Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Apr Fri 19, 2019 11:20 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 3 posts ] 
Author Message
 Post subject: Jackson 648 meter sensitivity adjustment
PostPosted: Jun Wed 25, 2003 3:48 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 659
Location: BENWOOD,WV
Is there any way to make sure the wirewound adjuster in the Jackson 648 that is in the circuit with the plate pot is properly adjusted? This 648 is the one with maroon knobs that came in the green covered cabinet-later 1950's.<P>------------------<BR>


Top
 Profile  
 
 Post subject: Jackson 648 meter sensitivity adjustment
PostPosted: Jun Thu 26, 2003 7:12 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 446
Location: Winnipeg, Manitoba, CANADA
Sounds like my 648A. I have had that tester forever, and still learn something about it every other month. I still haven't figured what the 1S5 does (I have a hunch, though), and I do not know what the 'other' WW pot does. I see two under the panel of my 648A, and I haven't touched them in twenty years. Good luck following the schematic. <BR>If anyone else ends up telling you, I want to watch this spot closely. I never did seem to be worried about it, but now you have me thinking; maybe it can be a little more accurate. Hmmm.<P>------------------<BR>


Top
 Profile  
 
 Post subject: Jackson 648 meter sensitivity adjustment
PostPosted: Jun Thu 26, 2003 2:17 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 2846
Location: Warwick,RI
In basic emission testers(as opposed to mutual conductance jobs)two pots...one to calibrate the line adjust control on the front panel and another to set the distance the meter needle travels into the "good" area<BR>while testing a tube for emission seems to be a standard feature,pretty much.<BR>As often pointed out by Chris,the line adjust calibrate pot needs to be correctly set *first* or <BR> the other setting won't mean much.<BR>You should be able to set the line adjust calibrate pot by connecting an AC voltmeter across the transformer secondary(one of the high voltage windings) and setting it so that that particular winding is on the nose voltage wise *simultaneously*with the line adjust on the front panel having brought the needle to the line adjust mark.<BR>I am not a first class expert on tube tester repairs;this is just general information.<BR>Malcolm<P>------------------<BR>


Top
 Profile  
 
Post New Topic Post Reply  [ 3 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Radiosmoker, wyoblacks and 5 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB