IC7000 transmits, puts out power, no audio


 

I have two IC7000s that I bought in unknown condition and neither worked.

I fixed them both since the front panel killed the +8 volt series resistor feeding the regulator.

One works OK with the one face plate I fixed and the other I thought was working,  but it outputs no audio when the mike is connected to either the front panel or the jack in the rear.

The mike drive is set just like the other unit, but no joy.

Any ideas where to start?

I assume I need to start at the mike and work my way into the radio.

Someone have a common area to check first?


Thanks,


KE4MD


Steve W3AHL
 

  1.  Have you done a CPU reset (p. 25 of manual)?
  2. Does the red TX LED come on when you PTT?  
  3. In FM mode do you get full TX power out?
  4. In SSB mode is there any ALC activity when you do a loud AHHHH into the mic.  What about if the mic gain is increased to max?
  5. If you Record a Voice Message for Transmit (p.96 of manual) and play it back to confirm, is there any audio locally through the speaker? 
Steve, W3AHL

---In ic7000@..., <jeter.d.barron@...> wrote :

I have two IC7000s that I bought in unknown condition and neither worked.

I fixed them both since the front panel killed the +8 volt series resistor feeding the regulator.

One works OK with the one face plate I fixed and the other I thought was working,  but it outputs no audio when the mike is connected to either the front panel or the jack in the rear.

The mike drive is set just like the other unit, but no joy.

Any ideas where to start?

I assume I need to start at the mike and work my way into the radio.

Someone have a common area to check first?


Thanks,


KE4MD


 

  1.  Have you done a CPU reset (p. 25 of manual)?  --- YES I tried that this AM
  2. Does the red TX LED come on when you PTT?  ___ YES It has always lit the TX LED
  3. In FM mode do you get full TX power out? --- YES with AM as well, but no modulation
  4. In SSB mode is there any ALC activity when you do a loud AHHHH into the mic.  What about if the mic gain is increased to max? - MIke gain all the way up no output in SSB
  5. If you Record a Voice Message for Transmit (p.96 of manual) and play it back to confirm, is there any audio locally through the speaker?  --- Yes I can record a message and play it back I can see the meter go up and down with modulation.
Any guesses as the why the SSB modulation (And AM and I don't know if the FM is or not)
The unit will output power on RTTY and CW.


 

I can see some wiggle on the power in AM, but I don't know how much modulation there might be there.
I can hear the monitor if I turn it on and up so there is modulation audio getting at least that far.


 

The VOX works as well.


 

Yes to all the monitor also works.
The recorder works and plays back
There may be a little modulation on the AM,I can't tell about the FM
No ALC on talking into the mike even with the gain all the way up.


 

I have done those things and it does everything that yu asked about except for the ALC or any SSB modulation.
I have tried to post, but it doesn't seem to post


Steve W3AHL
 

So it sounds like the DSP circuits are OK on the Logic board.  I forgot to ask if you had receive audio, if so most of the IF circuits are working.  If you do, then I would look at the TX audio into the 3rd IF mixer, IC1301.  It is located on the top side of the Main board and easily accessed with a scope probe.  In the Service Manual it is shown in the first Inside View photo, midway down on the left side as TX 3rd Mixer.  

Refer to the Main board schematic for IC1301 pin out.  Pin 1 is the 3LO at about 438 KHz.  Pin 3 is audio from the DSP.  Pin 5 is the 455 KHz output to the 2nd IF mixer.

If you have a scope you should be able to trace the signals through the IF, until the frequency gets too high.  If you don't see audio at IC1301-3 when you speak into the mic with PTT enabled in USB mode, then the problem is probably in the Logic card or its stacking connectors to the main board.

Sometimes a good visual inspection with strong light and a magnifier will reveal the problem easier than trying to scope the signals.   Use static (ESD) protection anytime you are working or handling the boards.

Let us know what you find.

