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  #1  
Old 06-21-2014, 04:19 PM
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Schanz Schanz is offline
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Help with transformer schematic

Working on an airline 62-177. Someone has done some work prior to me and cut some wires so it's made it a little harder for me cause I'm not that good at reading schematics yet. The issue I'm having is that there are two extra leads coming from the power transformer that I don't think I need. The schematic shows 7 lines coming out and I have traced all 7 to the rectifier or power output but there are two extra that are taped off. Is it possible this radio used a trans that had extra leads? I've studied the attached section and the only thing I'm unsure of are the leads marked "a".
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Old 06-21-2014, 05:42 PM
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The leads marked A are supposed to connect to all of the tube's heaters (except , of course , the filaments of the #80 rectifier , which has it's own tap off of the transformer)
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Old 06-21-2014, 10:32 PM
old_coot88 old_coot88 is offline
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The tubes' heaters are in parallel, BTW (not series).
Can't imagine why those leads would be taped off.
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Old 06-21-2014, 10:54 PM
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Got plenty of time on the bench tonight and replaced the caps. Couldn't resist plugging it in momentarily. Tubes lit and I actually tuned in a couple stations before quickly turning it back of. My eyes literally burn from tracing that schematic but I think I finally figured it out. The hardest part was locating the caps someone had already cut loose. I guess I must have done it right if it works?
BTW, there was some wax that appears to have run out of the transformer some time ago. Is it near toast?

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Old 06-22-2014, 12:02 PM
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Is the transformer the original unit to the set? If it is a replacement the taped-off leads are probably center taps on the filament windings that are not needed on this set.
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Old 06-22-2014, 12:44 PM
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Transformer certainly looks vintage but it could be a replacement. I think someone replaced some caps many years ago so it's possible. Radio works, all tubes light and she plays so maybe we're good.

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  #7  
Old 07-02-2014, 10:23 PM
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This is definitely a replacement transformer. My rectifier had burned out on me so I tested the voltage at the pins. 323 v at the rectifier ok? The schematic doesn't say. It lists the voltages for the other tubes. The heater voltage is correct though.

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Old 07-03-2014, 06:31 PM
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Quote:
Originally Posted by Schanz View Post
This is definitely a replacement transformer. My rectifier had burned out on me so I tested the voltage at the pins. 323 v at the rectifier ok? The schematic doesn't say. It lists the voltages for the other tubes. The heater voltage is correct though.

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The DC voltage at the positive side of C25 is what counts.
300 VAC from the transformer to the #80 IIRC is right.
Will give you 300 VDC full wave before filtering.

Most old power transformers are color coded. This link will
give you what you need and then some........
http://www.radioremembered.org/xfmr.htm

73 Zeno
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Old 07-03-2014, 07:53 PM
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That's good news, thanks. When I get a new rectifier in it I can test the other voltages.

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Old 07-06-2014, 01:46 PM
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Well, new rectifier doesn't light either. Time to lift a leg on all the old resistors and double check everything.

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Old 07-06-2014, 05:38 PM
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Quote:
Originally Posted by Schanz View Post
Well, new rectifier doesn't light either. Time to lift a leg on all the old resistors and double check everything.

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only reasons for the 80 not to light:

1) bad tube
2) bad tube socket
3) pwr transformer, no 5VAC on yellow wires to the 80
4) somethins wired wrong.

73 Zeno
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Old 07-06-2014, 08:59 PM
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Ok. Hard to tell what colors these wires are any longer. There are heavy "white" ones and heavy "black" ones and some thin red ones. I've been on the road all day, I'll have to check them later.

If it is the transformer, how do I spec it and where do I get a replacement?

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Last edited by Schanz; 07-06-2014 at 09:30 PM.
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