matt7941
100+
Mmmmmmm... Pork scratchings.....
Say cheese!!!!!
Posts: 215
|
Post by matt7941 on Mar 1, 2009 22:33:06 GMT
Good evening all.
Sorry to keep asking questions but this is on behalf of a friend of mine. He has a Technics A900mkII amp which sounds great until you turn the volume past 9 o'clock and then the protection circuit kincks in and the amp cuts out. Is this a common problem and is there a simple solution? I was wondering whether it was to do with the actual volume pot?
The amp never gets driven hard and whilst it has been powering two sets of speakers they are within the set guidelines regarding wattage and ohms.
I have taken a quick look inside and barring a couple of dry joints on the inputs there appears to be no bulging caps or excessive scorching etc.
Hope someone can help.
Cheers.
Matt.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 2, 2009 0:55:26 GMT
matt7941
There could be many possibilities, but overheating with higher power could also be a cause. It's a longshot, but check that the output devices are well secured to their heatsink(s). You could also remount them using fresh silicon grease if applicable.
As I said, a longshot !
SandyK
|
|
XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
Posts: 5,689
|
Post by XTRProf on Mar 2, 2009 14:12:02 GMT
Good evening all. Sorry to keep asking questions but this is on behalf of a friend of mine. He has a Technics A900mkII amp which sounds great until you turn the volume past 9 o'clock and then the protection circuit kincks in and the amp cuts out. Is this a common problem and is there a simple solution? I was wondering whether it was to do with the actual volume pot? The amp never gets driven hard and whilst it has been powering two sets of speakers they are within the set guidelines regarding wattage and ohms. I have taken a quick look inside and barring a couple of dry joints on the inputs there appears to be no bulging caps or excessive scorching etc. Hope someone can help. Cheers. Matt. Oh, it can also be the protection circuit is faulty. I had a Pioneer SA8100 integrated donkey years ago having similar kind of problem and the Pioneer service centre just reworked the protection circuit and the problem is gone. Hopes this helps ............  |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 2, 2009 16:30:13 GMT
When I was retailing we had 2 of your model go down with this fault, cause being as xtrprof suggests.
DEFINITELY worth checking this.
|
|
matt7941
100+
Mmmmmmm... Pork scratchings.....
Say cheese!!!!!
Posts: 215
|
Post by matt7941 on Mar 2, 2009 23:52:05 GMT
Thanks for everyone's input.
I rechecked everything as per Alex's advice and concentrated on anything that would cause overheating. I then noticed that the cooling fan was only cutting in intermittently. On closer inspection one of the wires was loose within the connector connecting it to the main circuit board. A few minutes with a pair of snipe nose pliers and the connection was tightened. The cooling fan is now working continuously and the protection circuit is no longer cutting in.
Another simple explanation but most frustrating. The only frustration left is that my friend didn't tell me earlier. Apparently the problem has been ongoing for a while and he'd gone out and bought a Marantz PM7200 in the meantime which he swears doesn't sound half as good! He's now left with a Marantz he has no use for, c'est la vie!
Thanks everyone
Cheers
Matt
|
|
