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Author Topic: TS-940S - no audio from rear audio input  (Read 1094 times)
NZ5N
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« on: March 28, 2009, 09:11:02 PM »

At our club station, we have been using an interface that connects to the front microphone jack for digital work with DM780.  To avoid having to connect and disconnect the microphone each time someone wants to work digital, we came up with the idea of an interface that connects to the ACC2 port on the back.

Tested out the new interface today but could not get it working.  The PTT works as it should and keys the radio to transmit, but no audio is getting out of the radio.  The radio goes into transmit but there is no modulation, even with mic gain at max and the sound card's output at max.

As a test of the computer and interface, we connected a pair of headphones to pins 11 and 12 (audio input) of the 13-pin DIN plug that connects to ACC2, and we could hear the tones fine, so it seems the problem is within the radio itself.  Are there any buttons that need to be pushed or adjustments that need to be made to open the rear audio input port?

Any thought?

73, Bill NZ5N
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W8MW
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« Reply #1 on: March 29, 2009, 06:32:36 AM »

Long ago I had a TS-930 and fed audio into it thru a rear panel RCA jack.  They called it Phone Patch but worked with all line level audio sources.  Does the 940 have one of these and can you try it?

73 Mike
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NZ5N
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« Reply #2 on: March 29, 2009, 07:05:02 AM »

Mike,

Thanks for the reply.  Yes, the 940 also has an RCA jack for phone patch.  Guess we could try that if we can't get it to function on ACC2.  But itshould work on ACC2, shouldn't it?

Could it possibly be an impedance mismatch situation?  The manual mentions that phone patch input is 600 ohms and the microphone jack input can be used with anything from 500-5000 ohms.  But no mention of the impedance on pins 11 and 12 of ACC2.

73, Bill NZ5N
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K0UA
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« Reply #3 on: March 29, 2009, 08:01:57 AM »

when I had an TS-940, it worked well using the ACC2 rear panel connector. (pin 11 and 12).  sounds like a contact problem or a defect in the 940. Sorry.
james
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AB8SG
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« Reply #4 on: March 29, 2009, 08:10:47 AM »

If you have the service manual for the TS940 you can trace out the lilely problem. The audio from the front panel mic input routes to the mic amp through a different set of connectors to the IF board. Con 1 vs Con 2 at the IF board. Reseat the connectors might be the only problem you have. If not, follow the circuit from MIN on Con 1 to the base of Q36 until you find the resistor that is open.
73
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KL0S
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« Reply #5 on: March 29, 2009, 08:46:25 AM »

Once you get it working you should also consider a well documented mod that mutes the mic audio when you input tones into the ACCY2 connector.

Connect a diode (1N914 is fine) between pins 9 and 13, with the cathode on pin 9.   This prevents a "hot-mic" when you're doing digital and precludes audio getting into the stream from the front panel mic jack.

There is no switch/adjustment for the ACCY2 input; it either functions or it doesn't.  The likelihood that the rig connector has failed is pretty small.  A breakout box like the one made by LDG was VERY useful when I was troubleshooting similar problems in my shack.

Dino KL0S
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W8MW
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« Reply #6 on: March 29, 2009, 01:40:43 PM »

Bill, I think the above posters have given you good input.  I mentioned going to the RCA jack thinking it might be less likely than the DIN assembly to have a simple electro/mechanical glitch.

No, wouldn't expect impedance differences to have much effect.  It's common to sometimes need adjustment of the input signal for optimum drive level.  Also I've run into ground loop/hum issues when interfacing outboard gear.  There's always a straightforward solution.

Mike
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W2AEW
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« Reply #7 on: March 29, 2009, 03:40:03 PM »

I have a TS-870S and seem to recall that there were two different keying lines on the ACC jack.  One would key the rig like the PTT and use the front-panel mic input as the audio source, and there was a 2nd TX line that, when keyed, would take audio from the ACC jack.  You might want to see if the 940S is the same.
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NZ5N
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« Reply #8 on: March 31, 2009, 09:33:53 PM »

Thanks for the replies.

