[MRCA] T-195 Auto-NoTune

[grasshopper]

Mine will not even start with less than 28 volts.  The filament relay closes
but the low voltage dynamotor relay won't close.  

 

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From: MRCA [mailto:mrca-bounces at mailman.qth.net] On Behalf Of
aj1g at comcast.net
Sent: Wednesday, July 15, 2015 9:26 PM
To: WA5CAB at cs.com
Cc: MRCA MAILING LIST; ARC-5 List
Subject: Re: [MRCA] T-195 Auto-NoTune

 

i  am in total agreement with you Robert.  Not clear why the the auto-tune
system gets sluggish at normal supply voltages expected for a nominal 24 to
28 volt vehicle electrical system, I have in the past had trouble with slow
tuning if my DC  bus supply float batteries were a bit low on charge, after
a good recharge the set would always tune OK.  Maybe what Jeep and others
have observed with their sets working better at an elevated DC supp;y
voltage is akin to how the electromagnetic clutches on automobile air
conditioner compressors lose field strength over time and have to be shimmed
to close up clearances in order to get the clutches to engage.  Considering
how mine suddenly lost the auto-tune function with my DC supply voltage
exactly where it should be leads me to suspect  component failure (most
likely the discriminator diodes) or bad plug connector contact.

 

  _____  

From: WA5CAB at cs.com
To: aj1g at comcast.net
Sent: Wednesday, July 15, 2015 2:56:45 AM
Subject: Re: [MRCA] T-195 Auto-NoTune

 

I have owned several T-195(*)'s but have never even lit one off.  However,
if I had one that I wanted to work, I would fix the root problem instead of
trying to boil the batteries.  Anything over 28.0 volts will quickly destroy
the batteries.  Optimum for the batteries is about 27.6 volts.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 07/14/2015 23:09:26 PM Central Daylight Time,
aj1g at comcast.net writes: 




Just a quick follow up on the Auto No-tune issue:



To see if for some reason the deep cycle batteries were limiting the output
voltage being supplied by the PP-7333, I open circuited the batteries
leaving the PP7333 alone to carry the T-195 AFTER I had started the HV dyno
in the CW mode. (Only after I tried to start the big dyno without the
batteries and got the expected result, tripped the PP7333 output breaker and
shut down the transmitter).  After I started the HV dyno and open circuited
the battery, the DC voltage being supplied to the transmitter from the
PP7333 under full load while tuning was still only 26.7 volts, essentially
the same as with the batteries floated on the supply output.  And, not
surprisingly, if Jeep's observation holds true, the set did not auto-tune.
After turning off the transmitter, the no load output voltage of the power
supply did rise up to 28.1volts,so apparently, the voltage regulation is not
all that tight.  So it looks like the next step is to figure out how to bump
up the 7333 output voltage  by a couple of volts, at least while attempting
a tune cycle.










 

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