Paul,
The problem is the 8.5 volt regulator needs about 3 to 4 volts above
8.5 to stay regulated. When the main supply voltage drops below 12.5
this regulator drops out of regulation. It is very important for the main
supply voltage to stay above 12.5 volts.
Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: "MW0CDO" <gw7lhi@hotmail.com>
To: "Ten-Tec List" <tentec@contesting.com>; <VE1BN@aol.com>
Sent: Saturday, March 30, 2002 10:04 AM
Subject: Re: [TenTec] RE: Omni V Fm'ing
> Thanks for the info Don.
>
> Yes, I've double checked, and none of the oscillators I can find on the
> schematic are powered directly by the incoming +Vcc, all are powered from
> REG+ 8.5v or 5v in the PLL compartment. Which ones in the OMNI VI+ are
> powered directly from +Vcc? I'd have thought this wouldn't be good
practice,
> running an oscillator from the main power bus that is likely to fluctuate?
>
> I will replace the screws that are missing, as you say this may be the
> answer since TT use the mounting points as earth routes as well. I had to
> isolate the sidetone board from the chassis, as I was getting a lot of
> talkthrough on the internal speaker and the headphones. This cured the
> problem completely.
>
> I did buy the radio used, one previous owner. It was deaf on RX, due to a
> faulty external RX ANT switch. He's a good friend of mine, and did mention
> that he had sent the radio off a couple of times for repair. It was cheap
> tho'! :-)
>
> I'm still waiting for the agc hiss modifications from TT by mail.
>
> Once I have these 2 problems solved, the next step is one of Carl N4PY's
v.9
> microprocessor replacements. I'm looking for a source of the processor
> MC68HC705C8ACP here in the UK, otherwise I'll have to order from Newark
> Electronics.
>
> Thanks for your input!
>
> Paul MW0CDO.. another glorious sunny morning here.
>
> ----- Original Message -----
> From: <VE1BN@aol.com>
> To: <gw7lhi@hotmail.com>
> Sent: Saturday, March 30, 2002 12:46 AM
> Subject: Re: [TenTec] RE: Omni V Fm'ing
>
>
> > Hello Paul -
> >
> > Thanks for the reply.
> >
> > Must admit I am still curious about a regulator for +8.5 volts. Don't
> recall
> > ever seeing one. If your schematic says that, then guess I will have to
> > accept it (ha).
> >
> > About the missing screws, yes they should definitely be replaced. Two
> sheet
> > metal types hold the TX audio/BFO board mounting bracket to the back
> panel.
> > Better grounding and mechanical stability when you replace these! May
be
> the
> > fix you are looking for? Ten-tec boards usually ground through mounting
> > screws to complete short earth paths.
> >
> > Odd they are missing, but then I seem to remember you saying something
> about
> > getting your OMNI from a previous owner.
> >
> > My OMNI is a 6+, not a 5. The screws to be replaced on yours are in the
> same
> > location.
> >
> > Hope this helps. Good luck, Paul.
> >
> > 73 - Don
> >
> >
> >
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