D
Deleted member 543346
Hi.
I have a Nad 317 that i changed most of the electrolytic capacitor , since the power board capacitors was way out of spec.
Amplifier works good besides one thing...it makes a pop in left channel when turning off.
I have separated pre amp with poweramp , to find out where the issue starts.
Issue is in the pre amp section , and the pop gets louder with increased volume.
This issue was there before i recapped the amp , and i also double checked tonecontrol board along with volumecontrol board and input board for cracked solderjoints.
Any ideas where i should look next for clues?
Ty
I have a Nad 317 that i changed most of the electrolytic capacitor , since the power board capacitors was way out of spec.
Amplifier works good besides one thing...it makes a pop in left channel when turning off.
I have separated pre amp with poweramp , to find out where the issue starts.
Issue is in the pre amp section , and the pop gets louder with increased volume.
This issue was there before i recapped the amp , and i also double checked tonecontrol board along with volumecontrol board and input board for cracked solderjoints.
Any ideas where i should look next for clues?
Ty
Attachments
Do you have an oscilloscope?
Does the pop occur in the same way with all inputs? Any change if you install a short at the selected input.
Are there any relay clicks at same time as the pop?
Does the pop occur in the same way with all inputs? Any change if you install a short at the selected input.
Are there any relay clicks at same time as the pop?
D
Deleted member 543346
Hi and thank you for your reply.
No i have ordered a oscilloscope from aliexpress , so it would take a few more weeks before it arrives.
Yes the pop happens with all inputs i think (will double check this).
Not tried to short the input used...you meant to put a rca between left and right input thats used?
Not sure if there is any relay click while power off
No i have ordered a oscilloscope from aliexpress , so it would take a few more weeks before it arrives.
Yes the pop happens with all inputs i think (will double check this).
Not tried to short the input used...you meant to put a rca between left and right input thats used?
Not sure if there is any relay click while power off
D
Deleted member 543346
I tried again. When there is nothing connected to input there is no noise when turning off.
Using short betweed input did not change anything.
Discovered there is noise when i turn the volume up , with cables connected to input.
Also no noise when disconnected.
Using short betweed input did not change anything.
Discovered there is noise when i turn the volume up , with cables connected to input.
Also no noise when disconnected.
D
Deleted member 543346
Since i only had pop in one speaker when turning off amplifier , i ruled out arching from powerbutton and defective snubber.
But it actually dont pop when i pull the powercable to turn it off.
Kinda lost in the forest , and cannot see the trees🤔
But it actually dont pop when i pull the powercable to turn it off.
Kinda lost in the forest , and cannot see the trees🤔
Have you looked at the speaker Relay 201? Possibly it is arching or sticking on that channel? Also, did you replace all the caps around/part of that relay circuit? Sounds to me like either the relay is bad, going bad, or a smoothing cap in the relay circuit is out of spec on that Left channel.
Can you measure the voltage of the pop, so we can see the magnitude with a DMM (hold or max setting) while you wait for the O-scope?
These are places to start, but not for sure fix at this point.
Can you measure the voltage of the pop, so we can see the magnitude with a DMM (hold or max setting) while you wait for the O-scope?
These are places to start, but not for sure fix at this point.
D
Deleted member 543346
Actually it does pop without input and by pulling powercable , but seem to be less loud.
Starting to think it increase with temp.
I had both relays out and try removing any pitting/oksidation in contacts , but there is still a chance it was not enough and one of the contact arching in relay.
I tried to check voltage on terminals on both sides , and they are similar.
The pop comes right after turning off , while dmm showing a rise to about 160mv a few seconds after the unit is powered off.
I have changed all electrolytes besides one in the front panel , and one with volume controle.
Starting to think it increase with temp.
I had both relays out and try removing any pitting/oksidation in contacts , but there is still a chance it was not enough and one of the contact arching in relay.
I tried to check voltage on terminals on both sides , and they are similar.
The pop comes right after turning off , while dmm showing a rise to about 160mv a few seconds after the unit is powered off.
I have changed all electrolytes besides one in the front panel , and one with volume controle.
D
Deleted member 543346
I took out relay 201 once more and sanded , cleaned it again.
Pop still here...and then i saw i had not changed c222 and c223 at psu since i dont have 0.47uf 100v.
I got 1uf 100v and 0.47uf 63v.
Could those be the issue?
Pop still here...and then i saw i had not changed c222 and c223 at psu since i dont have 0.47uf 100v.
I got 1uf 100v and 0.47uf 63v.
Could those be the issue?
Are you sure both speakers are connected properly? lol. Also, did you measure the DC offset on each channel output? Are they similar?
Is the pop only on the left channel? Any confirmation/clarification? Is it definitively known that the amp should be well behaved re pop behavior at power off/on?
This is an interesting design. The power amp has relatively large gain of 101 (40dB), i.e 1+R385/R381. It does not have a relay controlling the speakers directly, but rather a relay does appears to control activation of servo nulling (RL201). Further, Q101 and Q102 shunt inputs when activated; I think C222 activates these shunting transistors at power-on; I'm not sure of power-down behavior via remote or front panel, nor about RL201 response. Does RL201 drop immediately at power off? These details might be insightful if you can determine them from experiment.
Would you measure both amp output voltages and servo amp voltages at IC201 pins 1 and 7?
Thanks!
This is an interesting design. The power amp has relatively large gain of 101 (40dB), i.e 1+R385/R381. It does not have a relay controlling the speakers directly, but rather a relay does appears to control activation of servo nulling (RL201). Further, Q101 and Q102 shunt inputs when activated; I think C222 activates these shunting transistors at power-on; I'm not sure of power-down behavior via remote or front panel, nor about RL201 response. Does RL201 drop immediately at power off? These details might be insightful if you can determine them from experiment.
Would you measure both amp output voltages and servo amp voltages at IC201 pins 1 and 7?
Thanks!