[Boatanchors] A5 Board on URT/RF-110A
eugene at hertzmail.com
eugene at hertzmail.com
Wed Dec 26 22:10:50 EST 2007
Hello again.
Looking for anyone who has one of these amps. As I noted yesterday, Q8
on A5 seems to be defective. I noticed that someone (either a company
or individual) has made some modification to my board that I cannot find
in the two manuals I have (my navy manual is completely different so it
was not much help). The modification directly affects the Q8 transistor.
I ask because it is conceivable that this modification could have caused
the demise of the transistor.
The mod adds an extra diode to the output collector of Q8 and then
brings that output to an unused card edge location "Z". I have drawn the
mod onto the existing portion of the schematic and can be seen here:
http://www.hertzmail.com/urt-23/A5-ckt-mod.JPG
I have no idea where card edge position Z goes to for this mod. My
manuals indicate Z is unused. My concern is that if whatever lurks
beyond "Z" is a short, then I can see any new transistor in this spot
having a very short life!
If an individual made an odd-ball "improvement" then I would probably
consider reversing it, to get it back to Harris specs and perhaps avert
a new Q8 meeting the same fate due to a bad idea for a modification.
If Harris (or Stewart Warner-the mfg of my particular unit) made this
mod, then reversing it could be a bad idea as it could be necessary for
proper operation! It is virtually impossible for me to attempt to trace
"Z" to see where it goes.
If you are interested, here is a page from the manual indicating the
original layout of this card A5.
http://www.hertzmail.com/urt-23/a5-layout.pdf
The area of interest are the two diodes (CR7, CR35) directly above the
right-most key-way notch in the card edge.
Here is a photo of my card. I have placed a black arrow pointing to an
additional diode coming off the collector of Q8.
http://www.hertzmail.com/urt-23/a5-top-annotated.jpg
And here is a photo of the underside. In a white circle I indicate the
wire that connects the output of this diode to card edge position "Z".
http://www.hertzmail.com/urt-23/a5-bottom-annotated.jpg
Anyone have an A5 board they can look at to see if you have the same mod
or not?
Anyone have an idea if this is a factory sanctioned mod?
As always, thanks for the bandwidth
73 Eugene W2HX
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