Karl vd Berg
Super Member
Hi all,
I have now a NAD 306 (1993-94) that I'm planning to replace the capacitors, the 2 relays (?) and cleaning switches and potentiometers, but first I'd like to ask you a few things about some components under heat.
Turned it on this morning and it seems to work fine, although the sound is not as clean and "full" than my other 304, little brother. The bias were pretty high on the left channel, around 18mV (instead of 7mV, acc. to SM), and around 9mV on right channel.
This is the amp, still in good condition.
:scratch2: Removingthe bottom cover, darker/burnt areas where a couple of NPN transistors - 2SC3467 (MP package) and a 22kΩ resistor (2W) get very HOT (see 3rd pic).
R425 resistor (22kΩ / 2W) and the 2 transistors are the main source of heat!
Some question are:
1. should I worry about these components, or is it better to replace them with higher wattage ones? And the other smaller resistors, too?
2. do they get hotter and hotter because of other aging components?
Another thing is that this amp has two relays. One is in the power amp board and another right next to the binding posts.
3. both of them have to go for new ones or just the one in the power amp board?
I really want to refurbish this unit into new one (inside). Any further advice and suggestions will be greatly appreciated.
Thank you. :thmbsp:
I have now a NAD 306 (1993-94) that I'm planning to replace the capacitors, the 2 relays (?) and cleaning switches and potentiometers, but first I'd like to ask you a few things about some components under heat.
Turned it on this morning and it seems to work fine, although the sound is not as clean and "full" than my other 304, little brother. The bias were pretty high on the left channel, around 18mV (instead of 7mV, acc. to SM), and around 9mV on right channel.
This is the amp, still in good condition.
:scratch2: Removingthe bottom cover, darker/burnt areas where a couple of NPN transistors - 2SC3467 (MP package) and a 22kΩ resistor (2W) get very HOT (see 3rd pic).
R425 resistor (22kΩ / 2W) and the 2 transistors are the main source of heat!
Some question are:
1. should I worry about these components, or is it better to replace them with higher wattage ones? And the other smaller resistors, too?
2. do they get hotter and hotter because of other aging components?
Another thing is that this amp has two relays. One is in the power amp board and another right next to the binding posts.
3. both of them have to go for new ones or just the one in the power amp board?
I really want to refurbish this unit into new one (inside). Any further advice and suggestions will be greatly appreciated.
Thank you. :thmbsp: