[ARC5] RAK-7 caps - newest radio adventure

[Kenneth G. Gordon]

On 24 Aug 2015 at 9:34, Bill Cromwell wrote:

> Somewhere over the years I acquired some bad info about the caps in the 
> RAK/RAL radios.

You may have gotten some of that from me, Bill.

> I have a RAK-7. I have the BAMA manual for a RAK-5. It 
> was my understanding that the RAK/RAL used no paper caps and the caps 
> should never be a problem.

Well, I didn't say THAT, exactly: what I said was that all of the caps, except 
those between stages, are oil-filled and very seldom give trouble.

> Wrong! I took a closer look at the manual 
> because the performance of my RAK has deteriorated so badly. There are 
> 29 paper and oil caps in the beast and it's power supply. They are 
> around about 60 to 70 years old!!! I'm just happy I didn't let the smoke 
> out!

Well, I have never had one of those oil-filled jobs short out, or even go 
leaky...yet.

> Maintenance and TLC start with replacing those caps and checking all the 
> mica caps.

I strongly suggest you test the oil-filled caps before "shot-gun" replacing 
them. I think you will find that most, or even all, are just fine.

The mica caps (if they really ARE micas) are, routinely, leaky. As I said, you 
can tell this by listening to the receiver without an antenna connected. If you 
hear "static" one or all of those are bad. I have found so many of those bad 
over the years that I routinely replace them now.

> That will be followed by checking all of the resistors for 
> out-of-spec.

THOSE are far more likely to be out of spec than the oil-filled caps, Bill. FAR 
MORE likely.

Good luck.

Oh: BTW, the only real differences between the RAK-5 and the later models 
is the antenna input setup.

Ken W7EKB