This is often due to rf getting into the control circuits. Are you using an unbalanced antenna? EFHW perhaps?
|
I agree about Heathkit. I miss the HW101 I had in the late '70s. I could almost draw parts of? the schematic by memory. (Yes, I played/worked on it that often!) I stayed active in cw, ssb, rtty and even Air Force MARS back then.
Scotty
On Thu, Mar 6, 2025, 8:53 AM Gordon Gibby KX4Z via <docvacuumtubes= [email protected]> wrote: You're going to learn a lot in the process of this repair.? ?Be certain to protect Q101 with a small resistor in its drain lead or you are likely?to just repeat the whole performance all over again.
Q101's purpose is just to drain power from the transmitter side quickly, so the transmitter doesn't STAY ON when the receiver startups up-- this could lead to an RF loop.? ?At least I think that is what it is for!!
My V2 #1 has all these fixes in it (because it got damaged, and some of it may have been ME rather than IT)
My V2 #2 has none of this YET -- hurt my knee and just barely now able to walk and climb stairs.? ?A zillion projects going on.? ?And teaching two AP classes.? ?And a ham radio group.... so it may be a while yet before I get that done.? ? It will take half a day to do everything I need to do on that radio, even if I manage to put all the parts together in one place!! I looked inside my Icom 7300 once....(I've unsoldered diodes in there before on 2 or 3 units) and there is almost NOTHING I would be able to repair in there.? ? If it breaks, I'm toast.? Meanwhile, I have 50+ year old Heathkits that I'm able not only to repair but to upgrade!? ?We will move to jusst?dealing with "modules" at some point.
73 Gordon KX4Z
Old 2n7000 datasheet
?
73
Evan
AC9TU
|
You're going to learn a lot in the process of this repair.? ?Be certain to protect Q101 with a small resistor in its drain lead or you are likely?to just repeat the whole performance all over again.
Q101's purpose is just to drain power from the transmitter side quickly, so the transmitter doesn't STAY ON when the receiver startups up-- this could lead to an RF loop.? ?At least I think that is what it is for!!
My V2 #1 has all these fixes in it (because it got damaged, and some of it may have been ME rather than IT)
My V2 #2 has none of this YET -- hurt my knee and just barely now able to walk and climb stairs.? ?A zillion projects going on.? ?And teaching two AP classes.? ?And a ham radio group.... so it may be a while yet before I get that done.? ? It will take half a day to do everything I need to do on that radio, even if I manage to put all the parts together in one place!! I looked inside my Icom 7300 once....(I've unsoldered diodes in there before on 2 or 3 units) and there is almost NOTHING I would be able to repair in there.? ? If it breaks, I'm toast.? Meanwhile, I have 50+ year old Heathkits that I'm able not only to repair but to upgrade!? ?We will move to jusst?dealing with "modules" at some point.
73 Gordon KX4Z
Old 2n7000 datasheet
?
73
Evan
AC9TU
|
Old 2n7000 datasheet
?
73
Evan
AC9TU
|
Yes, 2n7000 and 2n7002 are the same devices in different packages.
?
73
Evan
AC9Tu
|
Yes, I was somewhat relieved that I am getting the proper Tx signal. I feel that I may need to remove Q9, Q10, Q101 and check the continuity, rule out damaged pads/traces, and swap in new components. Also when I mentioned using through hole
for Q10,Q101, I was thinking about using regular 2n7000 in place of the sot23 2n7002. Would those work?
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-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/6/25 2:07 AM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Michael,
?
The TX signal works (recieve at 0.15 volts, transmit at 3 volts).
?
?
The pins on Q9 are marked in this photo:
?
The gate (pin 1) of Q9 should be higher, and the tab (Pin 2 or drain) should be 0 volts when receiving and close to 12 volts on transmission.? It could be a failed Q9, Q10, Q101, or combination.? I would start with Q10, as it should pull down the gate
of Q9 to turn it on and supply the 12 volts to the driver stages.??
?
?
Q101 is a 2n7002 MOSFET.? This can not be replaced with a 2n2219.??
?
?
The above is based on not getting 12 volts on the tab of Q9.
?
73
Evan
AC9TU
?
-- Mike - K8MCB?
|
Hi, folks!
?
When I do a digital QSO with my uBITX v.6. it often stucks on TX and won't go back after PTT is released. To put it in Rx mode I have to unplug PTT/Data cable from MIC connector, put the original microphone in and press-release PTT switch on the mike. This started to happened after a year of doing PSK/RTTY with this nice rig without problems. It does'n happened in SSB or CW.
Is there a way to solve this? Is it that PTT relay is "softened" or something else..?
?
Thanks for advice.
?
Vule, E78CB?
?
|
Michael,
?
The TX signal works (recieve at 0.15 volts, transmit at 3 volts).
