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Nearly non-existent output power, no mod

Ted
 

It seems that I'm experiencing an issue with a V3 board where I get less than a watt of CW carrier, and nothing on SSB output except upon initially pressing the microphone. 

I did something that apparently sucked up too much amperage and took out Q90 (replaced) and one of the 4 pre-drivers (2N2222, replaced) and the finals (replaced).  As said, I get barely any output on CW key-up.  Final bias is set to the designated level, etc. Touching the metal body of the drivers and the finals increases the RF heard on the nearby receiver, as expected.  On the SSB end, when I key the mike with no audio, I get a chirp on a nearby receiver and a wide power meter swing of a couple of watts but as it's an analog meter the buffering of needle mass really leaves the peak at a guess, since it's so brief a blip.  After the blip, no audio comes across and zero power deflection.

All test points on the available troubleshooting guide for Q6, & Q20 thru Q94 & Q95 come out spot on where they should be.  The 2 pre-drivers and 4 drivers get plenty warm, and the finals get warm though not hot like they used to do.  Though the RX seems OK, K3 has come to mind since of course only half the contacts could have converted to vapor (and it fails to answer why there's no audio on SSB aside from a quick chirp.

Any suggestions?


Tnx,

Ted
K3RTA







 

If Q90 was blown then D1/D2 could be blown.. replace. I had a bad solder on a test board.

Raj

At 29-08-19, you wrote:

It seems that I'm experiencing an issue with a V3 board where I get less than a watt of CW carrier, and nothing on SSB output except upon initially pressing the microphone.

I did something that apparently sucked up too much amperage and took out Q90 (replaced) and one of the 4 pre-drivers (2N2222, replaced) and the finals (replaced). As said, I get barely any output on CW key-up. Final bias is set to the designated level, etc. Touching the metal body of the drivers and the finals increases the RF heard on the nearby receiver, as expected. On the SSB end, when I key the mike with no audio, I get a chirp on a nearby receiver and a wide power meter swing of a couple of watts but as it's an analog meter the buffering of needle mass really leaves the peak at a guess, since it's so brief a blip. After the blip, no audio comes across and zero power deflection.

All test points on the available troubleshooting guide for Q6, & Q20 thru Q94 & Q95 come out spot on where they should be. The 2 pre-drivers and 4 drivers get plenty warm, and the finals get warm though not hot like they used to do. Though the RX seems OK, K3 has come to mind since of course only half the contacts could have converted to vapor (and it fails to answer why there's no audio on SSB aside from a quick chirp.

Any suggestions?


Tnx,

Ted
K3RTA

 

Hi Ted,

What was your source for the replacement finals?

Do you have an RF probe made, so you can make signal measurements?

73,


Mark

Curt
 

Ted

slow down it bit - it is very difficult to do that much damage to the ubitx - otherwise I would have done so myself! 

check integrity of connections with an ohm-meter - not transmitting - to insure nothing is short circuited or open.  After everything is confirmed to be okay, be gentle (short duration) with CW transmit.  check more than one band to exercise different relay paths.  the check how the microphone is wired before blaming the electronics. 

possibly rig is healthier than you perceive! 

Curt

Sam Tedesco
 

Ted...make sure the heat sinks on the finals aren't touching any of the coils.

_Dave_ K0MBT
 

The times that I have lost ssb output Ted, the mic element has gone bad. They seem very fragile but work good when they work. Probably gone though half a dozen in two years of running 4 uBITX and one BITX40 radios.

Will see just what you did a bump in the power when keyed. 
--
73
Dave
k0mbt
http://veloliner.com/ham/k0mbtkey.pdf

iz oos
 

That's very strange you changed so many mic elements. I haven't used that as much as you but I thought an electret could last decades. Are you sure the resistors supplying the elements have the correct value?


Il 30/ago/2019 15:27, "_Dave_ K0MBT" <davesters@...> ha scritto:
The times that I have lost ssb output Ted, the mic element has gone bad. They seem very fragile but work good when they work. Probably gone though half a dozen in two years of running 4 uBITX and one BITX40 radios.

Will see just what you did a bump in the power when keyed. 
--
73
Dave
k0mbt
http://veloliner.com/ham/k0mbtkey.pdf

_Dave_ K0MBT
 

iz-ooz
I have not looked at the values of the feed resistors but they are stock and the radios have been picked up from various sources.

I have replaced the elements from various sources as well. Some come from used telephones, others were purchased on ebay for cheap. I think I got 7 of them and have only 2 left. None of the original mic elements are still working. 

Perhaps there is something about my grounding or other issue that affects the mics. Might be a topic for another thread. 
--
73
Dave
k0mbt
http://veloliner.com/ham/k0mbtkey.pdf

 

Regardless,

The problem wouldn't be with the mic element as Ted gets almost no power out on CW either.

73,


Mark.

Ted
 

Raj,

I'll take a look at D1 & D2.


Mark,

I don't recall the source though I've picked up two different batches off the Bay over time. I know eBay sources are to be distrusted, though the ones I've used so far at least work.

-------------------

The curious thing is that the heat sinks are getting plenty hot. Something's making power but where is it going?  I now get maybe a watt out on 80, 40, and 30; up to maybe 2 on 20, then about nothing on 17 and 15.  The LPF relays get coil voltage seemingly [only] when they're supposed to have it.

I swapped out K3 (t/r relay) out of frustration, so at least it's now color-coordinated with the rest of the Axion blocks in that row :)   

I'll look at Raj's idea and come back.


Thanks, all.

Ted
k3rta

 

Hi,

I would bet it's the finals. Order some from a reputable company e.g. mouser, arrow, or digikey. They get hot because the drive is turning the on, but they can't make RF efficiently so not much comes out. 

73,


Mark

barry halterman
 

You might have an issue with your nano not selecting the appropriate filter, i.e., one filter is always selected regardless of the band. Check the relay drivers to verify the correct band is selected. 
I had a similar problem with my V4 board, with exactly the same condition you described.
Barry
K3Bo

On Sat, Aug 31, 2019, 2:07 AM Mark - N7EKU <n7eku@...> wrote:
Hi,

I would bet it's the finals. Order some from a reputable company e.g. mouser, arrow, or digikey. They get hot because the drive is turning the on, but they can't make RF efficiently so not much comes out. 

73,


Mark

Ted
 




On Sat, Aug 31, 2019 at 9:22, barry halterman
<kthreebo@...> wrote:
You might have an issue with your nano not selecting the appropriate filter, i.e., one filter is always selected regardless of the band. Check the relay drivers to verify the correct band is selected. 
I had a similar problem with my V4 board, with exactly the same condition you described.
Barry
K3Bo

On Sat, Aug 31, 2019, 2:07 AM Mark - N7EKU <n7eku@...> wrote:
Hi,

I would bet it's the finals. Order some from a reputable company e.g. mouser, arrow, or digikey. They get hot because the drive is turning the on, but they can't make RF efficiently so not much comes out. 

73,


Mark

 

Hi Barry,

Why was your nano selecting the wrong filter?  This doesn't seem like a typical problem -- at least I've not seen a lot of such reports here.  Were you using factory firmware, or something else?

73,


Mark.

barry halterman
 

The nano had a bad output pin that selects txa, b or c  relay driver. I don't recall which one but it kept one filter always selected, like if on 20 meters the 80 meter filter was constantly inline. Thus, little to no power from the finals for anything above 80 meters. IC for the finals was normal and they got hot but no power out.
Replacing the nano corrected the issue.
Barry

On Sat, Aug 31, 2019, 11:53 PM Mark - N7EKU <n7eku@...> wrote:
Hi Barry,

Why was your nano selecting the wrong filter?  This doesn't seem like a typical problem -- at least I've not seen a lot of such reports here.  Were you using factory firmware, or something else?

73,


Mark.

Ted
 

Excellent line of investigation to follow.  Having replaced the finals (from Mouser) with predictably no change, I swapped out the Nano. New, known supplier, etc. No change.

The relay power at K1 - K3 changes with band selection so unless a relay is stuck, the mystery
just gets deeper.   These are replacement Axicon relays, though anything can fail......


Ted
K3RTA





-Ted

Clark Martin
 

Use an RF probe or oscilloscope to trace the signal through the relays / filters.


Clark Martin
KK6ISP

On Sep 12, 2019, at 4:36 PM, Ted via Groups.Io <k3rta@...> wrote:

Excellent line of investigation to follow.  Having replaced the finals (from Mouser) with predictably no change, I swapped out the Nano. New, known supplier, etc. No change. 

The relay power at K1 - K3 changes with band selection so unless a relay is stuck, the mystery 
just gets deeper.   These are replacement Axicon relays, though anything can fail......

Ted
 

On Thu, Sep 12, 2019 at 07:42 PM, Clark Martin wrote:
Use an RF probe or oscilloscope to trace the signal through the relays / filters.
 
