Date   
Re: Overvoltage spike killed my V4

John Faivre
 

Back on the air. It turned out to be a shorted reverse protection diode. I’m not sure how it got blown by the overvoltage spike unless it exceeded the PRV. Anyway, very lucky. 


thanks for everyone’s help
--
John Faivre WA9SGD

Re: Ubitx V^ just assembled, VFO Doesnt Work, no receive/audio

stefan@...
 

SSB sounds garbled on all bands, cant tune it in.

Re: Ubitx V^ just assembled, VFO Doesnt Work, no receive/audio

stefan@...
 

Also, i tried calibrating the radio, but the local oscillator seems like I cant get a bead on it, and the BFO says tune it to 300-3000hz and it is at 11,000 and wont go lower.  I will try the wwv method again when I have my dummy load tomorrow.

Re: Ubitx V^ just assembled, VFO Doesnt Work, no receive/audio

stefan@...
 

Ok, the xmit issue is resolved, there was a short inside the mic Im assuming, i had another mic and it works normally. When i touch pin 3 on the audio amp I get the hum in the headphones. I hooked up a different speaker, and no audio on that one, and I know that one is good because I scavenged it out of a cb radio and I tested it beforehand. I will double check the speaker by checking the resistance on it when I get home with my meter. Evan, im not sure where you mean to go direct, straight from the board? Desolder and remove the  headphone jack and solder the wires direct through the board? or remove the pins on the board? OR go straight from the lm386? 

Re: Trustworthy 2N2222A?

Ted
 

Hey, Bob,

I'll have to double-check on the BFR106 and make sure I put it in the radio i think it went to.

Sorry the 2N5109's didn't pan out; I guess that was a deal.  Here are some 2N2222's I've used which were just fine - https://www.ebay.com/itm/323692855627  

If you want the radio to be more happy on 20, try the 2N2222's with an additional 20-ohm on Each emitter bias resistor - https://www.ebay.com/itm/301263873991  Then get a step-up buck converter https://www.ebay.com/itm/142697805000 to feed around 20 volts to the finals;  feed the rest of the radio 14 volts.   It's not quite as hot as with the 2N5109's in by experience to date, but it's worth doing. 








See the 5109's nesting in their natural habitat.






Ted
K3RTA




On Fri, Jan 31, 2020 at 16:28, Rob French (KC4UPR)
<robert@...> wrote:
Hey Curt,

I've got a V5.

Which device(s) in the Tx amplifier chain were you referring to?  I have not replaced any amps at all, this is my first "on-board" mod to the uBITX (I have previously installed the kit-projects AGC and BCI filter).  I see in the V5 bidi amplifiers there are BFR93W's, versus 2N3904 in the V4, so I'm guessing maybe the last thing you were referring to is moot.

In truth, I haven't actually measured my V5 output yet (waiting on my watt/SWR/antenna tuner) so I probably shouldn't go changing anything quite yet regardless.  But I definitely want to make sure I'm getting good power out at least down thru 20 meters--I'm using an attic antenna, would like to get whatever oomf out of the radio I can!

Rob KC4UPR

Re: Ubitx V^ just assembled, VFO Doesnt Work, no receive/audio

Michael Shreeve
 

Oh, and, transmitting into a bad antenna would probably take an extended time. Typically, if you've damaged the output section, you will get smoke ect. That RF probe would tell you a lot, but, if your output stages are working correctly, the should feel a little warm after say 10 seconds, especially if you relays or antenna are not correct. The output stage is completely different now, using four mosfet transistors, two in parallel, and two others in parallel. Also different parts. With a RF Probe you can tell if the rf is making it to the input of that stage. Some rf probes are two sensitive for the output stage, the diode would blow. Others are much better for higher voltages . All this said , I would get the receiver working first. Including making sure your audio section si wired correctly all the way from beginning to end.