?
?
The pins on Q9 are marked in this photo:
?
The gate (pin 1) of Q9 should be higher, and the tab (Pin 2 or drain) should be 0 volts when receiving and close to 12 volts on transmission.? It could be a failed Q9, Q10, Q101, or combination.? I would start with Q10, as it should pull down the gate of Q9 to turn it on and supply the 12 volts to the driver stages.??
?
?
Q101 is a 2n7002 MOSFET.? This can not be replaced with a 2n2219.??
?
?
The above is based on not getting 12 volts on the tab of Q9.
?
73
Evan
AC9TU
?
|
Hi Michael,
?
I had a typo on my last post.? I deleted it and provided the correct value for the TX signal of 0.06 and 3.3 volts.
?
The way the TR switch works to supply power to the drivers is as follows:
?
The radio is in Recieve mode, starting on Powerup and opening the sBitx program.
?
1 - The TX signal is low (0.06 volts)
2 - TX turns off Q10
3 - The drain of Q10 is close to the input voltage (nominally 12 volts)
4 - 12 volts on the gate of Q9 turns it off (note that the source is also connected to the input voltage).
5 - At the same time, the Q101 gate is at 12 volts, which turns it ON
6 - When Q101 is on, it pulls the TR line, feeding the drivers and the bias circuit to 0 volts.
7 - The radio is now in steady-state receive mode.? Q9 and Q10 are off,? Q101 is on.
?
To start transmitting,
1 - The Raspberry Pi (RPi) TX signal goes high to 3.3 volts
2 - Q10 turns on pulling both Q9 and Q101 gates to ground
3 - Q9 grounded gate turns on the P-Channel MOSFET and supplies power to the TR PTT line
4 - Q101 gate low tuns off Q101 removing the pull down on the power rail to the drivers and PA Bias
5 - The Radio is now transmitting with Q9 and Q10 on, and Q101 off.
?
Note that there can be a race condition for a very short time (nanoseconds in simulation) where both Q9 and Q101 are on.? Gordon Gibby found that this could cause a failure of Q101.? His solution is to put a 150-ohm resistor in the drain lead of Q101.? This was suggested by?Dr. William J. Schmidt - K9HZ in this post:
?
Gordon also placed a resistor in series between D20 and D21 to protect a direct short on the HV line that could happen when testing.
?
Here is the post from Gordon with a troubleshooting document:
?
I can't find Gordon's post that states the value of the series resistor between D20 and D21.? I assume it is around 500 Ohms.
?
73
Evan
AC9TU
|
So on Q10 Pin3 has 8v pin1 .15v pin2 0
Q9 has 8v on pin1 and 12v on pins 2&3.
This is in the receive state. The only change when in Tx is the voltage on Q10 pin3 increases from .15 to about 3v. Q101 pins 1 and 3 have 8v pin 2 0, this doesn't change in either state. R77 never sees voltage. The group of resistors, R73-76
remain very hot in either state.
?I think my problem is simply the lack of sight and dexterity to handle the smt components. I'm tempted to fabricate that group, Q10, Q101, R5, R6 with through hole components and see if anything changes. Thoughts??
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Show quoted text
-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/5/25 4:48 PM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Hi Michael,
?
The way the TR switch works to supply power to the drivers is as follows:
?
The radio is in Recieve mode, starting on Powerup and opening the sBitx program.
?
1 - The TX signal is low (0.6 volts)
2 - TX turns off Q10
3 - The drain of Q10 is close to the input voltage (nominally 12 volts)
4 - 12 volts on the gate of Q9 turns it off (note that the source is also connected to the input voltage).
5 - At the same time, the Q101 gate is at 12 volts, which turns it ON
6 - When Q101 is on, it pulls the TR line, feeding the drivers and the bias circuit to 0 volts.
7 - The radio is now in steady-state receive mode.? Q9 and Q10 are off,? Q101 is on.
?
To start transmitting,
1 - The Raspberry Pi (RPi) TX signal goes high to 3.3 volts
2 - Q10 turns on pulling both Q9 and Q101 gates to ground
3 - Q9 grounded gate turns on the P-Channel MOSFET and supplies power to the TR PTT line
4 - Q101 gate low tuns off Q101 removing the pull down on the power rail to the drivers and PA Bias
5 - The Radio is now transmitting with Q9 and Q10 on, and Q101 off.
?
Note that there can be a race condition for a very short time (nanoseconds in simulation) where both Q9 and Q101 are on.? Gordon Gibby found that this could cause a failure of Q101.? His solution is to put a 150-ohm resistor in the drain lead of Q101.?
This was suggested by
Dr. William J. Schmidt - K9HZ in this post:
?
Gordon also placed a resistor in series between D20 and D21 to protect a direct short on the HV line that could happen when testing.
