I recently purchased a NAD 2600 that appeared to be in beautiful condition - it was never worked on and cosmetically looked 10/10. It was clear the amp was rarely used and babied. However, once I plugged it in and powered it on, the protection light came on immediately and stayed on. This happens with or without any speakers/inputs connected.
What I have done: I took off the cover and checked all the fuses - each appears to be intact.
I looked at all the components and none seem to be burnt out - none of the electrolytic capacitors are bulging and no resistors are burnt.
What I have looked into: I have read up on the protection relays and do not this this is the issue because protection stays on. From other forum posts I have read, it seems like checking voltages is the next step.
My questions: Is there a good guide for how to safely power on an amp and check voltages hot? I have HV electronics experience but nothing on amps. Are their components that are known to go bad with age on this amp that I can check? I have a bench top multimeter and scope on hand. Has anyone had this issue and knows where to start?
Any insight or references would be greatly appreciated.
Thank you,
Josh 🙂
What I have done: I took off the cover and checked all the fuses - each appears to be intact.
I looked at all the components and none seem to be burnt out - none of the electrolytic capacitors are bulging and no resistors are burnt.
What I have looked into: I have read up on the protection relays and do not this this is the issue because protection stays on. From other forum posts I have read, it seems like checking voltages is the next step.
My questions: Is there a good guide for how to safely power on an amp and check voltages hot? I have HV electronics experience but nothing on amps. Are their components that are known to go bad with age on this amp that I can check? I have a bench top multimeter and scope on hand. Has anyone had this issue and knows where to start?
Any insight or references would be greatly appreciated.
Thank you,
Josh 🙂
Why haven't you checked the condition of the output devices ?
Look for a short circuit for a start , that doesn't require powering the amplifier up.
The protection is related to overload (current ) so the output would be the first logical step --if okay then check the overload detector and two relays .
A pretty good schematic is available on hi-fi engine , just login.
Look for a short circuit for a start , that doesn't require powering the amplifier up.
The protection is related to overload (current ) so the output would be the first logical step --if okay then check the overload detector and two relays .
A pretty good schematic is available on hi-fi engine , just login.
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google search " nad 2600 service manual "
from vintageshifi.com, no need to sign up.
just click the "nad 2600 service manual" it will automatically download.
read the manual , get familiar with the manual.
locate every part from the manual with the broad.
transistors C B E identification. also diodes, capacitors,
use your multimeter, diode mode, continuity, DC, AC volts....
from vintageshifi.com, no need to sign up.
just click the "nad 2600 service manual" it will automatically download.
read the manual , get familiar with the manual.
locate every part from the manual with the broad.
transistors C B E identification. also diodes, capacitors,
use your multimeter, diode mode, continuity, DC, AC volts....
page 15/21
Power supply
check all the voltages according to the schematic.
if all voltages normal--
page 11/21
check L302, R channel output, should be 0v or a few mV DC to ground, ( + or - )
check L301, L channel output, should be 0v or a few mV DC to ground, ( + or - )
if there were voltage, the protection relay won't activate and stay on protect mode.
check all the voltages according to the schematic to locate the fault.
Power supply
check all the voltages according to the schematic.
if all voltages normal--
page 11/21
check L302, R channel output, should be 0v or a few mV DC to ground, ( + or - )
check L301, L channel output, should be 0v or a few mV DC to ground, ( + or - )
if there were voltage, the protection relay won't activate and stay on protect mode.
check all the voltages according to the schematic to locate the fault.
The right channel output is 94V. The left channel output was 0.7V and is rising. I'm afraid it is one of the output transistors for both channels. How do I check them? I do not have a transistor tester.
if the right channel is outputting 94v, then the output devices Q332 and/or Q330 are likely blown- You need also to check Q324/Q328 and Q322/Q326 as well.
the 94v- is that +ve or -ve on the output?
there are a number of explanations for using a multimeter to check transistors, generally you can check then as two diodes and/or use resistance to check for shorts
the 94v- is that +ve or -ve on the output?
there are a number of explanations for using a multimeter to check transistors, generally you can check then as two diodes and/or use resistance to check for shorts
Ok I will look into checking transistors with the multimeter, thank you for your response. The 94V was positive as referenced to ground (+94V).
so the positive voltage may indicate the +ve side of the rail voltage- so Q330 and associated circuitry- also check the diodes and Q314/Q316/Q310.
check the voltage at D312/D310-should be 1.7v (+ve or -ve) and look for 8.9v at the base of Q212
these will help diagnose whether it is in the input/vas or output stages.
also check Q334- the bias transistor
check the voltage at D312/D310-should be 1.7v (+ve or -ve) and look for 8.9v at the base of Q212
these will help diagnose whether it is in the input/vas or output stages.
also check Q334- the bias transistor