No, your bias trimpot setting will not necessarily be the same for the new output device as it was for the old one.
Transistors, like tubes, vary from sample to sample. That is why the better gear includes matched pieces. |
Isn't the bias trim-pot the same since I did not touch it and I'm not replacing it? |
Apparently Creek Audio saves a bundle on legal counsel for them to even suggest a course of DIY action. My advice: if you do not know what you are doing, don't do it. You can hurt yourself fiddling around inside a power supply. Power supply caps pack a mean punch. |
What does he mean by powering the unit up with a stabilized power supply? Is he talking about a variac transformer? If you have the skill and the tools to fix it yourself, then why not do it. However, if you are just going to attempt it because the amp is not too valuable, consider your other equipment before powering it up! I think it would be wise to get a complete diagnosis of the problem before you begin fixing it. The Creek tech has a point in that it may be more than just output transistors. |
Replacement output transistors(like tubes) will have varying bias requirements. Without knowing the current setting for the design you're working on, you're headed for trouble. A setting to low or too high for the replacement outputs will cause premature failure. And the setting isn't something you can do by ear. If you can find out what the design parameters are, and where the bias trim-pot is: Go for it by all means! BTW: Very few amps have protection against shorted outputs. |
You've got to ask yourself one question: Do I feel lucky? Well, do ya, Royy? |
The cost to repair vs, the cost to replace tells me to go for it! Have some fun.
Since you say you have the Transistors, try to fix it yourself.
Once soldered ,start it up with some headphones first, then try some cheapo speakers. Listen really carefully for the warning signs the others have already posted.
If all works good, then go for it with your reg speakers.
Perhaps after the first 2 steps the Amp will show it is now garbage, but you had fun trying!.
If thats the case then use the repair money to buy another Amp. |
Royy - Bias current is not difficult to adjust but it's not the issue here. The issue is that you don't know what it is. You might make mistake and damage your speakers, as Tobias already stated.
Be aware, that you might have more damage than output transistors - transistors driving them often fail as well. 5350 uses Mosfets for the output, if I remember correctly, and I don't even know where usually operating point is set for Mosfets.
Whatever you do - unplug your amp. Switching OFF is not enough.
I'm surprised that 5350 doesn't have output protection. Cambridge A3i I had once had all sorts of protections (overcurrent, temperature, dc voltage) and was designed by Creek people. |
Yes, as Unsound says, you are in over your head. If you don't know what bias current is or how to adjust it, then after the repair the amp will sound horrible and may even oscillate ( and damage your speakers )--even if you do solder the new parts in correctly.
Royy, have the repair done by a competent technician or sell the amp as is, but don't take any chances with what's still not broken. It's too bad, but things like this do happen and they cost money to fix. I blew the outputs on the same NAD amp not once but twice, doing exactly what you did. |
I think your in over your head. It might be prudent to consider replacing the amp. |
You answered your own question- "I'm willing to..."
At $300 for a new one, or an even better one, I say go for it.
Of course, a good tech should not be hard to find in your area. May cost you $50-$100.
Considering that you seem eager to try it, and the cost to replace it, I say go for it.
Word of the day- careful! |
