From: Garey Barrell 
Subject: Re: [drakelist] AC-4 rebuild ???


Garey Barrell  made an utterence to the drakelist gang
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Keith -

Your supply is probably just fine..   I have several supplies that are 
considerably older than yours that still work as new.  There are too 
many variables, time in service, storage in humid or dry conditions, 
electrical and/or physical abuse, etc. to make a definitive statement.

That being said, there are a few things you can do to protect your 
supply.   First, and most important, be certain that the AC fuse is the 
correct size.   More than a few power transformers have been fried 
because someone put in a 10A fuse or in at least one case I have seen, a 
piece of #10 copper wire!!

The most critical circuit in the supply is the bias supply.  If this 
supply (-40 to -90V or so) fails, it can kill a transmitter faster than 
anything else, and it probably won't even blow the fuse.  A good interim 
step is to replace the filter capacitor and diode for this supply.  I'd 
also examine the two resistors visually and measure them with an ohmmeter.

Beyond that, replacing the diodes and caps for the two voltage doubler 
supplies and checking the resistors will make it good for another 30 
years.   For these, a shorted diode or shorted filter capacitor will 
blow the primary fuse pretty quickly.  A dried out filter cap on the LV 
supply will introduce noticeable hum long before it fails catastrophically.

The AC-4R kit looks like a good alternative to the difficult to find 
Twist-Lok capacitors, and certainly makes a neat installation.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
http://hr99.home.mindspring.com/R-4C_Servicez/>



Keith Hamilton wrote:

>"Keith Hamilton"  made an utterence to
the drakelist gang
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>I have read about the AC-4R rebuild kit from the Heathkit Shop. This seems
>like an excellent kit but it brings a question to my mind. I have begun to
>be a bit paranoid about my current power supply!
>
>Has anyone used this kit to rebuild their AC-4?  Should I worry about my
>AC-4 quitting on me? It seems to be working just fine but like I say this
>kit has made me a bit paranoid about my supply!  Should I rebuild it or wait
>until it quits? What criteria does one use to say when you should rebuild?
>My AC-4 has a relatively high serial number # 51464
>
>Thanks for letting me ramble on for a bit!
>
>73!     Keith Hamilton, W8GX
>  
>
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