Quad 909 dropped a channel

[chris b]

Hello folks, my 909 just dropped a channel for no reason. What do you think just return to quad for repair or could it possibly be something simple. Or if anyone fancies having a look.

[Light Dependant Resistor]

Hello folks, my 909 just dropped a channel for no reason. What do you think just return to quad for repair or could it possibly be something simple. Or if anyone fancies having a look.

Hi Chris
Can you connect a cheap speaker to the channel which is down, and see if you get any audio, this will check if your speaker lead you normally use might be at fault rather than the 909

The 909 whilst lacking fuses in the power amplifier boards, has an arrangement of two transistors, if there is a fault on the board then
usually one or both of the 2k2 resistors on the collector of T16 negative or T15 positive will fail. Another possible is failure of R33 a 10 ohm zobel this tends to indicate a fault usually in the Dc feedback involving the TLC271 opamp. The 909 is an excellent design and is not prone to any failure.

if you have a multimeter, you can set the meter for measuring Dc voltage, so without the speaker connected, a measurement across the speaker posts ie red probe to positive and black probe to negative will indicate if the amp has a Dc offset on the channel which is down. a good 909 will hardly have any Dc offset at all, typically 0.03v if even that. but if much higher would indicate a more problematic fault.

I think a call to Quad and booking in for a service might be the answer.

Cheers / Chris

[chris b]

Thanks I will borrow a multimeter, definitely the amp and not the cabling or speakers.

[Firebottle]

Hi Chris, I could take a look at it for you, I have fixed many different makes in my time, including Quad.

I'm not a huge distance from you, just north of Dudley, so delivery should be an option for you as it's a heavy amp.

[chris b]

Just like to update this and praise Quad service. 4 ps caps 3 output transistors some more small resistors and caps replaced for the princely sum of 134 quid including return. Super service.

[IHP]

Lovely outcome, I think it's marvellous Quad will repair/service pretty much everything they've ever made. Sustainable Hi Fi !