|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
74.130.29.193
In Reply to: RE: Amplifier problem posted by akolegov on June 03, 2016 at 09:37:41
Does it have some sort of thermal cutoff?
Let me say that I have no experience with tube amplifiers, but I'm wondering why anyone would operate any audio power amplifier at 95% power continuously. This would never happen when playing music. Furthermore, I don't think any audio power amplifier is designed to do that, but I could be wrong.
If the amplifier begins working again after it cools down, my guess is that you have triggered a thermal cutoff by overheating the amplifier.
Good luck,
John Elison
Follow Ups:
John,
I am not a technician, but I communicated your guess to that man. He said "Thermal cutoff? There is nothing to cut it off" (my note: thed schematic is very simple, the amp is point-to-point wired, there are no relays or a sophisticated protection system).
Re 90% of its power, he said there is no power, the sound is very low, it's a single ended amp, the maximum power is 10W.
My observation would be if the speakers are not sensitive (i.e., less than 87dB), a 10W amp would almost always lack power....
To get a more definite answer, a thorough check would be required.
"my guess is that you have triggered a thermal cutoff by overheating the amplifier."
That's a plausible explanation for a well engineered amplifier, but this is a cheap Chinese product.
"I'm wondering why anyone would operate any audio power amplifier at 95% power continuously. This would never happen when playing music. Furthermore, I don't think any audio power amplifier is designed to do that, but I could be wrong."
I build my tube amps with over rated power supplies, e.g. a 250mA plate transformer when 200mA is drawn by the circuit at full power. I generally break in an amp by injecting a sine wave sufficient to take the amp to clipping and then back off until I see no sign of distortion. I can leave it like that on the bench indefinitely. I check for signs of overheating and for distortion of the wave. High quality transformers barely get hot enough to make one's hand uncomfortable.
So far, this amp is working again. I suspect temporary overload at high output. Since it's working, the rectifier tube is OK.
I attach the pictures.
I suspect a solder joint opening up when it gets warm or a capacitor failing at higher power.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: