Posts: 34
Threads: 13
Joined: Feb 2013
City: Columbia, MD
Hey gang,
Ive been playing with a new Transitone 52-541 code 122. So far, new linecord, recap, some resistors, it plays really nice, but
I have a few questions....
how bright is the pilot lamp supposed to be?
mine is no brighter than a tube filament. socket voltage measures 11v and drops to two once the bulb is inserted. I tried a new 35Z5 tube, no change.
Do i have the correct schematic?
The schematic doesnt show this, but my radio has a series resistor between the 12BA6 and the 7A8, in the filament string, 1,365 ohms, and after playing for half an hour or so it measures 265 degrees F, is that OK? its all the way at the bottom of the photo.
also, the 35L6 tube in the radio, is shown as a 50L6 in the schematic.
[Image:
http://i818.photobucket.com/albums/zz105...4404c8.gif]
[Image:
http://i818.photobucket.com/albums/zz105...2ab9b0.jpg]
(This post was last modified: 04-02-2013, 06:25 PM by
conroyp.)
Posts: 1,106
Threads: 88
Joined: Jun 2011
City: Tacoma
State, Province, Country: Washington
First, that resistor (I assume you are talking about the one at the bottom of the pic) does not belong there. Someone probably put it there to try to allow for the use of the 35C5. I would bypass it and use the original tube. This, if you are using the proper dial lamp (a 47 or 1847), will fix your problems.
Posts: 34
Threads: 13
Joined: Feb 2013
City: Columbia, MD
thats what I thought about the 50L6, but the factory sticker on the bottom of the bakelite case shows a 35L6 not the 50. The wiring is identical to the rest in there, and the terninal strip is riveted to the chassis, You think its a factory switch?
Plus....I saw one of these same sets on ebay a few months ago.... with that exact same resistor.
Bulb is fixed, a new 47 took care of it.
(This post was last modified: 04-02-2013, 08:03 PM by
conroyp.)
Posts: 1,106
Threads: 88
Joined: Jun 2011
City: Tacoma
State, Province, Country: Washington
I suspect it was a mid-run change and there were a lot of spare 35L6 tubes that they wanted to use up. Since the 50L6 and 35L6 are both 150mA heaters, they can be interchanged if the inline resistance is added/removed. If that resistor is getting to 265 degrees F, it's woefully underrated (and has probably gone up quite a bit in value). Again, if you have a 50L6 handy, I suggest bypassing that resistor and using the 50L6. If not, I would at least replace that resistor with a good wirewound rather than that '20's type dogbone.
An appropriate replacement should be a 100 ohm 5 watt wirewound resistor. This would drop 15 volts at 150mA and should run a lot cooler since actual power would be 2.25W.
Posts: 1,113
Threads: 14
Joined: Feb 2013
City: Irvington, NY
It looks as if that dogbone style resistor might be a Globar type thermistor. It is designed to run hot and decrease in resistance as in warms up (negative temperature coefficient thermistor). It is probably there to reduce the current surge in the heater string when first turned on. Typically in a series heater string one heater will heat faster than the other and overheat until the rest catch up. The Globar resistor current limits the current until all heaters are up to temperature and then allows full voltage across them. Unless it is obviously bad, I would leave it as is, as it seems to be working properly if the tubes have the proper heater voltages when fully warmed up.
(This post was last modified: 04-02-2013, 10:40 PM by
Mondial.)
Posts: 73
Threads: 11
Joined: Feb 2012
Odd grouping of tubes in this radio, usually a set will have
35Z5-50L6-12SA7-12SK7-12SQ7
or newer
35W4-50C5-12AV6-12BA6-12BE6
7A8 seems a throwback to another era
Posts: 34
Threads: 13
Joined: Feb 2013
City: Columbia, MD
It figures, i get the odd step child.... Mondial, i think you are right, that resistor drops to 158ohms when its up and running, im going to leave it alone for now.
