Kaiser KA-9040 CB Radio Repair

Kaiser is a well known and very popular brand of CB radio sets manufactured in Germany. They were hugely popular in the 70's and 80's and it is great to see these old sets still alive today.

This little set had some very scratchy pots. Just a tiny touch on the volume control would wreak havoc with your ears. The old man also complained of low power output and the 7-Segment display was very intermittent. Parts of digits were not being displayed correctly. All pretty typical problems for this model and year of production.

The customer requested a full workover and alignment so it would work as new out of the box 50 years ago.

The first step was to crack the case open and begin with cleaning those scratchy Pots.

Now many of you may think that a whiff of contact cleaner is all you need. I would beg to disagree. In my experience Pots that are this old and require cleaning, need more that one go. I typically start with the first blast of cleaner, followed by a good mechanical back and forward working to get the cleaner into the spots needed. But then to let them dry out or blast them with compressed air and repeat the process several times.

In the bottom center of the picture above, you can see the rotary switch for the channel selector. This is notorious for bad intermittent contacts, leading to a partial 7-Segment display. The issue is indeed not with the display itself but with the rotary switch. I  required no less than 7 cleaning cycles to restore the display to normal. Yes - with drying out in between - a task than can spread over several days, depending on the amount of time you have available to spend on radios like these.

If you are considering doing this professionally, I can tell you that NO-ONE will pay for your time. It has to be a labor of love.

Once the 7-segment display was working again - best seen on channel 40, it was off to find the source of the low power output.

Now, many of you may be thinking that the finals are shot or a voltage regulator has given up its precious magic smoke, but the very first thing I do when I get a radio, is to try to reproduce the problem that the old man has reported. Quickly, I noticed the issue appears to be with the microphone PTT switch. A slight sideways depression on the mike key showed full power.

I cracked the mic open and cleaned the PTT switch. After a few goes, the radio was back to full power.

These radios were carefully crafted back in the day and a glimpse of the inside confirms the care and attention they gave to the wiring and layout of the PCB.

With a little bit of tender care and loving, this set is back to its original condition and one old man is very happy again.