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Marantz 2325 pops when turned off

runningdog

runningdog

AK Subscriber
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This Marantz 2325 pops when turned off. Adjusting the bias did not change it.
  • Both channels pop.
  • As high as 0.4V, measured using max value on a DMM.
  • The pop was present before rebuilding the receiver, and is still there afterwards.
  • If the 2325 has a preamp connected to the Main In jacks, there is no shutdown pop.
  • If the 2325 is connected to another amplifier using the Pre Out jacks, there is an extended shutdown pop.
Since the pop is present at the Pre Out jacks, the main amplifiers are ruled out as the source of the pop. Because it is present in both channels I suspect the power supply.

Your suggestions requested and appreciated.

2325 P800 rebuilt_resize.jpg
 
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Do you have a spare PE01 you can plug in to substitute to rule it out quickly?


You can also just unplug the PE01 to see what happens.



Bob
 
the relay should open its contacts before the pop so it should not happen .
does the relay have time delay at power on ?
dc offsets ok ?
 
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SPEAKER PROTECTOR RELAY CIRCUIT
The speaker protection circuit consisting of H805, H806, H807, and associated parts protects
the speaker system against any loud "pop" sound developed. This circuit is so designed that no
sound is heard for the first three or five seconds after the power switch is turned on by the time
constant circuit consisting of C813 and R816. This circuit also protects the speaker system
against some troubles due to DC unbalance between the speaker system terminals by instantly
operating the relay and cutting off the speaker system from the circuit. If the DC unbalance
voltage (positive) is developed between speaker terminals by possible defects such as broken
power transistor, short-circuits, or broken potentiometer R713, as the base of H808 is connected
to the speaker terminal, the transistor H805 is turned on by the offset voltage developed. This
turns the transistors H806 and H807 off, thus cutting off the relay and disconnecting the speaker
from the output circuit. If a negative offset voltage is developed, this voltage directly turns the
H806 and H807 off, which disconnect the speaker from the circuit and protected.
The circuit also protects the speaker system from possible damage if the amplifier is
over-driven by very low frequency such as 7 or lower cycles per second.
 
petehall347 said:
the relay should open its contacts before the pop so it should not happen .
does the relay have time delay at power on ?
dc offsets ok ?
Click to expand...

DC offsets OK. The relay has the usual 2325 long time delay at power on. The relay does not seem to be opening quite soon enough when the receiver is powered off.
 
Last edited:
[QUOTE="wlhd1610, post: 12187583, member: 105463
Do you have a spare PE01 you can plug in to substitute to rule it out quickly?
You can also just unplug the PE01 to see what happens.[/QUOTE]

I unplugged the PE01 and the pop is still present.
 
Well that’s odd because the preamp output should go directly to the rear panel output jacks.
Pull the rca plugs out of the amp modules themselves and try again.

You can also put in a lesser uf cap in the relay timing circuit so the relay drops out quicker.


Bob
 
wlhd1610 said:
Pull the rca plugs out of the amp modules themselves and try again.
Click to expand...
The pop is still there after pulling the RCA plugs on the main amps. It is not quite as loud as when the amps are hooked up.

wlhd1610 said:
You can also put in a lesser uf cap in the relay timing circuit so the relay drops out quicker.
Click to expand...
I'd like to track down the pop. But closing the relay sooner may help. Is the correct capacitor to change C812? C813?

2325 P800 protection circuit schematic.jpg
 
I'm not at the shop right now but I do know that part of my 2325 full restoration always includes installing a new 390k resistor at R816 because of past issues with relay on a few 2325's.

ymmv


Bob
 
Thanks for the tip on the R816 resistor. I replaced it, and replaced the C813 cap with a 100uf vs the original 220uF.
No change, except the delay before the contacts close has decreased.
 
Are the main filter caps original? One my be in poor shape and so one does something odd at power down causing the pop maybe? Put a scope on both and see if anything weird happens on power down. I have a 2325 on hand, unrestored, which I can look at waveforms to compare if your scope is one that can store. Like a digital model.
 
The 2325 no longer pops when powered off. A resistor on the P800 power supply board was open (R808). This prevented being able to adjust the output voltage, and the boards were getting higher voltage than they are supposed to get. With a new resistor in place and the output adjusted, the pop went away.

Thanks everyone for your help!

Don't touch that dial, there is more to come with this 2325.
 
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