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
Thank you all in advance for your thoughts and advice
PS(Yes I Know Get A New Receiver NOT SONY)
Thanks again
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
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
the thermal fuse should only open if there is severe overheating of the transformer, i.e. a lot worse than "hot".Bonsai said:
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.
andrew ....
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 ?????
AndrewT said:
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 ?????
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.
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.
Thanks Again
Thanks Again
richie00boy said:
While you'r in there, go ahead and check the secondary. The reason for the thermal fuse is to prevent fire, as stated. The overload will often be a shorted winding which can cause overheating without drawing enough current to blow a line fuse.
The thermal fuse is a spring loaded contact in wax. The wax melts, the spring springs.
This is my first post here (Hello) so I hope I have done this correctly.
Now that I see more replies on this thread.. A possible
solution..
very low melting point 100-150C.
Most sony trafo's I,ve seen DO have the Tfuse deep inside
(between former and E-core) but I am using one that
I "saved". This one had A bulge right under the outer tape,
I removed the tape to find the little bugger. What do you
have to lose ,cut the tape.
It also "jerks" me off about sony, JVC ,and others to
design "planned obsolecence" into their equiptment
Only DIY or rehabed professional stuff for me.
BTW STR-DG720 = 400VA 60-0-60V with only 10000uf FOR 7
discrete (IC driven darlington )channels Oh my god, no
wonder the poor trafo melted down
.
HULK
for free parts....
solution..
That thin piece of wire is a fusible alloy with a
very low melting point 100-150C.
Most sony trafo's I,ve seen DO have the Tfuse deep inside
(between former and E-core) but I am using one that
I "saved". This one had A bulge right under the outer tape,
I removed the tape to find the little bugger. What do you
have to lose ,cut the tape.
It also "jerks" me off about sony, JVC ,and others to
design "planned obsolecence" into their equiptment
Only DIY or rehabed professional stuff for me.
BTW STR-DG720 = 400VA 60-0-60V with only 10000uf FOR 7
discrete (IC driven darlington )channels Oh my god, no
wonder the poor trafo melted down
.HULK
for free parts....GREAT REPLY, YES 10000UF x 2 is it possible to have no standby power with a bad trans? should I get standby power only? or nothing at all? I have been checking caps for a while on the standby board and the dcdc converter board and cannot find any bad ones that show an open. any way to be absolutly certain it is a trans? I am equiped with no knowledge but a really cool multimeter and I am not afraid to use it.. lol
Thank you for all your reply's now and back there as well
Thank you for all your reply's now and back there as well
Transformers these days are undersized, a cost issue.
When overloaded for a long time the thermal fuse may open.
To prevent a future FIRE, only replace with a fuse of the same, or lower temperature.
Most of the time you can't get to the fuse. I have a pile of dead transformers from Sony, Denon, Yamaha, etc. Time to re-cycle for the copper.
When overloaded for a long time the thermal fuse may open.
To prevent a future FIRE, only replace with a fuse of the same, or lower temperature.
Most of the time you can't get to the fuse. I have a pile of dead transformers from Sony, Denon, Yamaha, etc. Time to re-cycle for the copper.
On my blown Sony, standby was a little 12v separate
transformer with it's own fuse. So it still worked regardless.
As far as your transformer , take it completely out of unit
(my sony Xformer plugged in , 1 plug for 120V in , 1 plug for main
40-0-40 AC and a 5pin aux voltage plug/ 12-0-12 VAC +
5VAC)
I then cut the tape on the 120V side ,found the Tfuse, removed it,
ran 120v right to winding. It worked...
In my new amp I fused both sides (120v and 40-0-40v).
I think Sony puts these Tfuses in to sell transformers, If
enough windings short to cause smoke/fire the line fuse
will surely blow anyway.
BTW... my poor sony stripped w/ "trafo"(enough parts for
a new amp)
transformer with it's own fuse. So it still worked regardless.
As far as your transformer , take it completely out of unit
(my sony Xformer plugged in , 1 plug for 120V in , 1 plug for main
40-0-40 AC and a 5pin aux voltage plug/ 12-0-12 VAC +
5VAC)
I then cut the tape on the 120V side ,found the Tfuse, removed it,
ran 120v right to winding. It worked...
In my new amp I fused both sides (120v and 40-0-40v).
I think Sony puts these Tfuses in to sell transformers, If
enough windings short to cause smoke/fire the line fuse
will surely blow anyway.
An externally hosted image should be here but it was not working when we last tested it.
BTW... my poor sony stripped w/ "trafo"(enough parts for
a new amp)
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