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Proton D1200 - Need replacement power transformer

J

jbtaylor

New Member
I recently started to hear a loud popping noise coming from my D1200 even when not connected to speakers or any input device, only when plugged in. Then during the process of doing some cleaning and resoldering iffy connections, i would plug it in and see if there was any improvement. There has been some improvement, the popping stopped, but now everything on the left side of the amp is dead. I'm getting nothing from the outputs from the power transformer. The Proton item number is 29-2149-1. It steps down and up the 120v from the wall outlet to 3 different voltages.

How do i go about finding the proper replacement transformer.

Thank you for your help,
Joe
 
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Not impossible, but it is pretty rare for a transformer to fail especially without some sort of acompanying symptom like being super hot or blowing a fuse or...

I'd suggest doing a triple check on that given the relative rarity of actual transformer failure.
 
I believe i discovered at least a big part of the problem. The left power transformer (that the 120V plug and cord connect to just downstream of the power switch) has some sort of fuse or thermal protection built into the transformer. Attached are pictures. you can see the burnt looking spots on the insulating material that lays on top of the primary wires. The primary wires go into the brown perforated sleeve and connect to the black transformer wires. I tore away the brown sleeve (like a gorilla) to expose what im guessing is a thermal or current protection device. Before taking anything apart, i was getting no continuity between the red and brown primary leads. Between the red and brown primary leads on the other (right channel) transformer i get 1.6 ohms. On the bad transformer i get 1.6 ohms on the primary leads if i measure without including the thermal/current protection.
So, i guess i have two problems. One, finding a replacement transformer or the appropriate protection device. And two, figuring out why the protection device got fried. I had the amp in my work shop garage stereo system which sees new jersey winter and summer temperatures. Is it possible just from age and temperature swings that the protection device just broke down?
Would a short on the secondary side of the transformer create higher current on the primary side? If not, then its most likely just this protection device crapping out.
 

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Not an expert, but my first thought was bypass the device and see what happens, but that could end up badly if it failed due to an overload and not NJ temps. Have you checked the voltage before it to make sure that is correct?

I see the light brown orange material, but no "obvious to me" burned or electrically fried material, unless the black halves are burned black, versus made of a black material.

You could open the good one up and test it to see what its function is. Could be a thermocouple, by testing the good one could find a new replacement. But in my experience, a thermocouple activates a relay based on temperature, and that is self-contained right?

Looked again at the pics, so the "device" was separated into two black halves when you pulled the casing apart, right? Do you have a service manual, or can you get one? it should say what that is and give the specs.
 
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You really need to disconnect the black twin primaries and determine if you have any insulation related issues from what is most likely, some overheating/OC at some stage. It looks like the transformer is wired with two 110/120V primaries in parallel and could be re-configured for 220/240V by connecting in series.

The thermal fuse was clearly in line with the red wire. You can bypass that to test the unit after cleaning up the mess and insulating the windings properly from each other and from themselves.

I think you'll likely be able to resurrect that TXF.
 
Thermal fuses are readily available. I fixed an old receiver by replacing one. I forgot how common they on things with BIG power transformers.
 
jbtaylor said:
I replaced the thermal protection (bimetallic disk type) that was wrapped within the transformer and had blown.
Problem Solved !!!!
I have my proton D1200 back. :)

Thanks for all your help!

Joe
Click to expand...
So why did the thermal protection blow in the first place?
 
I dont know what caused it to fail. I was wondering if the amp being used in an unheated garage could have something to do with it.
 
Hello , my proton d1200 failled in the exact same way . What voltage, température and current rating thermal protector did you use ?

5a , 250v , 135 celsius ?

Thanks in advance
 
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