Re: MH-36D Microphone puzzle
Right, pin 8 is mike, and pins 5 & 7 are the grounds.
So, leaving pin 5 unconnected seems to have helped a bit, but there's still a hum.? After some troubleshooting on the local repeater, we noticed that placing my hand on the transceiver itself while transmitting (holding the mike) made the hum go away, indicating a capacitive problem somewhere.? Bridging an extra decoupling cap across the power internal to the mike didn't change anything, however.
The new theory is that the problem might be a shorted cap in the microphone line (pin 8).? Guessing C104, according to That would explain the high voice volume, as well as perhaps the hum.
I'm measuring about 28k ohms across it (in-circuit), with the probes in either polarity.? So, it's not shorted, but perhaps really leaky?
Before digging in (it's a more invasive fix for me), does that sound plausible?
Thanks for the help!
Greg? KO6TH
Omni wrote:
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I think you have the mic wired wrong. Pin-8 is the mic input not ground, which would explain the hum. Also, do not tie the mic ground (Pin-7) and the "other" ground (Pin-5) together. They are separated for a reason, so keep them that way. The POT controls the DTMF signal level and I would not suggest messing with it.
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Re: MH-36D Microphone puzzle
Make sure there is a 560 ohm resistor across the mic!
BR
Andrew
Get
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Re: MH-36D Microphone puzzle
I think you have the mic wired wrong. Pin-8 is the mic input not ground, which would explain the hum. Also, do not tie the mic ground (Pin-7) and the "other" ground (Pin-5) together. They are separated for a reason, so keep them that way. The POT controls the DTMF signal level and I would not suggest messing with it.
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Greg D Sent: Friday, August 26, 2022 1:22 PM To: [email protected]Subject: [YaesuFT847] MH-36D Microphone puzzle Hi folks, I've been using an MH1-B8 microphone for a while (few years), substituting for the rig's original MH-36D which had the disintegrating rubber cord problem. Following up on recent suggestion on the Amsat forum, I ordered and received a replacement cord meant for the MH-36 with the RJ plug. Cut off the RJ and connected the 8-pin round connector, and it seems to work, including the DTMF keys which is why I wanted to do the repair. But, I'm getting reports that my audio has a sort of hum on it, and the volume is rather hot, even with the microphone gain turned all the way down. I double checked the wiring, and I think it's right. The new cable has 6 wires instead of 7, so left the missing "Fast" line unconnected on the 8-pin. The MH-36D has no such button, so no loss there. The 2 grounds (mike and other) are connected together at the 8-pin connector; there's no "shield" on the cable, nor was there one on the original. Is this behavior - the hum and loudness - "expected", or is there something else going on? I see what appears to be a small potentiometer inside the mike, just above the connector. Does that need to be adjusted? What is it for? I haven't touched it as yet, but I'm not the radio's original owner. Thanks, Greg KO6TH
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Hi folks,
I've been using an MH1-B8 microphone for a while (few years), substituting for the rig's original MH-36D which had the disintegrating rubber cord problem.? Following up on recent suggestion on the Amsat forum, I ordered and received a replacement cord meant for the MH-36 with the RJ plug.? Cut off the RJ and connected the 8-pin round connector, and it seems to work, including the DTMF keys which is why I wanted to do the repair.
But, I'm getting reports that my audio has a sort of hum on it, and the volume is rather hot, even with the microphone gain turned all the way down.? I double checked the wiring, and I think it's right. The new cable has 6 wires instead of 7, so left the missing "Fast" line unconnected on the 8-pin.? The MH-36D has no such button, so no loss there.? The 2 grounds (mike and other) are connected together at the 8-pin connector; there's no "shield" on the cable, nor was there one on the original.
Is this behavior - the hum and loudness - "expected", or is there something else going on?? I see what appears to be a small potentiometer inside the mike, just above the connector.? Does that need to be adjusted?? What is it for?? I haven't touched it as yet, but I'm not the radio's original owner.
Thanks,
Greg KO6TH
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Re: Distorted audio signal on shortwave (rx!)
@Spence: well great Idea!
I will record a video and upload it to youtube. Then I share the
link here...
It takes a couple of days since I am in
vacation now.
@Andy, I speak about low frequencies (ca.
300 ... 800 Hz) and not low volume.
The effect can be shown by putting a sound generator at the
input of the TDA and wobble the frequency then...
I'll be back after my holidays...
73, Tom
Am 18.08.2022 um 23:33 schrieb Spence
M0STO via groups.io:
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Can I please inject a suggestion.....?
Make a short video and post it on YouTube as private for
those with a link so we can all see the issue.
? Failing that I will create a guest account on my FTP server
and upload it there!
De Spence M0STO?
Sent while portable! please excuse
typos.
When you say "at low audio frequencies", do you mean low
frequencies, or low AF Gain on front panel?
I think there may be a translation problem.
Regards
Andy
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Re: Distorted audio signal on shortwave (rx!)
Can I please inject a suggestion.....?
Make a short video and post it on YouTube as private for those with a link so we can all see the issue.
? Failing that I will create a guest account on my FTP server and upload it there!
De Spence M0STO? Sent while portable! please excuse typos.
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On 18 Aug 2022, at 22:03, Andy Bosworth < sidthepop@...> wrote: When you say "at low audio frequencies", do you mean low frequencies, or low AF Gain on front panel?
I think there may be a translation problem.
Regards
Andy
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Re: Distorted audio signal on shortwave (rx!)
