[MRCA] T-195 Auto-NoTune

[aj1g at comcast.net]

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. 

----- Original Message -----

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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