ic-7000 alc voltages on IC-1601 and Q1604


I think I wrote something on this long enough ago that I have forgotten most of it. Do a search and see. I worked on the ALC extensively at one time, but I forget the specifics.

ve6ars Ross

Thanks Steve,

I was already using your measurements from your past post to troubleshoot this units operation.   At R1624 and Q1606, Im getting about 2.5 volts no ptt, and 1.4 with ptt, both being quite unstable.  14.2 Mhz fm, max power setting. That results in about 350mW from PA and solid red alc.  Somewhere, the alc line is being pulled slightly lower than it should.  The hunt continues...

Thanks for all your good info about the 7K over the years.


Steve W3AHL

Looks like I can't upload a file to the Group, so here a copy & paste of some levels I took In 2012 at a slightly different component:

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

ve6ars Ross

Has anyone recorded the proper voltages under any condition at IC1601, particularly pins 8, 9 and 10. And the area of Q1604?

If so, thanks!