I'm currently testing my Quad 909 power amp and have ran into a problem where the circuit breaker trips before it reaches full power (140w) I've measured 32.2v (129w) and 25v (78w) across my 8ohm dummy load using a 1k sine but at 32.2v it trips pretty much straight away and at 25v it takes a few minutes, anyone have any ideas what's happening with it?
Would it be a good idea to disconnect one channel at a time and test?
Would it be a good idea to disconnect one channel at a time and test?
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So I disconnected power to the left channel and just left the right connected, full output 140w for 15 mins, so all good there. Will try the left channel on its own next.
I did notice when both channels connected that you can hear the sine wave from the amplifier itself, just the right channel don't really hear it.
Any ideas?
I did notice when both channels connected that you can hear the sine wave from the amplifier itself, just the right channel don't really hear it.
Any ideas?
You don't say where the breaker is. Part of the amp or in your mains supply. Either way it would suggest the amp with both channels approaching full power exceeds the rating of the breaker. The fact you are hearing the test tone with both channels suggests the power supply transformer is beginning to saturate and reaching maximum power.
I wouldn't say there is anything wrong. Asking a consumer amp to supply full power to both channels with a single tone is a hard task.
I wouldn't say there is anything wrong. Asking a consumer amp to supply full power to both channels with a single tone is a hard task.
Hearing sound from the amplifier hints at bad reservoir electrolytics, a known issue with some 909s
The caps were replaced by Quad with BHC caps back in 2010, it is a made in England one, not a Chinese made
So with one channel connected at a time that channel makes its full power 33.5v AC across an 8ohm dummy load, put both channels on at the same time it trips the circuit breaker which is on the mains supply.
With the left channel you can here the sinewave emitting from the amp.
I'm at a bit of a loss here, surely even if this type of test is hard on an amp it should be able to manage 80w without tripping?
So with one channel connected at a time that channel makes its full power 33.5v AC across an 8ohm dummy load, put both channels on at the same time it trips the circuit breaker which is on the mains supply.
With the left channel you can here the sinewave emitting from the amp.
I'm at a bit of a loss here, surely even if this type of test is hard on an amp it should be able to manage 80w without tripping?
Around 2010 was when the market started to be flooded with fake capacitors. Many major brands unwittingly installed them so davidsrsb and ejp could be right.
Do you have anything else running through the same breaker drawing the bulk of the power?
The use of CapXon capacitors coincided with the move of production to China. 909s with them are known not to meet their THD specification, and replacing them fixes it.
