Spectra

There is quite a bit of information on several excellent web sites. Batlabs, Repeater-Builder and open.org are a few. With their good information, I don't want to rehash everything but hopefully my experience may add to the big picture about this particular radio.

This radio works great but upon opening the case to check for the inevitable 'time-bomb' capacitors, I found out that in fact my radio had suffered an attack. The good news was it was isolated to the RF board but 4 out of the 5 capacitors had leaked and caused minor damage. If you weren't aware of what you were looking for, this minor damage could have easily turned into major damage.

Before

This is the picture when I first opened the case. As you can see, the damage could easily be missed as the color blends in with the rest of the circuit board. The acid from the leaking capacitors leaks under the trace lacquer and begins to corrode the copper. You'll need to scrape the loose lacquer off the copper in order to remove the corrosion as best you can. Notice also that the acid can follow the trace far away from the source. In this case it seeped under the large yellow capacitor at the bottom of the picture. The lacquer can be removed by scraping. A blunt dental tool is what I used.

In this picture, the lacquer has been scraped off of the corroded copper. I was lucky that only in a few areas did the acid actually etch very deeply into the trace. Most was just severely tarnished with slight etching.

The easiest way to remove the old capacitors is just with a pair of needle nose pliers. They are very soft and it takes little effort to rock them back and forth and pull them off their leads.  It's a lot easier than prying and there is less chance of slipping and causing more damage. Then, I used a small pair of tweezers to just bend the leads a few times and they fell off. Remove the base and see what's beneath. In this case, nasty corrosion.  There will be a small piece of the lead on the pad but it is removed easily. Some isopropyl alcohol and a little baking soda seemed to do a fair job on the corrosion. The traces did need to be scraped to clean them up.

This is what it looks like cleaned up. I even tried to tin the corroded trace with solder and although it could be done, I didn't want to risk damage to the trace by using excessive heat. It does need to get fairly hot to clean and get the solder to stick.

The other end of the RF board had the same problem.

Cleaned up. There is probably some corrosion under the filter but I wasn't going to remove it.

Mouser part numbers as ordered are...

80-T498D106K050ATE1K0 - $2.93@ (4)
80-T495D476K020ATE175 - $1.40@ (1)
80-T498B106K016ATE2K8 - $0.47@ (7)
as of 4 Sept, 2007.

Your particular configuration may require a different number of parts.

Installation of the 10/16 capacitors was not too difficult as they fit the pads well. Except for a few tight areas where it was difficult to get the soldering iron tip in the right position, they didn't cause much problem.

The 47/20 (yellow in the following picture) also fit the pads well.

The problem was the 10/50's that are a bit too long to be able to flow solder from the end of the capacitor down to the pad. By prewarming the pad and then heating the end of the capacitor lead, you can melt the solder under the capacitor and get a good connection.

(Command Board)

(PA)

The only real difficulty so far was not ordering the correct number of capacitors. Although I intended to order enough to recap 3 radios, I had written down my little matrix incorrectly and now have more parts on the way!

 UPDATE 10-31-07
After I had recapped a high-power Spectra, I started experiencing some audio problems. The audio level would go low and turning the radio on and off would seem to make it ok for a while. It finally got worse and going through a long sweeping curve at about 60 mph the audio level started to ramp back up until it was back full volume again at the end of the curve. A good indicator it was a loose connection somewhere.

I started with the speaker and wiring but came up short. I put the radio on the bench and started poking around to see if one of the caps was loose and when pressing on a cap near the area of the audio amp I could get the audio to go up and down.

After a little magnifying glass work, the problem turned out to be a bad solder joint on one of the pins on the audio amp IC. My working on the caps must have made the final break in the solder and let to a moving connection. You could actually see around the pin through the hole in the circuit board. Actually, several of the pins looked like they were poorly soldered. Solder applied. Problem solved.

(page last updated on Wednesday November 07, 2007)