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Author Topic: TS-940 TR relay: can you hear it switching?  (Read 4559 times)
N6QWP
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Posts: 231




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« on: October 26, 2017, 08:29:28 PM »

Having a problem with my TS-940 and not getting output.  If you have a 940, can you hear the TR relay when hitting the PPT on mic?  Transmit light (red) does indicate when in xmit.  

Have another thread started in Repair....but need to know if one can actually hear the TR relay clicking on a TS-940 when put in transmit?  Hoping that someone who is a 940 user can let me know if you can actually hear the relay when put into xmit??

An answer to that singular question will let me know if my problem is isolated to that relay....or another issue all together.
« Last Edit: October 26, 2017, 08:33:00 PM by N6QWP » Logged
KC4ZGP
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Posts: 1637




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« Reply #1 on: October 27, 2017, 07:22:40 AM »


You don't hear relays? Never met a relay-quiet radio.

Might have to open 'er up and give a listen. If the transmit light is on and you
don't hear a relay, your finals might be suffering dumping their RF to nowhere.

I take it you're looking at the transceiver's meter. Have you tried an external meter?

Kraus



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N6QWP
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Posts: 231




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« Reply #2 on: October 27, 2017, 07:47:16 AM »

I previously posted that I could only get about 5 watts out on the meter in my external antenna tuner.  I measured 29 vdc to the finals both on the rigs meter and on a dvm.  That was the only voltage that I checked on final unit.

Will check to make sure that I also have 13 vdc on that board.  Any other voltages I should check for?  Anything else that could keep the final amp from working?  As I stated in my repair post, I replaced the entire final unit with the same results for lack of output.

I thought that I should be able to hear the TR relay,,,,,but do not.  If rely is not working, where will all that rf go?  As I said, no indication of IC or power out on rigs meter.

Other than relay failure, is there any other possible cause of these symptoms?

UPDATE! I am told that there is NO TR RELAY=940 is using diode switching for TX???  If that is the case, what else then, can cause the lack of amplification in the final unit (that has already been replaced)?
« Last Edit: October 27, 2017, 08:03:19 AM by N6QWP » Logged
KC4ZGP
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Posts: 1637




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« Reply #3 on: October 27, 2017, 10:52:34 AM »


I don't own a TS-940.

29 volts eh. I say that's normal. To produce 250 watts, 28vdc devices are employed. My 300 watt
EB-27A uses a pair of MRF-421. They require 28vdc.

Bias voltage measured at the base should be .6vdc to .7vdc.

Lift the bases and check each transistor's rectifying properties.

Find way to measure input signal at the base. The finals could be faulty but still let the driver's
RF signal through to the meter.

Kraus
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N6QWP
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Posts: 231




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« Reply #4 on: October 27, 2017, 12:21:31 PM »

As I posted before, I just replaced the entire final unit with one that was working in another radio=I am still getting the exact same symptoms as before with original final unit.

That leads me to believe that the problem is on the rf board--or some peripheral supply circuit?  What and where is the question?

Looking for some advise from someone familiar with the TS-940.  I will be pulling plugs and reseating the rf board.....but still not focused on any singular cause.  I am hoping that someone who has worked on or has had a 940 can help to isolate the problem.

Can anyone familiar with the 940 and who has a schematic, please check for where any other measurable voltages should be on the final board?  I keep having a nagging feeling that it could be a problem of a supply voltage (other than the 29 vdc to finals) that might be the problem???  Anyone see where such an issue could keep a good final unit from functioning???
« Last Edit: October 27, 2017, 12:38:09 PM by N6QWP » Logged
KM1H
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Posts: 2499




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« Reply #5 on: October 28, 2017, 07:06:39 AM »

The 940 relay is very quiet, and Ive owned mine since the mid 80's but havent experienced your problem.

Those radios are notorious for poor connections and soldering on the various connectors, pin and coax type. A tiny drop of DeOxit D-100 on pins and reseat several times takes care of the oxidation. Then wiggle connectors and solder when you have an intermittent.

It took me a few years to get mine fully reliable.

Carl
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N6QWP
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Posts: 231




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« Reply #6 on: October 28, 2017, 08:24:51 AM »

Carl--Can you clarify whether or not there is or is not a relay in the TR circuit--OR if rig uses PIN diode(s) for this function???  I am still waiting for a manual to arrive.

If there is a relay, wondering if one set of contacts could perform switching function on all but antenna switching?  Same question if using diode(s)Huh

I can visualize a failed TX antenna connection possibly giving these symptoms.

Other than that, I am searching for some problem (other than the final unit itself) that could keep the final unit from passing and amplifying a TX signal on through to the antenna jack.

Anyone else familiar with the 940 have any other thoughts?
« Last Edit: October 28, 2017, 08:37:29 AM by N6QWP » Logged
WB8PFZ
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Posts: 201




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« Reply #7 on: October 28, 2017, 09:55:02 AM »

What does the IC function of the meter read when transmitting?
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N6QWP
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Posts: 231




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« Reply #8 on: October 28, 2017, 10:17:47 AM »

Absolute zero IC on xmit.....NO other meter readings at all EXCEPT for 29 vdc VC to finals on xmit.

Seems to indicate that signal is stopping BEFORE the final unit???

Would not the fact that I can hear the xmit audio and get an extremely loud, clear signal on my other receiver even with no antenna=indicate that the xmit rf unit is working properly???

Once again, let trying to isolate what other cause could interfere here???
« Last Edit: October 28, 2017, 10:40:50 AM by N6QWP » Logged
WB8PFZ
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« Reply #9 on: October 28, 2017, 10:37:26 AM »

I would think you would see some current indication on the meter.
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WB8PFZ
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« Reply #10 on: October 28, 2017, 10:38:36 AM »

I hear NO relay in mine.
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N6QWP
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Posts: 231




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« Reply #11 on: October 28, 2017, 10:44:47 AM »

Thanx for info about not hearing relay (is it due to a lack thereof)?  

I was typing on top of previous reply about "thought there would be some IC".....there is NONE!

So, why???  What would or could cause a "working" final unit to have absolutely none?
« Last Edit: October 28, 2017, 10:49:54 AM by N6QWP » Logged
WB8PFZ
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« Reply #12 on: October 28, 2017, 11:39:25 AM »

Time to grab the schematic. Mike
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N6QWP
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Posts: 231




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« Reply #13 on: October 28, 2017, 11:50:17 AM »

Yup...but, in the meantime, only have one for the TS-930 (which has the same final amp board) but other boards, supply  and switching are different.  While waiting for a 940 manual, I thought I might get some help from someone more knowledgeable who has the 940 manual and who might come up with a cause/fix.

Anyone care to step up?  Thanx
« Last Edit: October 28, 2017, 12:03:56 PM by N6QWP » Logged
WB8PFZ
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« Reply #14 on: October 28, 2017, 12:22:13 PM »

Check for voltage on the collectors in the final?
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