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Hi,
If its the CPU itself generating the Hi-Lo tone irrespective
of the synthesizer OOL state then It would appear that the CPU may have
a permanent 'on' signal on the CPU input pin which monitors for OOL..

Have you checked for this condition?

If this condition exists, then work backwards from the cpu until the
'on' signal disappears. It could be that a transistor or i.c. switch may
be s/c and need replacing.

Wal. G4CGF

------ Original Message ------
From: "Peter Gottlieb hpnpilot@... [Racal-manpacks]"

To: Racal-manpacks@...
Sent: Tuesday, 17 Sep, 2019 At 02:51
Subject: Re: [Racal-manpacks] Question on Syncal 2000 - Chapter 2

I was finally able to get the radio to the bench.

The hi-lo tone is always in the background low on receive, and loud
during tune
and PTT.? According to the manual this is indeed the synthesizer out of
lock.

I tested with heat and cold but it is now quite solidly on and
insensitive to
temperature.? I guess that's helpful.

On the synthesizer board there are two out of lock (OOL) indications,
OOL1 and
OOL2.? Each goes to an I/O expander on the SPI bus.? They also are both
or'ed
from a different point in the circuit to disable the transmitter.

The transmitter is not disabled, indicating the there is no OOL
condition.
Both OOL signals show false at the I/O expander chip.
All self tests pass, and the manual states that self test checks for an
OOL
condition.
Receive seems ok and transmit puts out a good modulated signal.

I am thinking that:

1)? Transmitter enabled, receive and transmit good, and both OOL signals
false
indicate there is no synthesizer unlock condition present,
2)? Since self-test isn't seeing this problem, the I/O expander is good
and the
control processor isn't seeing this fault.

That leads me to the tone generation circuits as a possible problem,
falsely
indicating a fault when there is none.

Further analysis in that direction will be for Chapter 3.

Peter
KB2VTL

On 8/30/2019 8:50 AM, M0ORE m0ore@... [Racal-manpacks] wrote:
>
> Did you check the supply voltage at source i.e. battery terminals or
> actually at rig. Might be a significant voltage drop due to leads not
> thick enough or a poor connection.
>
> On 30/08/2019 13:24, Scott Dorsey kludge@... [Racal-manpacks]
> wrote:
>>
>> Synthesizer is out of lock. Look for bad decoupling capacitors which
>> might
>> be fine in an air conditioned shop but will go out of spec in the hot
>> sun.
>> --scott
>>
>

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