 
OK, here we are: 

On 80m and 60m, only the filter between the T/R relay and KT3 shows strong RF.  Power out on 80m is 2 watts CW, 1/2w SSB. 60m shows 1 watt/1/2 watt.

On 40m and 30m,  only the filter at KT3 shows strong RF. Power out on 40m is about 3/4w CW and 1/2w SSB; 30m shows 1w CW.

On 20m and 17m, only the filter at KT2 shows strong RF with power out the best: 2.5w CW but only 1/4w SSB on 20. 17m shows about 1/3 & 1/4 if that....

15m and 10m show strong RF on the filter near KT1, with output on both bands less than 1/4w either mode (or should I just say, at barely detectable limits).



The meter used is the analog dial on a MFJ 949D as my 5W slug is missing from the Bird wattmeter  :(

The two predrivers and 4 drivers are all steel-can 2N2222's with 10-ohm bias resistors.  All six run fairly hot - with heat sinks added - though the 4 more so than the pair. The finals (even reputable ones) certainly get hot enough, too. if i put my fingers on the predrivers or drivers, the RF power (such as it is) decreases somewhat. Q90 is also a 2N2222 can with I believe a 15-ohm bias chip on it.  None of this changed prior to the output failure. 

Obviously, energy is being produced but to what end?  It certainly isn't going into the dummy load or out the aerial/antenna/wirethingy.

More guidance would sure be fantastic.  Thank you, all, for your input.



Ted
K3RTA

Clark Martin
 

Sorry, but you description below is akin to bad driving directions… (turn right at the green house, etc).  

It would be far easier and more accurate to specify where the signal was measured (and how).  
i.e. 
KT2-14 2.6V
using an RF probe and DC voltmeter

check on both sides of the filter (input and output) and on each of the contact pins of the relay in question.



Note: all the resistors connected to the driver and pre-drivers are “bias” resistors.  The 10 ohm would, presumably, be the emitter bias resistor.

You replaced the final transistors, did you readjust the bias pots (RV2, RV3)?


Clark Martin
KK6ISP

On Sep 16, 2019, at 5:49 PM, Ted via Groups.Io <k3rta@...> wrote:

On Thu, Sep 12, 2019 at 07:42 PM, Clark Martin wrote:
Use an RF probe or oscilloscope to trace the signal through the relays / filters.
 
 
OK, here we are: 

On 80m and 60m, only the filter between the T/R relay and KT3 shows strong RF.  Power out on 80m is 2 watts CW, 1/2w SSB. 60m shows 1 watt/1/2 watt.

On 40m and 30m,  only the filter at KT3 shows strong RF. Power out on 40m is about 3/4w CW and 1/2w SSB; 30m shows 1w CW.

On 20m and 17m, only the filter at KT2 shows strong RF with power out the best: 2.5w CW but only 1/4w SSB on 20. 17m shows about 1/3 & 1/4 if that....

15m and 10m show strong RF on the filter near KT1, with output on both bands less than 1/4w either mode (or should I just say, at barely detectable limits).



The meter used is the analog dial on a MFJ 949D as my 5W slug is missing from the Bird wattmeter  :(

The two predrivers and 4 drivers are all steel-can 2N2222's with 10-ohm bias resistors.  All six run fairly hot - with heat sinks added - though the 4 more so than the pair. The finals (even reputable ones) certainly get hot enough, too. if i put my fingers on the predrivers or drivers, the RF power (such as it is) decreases somewhat. Q90 is also a 2N2222 can with I believe a 15-ohm bias chip on it.  None of this changed prior to the output failure. 

Obviously, energy is being produced but to what end?  It certainly isn't going into the dummy load or out the aerial/antenna/wirethingy.

More guidance would sure be fantastic.  Thank you, all, for your input.


Clark Martin
 

Additionally, for the SSB tests what was the AF signal source?


Clark Martin
KK6ISP

On Sep 16, 2019, at 6:39 PM, Clark Martin <kk6isp@...> wrote:

Sorry, but you description below is akin to bad driving directions… (turn right at the green house, etc).  

It would be far easier and more accurate to specify where the signal was measured (and how).  
i.e. 
KT2-14  2.6V
using an RF probe and DC voltmeter

check on both sides of the filter (input and output) and on each of the contact pins of the relay in question.



Note: all the resistors connected to the driver and pre-drivers are “bias” resistors.  The 10 ohm would, presumably, be the emitter bias resistor.

You replaced the final transistors, did you readjust the bias pots (RV2, RV3)?