We still have not corrected the problem, but W2AEW may be on to something.  We have learned that, on a TS-2000, the rig accepts audio via ACC2 pins 11 and 12 if, but only if, the pin 9 PTT is engaged.  We are using pin 13 to key the PTT.  So that's likely the problem, if the TS-940 is the same as the TS-2000.

But are they the same?  KL0S seemed to suggest that audio does work from ACC2 even if pin 9 is engaged, and that the only purpose of keying pin 9 is to avoid a "hot-mic" when you're doing digital.

We have rewired the interface so that audio input goes to the RCA phone patch input jack and will just use it that way if it works.  Will visit the club later this week and report the result.

73, Bill NZ5N

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KL0S
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« Reply #9 on: April 01, 2009, 06:30:53 AM »

Bill -- the 940S ACCY2 inputs SHOULD work simply as described in the manual.  If you have a breakout cable for a 13-pin DIN you should be able to check each function separately.  Keying can be done either via ACCY2 OR the front panel "Send/Rec" switch.  The 1N914 mod simply decouples the mic audio from the chain and doesn't have anything to do with the keying function.

One way to check if the tones are getting into the rig is to just engage the "Moni" function since you should be operating in a SSB mode (it works the same actually in the FSK position since the rig is really using AFSK -- the mark/space signals are actually audio tones derived from the 20 MHz master oscillator, it's not true FSK but obviously close enough!).

I had a very frustrating keying problem with a cable from one of the big interface manufacturers and it turned out to a missing ground connection in the 13-pin DIN plug as the cable had been incorrectly constructed.  For some reason nothing ever seems easy going to ACCY2 on a 940S!  ;-)

Let us know how it turns out.

Dino KL0S
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NZ5N
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« Reply #10 on: April 01, 2009, 05:29:52 PM »

Dino,

Are you saying we should get modulation if audio is applied to pins 11 and 12 and PTT is engaged on pin 13 and pin 9 is left empty?  That's how we are set up and it's just not working, not getting any audio at all through the radio with this configuration.

We are up and running now, applying audio through the RCA phone patch input.  Thanks to W8MW for this tip.

Some day when no one has anything better to do, maybe we'll open up the DIN, run a diode to pin 9, and see if that allows audio to enter on pins 11 and 12.

73, Bill NZ5N
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KL0S
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« Reply #11 on: April 02, 2009, 04:39:04 AM »

Hi Bill....bottom line: if you apply your audio tones to pins 11 and 12 (hot lead to pin 12 and ground lead to pin 11) then toggle over to transmit either by pushing the mic PTT or the "SEND/REC" you SHOULD get modulation; do you by any chance have those leads reversed???

There is no requirement for the diode between pins 9/13; that mod just keeps the mic audio out of the chain if your inputting tones thru ACC2.

I know how frustrating this issue can be....been there, done that, got the tee shirt!

73 -- Dino KL0S
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NZ5N
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« Reply #12 on: April 02, 2009, 06:19:21 AM »

Dino,

I think you meant to say hot to pin 11 and ground to 12, right?  See p.30 of manual.

Anyhow, we are just not getting modulation through pins 11 and 12, we can copy the audio on headphones attached directly to those pins, so the connections seem OK, but it's just not working.  On the TS-2000, we have confirmed that pin 9 must be grounded to make the pin 11 and 12 audio work, maybe someone modified this TS-940S to do the same thing.  Who knows.  I'm just glad it is working through the phone patch input.

73, Bill NZ5N
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N5LRZ
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« Reply #13 on: April 02, 2009, 06:31:35 AM »

Get the owners manual and reference the information for pin configuration of the plug.   Look in the manual for a setup for RTTY.  This should also work for other digital modes such as PSK .

On my Yaesu the same pin configuration for RTTY also works for non digital  analog modes as well.
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KL0S
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« Reply #14 on: April 02, 2009, 11:03:36 AM »

Bill -- you're right, I fat-fingered the leads and got 'em backwards.

Hope you can figure it out!

73 -- Dino
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