Another Yamaha C-80 problem

[Moondog55]

Another Yamaha C-80 problem

I just went to turn the volume down ( yes I know but the wife sort of insisted ) and I got a shock when my fingers touched the volume knob.
I have of course switched off and disconnected, opened the case and my untrained eye can see no bare wires or anything obvious.
Any thoughts or comments??
I like the phono stage and Parametric EQ in this model so don't want to change, also we just committed to buy a house so the money for a new pre-amp isn't there.
As you can see from my avatar we are now in Geelong so my old tech-weenie friends are elsewhere and too far away

[col]

sure it wasn't just a static shock from your body discharging touching the(grounded) volume knob? Are your floors carpeted, what material are your shoe soles made of?

col.

[Moondog55]

Is that possible with double insulated cases??
You know I never even thought of that, maybe I am looking at worst case scenarios, I was wearing my new Croc slippers and it is wool carpet

[col]

Somebody please correct me if I'm wrong. Usually, anything that is metallic and is exposed has to go to the ground pin on the power socket. So if your Yamaha has an aluminium volume knob......

is there a URL for those croc slippers?

edit: http://www.fatshoesday.co.uk/images/crocs mammoth.jpg

!!

col.

[Moondog55]

Hey Col that link is 404

Maybe I was panicking a little, while the top is off the case I'll now do the replacement of the storage caps as they are all showing signs of bulging.

I noticed that the wires leaving the entry point and leading to the power switch on the front panel are not themselves insulated any further than the PVC sheath and are not twisted together.
Query ? Should I twist them and get some cover tubing for the 240V mains wires?
Also can anyone tell me why Yamaha didn't fuse this pre-amp? And should I do that, fit a fuse I mean??

[eyoung]

Hola Y'all...


Is the power cable 2 prong or 3 prong... some older hi fi had 2 prong non polarized plugs ...

regards, Elwood

[Moondog55]

Australian 2-prong plug; 2-core cable no safety earth wire .
Not an IEC connection; cable goes thru a plastic gland

[col]

how about a photo of the insides?

col.

[Moondog55]

OK here are Flickr links




http://farm3.static.flickr.com/2601/...f552817565.jpg

http://farm4.static.flickr.com/3544/...b7ddd8eec8.jpg

http://farm4.static.flickr.com/3594/...f0a8cc2336.jpg

http://farm4.static.flickr.com/3507/...e21ffe8f61.jpg

http://farm3.static.flickr.com/2639/...22eef5109c.jpg

[ekidnah09]

moondog,
Is your house supply fitted with a safety switch or sometimes called an RCD (residual current device) this is at your meter box switchboard?
The safety switch if fitted would of tripped your supply off if the ac was live and you touched the case, providing the zap was over the tripping current which is very low (I think 50mA). This is the current that flows through your body to ground the safety switch picks this up and trips off the supply.
If you have a multimeter check resistance between each of the ac prongs and the case to be sure there are no shorts to the case the resistance must be infinity.
If in any doubt get the item electrically tested by a qualified electrican.
You might get him to install an IDE socket that way you can install an earth. There are also IDE socket power filters if you have room. Jaycar sells one for under $10.
While you are replacing the power caps I would insulate any exposed 240v wiring with heat shrink, PVC tube or PVC tape. I hope this helps remember any doubts and get it electrically tested. As you like the unit it will not cost a lot to fix if it has a problem that is. By the way have you thought about replacing the doides with Schottkys. Good luck