Re: uBITX v6 Low Audio - Back at it again
Hi Richard,
Really sorry, my mistake, I have measured C10 again to the ground and this is also ~823 ohm.
But don't bother with C10, nor C30. This is the same as measuring resistance from base of Q10 and Q30 to GND.
In both there is ~823 ohms. Your measurements brings confusion as I was thinking we have only trouble at 2nd RX chain,
are you sure its not 0.82 kOhm? If this is 0.82k then its OK.
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Anyway 50 ohm on base of Q30 is NOK.
Can You de-solder C30 and measure voltages on Q30 before replacing Q30?
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Regards
Tomasz
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Wojtek, the scope photos were very helpful.
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That transformer is supposed to Step UP the voltage, not down.? ?So something is terribly wrong, and it appears tht bothof your FETs are doing fine.
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You can divide the system in half and help to figure out where the real problem is, by lifting the Orange wire that goes to the CAPACITORS and send it instead to a 50 ohm dummy load of suitable power handling capacity.? ?Then measure the voltage or power in that line.? ?Of course it will have sizeable HARMONICS so you dont' want to send it to an antenna, but sending it to a dummy load will allow you to check that the transformer is still working properly.? ?You should get PLENTY of power out of the orange wire.? ??
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Assuming you DO get power out of the Orange wire -- then the problem is in the LPF system; something is indeed shorting out your power.
If you do NOT get power out of the Orange wire -- then there is something wrong with the transformer.? ?I didn't see enough in your tofigure it out.? ?It should have two brass rods that are probably soldered together on one side and not on the other, but I'm not able to see mine and not exactly sure how they are assembled.
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Splitting the system into? ?MOSFETS+TRANSFORMER? one one side and? LO PASS FILTERS out of the question will help you figure otu where the problem lies.
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73
Gordon KX4Z
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Re: Looking for the V2 Hardware Upgrade Info
This is from Farhan re upgrading my V2, "The standing current in the diodes that switch the LPFs was found insufficient on 3.5 MHz, hence, the resistors R201, R202,
R203 and R204 are changed from 470 ohms to 330 ohms."
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Joel
N6ALT
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Re: Looking for the V2 Hardware Upgrade Info
Joel,
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FYI, changing the resistors increased the bias current on the PIN diodes for the LPF and T/R switching diodes.? This was to reduce spurs and improve power output,
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73
Evan
AC9TU
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Re: Looking for the V2 Hardware Upgrade Info
One of the things to change is R201-R204 to 330ohm 1/4 resistors, I remember doing mine but I don't remember why, other than that I don't recall doing anything else.
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Joel
N6ALT
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Re: uBITX v6 Low Audio - Back at it again
Before I stat removing components, I'll report the following based on your last suggestions:
Resistance from base of Q30 to GND = 50.8 ohms, no where close to 836 ohms.
Resistance from base of Q10 to GND = 0.82 ohms, no where close to 102 ohms.
Resistance across C30, in circuit, = 50.6 ohms.
I light of that, what's your opinions? Start pulling and ordering some parts?
73, Richard AG5M
On Thursday, February 27, 2025 at 07:15:47 AM PST, tomekdm sp7etd via groups.io <tomekdm@...> wrote:
ok. got some measurements. While measuring resistance from base of Q30 to ground (top node of C30 to GND) is around 836 ohm. While base of Q10 to GND (top node of C10) has 102 ohm (different transformer). Richard, if You will have much lower than 100 ohm - C30 (100nF) is also suspected to have short.... less than 90 ohms.
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Wojtek,
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Is your power supply voltage dropping?? Strangely, the drain voltages drop when you key the mic.? This could suggest that T7 has an issue.? Confirm that you are seeing the drain voltage drop on the IRF510s.
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As shown in the scope images, the DC of the drain voltages remain at ca 12V. It was the DC multimeter that got crazy when measuring the voltage with RF.
73,
Wojtek
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Re: Looking for the V2 Hardware Upgrade Info
JJ,
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I do not have the documentation; I have only the GitHub files with the original V2 schematic. The zip file is attached.
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73
Evan
AC9TU
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Wojtek,
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Is your power supply voltage dropping?? Strangely, the drain voltages drop when you key the mic.? This could suggest that T7 has an issue.? Confirm that you are seeing the drain voltage drop on the IRF510s.
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Does the bias control work?? Can you adjust the radio's current when following the set bias process?? From sbitx.net:
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How to set the bias
Siegfried Jackstien, DG9BFC (modified by me for v3 circuits)
- Set both the POTS to the minimum current
- Select Mode as USB. Reduce the MIC to zero.
- Set the Drive Level to 1
- Press the PTT.