Re: Ubitx V^ just assembled, VFO Doesnt Work, no receive/audio

Michael Shreeve
 

Yes, if I understand what evan is saying, and put my twists on it, what you need to do it take audio right from the board, not going through the speaker jack at all (disconnected it) , and go to either headphones or a speaker direct. Why ? Well, wiring through a little headphone /speaker jack is notoriously done incorrectly and one of the worst problems is that quite often the output from the board is wired in such a way to short it out.  So, disconnecting the jack and connecting right from the board to the speaker/headphones eliminates that possibility. But then, you need to check the audio stage. Ashhar , early one, recommended, and quite a few of us do this, , to touch the input of the LM386 while the speaker is connected directly. That would be pin 3 on the lm386, touching with a un insulated wire your holding with your hand. You should hear clicks, pops, and a little hum. If you don't hear this when your going through your headphone jack, its obviously wired incorrectly, which is very common. In fact , with the original v3, the company put out incorrect wiring instructions, and none of them worked till corrected. So, once you've verified the speaker/amp (lm386) is working, you can move on. When you change the firmware, the radio needs to be completely re-calibrated. I'm not sure how they do it now, but, versions after the v3 were best done with access to 10mhz , and a way to verify it both on a receiver. I found that , by getting just enough of the signal from wwv, and some signal from the radio (usually I plug the output of the radio into a 50ohm resistive load) and can hear the radios output signal beating with wwv. This is part one. The second part is the BFO. But, by then you should hear a LOT of rf noise coming from the receiver, garbled most likely.. Pay special attention to the v6 calibration procedure, I'm sure its different but I haven't looked at it. As I said, I have a v3 and I think a v4. Firmware is different for even those radios.

Re: Trustworthy 2N2222A?

Doug W
 

On Fri, Jan 31, 2020 at 02:10 PM, Rob French (KC4UPR) wrote:
I'm looking to get some 2N2222A
Have you looked at Tayda?

https://www.taydaelectronics.com/pn2222a-pn2222-transistor-npn-40-volts-1a.html
https://www.taydaelectronics.com/t-transistors/2n-series/2n2222a-2n2222-npn-transistor-0-8a-40v-to-18.html
 
--
www.bitxmap.com

Re: Overvoltage spike killed my V4

Evan Hand
 

John,

I would start as Adrian has suggested and try to power up the board without the connection to the power amp (the brown wire on the three wire power connector).  If the fuse does not blow, then you know that at least one of the finals is blown (the other parts of the transmitter power circuits would not be powered until the rig is put into transmit mode.

If the over current continues with the Power Amp (PA) power feed removed, then there is something shorting on the receive side, as power is not applied until the TX/RX relay is energized.  I would suspect the audio sections of the rig before the bidi amps.  If you check with the schematic, you will see resistors between the 12 volt RX source and the preamp (Q70 - R52) and the final audio amp (Q71,72,and 73 - R71).  Remove one of these at a time to try to isolate which section is shorted.

Above are just suggestions.  The very first thing to do is to verify all wiring and any external components.
73
Evan
AC9TU

Re: Trustworthy 2N2222A?

 

Hmmm,

Well these are the CW power measurements for my ver3: 

2019.02.10
Power measurements on as-delivered uBITX.
Supply: 13.8VDC, Current: 0.17A on RX
 
Band Freq, kHz Vrms A W
75/80 3500 22.9 1.81 10.5
75/80 3750 25.1 2.04 12.6
75/80 4000 26.9 2.4 14.5
40 7000* - - -
40 7001 20.4 1.69 8.3
40 7150 20.6 1.76 8.5
40 7300 20.9 1.82 8.7
30 10100 15.1 1.3 4.6
30 10150 14.8 1.28 4.4
20 14000 16.6 1.63 5.5
20 14175 16.5 1.66 5.4
20 14350 16.4 1.68 5.4
15 21000 7.54 1.06 1.1
15 21225 9.7 1.06 1.9
15 21450 9.62 1.07 1.9
10 28000 7.5 1.05 1.1
10 28850 7 0.88 1.0
10 29700 5.8 0.81 0.7


I haven't done any mods, but the rig certainly could use some help where ever it could be found I think.  Anyway, I don't think $10 or so is too much to spend for some improvement.  How much in total have some here spent on their bitx projects?  I'm sure some have spent many hundreds of dollars judging by the number of ubitx's and accessory kits purchased...

73,


Mark.

Re: Trustworthy 2N2222A?

Rob French (KC4UPR)
 

Hey Curt,

I've got a V5.

Which device(s) in the Tx amplifier chain were you referring to?  I have not replaced any amps at all, this is my first "on-board" mod to the uBITX (I have previously installed the kit-projects AGC and BCI filter).  I see in the V5 bidi amplifiers there are BFR93W's, versus 2N3904 in the V4, so I'm guessing maybe the last thing you were referring to is moot.

In truth, I haven't actually measured my V5 output yet (waiting on my watt/SWR/antenna tuner) so I probably shouldn't go changing anything quite yet regardless.  But I definitely want to make sure I'm getting good power out at least down thru 20 meters--I'm using an attic antenna, would like to get whatever oomf out of the radio I can!

Rob KC4UPR

Re: : #V6 software issues help please #v6

Evan Hand
 

WB0WQS,

The most likely adjustment for the "bassy" is the BFO.  The electret mic would not normally be bassy.

