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Old 25th September 2008, 03:19 AM   #1
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Default Transformer Issue?

Hello folks, I have a sony STR-DG720 that is completely dead, I tested the power going accross the supply and ofcourse have no power to the transformer, Next I applied power directly to the transformer and still no action, any suggestions? Does this mean that the transfomer is blown, I heard somewhere that by doing that you are bypassing all protection, and that it shoud light up.

Thank you all in advance for your thoughts and advice

PS(Yes I Know Get A New Receiver NOT SONY)

Thanks again
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Old 25th September 2008, 04:02 AM   #2
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I blew my sony , too . I fear your tranny has a thermal fuse
"buried' deep in the windings, your best bet is to find another
receiver to swap out tranny or just part it out to build
A DIY amp (my sony is in another home made amp now)
Sorry about that....
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Old 25th September 2008, 05:21 AM   #3
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So the tranny is toast if I apply power to it and it does not turn on right?

And thank you
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Old 25th September 2008, 08:39 AM   #4
Bonsai is offline Bonsai  Taiwan
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It really jerks me off when companies do this. Why put a thermal fuse inside a transformer on a consumer amp? There are millions of amps out there that do not use this approach, but just straight fusing, and the majority of them (99.999%?) work jus t fine.
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Old 25th September 2008, 09:00 AM   #5
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Default it could be

possible that the thermal fuse is not that deep inside .... some times also the pins of the thermal fuse is also solded in the same bay with connection leads .....

its pretty obvious since fuse normally have silver leads and then trafos leads are coper only thing you have to do is to short the thermal fuse and add some normal fuse
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Old 25th September 2008, 09:20 AM   #6
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Bonsai
It really jerks me off when companies do this. Why put a thermal fuse inside a transformer on a consumer amp? There are millions of amps out there that do not use this approach, but just straight fusing, and the majority of them (99.999%?) work jus t fine.
the thermal fuse should only open if there is severe overheating of the transformer, i.e. a lot worse than "hot".
This can only come about due to overloading for a long period of time.

The mains fuse should rupture long before the thermal fuse ever nears it's trigger temperature.
However, fitting larger than required mains fuse or supplying two or more transformers from a common fuse will increase the likelyhood of tripping the thermal fuse.
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Old 25th September 2008, 09:34 AM   #7
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Default andrew ....

Quote:
Originally posted by AndrewT

the thermal fuse should only open if there is severe overheating of the transformer, i.e. a lot worse than "hot".
This can only come about due to overloading for a long period of time.

The mains fuse should rupture long before the thermal fuse ever nears it's trigger temperature.
However, fitting larger than required mains fuse or supplying two or more transformers from a common fuse will increase the likelyhood of tripping the thermal fuse.
it is a habbit to call these fuses "thermal" fuses but not always this type of fuse is installed inside transformers .

often these fuses work as overvoltage protection against spices now why you want an overvoltage protector fuse winded inside a trafo has no explanation besides that the company will sell another trafo as long as the fuse is gone ( while still producing trafos fused and with in CE or other specs )


can it be that fuse povide both thermal and overvoltage protection ???? most of them i gutted was just a tiny piece of wire now how can this provide thermal protection ?????
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Old 25th September 2008, 10:19 AM   #8
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Having worked in a factory where they designed and made transformers I can tell you they are thermal fuses and that is all. Andrew is totally right, the thermal fuse is a last ditch attempt to save the amp from setting on fire, usually due to improper user use such as overloading and/or insufficient ventilation.
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Old 25th September 2008, 10:23 AM   #9
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Default in UK probably

Quote:
Originally posted by richie00boy
Having worked in a factory where they designed and made transformers I can tell you they are thermal fuses and that is all. Andrew is totally right, the thermal fuse is a last ditch attempt to save the amp from setting on fire, usually due to improper user use such as overloading and/or insufficient ventilation.
try to gut of
a chinese transformer from a wirless dect phone ( of any brand ) and will understand what i am talking about ....
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Old 25th September 2008, 05:21 PM   #10
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I don't see any silver lead comeing from the trans, Thank you all for the great conversations, But how do I tell if this is bad when there is no power going to it? I have to assume it is only powered on when the switch is pressed, since it doesn't light up at all, could the Trans be bad? I did supply voltage directly to it with no results. Here is a picture of the leads coming out.

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