Vic,
One of the two transistors could have an open B/E link, with resistance on the collector to emitter.? The voltage measurements could be measuring the good transistor.? The output could be reduced due to the second one not functioning.? Maybe you can check them when you pull to replace them.? I use this device to check 3 terminal active devices.
73
Evan
AC9TU
|
Getting closer to the solution. Here's what I found probing around: RF probe readings today (they fluctuate a bit from day to day)
TP3: 384
Q911 base: 362 Note that when I attach the probe here I actually see output power on the wattmeter (?)
Q911 Collector: 31 (!!)
T9 pin 4: 30
T9 pin 3: 20
T9 pin 2: 7
T9 pin 6: 6
T9 pin 1: 3
So it looks like either or both Q911 and Q912 are bad? I am out of similar 2N3904 or 2N2222A and have some coming this week, so I'll look at replacing them. Interesting that the bias voltages look fine, but clearly they are not amplifying.
I may have to make up a permanent RF probe! This one is cobbled on a small piece of perf board with clip leads to probe leads, but it is proving most helpful.
=Vic=
|
Re: Some capture from sbitx
On 6/9/22 9:41 PM, Ashhar Farhan wrote: Shirely,
We, unfortunately, got the displays for all just about managed to get the raspberry pis for an unimaginably high price.
The radios are all tested and ready to ship. They are just waiting for me to complete the software.
On raspberry pi 4, they changed the way the internal pullup resistors of the GPIO work. As a result, the iambic keyer and the ptt stopped working. If I can figure it out today we will open the booking over the weekend. Otherwise we will have opened up 200 packed radios and hand solder resistors.
Do you think we should have a separate group for those hacking the sbitx? This is very exciting! I learned about the sBITX project as I was making plans for getting into HF, so I've been eagerly anticipating the "ready to ship" state. While I haven't worked with rpi before, I'm fully confident in working with beta-status software and I hope to be able to contribute some improvements. Are there photos and/or spec sheets available yet for this initial build? I'm curious about things like power connectors and other ports. I concur with another comment that we should wait to start a separate group for sbitx (or sbitx-hackers) until we see that the volume on this group is too much. I learn things on the air by listening to conversations I'm not participating in, and the same can be true for a mailing list. Excitedly awaiting a further announcement, KF0FTJ -- =-=-=-= Trevor Stone -=- [Flwyd] -=- <tstone @ trevorstone.org> =-=-=-= Computer science, eclectic philosophy, games, wits, esoterics, odd hats Thou craven beetle-headed egg-shell! {embrace adaptation} BATMAN does it with Robin. What upsets me is not that you lied to me, but that from now on I can no longer believe you. -- Nietzsche
|
Re: I'm sorry if this isn't allowed
#forsale
Thanks for the tempting offer. There is no more space under our
bed!
On 13/06/2022 7:38 PM, Shane wrote:
toggle quoted message
Show quoted text
But I have a nice B210 SDR with accessories for sale on ebay if
anyone is interested!
|
I'm sorry if this isn't allowed
#forsale
But I have a nice B210 SDR with accessories for sale on ebay if anyone is interested!
|
Don, you are spot on! The guys providing common sense support are excellent. And I can¡¯t say enough about the time and effort that Evan puts in. It has to be a true labor of love!
Thanks to all!
toggle quoted message
Show quoted text
On Jun 12, 2022, at 10:44 AM, Don - KM4UDX <dontAy155@...> wrote:
? Evan + Others ¡ª your help desk like support enables MANY of us to accomplish what, on our own, we could never do. ?
Evan¡¯s observations ¡®bout where to find help on a specific topic/issue are spot on. Searching the wiki, files area, posts, HF signals, FB, redit, ?the global web, etc etc are all hazardous and uncertain.?
in a way, you most helpful folks are like modern day wizards of the cosmic library. You have the technical scope and institutional memory to point us to the published remedial text.?
Why does it work this way? Most all newbies stumble at familiar points. ?The uBITX is well established and understood. ?But to us neophytes, every pot hole, self inflicted wound, error, boo-boo, is 100% new and unexpected and novel. ?But also well worn and predicable ?to the ¡°help desk staff¡±.?
I¡¯m only one of hundreds (more?) who are successfully because of your kindly ¡°help desk¡± like ?support.
So thank you!!
Don
km4udx
|
Evan + Others ¡ª your help desk like support enables MANY of us to accomplish what, on our own, we could never do. ?
Evan¡¯s observations ¡®bout where to find help on a specific topic/issue are spot on. Searching the wiki, files area, posts, HF signals, FB, redit, ?the global web, etc etc are all hazardous and uncertain.?
in a way, you most helpful folks are like modern day wizards of the cosmic library. You have the technical scope and institutional memory to point us to the published remedial text.?
