

Mark Hatch
 

Joel

thanks for this!  Have you measured watts out with and without the bridge?  Read somewhere about a watt penalty of 1 watt when it was in circuit. 


mark

Re: 5/7" Nextion Firmware location

Mark Hatch
 

Can you get me a screen shot. I will look into it. 


mark

Re: Unexpected Blowing of Fuses on Transmit

MVS Sarma
 

You cant have all of 
1. Preset gate more than 100mA drain current,
2. Hi rf drive with q90 collector preset and
3 boosted mic gain with presetbfor modulation level control. 

You may have to reduce at two of the locations. 

All the best 

On Sun, 1 Dec 2019, 9:49 pm harryoliver196410 via Groups.Io, <harryoliver196410=yahoo.com@groups.io> wrote:
Still no joy - I had high hope from Raj's suggestion - which makes a lot of sense - unfortunately. the pins and the pots were all in excellent condition (never thought I'd say that ...).
So I'm still blowing fuses.
Any suggestions gratefully received.
Regards
Harry

Re: Unexpected Blowing of Fuses on Transmit

Jerry Gaffke
 

Here's an outline for a step by step procedure to find the fault.
Whether you choose to follow it or not, it should give you some idea of what is going on.

We've all been assuming it's around the IRF510's, since those are the only things that typically pull a few amps.
So disconnect the PA-PWR connector pin in from the power supply, does the fuse still blow when you press PTT?
I assume not.

Now reconnect PA-PWR, with a DVM inline, set to 10 Amps max.  A $2 Harbor Freight DVM will work fine.
Pull up one end of L8,  and also of L9.  So PA-PWR cannot get to the IRF510 drains.
Rotate RV2 and RV3 fully clockwise for 0v at the IRF510 gates (minimum is clockwise, backwards from most pots!)
With 0v on the gates, the IRF510's will not conduct.  They start conducting when there is 3 or 4 volts on the gates.
Apply power and press PTT, does it still blow? 
I assume not.

Should be just a few milliamps going into PA-PWR when you press PTT, I'd guess down around 10ma or so.
A very rough guess, I have not measured it.
But with the DVM at 10 Amps, you should see pretty much zero current on the meter.

Measure the voltage at the IRF 510 gates with PTT pressed, should be zero volts.
(Ideally this would be done with a second DVM, as we will soon need to measure PA-PWR amps again.)
Adjust pots RV2 and RV3, verify that the gate voltage on Q95 and Q94 respectively 
goes from 0v to 5v as you rotate the pot counter clockwise.
Return both pots to 0v, fully clockwise.

Reconnect first L8, press PTT, does it blow?
If not,reconnect L9, press PTT, does it blow?
Since the gate voltages are both still at zero with RV2 and RV3 fully clockwise, the IRF510's are not conducting.
Even though both L8 and L9 are restored, that roughly 10ma of current into PA-PWR should not have risen hardly at all.

Now with PTT pressed, first rotate RV2 counterclockwise very slowly until the PA-PWR current rises to 100ma.
This will happen very suddenly when the gate voltage reaches 3 or 4 volts, so be careful.
If rotating RV2 can bring PA-PWR up to 100ma, then the IRF510 at Q95 is probably ok.

Then rotate RV3 until PA-PWR current increases another 100ma to 200ma total.
If that works, then the IRF510 at Q94 is ok.
Rig is ready to use.

I assume somewhere in that procedure, something went terribly wrong for you.
At exactly what step things when haywire will be a significant clue.

Jerry, KE7ER

Re: KD8CEC ‘s SWR senser

Joel Trenalone
 

For information, here is a sketch of what I did. The home brew Stockton bridge that Ian (CEC) used apparently did not have this problem. 

Re: Unexpected Blowing of Fuses on Transmit

harryoliver196410@...
 

Agreed Gordon - Just started doing something along those line now.
Regards
H

Re: Unexpected Blowing of Fuses on Transmit

Gordon Gibby
 

Well, you were going to have to divide up the paths where all the current can go, and interrupt some or all of them until you work out where it is going.    Now is the time to take a look at the schematic


On Dec 1, 2019, at 11:19, harryoliver196410 via Groups.Io <harryoliver196410@...> wrote:

Still no joy - I had high hope from Raj's suggestion - which makes a lot of sense - unfortunately. the pins and the pots were all in excellent condition (never thought I'd say that ...).
So I'm still blowing fuses.
Any suggestions gratefully received.
Regards
Harry

Re: Unexpected Blowing of Fuses on Transmit

harryoliver196410@...
 

Still no joy - I had high hope from Raj's suggestion - which makes a lot of sense - unfortunately. the pins and the pots were all in excellent condition (never thought I'd say that ...).
So I'm still blowing fuses.
Any suggestions gratefully received.
Regards
Harry

Re: Unexpected Blowing of Fuses on Transmit

harryoliver196410@...
 

Thanks Raj, 
Yes, that makes sense. 
I'll have a crack at it this afternoon. 
Regards
H

Re: V4 TX selective failure #ubitx-help #cat

Evan Hand
 

First off, does it still receive as before?  That helps from the standpoint that the same clocks, mixers and filters are used for both receive and transmit.

The second question is how are the mic and audio from the digital interface connected?

Last question is what test equipment do you have?  For tests beyond static bias measurements, a scope or rf probe is required.   I have traced the signal through the TP's on the board using a 100 MHz scope and the power to the finals removed.  This would help in isolating the stage that is not amplifying, again IF the receiver still works as before.

Really need the answer to the first question before going forward with speculation.  

Take the above with a grain of salt and verify when possible.
73
Evan
AC9TU

Re: Unexpected Blowing of Fuses on Transmit

 

Harry,

I think a pin is broken and still connected. If the ground pin momentarily disconnects then the IRF
will draw high current and blow the fuse. I've seen stranger things!

Raj

At 01-12-19, you wrote:
Hi Raj,
That's interesting and I've seen your post regarding this from a day or two ago.
I can see the logic to what you're saying and I'm definitely going to have a look at them this afternoon - I just think it's strange that this problem would 'suddenly' occur? Or am I being stupid and this is something that would randomly occur?
Thanks again.
Regards
H

Re: Unexpected Blowing of Fuses on Transmit

harryoliver196410@...
 

Hi Raj,
That's interesting and I've seen your post regarding this from a day or two ago.
I can see the logic to what you're saying and I'm definitely going to have a look at them this afternoon - I just think it's strange that this problem would 'suddenly' occur?  Or am I being stupid and this is something that would randomly occur?
Thanks again.
Regards
H

Re: Unexpected Blowing of Fuses on Transmit

harryoliver196410@...
 

Hi Evan and thank you,
I was using my 'droopy' dipole, but all testing has since been done into a dummy load - which I have also checked as I have two.
Regards
H