Topics

No TX #ubitx

joe kallo <quietglow@...>
 

Finally got around to putting my ubitx into a box, and I'm having trouble getting measurable output. I followed the bias tuneup procedure but when I got to the part where you HAAALLLLOWW into the mic and watch for deflection on the ammeter, I got none. I also didn't see any movement on the power meter/swr/dummy load. So I hooked up a cw key and confirmed: no measurable output when keyed down.

Where ought I to start troubleshooting?

Thanks much and 73

Joe KD9JLV

joe kallo <quietglow@...>
 

Should have noted: the radio does go into tx mode when the PTT is pressed and when the key is down. 

 

Does it receive ?

Shake all trifilar toroids and any shorts may show up.

Check all the yellow toroids for bad solder.. check continuity with multimeter in beep mode..

Raj

At 02-01-2018, you wrote:
Finally got around to putting my ubitx into a box, and I'm having trouble getting measurable output. I followed the bias tuneup procedure but when I got to the part where you HAAALLLLOWW into the mic and watch for deflection on the ammeter, I got none. I also didn't see any movement on the power meter/swr/dummy load. So I hooked up a cw key and confirmed: no measurable output when keyed down.

Where ought I to start troubleshooting?

Thanks much and 73

Joe KD9JLV

joe kallo <quietglow@...>
 

It does indeed receive. 

I'll check out the toroids, thanks. It's funny you mention that as they looked a little flattened when I opened the kit.

Joe

 

Joe,

This means that you can ignore L1-L4 & T1 to T7 - these are common to TX and RX

Check T8 onwards.

Check TX on all the bands, the problem may be band specific.

Raj

At 02-01-2018, you wrote:
It does indeed receive.

I'll check out the toroids, thanks. It's funny you mention that as they looked a little flattened when I opened the kit.

Joe

joe kallo <quietglow@...>
 

Okay I fiddled with all the torroids with the key down and saw no evidence of shorts. Also no activity on the power meter. I tested tx in 80, 40 and 20m with the same results on all. I heard signals on 80&40 (it's too early for 20 here still). I didn't check solder continuity on the torroids as that will mean taking it apart. I'll do that next.

Also of note: I had the key down for 30-45 second periods while messing around and the finals transistors did not change temperature to the touch.

Reid Campbell
 

I got caught out by leaving the brown PA supply wire off while I got the
Rx working. Have you checked that?

Cheers

Reid Gi8TME/Mi0BOT

Okay I fiddled with all the torroids with the key down and saw no evidence
of shorts. Also no activity on the power meter. I tested tx in 80, 40 and
20m with the same results on all. I heard signals on 80&40 (it's too early
for 20 here still). I didn't check solder continuity on the torroids as
that will mean taking it apart. I'll do that next.

Also of note: I had the key down for 30-45 second periods while messing
around and the finals transistors did not change temperature to the touch.

 

Joe,

If you have a radio to monitor in the shack, put a short 6" wire to C80 and see if you can hear yourself on a receiver.

If OK try the next stage C84.

Check all the DC voltages in the TX stages with PTT pressed and mic disconnected.

Raj

At 02-01-2018, you wrote:
Okay I fiddled with all the torroids with the key down and saw no evidence of shorts. Also no activity on the power meter. I tested tx in 80, 40 and 20m with the same results on all. I heard signals on 80&40 (it's too early for 20 here still). I didn't check solder continuity on the torroids as that will mean taking it apart. I'll do that next.

Also of note: I had the key down for 30-45 second periods while messing around and the finals transistors did not change temperature to the touch.

joe kallo <quietglow@...>
 

By PA supply wire, do you mean the wire to the speaker/headphone jack? If so, yes that's hooked up. It's working as a receiver (i.e. I'm copying activity on the bands) playing through a pair of headphones.

Gordon Gibby <ggibby@...>
 

​no, he means the 2nd  connection for power to the power amplifier.


On the bitx40 it is a separate 2-conductor plug/pins


on the ubitx it is an additional wire on the 3-wire power connector....


if you don't have power going to the pwer amplifier....won't have any output


IN TX, the heatsink should go to +12 V DC.  you can check the tab of the irf510 with  voltmeter




gordon



From: BITX20@groups.io <BITX20@groups.io> on behalf of joe kallo <quietglow@...>
Sent: Tuesday, January 2, 2018 8:56 AM
To: BITX20@groups.io
Subject: Re: [BITX20] No TX #ubitx
 
By PA supply wire, do you mean the wire to the speaker/headphone jack? If so, yes that's hooked up. It's working as a receiver (i.e. I'm copying activity on the bands) playing through a pair of headphones.