- Without speaking into the microphone, Note the current.
- Keep the PTT on the microphone pressed, and increase the PA_BIAS POT until the current increases by another 200 mA.
- Release the PTT.
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The above is for the V3 or radios that have been upgraded, not the prior versions that have not been modified.? The Drive_Bias pot is either not there or has been disconnected in the upgrade to the V3 PA design.
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73
Evan
AC9TU
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 Do you have 1V here when you transmit?
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I have checked signals with the scope (measured with 1:10 probe with DC coupling, 500 mv/div so 5V/div considering probe).
Ground level:
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DC level on drains of finals without RF:
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Voltage with RF on the drain of the first final transistor:
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Voltage with RF on the drain of the second final transistor:
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At the same time, the voltage on the secondary coil of the output transformer looks like below (100mV/div - 1V/div considering probe)
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Is it possible that the transformer got broken due to overheat, or that something in the LPF filter shortens the signal?
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73,
Wojtek
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Re: Looking for the V2 Hardware Upgrade Info
On Fri, Feb 28, 2025 at 06:14 AM, WK4DS wrote:
Here you go JJ
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I was finally able to return a small favor for all your hard work on these awesome radios…
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David
WK4DS?
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Thanks David. Although this doesn't address the necessary upgrades to keep the IRFZ24Ns in place; it does help to convert a V2 to a V3.
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Hello Evan,
I have verified that bias circuitry works properly. I have even checked that the finals have full power suply voltage on their? drains (13.3V) and that its DC value drops to ca 1V when I press the key.
So it looks like I need to check the path via the LPF filter.
I have found that the HV voltage measured on R213 remains 12.6 V even when I start to transmit. Is the voltage multiplier broken then?
73, Wojtek
Hello Wojtek,
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I had similar problems with my DE.? That turned out to be overheating drivers in one instance and a failure in the Q9 and Q101 equivalent circuits (the DE documentation did not have Q101 listed).? Verify that there are 12 volts on the drain of Q9 (the tab) when the PTT is pressed.? Also, verify that Q12 to Q15 are on with a 0.6-volt drop from Base to Emitter.? This may be difficult to determine if one has failed since the two are connected in parallel.? The other test is to verify the voltage on the emitter resistors to check for the transistor being on.? They should all be close to the same.
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Another possibility is that the PA_Bias1 circuit has failed. Verify that D6 has 5.6 volts on the banded side when the PTT is pressed.
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Here is the relevant circuitry:
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I agree with Gordon that a shorted IRF510 is unlikely. The first step is to check for proper soldering on the devices.??
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I also strongly agree with Gordon about installing the AlN insulators instead of the mica.? Do this while you add the external fan. As Gordon said, the AlN will make the heat sink even hotter.
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The sbitx uses a bar to hold down the transistor, so you do not need a hole and screw insulator.? If you have other applications, buying the insulators with the hole may be a better choice.
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Post on 开云体育:
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Note: Ashhar Farhan has stated that these are not needed with the new mounting method for the finals.? They do not hurt, so cheap insurance helps with heat dissipation.
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73
Evan
AC9TU
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-- Wojciech M. Zabo?otny
My GPG/PGP keys:
standard: 8192R/7E17F00A (B53C 1F09 BEA9 ED46 51B6 ?2C2E 4344 F292 7E17 F00A)
confidential: 16384R/1FEDB03C (3412 2330 E225 D57D 70C3 ?2340 B294 9408 1FED B03C)
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Fred,
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There is a different answer for each individual.? Do you want to operate CW regularly?? Do you use headphones regularly?? ?Do you want to gain skills in hardware, software, or both?? These questions can drive where you want to spend your time and money.
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The trend is toward software, so the sbitx was my logical choice.
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The reason for the v5 from AmateurRadioKits is that from a circuitry view, the v5 and v6 are the same.? The controls are mounted on the HFSignals board and externally on the AmateurRadioKits board.? ?The other main difference is the Raduino.? HFSignals added the TFT display to the v6.? That is not provided on the other radio.? I assume that performance is equivalent.? I have not built the AmateurRadioKits Micro BiTx.
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If you want CW capability at the 25-watt level, then the sbitx is the choice.? The zbitx has not yet been delivered, so it is too early to rate that radio.? It looks like the zBitx is focused on a portable, 5-watt level.? CW works well on the sbitx, so I assume it will be the same as it uses the same software.
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On the other hand, many hardware upgrades are possible on the uBiTx series.? I listed the obvious in my prior post.? In addition, upgrades are possible to the audio, both receive and transmit that would give experience in SMD and hardware mods in general.
