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
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
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.
col.
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
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
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.
is there a URL for those croc slippers?
edit: http://www.fatshoesday.co.uk/images/crocs mammoth.jpg
!!
col.
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??
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??
Hola Y'all...
Is the power cable 2 prong or 3 prong... some older hi fi had 2 prong non polarized plugs ...
regards, Elwood
Is the power cable 2 prong or 3 prong... some older hi fi had 2 prong non polarized plugs ...
regards, Elwood
Australian 2-prong plug; 2-core cable no safety earth wire .
Not an IEC connection; cable goes thru a plastic gland
Not an IEC connection; cable goes thru a plastic gland
OK here are Flickr links
http://farm3.static.flickr.com/2601/3806543122_f552817565.jpg
http://farm4.static.flickr.com/3544/3806542766_b7ddd8eec8.jpg
http://farm4.static.flickr.com/3594/3806542430_f0a8cc2336.jpg
http://farm4.static.flickr.com/3507/3806543522_e21ffe8f61.jpg
http://farm3.static.flickr.com/2639/3805726303_22eef5109c.jpg
http://farm3.static.flickr.com/2601/3806543122_f552817565.jpg
http://farm4.static.flickr.com/3544/3806542766_b7ddd8eec8.jpg
http://farm4.static.flickr.com/3594/3806542430_f0a8cc2336.jpg
http://farm4.static.flickr.com/3507/3806543522_e21ffe8f61.jpg
http://farm3.static.flickr.com/2639/3805726303_22eef5109c.jpg
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
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
Thanx for the reply
I'm thinking that Col was right and I got a huge static shock.
Yes the house has a new switch-board with RCD devices fitted.
I did check continuity and there is no leakage to the knob or case. but I am still wondering where the connection to earth is to allow the static to discharge.
I had the circuit diagram somewhere on my hard disk but cant seem to find it now.
I was going to do as you suggest and further wrap the live wires in PVC or polyethylene tubing; should they be twisted?? there is enough slack in the wire to do that
regards
Ted
I'm thinking that Col was right and I got a huge static shock.
Yes the house has a new switch-board with RCD devices fitted.
I did check continuity and there is no leakage to the knob or case. but I am still wondering where the connection to earth is to allow the static to discharge.
I had the circuit diagram somewhere on my hard disk but cant seem to find it now.
I was going to do as you suggest and further wrap the live wires in PVC or polyethylene tubing; should they be twisted?? there is enough slack in the wire to do that
regards
Ted
There doesn't need to be a connection to earth - you are charged and when you touch the case of the pre-amp you are equalizing the charge between you and the preamp metal mass.
Just like when you touch a doorknob.
Just like when you touch a doorknob.
Duh!!!!
OK!
So the case then slowly dissipated to the atmosphere?
That makes sense, it was quite a severe shock but no long term numbness in my arm so not AC then.
I have a grounding mat somewhere, I may put it in front of the rack that holds most of the powered stuff; just in case it happens again
If I can find it that is>
Thanx
OK!
So the case then slowly dissipated to the atmosphere?
That makes sense, it was quite a severe shock but no long term numbness in my arm so not AC then.
I have a grounding mat somewhere, I may put it in front of the rack that holds most of the powered stuff; just in case it happens again
If I can find it that is>
Thanx
Moondog,
As the case is not earthed, the discharge was the equalisation of charge between you and the preamp. I was thinking you could put a multimeter say positive on the case and then hold on to the negative lead (multimeter on volts) to see if there is a constant charge being generated on the case. Does this unit have the power amp on top of it?
Maybe the stray magnetic fieds from the power amp transformer generated this charge, just a thought i am no expert on this it might of just been the static electricity from the carpet and shoes.
Wires are twisted togeather so that any magnetic or electrical interference induced in the wires cancels out as the wires change position as they move through the electromagnetic fields. I can see no problems with twisting them togeather and if it does create problems it is easy to reverse.
Good luck
As the case is not earthed, the discharge was the equalisation of charge between you and the preamp. I was thinking you could put a multimeter say positive on the case and then hold on to the negative lead (multimeter on volts) to see if there is a constant charge being generated on the case. Does this unit have the power amp on top of it?