Reid Campbell
 

No, there are 3 wires to the power plug, I think they are Black (0v), Red
(12v Rx power) and Brown (12v/24V PA power). The Brown and Red wires
should both be connected to the 12V power via the on/off switch on the
volume control.

The two supply wires allow you to feed a different (higher) voltage to the
PA transistors to achieve higher output power.

It just sounds like there is no power being applied to the PA stage.

By PA supply wire, do you mean the wire to the speaker/headphone jack? If
so, yes that's hooked up. It's working as a receiver (i.e. I'm copying
activity on the bands) playing through a pair of headphones.

 

Joe had earlier mentioned as far I remember that he had done the TX
current bit. So we have to look elsewhere!

Raj

At 02-01-2018, you wrote:
No, there are 3 wires to the power plug, I think they are Black (0v), Red
(12v Rx power) and Brown (12v/24V PA power). The Brown and Red wires
should both be connected to the 12V power via the on/off switch on the
volume control.

The two supply wires allow you to feed a different (higher) voltage to the
PA transistors to achieve higher output power.

It just sounds like there is no power being applied to the PA stage.

By PA supply wire, do you mean the wire to the speaker/headphone jack? If
so, yes that's hooked up. It's working as a receiver (i.e. I'm copying
activity on the bands) playing through a pair of headphones.

joe kallo <quietglow@...>
 

Actually, I was going to post this as a separate issue, but in the PA bias step my initial reading was outside the range mentioned in the directions. With both bias pots at fully clockwise, I measured 420 mA when PTT is depressed. The directions indicate it should be 470 - 500. Could this be the problem?

Fwiw, my power supply is a 30A 12v deal.

Again, many thanks for the help!

Joe

 

Fully clockwise is the minimum current!

At 02-01-2018, you wrote:
Actually, I was going to post this as a separate issue, but in the PA bias step my initial reading was outside the range mentioned in the directions. With both bias pots at fully clockwise, I measured 420 mA when PTT is depressed. The directions indicate it should be 470 - 500. Could this be the problem?

Fwiw, my power supply is a 30A 12v deal.

Again, many thanks for the help!

joe kallo <quietglow@...>
 

Right, so the directions say to go to min and then turn one pot until the current is 100mA higher, then to do the same w the other. Thats what I did, but my starting min current was 50mA lower than the spec in the directions. I didn't think it was enough it make a difference, but now with it not working I'm wondering.

To be clear, once I adjusted the bias as per the instructions, I measured 620mA when PTT was depressed.

Joe

joe kallo <quietglow@...>
 

Just got home from work and checked: brown wire properly hooked up. I measure 13.5v to the heatsink  w/o the key down and ~13v with it keyed.

Gordon Gibby <ggibby@...>
 

​rats.   wished it could have been something simple.....

sorry.....




From: BITX20@groups.io <BITX20@groups.io> on behalf of joe kallo <quietglow@...>
Sent: Tuesday, January 2, 2018 6:10 PM
To: BITX20@groups.io
Subject: Re: [BITX20] No TX #ubitx
 
Just got home from work and checked: brown wire properly hooked up. I measure 13.5v to the heatsink  w/o the key down and ~13v with it keyed.

joe kallo <quietglow@...>
 

Me too! I even turned up the bias pots a little. Didn't help. I also removed the radio from the box and set it up again with jumpers, also with no effect.

Raj I am not sure exactly what you mean re: putting the wire to c80. I see c80, but I am not sure what you're suggesting I try to do.

Joe

Gordon Gibby <ggibby@...>
 

​I thought he was trying to create a tiny "antenna" to allow you to listen with another receiver and ascertain which STAGES were ampplifying.....




From: BITX20@groups.io <BITX20@groups.io> on behalf of joe kallo <quietglow@...>
Sent: Tuesday, January 2, 2018 6:53 PM
To: BITX20@groups.io
Subject: Re: [BITX20] No TX #ubitx
 
Me too! I even turned up the bias pots a little. Didn't help. I also removed the radio from the box and set it up again with jumpers, also with no effect.

Raj I am not sure exactly what you mean re: putting the wire to c80. I see c80, but I am not sure what you're suggesting I try to do.

Joe

 

That is fine Joe. Every board will not behave the same or even meters read the same.
Check why there is no RF getting to the finals.

At 02-01-2018, you wrote:
Right, so the directions say to go to min and then turn one pot until the current is 100mA higher, then to do the same w the other. Thats what I did, but my starting min current was 50mA lower than the spec in the directions. I didn't think it was enough it make a difference, but now with it not working I'm wondering.

To be clear, once I adjusted the bias as per the instructions, I measured 620mA when PTT was depressed.

Joe