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So it is up to you to decide the best path forward.
73
Evan
AC9TU
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Re: zBitx - Progress Update
Excellent update. It is great to see the work being accomplished.?
I will? be ordering after the rush dies down.
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Re: #zbitx Spam, Fishing, and Unwanted Email
#zbitx
Humans are truly the biggest risk and it is enough to stumble once.
--
Gyula HA3HZ
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Re: Looking for the V2 Hardware Upgrade Info
As far as I remember, several people tried several solutions that were discussed in the forum. Personally, I implemented a different version, a more complicated solution. This involves more work and may be alarming for those who do not like DIY. If my memory serves me correctly, I read it on the F5NPV website, which worked for me. By the way, v2 started with a mechanical defect, which was fixed by the manufacturer. Mounting the IRFZ24 to the heatsink was problematic.?
--
Gyula HA3HZ
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Thank you all for the comments. I will dig into some of the recommended?mods for the v3 and see what I can do!
-Fred KC3HMS
On Fri, Feb 28, 2025 at 10:54?AM Fred Buecker via <tfbiii2002= [email protected]> wrote: Thanks Evan! ? If the best option is to upgrade, it might be best to just get the newer kit from AmteurRadioKits. What am I missing tho in that they use a v5 for that as opposed to the v6? Is it maybe better to just jump to an sBit? ? I agree that has always been the “best source”, outside of this list. That said, there has not been a new post to it since 2020, so it made me wonder if there was some new home for information. ? Fred KC3HMS ? ? The best source for uBiTx info that I know of is: To truly reach v6 status, the layout of the mainboard needs to be changed to correct the LPF bleed-through issues.? Some fixes have worked for others on the site.? Upgrading the TFT display is more challenging.? You might find an update in the group files or wiki.? I think the most used display upgrade is to the Nextion display, which is a step above the v6 display.? The Nextion upgrade is listed on the site. As you have mentioned, some of the information is old.? Most are still applicable. ? - replace the LPF relays to reduce harmonics ? - Change inductors between the two IFs to eliminate spurs above 20 meters. 2 - repair the Audio chip (if needed) 4 - Flatten out power across bands: You can then expand on the v6 to add AGC, an S-Meter, and a CW audio filter, available elsewhere on the web. I would only do the above if you want to learn more about the radio.? If you do not have the parts in your spare bin, you could spend close to $209 on a new V6.? AmteurRadioKits sells a new Micro Bitx v5 with enclosure, less the display, for $99 It may be challenging to find a case that matches the Nextion 2.8" screen, but there is a 5" display case that requires adding another 5Volt source for the larger display.
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Re: #zbitx Spam, Fishing, and Unwanted Email
#zbitx
Believe me, I'm covered.? I deal with cybersecurity every day but these emails can, and probably will, snag someone else with fewer security checks.? Another aspect to consider is the groups.io terms of service.
/static/tos
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Thanks Evan! ? If the best option is to upgrade, it might be best to just get the newer kit from AmteurRadioKits. What am I missing tho in that they use a v5 for that as opposed to the v6? Is it maybe better to just jump to an sBit? ? I agree that has always been the “best source”, outside of this list. That said, there has not been a new post to it since 2020, so it made me wonder if there was some new home for information. ? Fred KC3HMS ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Evan Hand via groups.io
Sent: Thursday, February 27, 2025 5:58 PM
To: [email protected]
Subject: Re: [BITX20] uBITx v3 upgrade? The best source for uBiTx info that I know of is: To truly reach v6 status, the layout of the mainboard needs to be changed to correct the LPF bleed-through issues.? Some fixes have worked for others on the site.? Upgrading the TFT display is more challenging.? You might find an update in the group files or wiki.? I think the most used display upgrade is to the Nextion display, which is a step above the v6 display.? The Nextion upgrade is listed on the site. As you have mentioned, some of the information is old.? Most are still applicable. ? - replace the LPF relays to reduce harmonics ? - Change inductors between the two IFs to eliminate spurs above 20 meters. 2 - repair the Audio chip (if needed) 4 - Flatten out power across bands: You can then expand on the v6 to add AGC, an S-Meter, and a CW audio filter, available elsewhere on the web. I would only do the above if you want to learn more about the radio.? If you do not have the parts in your spare bin, you could spend close to $209 on a new V6.? AmteurRadioKits sells a new Micro Bitx v5 with enclosure, less the display, for $99 It may be challenging to find a case that matches the Nextion 2.8" screen, but there is a 5" display case that requires adding another 5Volt source for the larger display.
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tomekdm sp7etd
Joel Caulkins/N6ALT
Richard AG5M
HA3HZ
Kevin