NAD 7240PE - Need Resistor Values
 

Hello,

I am currently working on a couple of NAD 7240PE receivers. On one of
them, the soft-clip feature is not functioning properly (enabling it
causes the right channel to clip at a low level).

The problem seems to be four cracked resistors at the back of the unit,
near the soft-clip switch. They are labeled R413, R423, R414, and R424.
I need the values for these four parts. On the unit where this feature
works OK, all four of the resistors are 1/2 W 10 kOhm with 1%
precision. The bad resistors are 1/4W 8.2 kOhm with 5% precision.
Unfortunately, it appears that all of these are replacements; I don't
have the original parts. I could use 1/2W 10k's in the bad unit, since
they seem to work in the other one, but I'd rather be certain of having
the optimal values [especially since I am planning to sell the amp
after fixing it]. I know that some of you have the service manual. If
you could provide the original values, I would appreciate it _very
much_.

Thanks :-)
Matthew Varney

Matthew,

The shop manual calls for 8.2K, carbon, 1/2 watt. These resistors tend
to run hot, so I would space them up off the board a bit for better
cooling. I've also seen the diodes go bad. D405 and 406 are RD15ESB3,
which I believe are 15V zeners. D401-404 are 1N4148.

Regards,
Tim Schwartz
Bristol Electronics


mattvarney wrote:

Hello,

I am currently working on a couple of NAD 7240PE receivers. On one of
them, the soft-clip feature is not functioning properly (enabling it
causes the right channel to clip at a low level).

The problem seems to be four cracked resistors at the back of the unit,
near the soft-clip switch. They are labeled R413, R423, R414, and R424.
I need the values for these four parts. On the unit where this feature
works OK, all four of the resistors are 1/2 W 10 kOhm with 1%
precision. The bad resistors are 1/4W 8.2 kOhm with 5% precision.
Unfortunately, it appears that all of these are replacements; I don't
have the original parts. I could use 1/2W 10k's in the bad unit, since
they seem to work in the other one, but I'd rather be certain of having
the optimal values [especially since I am planning to sell the amp
after fixing it]. I know that some of you have the service manual. If
you could provide the original values, I would appreciate it _very
much_.

Thanks :-)
Matthew Varney

mattvarney wrote:
Hello,

I am currently working on a couple of NAD 7240PE receivers. On one of
them, the soft-clip feature is not functioning properly (enabling it
causes the right channel to clip at a low level).

The problem seems to be four cracked resistors at the back of the unit,
near the soft-clip switch. They are labeled R413, R423, R414, and R424.
I need the values for these four parts. On the unit where this feature
works OK, all four of the resistors are 1/2 W 10 kOhm with 1%
precision. The bad resistors are 1/4W 8.2 kOhm with 5% precision.
Unfortunately, it appears that all of these are replacements; I don't
have the original parts. I could use 1/2W 10k's in the bad unit, since
they seem to work in the other one, but I'd rather be certain of having
the optimal values [especially since I am planning to sell the amp
after fixing it]. I know that some of you have the service manual. If
you could provide the original values, I would appreciate it _very
much_.

Thanks :-)
Matthew Varney

The magic Numbers are 8.2K + - 5% 1/2W for all 4

Glenn,

According to the service manual, the resistors are 8K2, 1/2 watt 5%.
Also check that the 2 zener diodes (D405/406) are OK. (They are
RD15ESB3, 15V zeners as I recall.) I suggest standing the resistors off
the board a bit for better cooling. Also check or change the 1 or 2
small electrolytic caps in the area that might have been baked to death.

Regards,
Tim Schwartz
Bristol Electronics


Glenn Barry wrote:

mattvarney wrote:
Hello,

I am currently working on a couple of NAD 7240PE receivers. On one of
them, the soft-clip feature is not functioning properly (enabling it
causes the right channel to clip at a low level).

The problem seems to be four cracked resistors at the back of the unit,
near the soft-clip switch. They are labeled R413, R423, R414, and R424.
I need the values for these four parts. On the unit where this feature
works OK, all four of the resistors are 1/2 W 10 kOhm with 1%
precision. The bad resistors are 1/4W 8.2 kOhm with 5% precision.
Unfortunately, it appears that all of these are replacements; I don't
have the original parts. I could use 1/2W 10k's in the bad unit, since
they seem to work in the other one, but I'd rather be certain of having
the optimal values [especially since I am planning to sell the amp
after fixing it]. I know that some of you have the service manual. If
you could provide the original values, I would appreciate it _very
much_.

Thanks :-)
Matthew Varney

The magic Numbers are 8.2K + - 5% 1/2W for all 4