Steve, W3AHL

---In ic7000@..., <jeter.d.barron@...> wrote :

Yes to all the monitor also works.
The recorder works and plays back
There may be a little modulation on the AM,I can't tell about the FM
No ALC on talking into the mike even with the gain all the way up.


 

I get a very small signal on my TEM TAS645 at pin 3 or more properly at R1310 ,but I think it is too small.
The big cap C2610 is hotter than I would expect, but it behaves like a good cap when removed and checked with a meter.
I think I will have to trace the signal back to the audio circuits and see where it is going south.
I did notice that the fan runs as soon as I key on the transmitter.
The other radio does not run the fan until the finals heat a little.
I also noticed that the ALC is pegged out when on SSB and not on CW and RTTY.
The power might be folded back on SSB and this might be connected with the fan running.
It puts out full power an RTTY.
The COM bar graph modulates with voice.
Even with the power cut way back this is what happens 
With the power turned back on RTTY and FM it still puts out full (or close) to full power.


Steve W3AHL
 

More detail is always helpful when trying to troubleshoot a radio over the Internet.  

Can you quantify "very small signal" in millivolts?

The ALC should not be pegged in SSB, so that would indicate there is a more basic problem with the IF chain than no mic audio.  Note that in constant carrier modes (AM, CW, FM & RTTY) as you decrease the TX PO setting toward zero, the ALC reading will increase.  But this should not happen in SSB.

Rather than check the audio levels, you should see what the IF output voltage is.,  In the Files area look for the "7K TX RF Levels 3.pdf"  document.  The first section might prove useful.  Pay attention to the note on the scope probe grounding used.  A regular ground lead will give erroneous measurements.

Please sign your posts....

Steve, W3AHL

---In ic7000@..., <jeter.d.barron@...> wrote :

I get a very small signal on my TEM TAS645 at pin 3 or more properly at R1310 ,but I think it is too small.
The big cap C2610 is hotter than I would expect, but it behaves like a good cap when removed and checked with a meter.
I think I will have to trace the signal back to the audio circuits and see where it is going south.
I did notice that the fan runs as soon as I key on the transmitter.
The other radio does not run the fan until the finals heat a little.
I also noticed that the ALC is pegged out when on SSB and not on CW and RTTY.
The power might be folded back on SSB and this might be connected with the fan running.
It puts out full power an RTTY.
The COM bar graph modulates with voice.
Even with the power cut way back this is what happens 
With the power turned back on RTTY and FM it still puts out full (or close) to full power.
 


 

Steve.
Thanks for the info.
I need to do a few things to get my ducks in a row here.
One of them is to find the grounding clips and wires for my scope probes.
To add some information I noticed that on AM,FM  and RTTY the unit puts out power and the ALC gose to the red line but not into the red
On SSB the ALC "pegs" to readout and the fan turns on full speed. 
The fan runs for a while after the PTT is released.
I have been checking the OP AMPs and the blocking diodes.
The side towards the OP AMPS is 6.5 vdc + and 0 on the other side.
The fan is turned on by the CPU as I can determine.
 The SWR stays low and the COM dances with audio quite a bit.
I think that there is some problem with the ALC circuit and I have more tracking to do,
I can't give you a good answer on the RF until I get the scope probes correct.
Thanks again, Steve.

73s J.D. Barron KE4MD


Steve W3AHL
 

Typically the problem isn't with the ALC circuit, but with the IF amplifiers, which the ALC controls the gain of.

Here's some info I sent to another 7K owner who had some issues with ALC he thought.  It might be useful a useful reference for you:

"Set your 7K to 14.2MHz, FM Mode, 100% TX PO into a dummy load. Measure ALC
voltage at junction of R1624 and Q1606 with DVM or scope. With mic unkeyed ALC
should measure about 2.88 VDC. With mic keyed it should be about 1.99 VDC and
the ALC display should have all green bars on.

Change TX PO to 50%. With mic keyed ALC should be about 1.91 VDC and ALC
display should have red bars on.

Change TX PO to 10% and ALC should measure about 1.86 VDC.

For reference, in SSB mode with mic unkeyed ALC measures about 2.76 VDC. With
mic keyed and normal voice level (only 1-2 green bars on ALC display voltge is
still about 2.76 VDC. Turn mic gain up and give a loud AHHHH into mic and ALC
goes to 2.25 VDC and most red bars on ALC display should be on.

This gives you an idea of how little of a variation in ALC is used to control
bias of the IF gain to control power output.

Actual voltages will vary a little depending on overall TX gain, power supply
voltage, temperature, etc."


Steve, W3AHL

---In ic7000@..., <jeter.d.barron@...> wrote :

Steve.
Thanks for the info.
I need to do a few things to get my ducks in a row here.
One of them is to find the grounding clips and wires for my scope probes.
To add some information I noticed that on AM,FM  and RTTY the unit puts out power and the ALC gose to the red line but not into the red
On SSB the ALC "pegs" to readout and the fan turns on full speed. 
The fan runs for a while after the PTT is released.
I have been checking the OP AMPs and the blocking diodes.
The side towards the OP AMPS is 6.5 vdc + and 0 on the other side.
The fan is turned on by the CPU as I can determine.
 The SWR stays low and the COM dances with audio quite a bit.
I think that there is some problem with the ALC circuit and I have more tracking to do,
I can't give you a good answer on the RF until I get the scope probes correct.
Thanks again, Steve.

73s J.D. Barron KE4MD

 


 

Thanks Steve.
I have measured the voltage at this point, but had no idea what it should be.
On the line there is 0 volts, but on the other sides of the D1606, 7 , and 8 there is 6.5 - 7 volts.
My original thought was that there was some signal coming into the ALC circuit that was shutting the thing down on SSB and there still might be.
I think we might be getting closer, but I still have some work to do to get aet up where I can work comfortably with the irty-bitsy parts.
I will check some more voltages and perhaps compare with the one that is working, although I hate to convert a working radio to the same condition as the non-working!
Thanks again

J.D.

KE4MD


Steve W3AHL
 

The Service Manual has a useful description of the ALC circuit sections on page 3-6.  On the schematic, if you trace the ALC line at R1624 tot he right and up, it is tied to 5 VDC.   The normal dynamic control of ALC is via IC1601 through D1606.  The nominal ALC voltage is about 2.9 VDC when not transmitting.  IC1601 will pull the voltage down to about 2 volts to control the IF circuit gain, regulating the output power.  The other diodes you reference are primarily ORing various error conditions together, which will pull the cathode of the diode toward ground, resulting in the ALC line being pulled below one volt, shutting down the IF drive.  It's not quite that simple, but you get the idea....

Yes the small parts can be a challenge to probe, especially as the eyes age!  I use a stereo inspection microscope with a ring light when possible to keep me out of trouble....

I would offer to measure any questionable voltages on my units for reference, but am getting ready to travel  for a while soon and won't have any test equipment with me.  And may have limited Internet access until I get home again.

Steve, W3AHL

---In ic7000@..., <jeter.d.barron@...> wrote :

Thanks Steve.
I have measured the voltage at this point, but had no idea what it should be.
On the line there is 0 volts, but on the other sides of the D1606, 7 , and 8 there is 6.5 - 7 volts.
My original thought was that there was some signal coming into the ALC circuit that was shutting the thing down on SSB and there still might be.
I think we might be getting closer, but I still have some work to do to get aet up where I can work comfortably with the irty-bitsy parts.
I will check some more voltages and perhaps compare with the one that is working, although I hate to convert a working radio to the same condition as the non-working!
Thanks again

J.D.

KE4MD


 

Thanks < Steve,
My schematic shows the ALC line going right and up and just stops.
I see two 2.2 meg resistors going to the +8 volt line down and to the left.
I would have an easier time comparing the two radios if I had two working front panels!
I think I will concentrate a little on the front panel and I have the parts to work on it and get it fixed where it doesn't blow the 4.7 ohm resistor on the main board.

Enjoy your travels

Thanks,

J.D.

KE4MD