Quad 909 resistors

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15-Jun-2017 08:14 AM

Eric

Eric

Posts: 35

Can anyone tell me what is the correct voltage for R1 & R2?

Also do i need pay attention to PPM/C?

Thankyou

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15-Jun-2017 08:45 AM

Joost Plugge

Joost Plugge

Posts: 912

Every low power,500mW, Metal film will do. Stability is more important than absolute accuracy. So select resistors with a low voltage and temperature coefficient, not every datasheet will tell you this, but lucky for us, normal metal films already have a very low voltage and temperature coefficient.

Joost Plugge

DaDa Engineering

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16-Jun-2017 01:12 PM

Eric

Eric

Posts: 35

Thankyou, how about the voltage for R16 & R17? Is it different requirements?

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16-Jun-2017 05:17 PM

Joost Plugge

Joost Plugge

Posts: 912

For a resistor in audio applications the voltage is not so important, the dissipated power is. The power is the square of the voltage divided by the resistor value. So for R17 the dissipated power is 20x20/560 is 0.7W. But when a signal applied the situation is different. The maximum voltage across R16 and R17 is about 100V, so the power is 100x100/ 1120 is about 9W, about 4.5W per resistor. The 100V example is a exception, so Quad decided 3W types are ok. See also the service manual of the 909, most resistors are also specified by the Wattage value.

Joost Plugge

DaDa Engineering

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17-Jun-2017 08:15 AM

Eric

Eric

Posts: 35

When i am trying to purchase resistors, what voltage do i need to look for R16, R17? Are you saying 100V? Or any volts is ok?

The Quad manual doesn't list VOLTS. Please help!

R1; 560R 1/4W 1%

R2; 22K 1/4W 1%

R16 & R17; 560R 4W 5%



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17-Jun-2017 09:52 AM

EJP

EJP

Posts: 1357

Just buy to hose specifications, assuming there is something wrong with the resistors that are already there. Make sure that R16/17 can take 100V as Joost said, but I doubt you will find resistors that can't.
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21-Jun-2017 10:26 AM

Eric

Eric

Posts: 35

Thankyou everyone, much grateful.

Just noticed there are two different specs for R1 listed in the Quad service manual, does this mean there are two different locations on the board with each being called R1?

I didn't take out the amp boards yet.

I'm interested in R1/R2 in signal path and want to replace


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21-Jun-2017 11:39 AM

EJP

EJP

Posts: 1357

It means there are two different R1s. One on the main PCB, 560R, and one on the Quadlink board, 68R.
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22-Jun-2017 09:05 AM

Eric

Eric

Posts: 35

Yup that makes sense. I understand everything said so far, including any volts over 100 ok for resistors ect, but i also like to ask is it useful for the volts to match for R1 and R2? (for example 300V for both R1/R2, as oppose to say 300V for R1 and 350V for R2, does this effect stability or anything else?

Is it ideal to have same volts for these?

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22-Jun-2017 10:00 AM

EJP

EJP

Posts: 1357

It doesn't matter at all as long as they are suitably rated.
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26-Jun-2017 08:31 AM

Eric

Eric

Posts: 35

Thankyou, 

909 service manual says R16/R17 are 4Watts, is this a typing mistake? I have a STRONG hunch these are supposed to be 5Watt.

Can anyone confirm?

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26-Jun-2017 04:48 PM

Joost Plugge

Joost Plugge

Posts: 912

On most of the pictures of 606/909 boards they installed 5W types. So you are probably right.

Joost Plugge

DaDa Engineering

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27-Jun-2017 01:17 PM

Eric

Eric

Posts: 35

Thankyou Joost : )

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