When you say "at low audio frequencies", do you mean low frequencies, or low AF Gain on front panel?
I think there may be a translation problem.
Regards
Andy
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Re: Distorted audio signal on shortwave (rx!)
...as I wrote "also at the speaker jack"
It is the same with an external speaker.
Yes, I mean regular SSB on hf bands ...
73, Tom
Am 17.08.2022 um 22:49 schrieb Andrew
Lenton:
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Shortwave? Do you mean HF, first try an external
speaker.
73
Andrew?
Remember AM shortwave broadcast station
require a wider filter 6 KHz
Get
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Re: Distorted audio signal on shortwave (rx!)
Shortwave? Do you mean HF, first try an external speaker.
73
Andrew?
Remember AM shortwave broadcast station require a wider filter 6 KHz
Get
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Distorted audio signal on shortwave (rx!)
Hi all,
I have noticed on my "new" FT-847 that the receive audio signal on
shortwave is distorted at low audio frequencies. I suspect that the
TDA2003H has a defect. At the input pin the signal still looks good, but
at the output (also at the speaker jack) it is distorted. Does anyone
know the problem? The capacitors in this area look good.
Also, the attenuator does not work on shortwave. If you press the
button, the audio signal crackles.
Bad shopping?
73 de Tom, DJ6TB
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Re: FAST button not working through mic jack
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Re: FAST button not working through mic jack
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So the next question is...how do I center the SHIFT control. I'm a little confused by the instructions in the SM.
Max
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Re: FAST button not working through mic jack
So the next question is...how do I center the SHIFT control. I'm a little confused by the instructions in the SM.
Max
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Re: FAST button not working through mic jack
Solved,
R6573 was open, jumpered with a 2K and FAST button now works from the mic.
Max
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Re: FAST button not working through mic jack
I've measured for continuity between the components. No open traces.
R6568 is reading good at 100.7K
R6571 and R6572 are reading a bit high at 2.8K (SM shows 1K)
R6573, in series with the FST line is showing open. No reading across it at all
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Re: FAST button not working through mic jack
I've got nothing on pin 4. I shorted it to pin 5 without success. Also tried 10 between pin 2 (5V) and pin 4 without success.
I've got it apart now taking a look
Max
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Re: FAST button not working through mic jack
Some radios have Pin4 connected with Pin2 (+5V).
Shorting Pin4 with Pin5 enables FAST.
Check on the radio that Pin4 has no voltage, if so take appropriate measures for correct wiring.
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On 2022-08-12 10:56 AM, Greg D wrote:
I have the MH-1b8 mike on my 847, and the Fast button works as expected.? Greg? KO6TH
William Shadid wrote:
Max,
?
I first ran into this difference years ago when trying to use my MD-1 Desk Microphone with a newly acquired (at the time) FT-920 Transceiver. If you look at the schematic of, for instance, the MD-1 compared to the MD-100 you can see the difference. BUT, note also that there was a later version of the MD-1 that had the updated wiring. Seems, if I recall correctly, that there was an MD-1b8 that I had but that the later version, MD-1c8, had that wiring updated. I have since updated both MD-1's that I have here to "c8 status." If you cannot find the details, let me know and I can do some digging here to help you.
?
73, Bill, W9MXQ
?
?
Thanks Bill,
I'll have to trace the lines from the mic jack to the front panel board and try and sort out which is which.
Max
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Re: FAST button not working through mic jack
I have the MH-1b8 mike on my 847, and the Fast button works as
expected.?
Greg? KO6TH
William Shadid wrote:
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Max,
?
I first
ran into this difference years ago when trying to use my
MD-1 Desk Microphone with a newly acquired (at the time)
FT-920 Transceiver. If you look at the schematic of, for
instance, the MD-1 compared to the MD-100 you can see the
difference. BUT, note also that there was a later version of
the MD-1 that had the updated wiring. Seems, if I recall
correctly, that there was an MD-1b8 that I had but that the
later version, MD-1c8, had that wiring updated. I have since
updated both MD-1’s that I have here to “c8 status.” If you
cannot find the details, let me know and I can do some
digging here to help you.
?
73, Bill,
W9MXQ
?
?
Thanks Bill,
I'll have to trace the lines from the mic jack to the front
panel board and try and sort out which is which.
Max
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Re: FAST button not working through mic jack
Max, ? I first ran into this difference years ago when trying to use my MD-1 Desk Microphone with a newly acquired (at the time) FT-920 Transceiver. If you look at the schematic of, for instance, the MD-1 compared to the MD-100 you can see the difference. BUT, note also that there was a later version of the MD-1 that had the updated wiring. Seems, if I recall correctly, that there was an MD-1b8 that I had but that the later version, MD-1c8, had that wiring updated. I have since updated both MD-1’s that I have here to “c8 status.” If you cannot find the details, let me know and I can do some digging here to help you. ? 73, Bill, W9MXQ ?
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From: [email protected] < [email protected]> On Behalf Of Max Donoghue Sent: Wednesday, August 10, 2022 2:32 PM To: [email protected]Subject: Re: [YaesuFT847] FAST button not working through mic jack ? Thanks Bill,
I'll have to trace the lines from the mic jack to the front panel board and try and sort out which is which.
Max
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Re: FAST button not working through mic jack
Thanks Bill,
I'll have to trace the lines from the mic jack to the front panel board and try and sort out which is which.
Max
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Andrew Lenton
Spence G5STO
Andy Bosworth