?
Here is the post from Gordon with a troubleshooting document:
?
I can't find Gordon's post that states the value of the series resistor between D20 and D21.? I assume it is around 500 Ohms.
?
73
Evan
AC9TU
?
?
-- Mike - K8MCB?
|
Re: uBitxV6 -by transmitting resets-
I tried one of the voltage converter/regulators posted earlier. Not a speck of noise.? It's staying.?
?
|
Re: Homebrew satellite control system that can run on sBitx
Thanks W0ZF!? ?I'm just a beginner.
?
tonight I tested the "winkeyer-repurposed-as-a-rotator-controller-wannabe"? with rotctl (interative) and it worked perfectly.? ?I have limited ability to control anything, so I was watching outputs with a VOM.
?
Then I moved it to rotctld (daemon) and coaxed Gpredict by putting myself way up in Canada so I could be in the footprint of a satellite.
?
It remained engaged and continued to track continuously.? ? So I think the communications works now, the read out works, and to the degree that I have any output I can WATCH, those are working (this is now just code.....)
?
I ordered two little "relay sets" that have optocoupler separation and enough relays that I can make the quivalent of DPDT to reverse the polarity of power sent to a DC motor.? ?Now start working on a PCB and potentially at least aximuth control to start with.
?
Thanks to Ashhar and others for all the help.? ?Peoiple have put a lot of work into documentation elsewhere and it was hugely helpful to me.
?
73
Gordon KX4Z
?
|
Re: Differences between the sBitx and the zBitx
You might want to look into the biasing circuit for every single stage. Because when you change the circuit voltage, the biasing calculations may be different. ? ?
Gordon kx4z?
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On Mar 5, 2025, at 16:51, eb3am via groups.io <eb3am@...> wrote:
? " ?The circuitry is optimized to work between 6v and 9v. At 12v, the heat from the 5v regulator will be significant."Is that the only reason not to put the Zbitx at 12v? Can the rest of the machine withstand it? In the schematic ( /g/BITX20/topic/zbitx_schematic_and_pcb_xray/110289914) that has been published in this group, the 5v regulation part is not visible, since it says that it is powered at 5v, and there are only 3.3v regulators. So I understand that finally there is a 5v regulator for the entire zbitx, is that so? Or could it be that the power transistors are not affected by the 5v regulation? If that were the case, the regulator would suffer less, and more power could be generated at 12v than at 9v. Well, we will find out with the equipment in hand, and with a definitive schematic. How excited I am to have it at home!
|
Re: Differences between the sBitx and the zBitx
" ?The circuitry is optimized to work between 6v and 9v. At 12v, the heat from the 5v regulator will be significant."Is that the only reason not to put the Zbitx at 12v? Can the rest of the machine withstand it? In the schematic ( /g/BITX20/topic/zbitx_schematic_and_pcb_xray/110289914) that has been published in this group, the 5v regulation part is not visible, since it says that it is powered at 5v, and there are only 3.3v regulators. So I understand that finally there is a 5v regulator for the entire zbitx, is that so? Or could it be that the power transistors are not affected by the 5v regulation? If that were the case, the regulator would suffer less, and more power could be generated at 12v than at 9v. Well, we will find out with the equipment in hand, and with a definitive schematic. How excited I am to have it at home!
|
Re: Homebrew satellite control system that can run on sBitx
Following your progress with interest! I built a K3NG controller a couple years ago (azimuth only) and had good results tracking linear birds. Lacking an elevation rotor, I just mounted the antennas at about 20 degrees fixed elevation and was able to work RS-44 and some other on SSB. I feel your pain on the mechanical side- I too have woodworking skills and tools but am pretty limited on the metalwork side. There are several designs out there that use 3D printed parts, but I have yet to jump into that rabbit hole, although it looks like it could be fun. I’ve been toying with the idea of repurposing an old TV rotor for elevation and extending my K3NG controller to handle it. Your experiments with using the SBitX as the IF rig and computer in one is pretty interesting. However, I moved away from transverters for my weak signal VHF+ work a few years ago when I got an Icom 9700, so will probably not go that route. It still sounds like a nice setup though. Good luck with your project! 73 de W0ZF?
On Wed, Mar 5, 2025 at 2:20?PM Gordon Gibby KX4Z via <docvacuumtubes= [email protected]> wrote: Hooray!? ?I figured out what was causing those "communications errors' that were causing the disconnects.
Using interactive version rotctl (not daemon rotctld) I tested changing to Yaesu 232B instead of Yaesu "generic" and bingo! all the communications errors disappeared and it provided perfect angles.
?
When I get time again, I will try simulating "tracking" and I think it will "track" (even though it has nothing it can control).? ? I'll report when I have that done.? ? Maybe tonight.??
