Spectra A9 control head HCN1073E dimmer not functioning

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miken8eqd
Posts: 18
Joined: Thu Dec 28, 2006 9:00 pm

Spectra A9 control head HCN1073E dimmer not functioning

Post by miken8eqd »

I have another conventional VHF A9 Spectra that the dimmer switch on the front panel doesn't function.

Head P/N is HCN1073E. Could not find anything in the software that would enable this function. What would be the procedure to enable this function?

Thanks
Mike
Jim202
Posts: 3609
Joined: Sun Sep 09, 2001 4:00 pm

Re: Spectra A9 control head HCN1073E dimmer not functioning

Post by Jim202 »

miken8eqd wrote:I have another conventional VHF A9 Spectra that the dimmer switch on the front panel doesn't function.

Head P/N is HCN1073E. Could not find anything in the software that would enable this function. What would be the procedure to enable this function?

Thanks
Mike


I could be wrong, but to my knowledge, there is no software setting to enable or disable the dim button function. Every head I have and that is a bunch of different model numbers, they all work. If yours doesn't work, I would first look for leaky caps causing circuit board damage.

If you don't find any, then get out the scope and start looking on the circuit board for the problem. It could be as simple as the button conductor pad is dirty.

Jim
miken8eqd
Posts: 18
Joined: Thu Dec 28, 2006 9:00 pm

Re: Spectra A9 control head HCN1073E dimmer not functioning

Post by miken8eqd »

ok. thanks for the information.

hmm.. leaky caps... oh fun lol!

mike
Jim202
Posts: 3609
Joined: Sun Sep 09, 2001 4:00 pm

Re: Spectra A9 control head HCN1073E dimmer not functioning

Post by Jim202 »

Motorola chose a number of years back to use some low cost electrolytic capacitors. These are surface mount type with round aluminum looking cans on top. The size will vary depending on the amount of filtering the circuit required. The radio has a number of them installed, but the control head has like 3 or 4 if I remember correctly.

Over time, the internal goop they used will start to leak out. It most of the time looks like a clear oil or grease stain on the circuit board. The goop is very corrosive and can eat the circuit traces on the board. Most of the time with the control heads, the problem shows up as one position on the display will stop working.

In the radio, the most common problem is a pop sound in the audio or distorted audio. Then it moves on to low audio and eventually, no sound coming from the speaker. There are 3 or 4 caps on the control board in the radio that are the cause of these problems.

I think there are 3 caps on the RF board that will cause problems with time. Generally they cause a problem with the VCO not wanting to work correctly.

The Spectra radios are a fine radio for ham use. Just because you run into some bad caps inside them is no reason to shy away from them or consider junking the radio. Some time on the work bench with a soldering iron, some Q tips and some baking soda paste will resolve the issue. New caps are available from a number of sources.

There are some tips on different web sites on the actual repair and replacement of these caps.

Have fun fixing your radio and control head. The experience will add to your skills.

Jim
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