Maybe the stray magnetic fieds from the power amp transformer generated this charge, just a thought i am no expert on this it might of just been the static electricity from the carpet and shoes.
Wires are twisted togeather so that any magnetic or electrical interference induced in the wires cancels out as the wires change position as they move through the electromagnetic fields. I can see no problems with twisting them togeather and if it does create problems it is easy to reverse.
Good luck
HI ekidnah09
No the pre-amp sits on its own shelf above all other components. 70mm air-gap between each component.
At the moment it is a very cheap K-Mart steel shelf arrangement, and not acting as a Faraday cage because of the plastic compression cams which hold the shelves in place.
Probably just static discharge
No the pre-amp sits on its own shelf above all other components. 70mm air-gap between each component.
At the moment it is a very cheap K-Mart steel shelf arrangement, and not acting as a Faraday cage because of the plastic compression cams which hold the shelves in place.
Probably just static discharge
So come on then, what upgrades are you going to do? That thing is a modders paradise 😉
Schottkys,
capacitors,
crystals,
metal film resistors,
cables,
connectors,
pots,
regulators,
etc.....
The list is endless. Now you are on a "house buying" budget, you'll have to reduce your budget to the smaller things in life (electronic components) 😀
col.
Schottkys,
capacitors,
crystals,
metal film resistors,
cables,
connectors,
pots,
regulators,
etc.....
The list is endless. Now you are on a "house buying" budget, you'll have to reduce your budget to the smaller things in life (electronic components) 😀
col.
Several problems there Col;
I wouldn't know what to replace or what to replace them with??
What would I use while it was out of commission??
Where would I get the money??????????????????
😀
I bought the reserve capacitors a while ago when the unit was having problems; although those problems disappeared when I opened up the case and it was running cooler I still need to replace the bulging smoothing caps as I'm told that is a sign that they are at the end of their life
I wouldn't know what to replace or what to replace them with??
What would I use while it was out of commission??
Where would I get the money??????????????????
😀
I bought the reserve capacitors a while ago when the unit was having problems; although those problems disappeared when I opened up the case and it was running cooler I still need to replace the bulging smoothing caps as I'm told that is a sign that they are at the end of their life
yeah those caps do look a bit bulging out, did you get the correct values or bigger ones 😉
as ekidnah09 mentioned earlier changing the diode bridge for Schottkys could be a worthwhile upgrade. I would be looking at changing those pots for ladder attenuators if they are not VCA. I would also be looking at upgrading any regulators but as you stated not worth doing if you don't have something to take it's place while you do the modding and if there ain't no readies.......
col.
as ekidnah09 mentioned earlier changing the diode bridge for Schottkys could be a worthwhile upgrade. I would be looking at changing those pots for ladder attenuators if they are not VCA. I would also be looking at upgrading any regulators but as you stated not worth doing if you don't have something to take it's place while you do the modding and if there ain't no readies.......
col.
Replacement caps are much bigger
Rubycon CE 69 W
Still 85C but 63V and 6800u F
15mm taller than the old ones so thats why i had to cut the case open in the first place, please explain about Schottkys
Rubycon CE 69 W
Still 85C but 63V and 6800u F
15mm taller than the old ones so thats why i had to cut the case open in the first place, please explain about Schottkys
you should be able to find plenty of info on the web about schottky diodes.
http://en.wikipedia.org/wiki/Schottky_diode
I'm using Phillips BY329X fast soft-recovery diodes in the power supply of my preamp. Which is made up of ESP modules:
http://pix.minirig.org.au/main.php?g2_itemId=1150
There may be a few components in your C-80 that would be worth changing that won't cost a fortune but I wouldn't experiment on it if you don't have a drop-in replacement.
col.
http://en.wikipedia.org/wiki/Schottky_diode
I'm using Phillips BY329X fast soft-recovery diodes in the power supply of my preamp. Which is made up of ESP modules:
http://pix.minirig.org.au/main.php?g2_itemId=1150
There may be a few components in your C-80 that would be worth changing that won't cost a fortune but I wouldn't experiment on it if you don't have a drop-in replacement.
col.
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