?
I'm looking at small relay pcbs on Amazon that would save me printed circuit board design work and make it easier to replace the output relays.? ?I read a bit about how AC rotators change direction.? ?Soon I think I can start laying out a board.? ?I'll buy at least one of the relay boards first to get sizes etc.? ??
?
Then I have to start putting together rotators in earnest.? ??
Mechanically adept people with a METAL WORKING SHOP would be far better off than me; I only really have wood working abilities.
?
But it can be done!? I'll start simple with azimuth first and then add my 2nd rotator and the cool 90 degree gearbox I got from Amazon.
?
Gordon KX4Z
?
|
Re: Homebrew satellite control system that can run on sBitx
Hooray!? ?I figured out what was causing those "communications errors' that were causing the disconnects.
Using interactive version rotctl (not daemon rotctld) I tested changing to Yaesu 232B instead of Yaesu "generic" and bingo! all the communications errors disappeared and it provided perfect angles.
?
When I get time again, I will try simulating "tracking" and I think it will "track" (even though it has nothing it can control).? ? I'll report when I have that done.? ? Maybe tonight.??
?
I'm looking at small relay pcbs on Amazon that would save me printed circuit board design work and make it easier to replace the output relays.? ?I read a bit about how AC rotators change direction.? ?Soon I think I can start laying out a board.? ?I'll buy at least one of the relay boards first to get sizes etc.? ??
?
Then I have to start putting together rotators in earnest.? ??
Mechanically adept people with a METAL WORKING SHOP would be far better off than me; I only really have wood working abilities.
?
But it can be done!? I'll start simple with azimuth first and then add my 2nd rotator and the cool 90 degree gearbox I got from Amazon.
?
Gordon KX4Z
?
|
It looks as if I have pulled up the pcb trace to one of the Q101 pads. I'll try to repair that and put in a new 2n2219. Surface mount components have always presented a challenge for me
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-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/5/25 9:13 AM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Michael,
?
I've added more instructions to the spreadsheet.?
?
To test D6, the PTT must be pressed, and the tab of Q9 at the line in voltage (12 volts in the spreadsheet case).
?
If the banded side of D6 is still less than 5.5 volts, then D6 is bad, or R77 is faulty.
?
Start with verifying that Q9 is switching on the 12 volts to the driver stages.
?
This is a good test for the clarity of the document.? Thank you for the feedback.
?
73
Evan
AC9TU
?
?
-- Mike - K8MCB?
|
Scratch that , the drain of Q101 isn't grounded. I'm sure I'm in the neighborhood?
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Show quoted text
-------- Original message --------
From: "Michael Bales via groups.io" <mikebales73@...>
Date: 3/5/25 1:10 PM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
The gate of Q101 doesn't seem to be grounded. This might explain it...
-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/5/25 9:13 AM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Michael,
?
I've added more instructions to the spreadsheet.?
?
To test D6, the PTT must be pressed, and the tab of Q9 at the line in voltage (12 volts in the spreadsheet case).
?
If the banded side of D6 is still less than 5.5 volts, then D6 is bad, or R77 is faulty.
?
Start with verifying that Q9 is switching on the 12 volts to the driver stages.
?
This is a good test for the clarity of the document.? Thank you for the feedback.
?
73
Evan
AC9TU
?
?
--
Mike - K8MCB?
-- Mike - K8MCB?
|
The gate of Q101 doesn't seem to be grounded. This might explain it...
toggle quoted message
Show quoted text
-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/5/25 9:13 AM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Michael,
?
I've added more instructions to the spreadsheet.?
?
To test D6, the PTT must be pressed, and the tab of Q9 at the line in voltage (12 volts in the spreadsheet case).
?
If the banded side of D6 is still less than 5.5 volts, then D6 is bad, or R77 is faulty.
?
Start with verifying that Q9 is switching on the 12 volts to the driver stages.
?
This is a good test for the clarity of the document.? Thank you for the feedback.
?
73
Evan
AC9TU
?
?
-- Mike - K8MCB?
|
So, I don't believe that Q9 is switching, I have .6v on the gate and 12v on drain and source. PTT doesn't change anything.?
toggle quoted message
Show quoted text
-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/5/25 9:13 AM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Michael,
?
I've added more instructions to the spreadsheet.?
?
To test D6, the PTT must be pressed, and the tab of Q9 at the line in voltage (12 volts in the spreadsheet case).
?
If the banded side of D6 is still less than 5.5 volts, then D6 is bad, or R77 is faulty.
?
Start with verifying that Q9 is switching on the 12 volts to the driver stages.
?
This is a good test for the clarity of the document.? Thank you for the feedback.
?
73
Evan
AC9TU
?
?
-- Mike - K8MCB?
|
Scotty R
Ted
EB3AM Jordi