Why does it work this way? Most all newbies stumble at familiar points. ?The uBITX is well established and understood. ?But to us neophytes, every pot hole, self inflicted wound, error, boo-boo, is 100% new and unexpected and novel. ?But also well worn and predicable ?to the ¡°help desk staff¡±.?
I¡¯m only one of hundreds (more?) who are successfully because of your kindly ¡°help desk¡± like ?support.
So thank you!!
Don
km4udx
|
Now that I think about it I have many rigs without apparent agc. The list is huge.?
A prime reason for agc is to reduce need to adjust the volume control. For many classic cw qrp rigs, for example small wonder labs SW series, we must learn to exercise the volume control. Anyone who has a K2 experiences needing to use the volume control for receiving weak signals but letting its IF AGC address large signals.?
For the ubitx I find the primary need is to address large signals for hearing comfort. As all solutions sense at audio note it's mostly the audio portion being addressed, even if solution adds attenuation at RF. The ubitx gain distribution is such that the RF and IF section do not experience overload even for uncomfortable audio output. Now if someone has immense antennas they might disagree some.?
There are differences in how audio is implemented across versions. I think this may relate to agc behavior. In my v4 the nd6t agc did nothing useful, while other v4 owners reported success. Instead I found great success with the LED photoresistor circuit. I had to modify the vk3ye published version to eliminate interaction with the volume control. The dark resistance needs to be significantly higher than max volume control resistance, and of course led must be bright enough to reduce photoresistance value well below the volume control for the loud signals to be addressed. As there is no diode clipping involved there is no perceived distortion. Although for other circuits that should be minimal also if it's only exercised over a narrow range.?
I think we should clarify these various solutions are high level agc, use of volume control still necessary for normal radio operation.?
I didn't watch video on that maxim product mentioned so I wonder how the microphone is bypassed. Seems like it has way too much gain for ubitx receive but I see it can be adjusted down by jumpers.?
Curt
|
Dave,
Thanks for the report. Didnt know if the mod on the mic amp helped at all.I changed r126 to 4.7 k and r123 to 10 ohms. might put it back to original and add an rf amplifier to it. maybe 25 to 40 watts.
thanks for the report,
73 David ac9xh
On Friday, June 10, 2022, 11:29:37 PM EDT, _Dave_ AD0B <davesters@...> wrote:
David
I heard you check in to midcars from Mo.
--
73
Dave
|
I should add that the information posted gets lost on the Groups.io site.? Even when put in the "files" or WiKi sections, no one seems to be able to locate the information.? Most of my replies are reposting of prior info shared.
I have started to keep track of solutions on both the web and file sections on my computer.? When a problem arises, I try to post the information I saved.? If there is a better way, then I do not know it.? This group is treated as a help desk, so it is up to the helpers to have the information available.? The average poster will not know all the locations to find solutions.
The above are my thoughts.? Others can have differing opinions, and that is OK.
73
Evan
AC9TU
|
On Sat, Jun 11, 2022, at 11:14 AM, Gerard wrote:
Evan,
I forgot, specify the bandwidth and model of your oscilloscope, the measurements can be different depending of our oscillo.
Thank's
I use a Siglent SDS 1102CML+ 100MHz scope. I have posted some of the other test points in prior emails.? The ones recently are for testing the transmitter.? I have not looked at the IF stages but have measured the clock signals (TP12, 15, and 18). I will post some of the other test points if I can find the time.? Right now, I am working on our build club process and presentation. 73 Evan AC9TU
?
|
I could sure use it also.?
toggle quoted message
Show quoted text
On Jun 11, 2022, at 12:09 PM, Gerard <kabupos@...> wrote:
? Evan,
?
You¡¯ve done a fantastic job with these oscilloscope screen copies.
But would it be even more interesting to actually have a scope screen of all the test points?? (20 i think)
It¡¯s a little more work, but it¡¯s worth it for troubleshooting and homebrewing.
Why not also integrate some screenviews of the hot spots (Ex Q90, mixer,...)
cdt
|
Evan,
I forgot, specify the bandwidth and model of your oscilloscope, the measurements can be different depending of our oscillo.
Thank's
?
|
Evan,
?
You¡¯ve done a fantastic job with these oscilloscope screen copies.
But would it be even more interesting to actually have a scope screen of all the test points?? (20 i think)
It¡¯s a little more work, but it¡¯s worth it for troubleshooting and homebrewing.
Why not also integrate some screenviews of the hot spots (Ex Q90, mixer,...)
cdt
|
Vic,
Your power supply is also low,please check voltage. You should
get more voltage on the collector.
