[TenTec] Triton IV 544 Digital

[Paul Christensen]

Mike,

Interesting.  If the 544 schematic is correct, the Display Board has no common +Vcc.  +Vcc is supplied individually to each 7-segment LED module via Q14-Q19 (PNP) on the Logic Board.  +Vcc on the Logic board is RF bypassed  with a 0.047uF cap at C6.   +Vcc on the Logic Board is also connected to IC-1 with ample decoupling, consisting of a 22 ohm resistor and a 0.1 uF cap at C7.  The 22 ohm resistor is mainly there to regulate current into a Zener diode that feeds +Vcc to IC-1 but it also functions to decouple.  

To me it looks like Ten Tec adequately decoupled one part of the Logic Board, but not the other going into the display board.   The only problem with duplicating R/C de-coupling on the +Vcc bus feeding Q14-Q19 is that any series resistance will make the display slightly dimmer -- and the green LED segments are already way too dim due to green-wavelength filtering through the smoked Plexiglass lens.  So, that leaves adding an additional RF bypass across C6 (0.047 uF). Possibly something like a 4.7 uF 'lytic cap in parallel with a 0.22 uF film bypass will do the trick.  

Paul, W9AC

-----Original Message-----
From: TenTec <tentec-bounces+w9ac=arrl.net at contesting.com> On Behalf Of Mike Bryce
Sent: Friday, February 26, 2021 10:47 AM
To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
Subject: Re: [TenTec] Triton IV 544 Digital

When you first hear it, you’d bet money that the calibrator is running. However, there isn’t one in the digital Triton 4. 
Decoupling the power supply will reduce the signal level to a point you won’t notice it with an antenna connected.

One of my Drake TR5s did the same thing. Its counter/display put a S-7 signal right on the MIDCARS freq of 7.258. Recaping the display pcb eliminated 94% of the problem


Mike, WB8VGE
SunLight Energy Systems
The Heathkit Shop
http://www.theheathkitshop.com/
J e e p
o|||||||o 

> On Feb 26, 2021, at 8:10 AM, Paul Christensen <w9ac at arrl.net> wrote:
> 
> Thanks, Mike.  I'll look into it.
> 
> Paul, W9AC
> 

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