dead transformer: denon pma 680 r

hello all!

my flat mate is getting a bit depressed without music: his denon pma 680 r amp quit working after a party some days ago. :(
i tried to find the reason of the silence and found that the primary coil of the transformer was burnt. i din't know that could even happen, but there is no doubt. :eek:
we wrote a mail to denon austria and they told us a new transformer would cost 170 euros :xeye: . that seems quite much to me!
we decided to find another solution. but: i din't find any place where to find a technical manual of this amp.
the people at denon were friendly enough to tell us that the amp needs about +50 - 0 - 50 volts of supply voltage (power supply out after rectifier and caps) and more than 200 watts.
i do not believe these suggestion is very accurate...

i don't want to buy a transformer and then ruin his amp with over-voltage :dead: . it is a remote controlled amp with lots of sensitive integrated circuits insinde, i guess...

does anybody of you own such an amp?
would it be possible to measure the secondary voltage?
do you know any other way to find out the data of the transformer?

thank you very much!


i thougt of that!
the problem is that the transformer was embedded is a steel can and sticked to it with some strange glue-sand-mixture. we tried to get the transformer out and had finally success by cooking(!) the whole thing in water for some time!:hot: i found nothing which seemed to be some kind of fuse and unfortunately some wiring was damaged by former attempts to get the transfomer out of the can...:xeye:


These transformers have thermal fuse but it is embedded in the potting compound (glue-sand mixture). It will normally be at the deeper centre of the torroid ring. U can identify it by the difference in the lead metal.
I fixed a denon trafo for a friend , but warned him not to connect his square wave UPS again.

Superficial damage to the wire can be repaired by insulating it.

Gajanan Phadte


2016-05-17 1:46 pm
hey, i have a original trafo from af defekt denon pma-680-r, and other spareparts for thi amplifier, contact me, or find transformator on diyAudio server HTTPS page

Hi Miguelovitch,
Your link doesn't work now, have you another one ?
I search a "PMA 680 R" shema and more particularly the primary transformer feature for change it.
All Denon I have seen have a thermal fuse in the inner core space near the wires. Easy fix. There is a video on youtube on that matter.
Just search for it.
Get the main wires loose and put in a new thermal fuse. DO NOT SOLDER! It will blow.
Have fixed several Denon transformers.
Use an 80 degrees C fuse.