73
Evan
AC9TU

Re: Ubitx V^ just assembled, VFO Doesnt Work, no receive/audio

Evan Hand
 

After you verity that the TX/RX issues is resolved, I would connect a pair of wires to the Tip and Sleeve, or Ring and Sleeve (both are connected to the output of the audio amp on the main board.  Unplug the speaker from the main board, and connect the wire from the temporary plug to the the wires of the speaker.  If the audio is there, then the speaker is OK.  If not, then look at the wire/speaker to verify that there is not a broken connection.

At this point the we know that the audio sections of the main board are working (you have audio in the headphones).  We just need to know where we are losing the audio in the link to the speakers.

BTW. you are removing the headphones when testing  the speaker?

73
Evan
AC9TU 

Re: Overvoltage spike killed my V4

Adrian Chadd
 

Hi!

Disconnect the power rail going to the finals transistors and see if
the rest of the bitx4 powers up and receives. It's possible one of the
finals transistors is a dead short after that.



-adrian
(kk6vqk)

On Fri, 31 Jan 2020 at 10:15, John Faivre <@WA9SGD> wrote:

My power supply regulator failed. The crowbar circuit kicked in at 15v and blew the fast blow fuse, but my board is dead. The voltage could have gotten as high as 27v before the fuse blew.

The 2 amp fuse blows as soon as it is powered on. I don’t see low resistance on either the main or final power circuits. I’ve meter checked all the transistors, diodes, an caps.

I have disconnected everything from the main board and it still blows. The Raduino still works if powered from the USB port.

Anyone have an idea how I might trouble shoot this?

I May be in the market for a V4 or V5 board, if anyone had one to sell.

--
John Faivre WA9SGD

Re: Trustworthy 2N2222A?

Curt
 

$2 each yikes!  for what improvement?  if you really want them, ask around your local ham club or visit a hamfest (or in the UK they call them Rallys I am told). 

kitsandparts.com (W8DIZ) is a reputable source - but don't see what you are looking for there now.  [and a few folk may be killing off some of the population preparing for FDIM no-smoke competition again]

Isn't the power roll-off in the uBITX a feature - since we tend to need more power at lower frequencies?  okay a healthy 10 watts at 28 MHz may be appreciated - but perhaps better solution is a new rig, if you really want that.  (maybe your track record of uBITX mods is much better than mine - so you need something new to do?  my last bug-a-boo was learning that a relay can go astray - while taking a little while to figure out it was the cause]

I don't know those little SMT 3904's look kind of cute!  have you already replaced the 45 MHz Tx amplifier devices with those high Ft critters?  seems like a more useful effort to me for a v3-v4. 

73 Curt

Re: V6s

Jim
 

Package pics -- I had already taken the radio out.  Let me know if you need more -- it was well packed.

Re: Trustworthy 2N2222A?

Rob French (KC4UPR)
 

Doh, looks like the 2N5109s are out of stock.

Which 2N2222's were you referring to?  

Re: Trustworthy 2N2222A?

Rob French (KC4UPR)
 

Hey Ted,  I'll check the link out... I guess I was skeptical right off the bat for anything from eBay.  I'll take your recommendation ;-).

As I mentioned in the other post, for the resistor I think I will just try to use the unused resistor in each pair as the additional resistor, i.e. since each pair of 2N3904's gets replaced by a single 2N5109.  

If I don't burn one up, I'll use the spare to make that wideband RF preamp you mentioned; looking at the kit from kitsandparts.com, I think I've got everything on hand except the transistor, so might as well just wire it up dead-bug style.

And you didn't change Q90, correct? Left it as a 2N3904, not a BFR106.

Re: Trustworthy 2N2222A?

Ted
 

.....but if you really want 2N2222's, these seemed OK when I bought some a while back -

Re: Overvoltage spike killed my V4

Clark Martin
 

If you have a variable voltage supply use that while monitoring the current to slowly increase the supply voltage until the current gets up to around 200 mA. Then start probing see where the current is going.

Clark Martin
KK6ISP

On Jan 31, 2020, at 10:15 AM, John Faivre <wa9sgd@...> wrote:

My power supply regulator failed. The crowbar circuit kicked in at 15v and blew the fast blow fuse, but my board is dead. The voltage could have gotten as high as 27v before the fuse blew.

The 2 amp fuse blows as soon as it is powered on. I don’t see low resistance on either the main or final power circuits. I’ve meter checked all the transistors, diodes, an caps.

I have disconnected everything from the main board and it still blows. The Raduino still works if powered from the USB port.

Anyone have an idea how I might trouble shoot this?

I May be in the market for a V4 or V5 board, if anyone had one to sell.