[R-390] 3TF7 replacement...newbie on first 390a

[R. David Eagle]

Ed,
This is interesting.  I wonder how long the solid state version would last since heat is always a concern. But there is no doubt that the 3tf7 would a more rugged option. I saw that someone on ebay is selling a plug in module that is a solid state replacemnt...I wonder how they perform....?
Thankfully, there are options and its a choice of picking your right medicine!
DaveKB8NNU 


 
 
  On Fri, Apr 8, 2016 at 10:21 AM, djed1 at aol.com<djed1 at aol.com> wrote:    I've been using a resistor in my R-390A for 30 years with no discernible effect on stability (replacement tubes were hard to find back then).  I've got a couple of spare 3TF7s, but have found no need to use them.  So I was interested to see Electric Radio publish an article in their Feb 2016 issue which quantified the benefit of filament regulation. The author, DH3PJ, tested the stability of the radio using a resistor, 3TF7 and a solid state regulator. Under a 8.5% change in line voltage, the frequency shift was 27 Hz for the resistor, 11 Hz for the 3TF7, and 2 Hz for the solid state.  So if you're listening to SSB, it probably doesn't matter.  If you're going for the ultimate in long term stability for digital modes, then the solid state is 5 times better than the 3TF7.  Since I use the radio for casual SSB and AM reception, I'm sticking with my resistor.

Ed W2EMN 
 
 
-----Original Message-----
From: R. David Eagle via R-390 <r-390 at mailman.qth.net>
To: Larry H <dinlarh at att.net>; 390 List <r-390 at mailman.qth.net>
Sent: Thu, Apr 7, 2016 11:49 pm
Subject: Re: [R-390] VU Meter Issue...newbie on first 390a

Larry,I appreciate the offer....I am going to see what I have laying around.  I guess this begs the question of whether a solid state replacement is worth it or should I stick to the original regulator.  This may open up the doors for a lengthy debate, BUT I am learning a lot from this rig and I can't wait for the day to finally slide it in the case on the desk!DaveKB8NNU  From: Larry H <dinlarh at att.net> To: R. David Eagle <kb8nnu at yahoo.com>; 390 List <r-390 at mailman.qth.net> Sent: Thursday, April 7, 2016 11:28 PM Subject: Re: [R-390] VU Meter Issue...newbie on first 390a Hi David, Bumberrrrrrr!  That's not good.  I hope the 2 oscillator tubes are ok.   I've had similar luck in the past, too.  When I'm tinkering with these guys I like to put a 12bh7 or 12BY7 or similar tube in the regulator socket with the 2 wire change on the socket.  Then when I'm done, I put whatever I want back in the socket.  There's a whole bunch of tubes that have the right current for this purpose.  If you don't have 1, I will send 1 to you.Regards, Larry From: R. David Eagle <kb8nnu at yahoo.com> To: Larry H <dinlarh at att.net>; 390 List <r-390 at mailman.qth.net> Sent: Thursday, April 7, 2016 8:11 PM Subject: Re: [R-390] VU Meter Issue...newbie on first 390a Larry,Thanks for the tip...I was going through these checks tonight as you suggested and a freak think happened to my upgraded sigma 3TF7 regulator replacement....it shot blue arcs across the top of the IERC shield to the top of the regulator....game over.  Back to tracking down more parts....I will recheck V604 and V602 with the tv7 and see how they check out.DaveKB8NNU From: Larry H <dinlarh at att.net> To: 390 List <r-390 at mailman.qth.net> Sent: Thursday, April 7, 2016 12:12 AM Subject: Re: [R-390] VU Meter Issue...newbie on first 390a Hi David,  Congratulations!  Welcome to the group.For the VU mtr - have you checked the jumper on tb103 11 to 12?  If yes, do you get audio on 10 and 13?  If no, replace V604 and then  V602.  If yes, check for audio on the VU mtr terms.  No need to disconnect it.As for cleaning the inside of our mtrs - some are easy to open and some are NOT.  Just be careful with any possible dust from the inside - you don't want to breath it.  A simple nose and mouth filter should be good, if concerned.  If you're careful, you should not need one.Good luck.Regards, Larry      From: R. David Eagle via R-390 <r-390 at mailman.qth.net> To: 390 List <r-390 at mailman.qth.net> Sent: Wednesday, April 6, 2016 7:22 PM Subject: [R-390] VU Meter Issue...newbie on first 390a  Hello all...Today was my first day of powering up my very first motorola 390a that I have been slowly working on over the last year.  I went through and checked all tubes with my tv7 and found a couple that needed to be replaced.  Today was the day that the speaker finally got hooked up and the rig warmed up.  Much to my surprise, I was copying cw on 40 after a few gleaming moments.One thing I noticed though, was my VU meter was not working what so ever and I have searched around for common fixes/problems but haven't turned anything up.  Is there any common problems to look for outside of replacing the meter?Also...I noticed that the carrier meter has a film on the inside of it that is almost brown.  I am somewhat reluctant to pull it apart due to the whole radioactive particle scare, but are these easy to disassemble and clean?Thanks in advance,DaveKB8NNU______________________________________________________________R-390 mailing listHome: http://mailman.qth.net/mailman/listinfo/r-390Help: http://mailman.qth.net/mmfaq.htmPost: mailto:R-390 at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.html  ______________________________________________________________R-390 mailing listHome: http://mailman.qth.net/mailman/listinfo/r-390Help: http://mailman.qth.net/mmfaq.htmPost: mailto:R-390 at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.html ______________________________________________________________R-390 mailing listHome: http://mailman.qth.net/mailman/listinfo/r-390Help: http://mailman.qth.net/mmfaq.htmPost: mailto:R-390 at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.html