[TenTec] Triton IV 544 Digital
n4py3 at earthlink.net
Fri Feb 26 20:43:11 EST 2021
You have to remove the antenna to hear the pulse at 14.0
Carl Moreschi N4PY
127 River Moss Way
Hertford, NC 27944
On 2/26/2021 7:55 PM, Winston wrote:
> After reading these posts, checked my 544. No such pulses anywhere. If they only appeared at 14.0, I wouldn’t care. I never operate on band edges.
> -de K4CWQ
> Sent from my iPhone
>> On Feb 26, 2021, at 7:03 PM, Bob McGraw<rmcgraw at blomand.net> wrote:
>> It is not at all unusual for electrolytic capacitors to decrease in value as they age. Thus an original 10mfd, after a few, years may effectively be a 1mfd capacitor. Although I don't care for the "shotgun" approach, this usually saves time and money.
>> Keeps life simple and less frustrating.
>> Bob, K4TAX
>>> On 2/26/2021 10:33 AM, Mike Bryce wrote:
>>> I’ve never done a shotgun approach when it comes to replacing electrolytic capacitors, but in the case of this particular display unit, that was alway the first thing I did.
>>> Then, and it’s been years ago, some smaller electrolytic caps (1mf) and .001 disc took care of it. Nothing I did eliminated it 100%
>>> Mike Bryce
>>> prosolar at sssnet.com
>>> "The eye is always caught by the light, but shadows have more to say"
>>>>> On Feb 26, 2021, at 11:20 AM, Paul Christensen<w9ac at arrl.net> wrote:
>>>> 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.
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