On 11/06/2022 2:17 AM, Vic WA4THR via
groups.io wrote:
toggle quoted message
Show quoted text
More probing...voltage checks on transistors Q92-3, Q95-7,
Q911-912 all read C:10.0, B:0.9, E:0.2 today
RF probe checks:
TP2: 103
TP3: 231
TP4: 5? <== so this is the oddball
TP5:152
TP6:142
TP7:445
TP8:1120
TP10: 1035
TP11:1033
C90: 5 <== certainly agrees with TP4
C91: 2 <== even lower!
So does this suggest that T9 itself is the problem? The base on it
is not discolored and wiring looks OK. I am guessing this is a
3-layer board as the traces are hidden between what I see on top
and the mostly ground plane on the bottom? T10 looks a little
funky, but the fact that the bias is OK on the transistors
suggests continuity there.
=Vic=
|
David
I heard you check in to midcars from Mo.
--
73
Dave
|
Vic,
As promised, here are the scope captures of the test points TP2 through 7.
Hope this helps.
73
Evan
AC9TU
|
Im looking forward to the sbix also.
Ashhar always has a good product.
agc for the bitx40,i havent installed yet on a unit i recently purchased off QTH.Ive installed the the harmonic fix, usb mod,and upgraded the software, and changed the resistors on-board in the microphone amp to give it more punch. checked into the midcars net yesterday, running about 4 watts on 40m.
plan on building an rf amp that puts out about 40 watts.
73
David
ac9xh
|
I've got a v3, but I believe all versions are just 2 layer boards.
Adding internal layers would be a considerable jump in price.
Could well be that the issue is around T9, and the discoloration you reported on T10 doesn't matter.
That seems more consistent with your RF probe readings of TP4 having a very small RF signal.
Let's assume that is the case.
I assume your DC voltage readings at pins of Q911,912, 92,93, 96,97 are all still
in agreement with what has been reported by others when transmitting.
For transistors in parallel, you only need to check one of the two transistors.
Note that the TX node supplies 12v to those transistor collectors only when transmitting.
Look directly at the base pin of Q911 using the RF probe, should see roughly the same
signal level as you see at TP3.? If not, then perhaps C83 is fractured open.
Look at pins 4,3,2 of T9 using the RF probe.? Pin 4 should have a very healthy signal,
much bigger than TP3.? Pin 3 should be about half that.? Pin 2 should have no signal?
(but does have a 12v DC supply present during transmit).? If that is true then the primary
of T9 is ok and Q911,912 are doing their job.?
If not then remove C90 and see if that improves things, since a shorted secondary?
can cause the primary of T9 to not have appropriately large RF signals.
If you still don't see the big signals at T9 pin 4, then I would probably cut the trace from T9 pin 4
that goes to the collectors of Q911,912.? From the collectors of 911 and 912 add a 200 ohm 1/4 watt resistor
to 12v.? Do you now see a good RF signal signal on those collectors?? If so, then T9 is bad.?
If T9 primary checks out as outlined above, double check that there is still no RF signal
at C90 and C91.? At this point I would remove C90 and short T9 pin 1 to ground.
If T9 is working properly, you should now see an RF signal at TP4 that is about half of
what is on T9 pin 4.
If T9 is not working properly, then pull it off the board by clipping the wires, leaving nubbins long
enough to grab with a pair of needle nose pliers, and pull them out of the board with help from
a soldering iron.? Blow the hot solder out of the 6 holes for T9.? Rewind T9 with new wire.
and re-install.? Verify you now have a good RF signal at TP4, then replace C90 and remove that?
ground to T9 pin 1.
Or, if that's all too complicated, you could just shotgun it:? Replace or rewind T9.
Jerry, KE7ER
.
toggle quoted message
Show quoted text
On Fri, Jun 10, 2022 at 01:47 PM, Vic WA4THR wrote:
More probing...voltage checks on transistors Q92-3, Q95-7, Q911-912 all read C:10.0, B:0.9, E:0.2 today
RF probe checks:
TP2: 103
TP3: 231
TP4: 5? <== so this is the oddball
TP5:152
TP6:142
TP7:445
TP8:1120
TP10: 1035
TP11:1033
C90: 5 <== certainly agrees with TP4
C91: 2 <== even lower!
So does this suggest that T9 itself is the problem? The base on it is not discolored and wiring looks OK. I am guessing this is a 3-layer board as the traces are hidden between what I see on top and the mostly ground plane on the bottom? T10 looks a little funky, but the fact that the bias is OK on the tran
|
Vic,
I am 99% sure it is only two layers for the board.?
I will look at my v4 again to see what I get for voltages using my oscilloscope ?
73
Evan
AC9TU
?
|
Vic WA4THR
Raj vu2zap
ETAPRIME
Gerard
_Dave_ AD0B
