[Drake] TR-7 : Display problem Only

[Don Buska]

Hi Joe,

I think you may be aging the TR7 a little bit to far back, hi.  From my 
service manual the three IC logic families used are TTL (74*** series), 
CMOS (14*** series) and ECL (10K Series).  I think RTL and DTL stuff was 
pretty much gone in designs by the early 70's.  I remember some of the 
early ham radio electronic keyers in QST from the late 60's used RTL 
stuff.  I think most of that came from Fairchild and used three digit 
part numbers beginning with a 9.  Most of those were in round packages, 
like transistors on steroids.  Thankfully the TR7 was even designed 
after the earlier 4000 series CMOS stuff which was very sensitive to 
static damage vs the later 14K series.  The ECL devices probably would 
be the hot running stuff as they were designed for speed, albeit at only 
a 1V differential low-high logic swing.

For Bill:  I notice on the schematic the display has a dedicated 7805 5V 
regulator identified as U9034.  All the regulators for the DR7 board are 
mounted on the chassis walls for heat sinking and connected to the board 
via a three wire cable and jack/plug combination.  You mentioned that 
connections appear fine so perhaps the regulator is shutting down.  A 
7805 is a cheap replacement.  You might want to feel it for warmth after 
it's on for a bit.  Perhaps it was removed in the past and it doesn't 
have enough heatsink grease between the body of the regulator and the 
chassis.  It should be simple to connect a DVM to the output of this 
regulator and just monitor the 5VDC.  If the display goes out does the 
5VDC disappear too?

73

Don N9OO


Joel Richey wrote:
> I have a late tr-7 (3 piece back panel) and I found over the years that most if not all problems could be solved by removing the boards and cleaning the connectors and reseating em, the TR-7 uses what is called RTL logic andthe DR-7 board runs a little warm, anyways try reseqting all connectors and good luck..
>
> Joe W2DBO
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