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 Post subject: Transformer Replacement for RCA Model 119
PostPosted: Sep Mon 20, 2021 8:12 pm 
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Joined: Feb Thu 18, 2021 3:09 pm
Posts: 118
Can anyone tell me what transformer can replace this model? It was working fine one day, I went to add in an rca jack into the circuitry which I've done on many sets and now no power is coming from the transformer. I undid what I did to add the rca jack and still no power or pilot light. No filament voltage either on any tube. I measured 120v going into the transformer but nothing at all coming out. Is it shorted? I'm at a loss.


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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Tue 21, 2021 1:44 am 
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Location: Mt. Rest, SC, USA
I can't see how adding an audio input could damage a transformer. I presume the radio has been fully recapped and was working ok before?

Verify you don't have a short from B+ to ground anywhere. For example, a short in the metal-housed resistor R18-R20 or from the field to ground. Also check the continuity of the primary of the power transformer. Hopefully there is just a bad connection somewhere and the transformer isn't really burned out.

A suitable replacement transformer would be AES part P-T273DX https://www.tubesandmore.com/products/transformer-hammond-high-voltage-plate-filament-vertical-mount or P-T273DZ https://www.tubesandmore.com/products/transformer-hammond-high-voltage-plate-filament-horizontal-mount. The transformers are identical except for mounting orientation.
(Ratings 5V@2A, 700VCT@103mA, 6.3V@3A)

If the transformer is open circuit then you need to find the fault before installing a new transformer as transformers virtually never fail unless shorted.

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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Tue 21, 2021 3:09 pm 
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Joined: Feb Thu 18, 2021 3:09 pm
Posts: 118
Thanks so much! The radio was working perfectly before and had been restored. Maybe the vibration of the drill to make holes for the rca input and toggle switch rattled a component loose? I don't see anything loose though. I'm going to check to make sure there's not a short from B+ to ground. I'll check the metal strip resistor because those are always suspect to going bad. Would a short from b+ to ground cause no filament voltage?

I would check the transformer for open circuits before I order a replacement


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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Tue 21, 2021 7:59 pm 
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Joined: Jan Mon 16, 2012 4:15 pm
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Location: Near Brandon, Iowa
Probably not a short. That would be accompanied by drama (sizzling noises, smoke, noxious odors, melted tar, possibly even fire). More likely you have an open between the power cord and the transformer primary winding: could be a broken wire or bad power switch. Worst case, the transformer primary has burned open.

Unplug the set and place an ohmmeter across the AC plug blades. Set the radio power switch to the "on" position. If the meter reads infinite ohms, you have an open connection between the power plug and the transformer primary.

With the set still unplugged, move the ohmmeter probes such that they are right across the power transformer primary leads. If the reading is still infinite, your power transformer primary winding is probably burned open. If the reading is a few ohms (10-15 or less) at the transformer primary leads then you have a broken AC wire or bad power switch.


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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Tue 21, 2021 10:05 pm 
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Joined: Feb Thu 18, 2021 3:09 pm
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The primary leads have resistance so that is a good sign. I also measured the leads going to the 80 rectifier tube on the secondary side and that has resistance as well. I am beginning to think the power pot is bad. It has resistance on the leads but none on the back of the pot. I'm not sure if the leads on the back are supposed to have resistance though.


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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Tue 21, 2021 11:27 pm 
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If you can measure a relatively low resistance thru the primary of the transformer than it is ok. I guessing you mean the power switch reads ∞ open-circuit?

Try spraying some contact cleaner into the power switch and operate it a couple of times.

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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Fri 24, 2021 12:42 am 
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Joined: Feb Thu 18, 2021 3:09 pm
Posts: 118
I tried contact cleaner and the volume pot isn’t doing anything still. Are the leads on the back supposed to have continuity between them or no? They have infinity resistance too when I connect them to the other leads of the pot


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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Fri 24, 2021 1:21 am 
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That is definitely a switch. It should read open in one position, and a short, low ohms, in the other. if not, it’s bad. You can sometimes take the switch off the control and clean/fix it.

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People may not remember how fast you did a job, but they will remember how well you did it.


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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Fri 24, 2021 1:23 am 
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I forgot to add, you can jumper the two wires together, which will bypass the switch and prove if the radio is good.

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People may not remember how fast you did a job, but they will remember how well you did it.


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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Fri 24, 2021 2:25 pm 
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Location: Mt. Rest, SC, USA
The thin black Bakelite disk on the back of the volume control is the power switch. There should be continuity between the two wires at the back when the switch is closed. (The actual volume control potentiometer is the larger metal and plastic cylinder on the front.) If there are no gaps or holes between the potentiometer and switch to spray the contact cleaner thru, then you will either have to disassemble it to clean it or replace it.

I would be careful when disassembling it not to damage the potentiometer section, since it may be difficult to find an exact replacement. The potentiometer has a tap on it, and it can be very hard to find replacement potentiometers with taps.

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 Post subject: Re: Transformer Replacement for RCA Model 119
PostPosted: Sep Fri 24, 2021 3:35 pm 
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Joined: Feb Thu 18, 2021 3:09 pm
Posts: 118
Thank you for all your help. I took apart the pot and a piece of plastic had broken off of the switch on the inside and lodged itself on top of the metal piece where the 120v would flow so no voltage was leaving the pot. I took out the plastic piece which thankfully didn't affect the operation of turning it on and off, and now it works! Very thankful it wasn't the transformer. I feel like those odds are pretty low that plastic piece landed in the perfect spot to cut off current but thankful it is resolved.


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