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2275 pops when powering on, and off

runningdog

runningdog

AK Subscriber
Subscriber
This Marantz 2275 pops when powering on, and less so when powering off. Not the 'thump' of a 1060 powering up. But a noticeable and measurable pop, in both channels. The pops are varying each time, peaking between .5 volt up to 3 volts.
  • When the main amps and relay are in circuit, the pop comes when the relay closes.
  • There is a normal delay time on the relay.
  • When the Pre Out jacks are connected to another amp, the pops are still there.
  • The pops remain after swapping in a different pre/tone amplifier board.
  • It is not affected by input or volume control settings.
I believe this rules out the main amplifiers, relay, and pre/tone amplifier. Since the pops are in both channels, could the power supply be where the issue is?

Thanks in advance...
 
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I’d say it’s the power switch or safety cap for the switch becoming more of a common problem now as these units age more and more
 
quadmatrix82 said:
I’d say it’s the power switch or safety cap
Click to expand...

I've wondered about this. Neither the snubber or the power switch has been replaced. I thought I ruled out the power switch by leaving it on, and powering the receiver on/off using a surge protector. But the snubber would still come into play. I'll replace it and see. Thank you!
 
35v power supply issue maybe?

Use the tape out jacks into another amp 's aux in to totally bypass the preamp circuitry.

Bob
 
wlhd1610 said:
Use the tape out jacks into another amp 's aux in to totally bypass the preamp circuitry.
Click to expand...
No pop when the tape out jacks are connected to the Aux jacks of another amplifier. Does this point back to the preamp and/or power supply as the source?

Oerets said:
Have you checked the DC at the speakers?
Click to expand...
Good question, since high DC offset can cause pops, usually when powering off. Both amps are set to +- 0.0mV. But using the Pre Out jacks for testing bypasses the main amps entirely.
 
Randy,
If you've swapped out the preamp board with another with the same results then that should rule out that board.
You've eliminated the amp modules since you've fed the signal into another amp via the preamp out jacks and still have the same issue but to prove it you could unplug the amp modules themselves in case they are "back feeding" a spike while still using the pre out jacks into that outboard amp.
That leaves the 35vdc power supply which feeds that board or possibly a missing or loose ground wire.
Possibly the PU01board but since it's both channels doing it I would suspect something they have in common like the P800 board.
Using the tape out jacks eliminated any input/selector switch wiring issues.


Bob
 
wlhd1610 said:
unplug the amp modules themselves in case they are "back feeding" a spike
Click to expand...
Unplugged both amps and there is no change.

wlhd1610 said:
That leaves the 35vdc power supply which feeds that board or possibly a missing or loose ground wire.
Click to expand...
I'll keep looking for grounding issues. And I'll check the 35vdc setting. Other than that, what can I check on the P800? It has been recapped, but no semi conductors have been replaced. I think I have replacements for all but I'm shy on shotgunning semi's.

Unfortunately I do not know if the pop occurred before it was recapped.
 
I replaced the TO220 2SD331 with a MJE15032G. No change, but a good thing to do regardless.

Scope is on the 35v output. The scope jumps upward when powered up, downward when powered off.

Should I disconnect the 35v+ lead at the power supply and see if there is a change?

Thank you for the offer of a P800. I have one if it comes down to that.
 
No change after removing the 35v+ leads from the power supply. Except of course no audible pop. I mean that the scope still jumps upwards and downwards. I do not know what is normal behavior.
 
Switch on from the wall and switch off from the wall leave power switch in the on position at the receiver if the pop doesn’t occur it’s the switch
 
After a talk with Bob, I worked on isolating the PE01 tone amplifier board and power supply as much as possible from other boards that could be the source of the issue. Searched for broken leads, especially grounds. For a while there was no pop when my 'spare' PE01 was installed, so a couple hours were spent going over and testing the unit's PE01 again. Then the pops returned even with the 'spare' PE01. Go figure. They have not been consistent.

I measure the peak voltage each time powering up, with no speakers hooked up. Spares my speakers, and I do not have to guess how 'loud' the pop is each time. And the dog hates the pops.

A never-before-mentioned symptom is that cycling the low filter results in horrendous pops. This goes away after a minute or two, mostly. Not always.

So I tried powering up with the low filter pressed in, and no pops!

The output from the PE01 board happens to go directly to the low filter switch. So the front chassis came apart again to get to the PT01 board. I disassembled the low filter switch, hoping to find it heavily corroded. Instead it was clean and shiny.

There is a 0.047uF cap and a resistor for each channel of the low filter switch. But it seems unlikely that there would be an identical component failure on each side so I'm reluctant to replace them.
 
I am interested in the outcome, too!

Kudos, Randy for sticking with finding the problem, this is the mark of good tech!

Tom
 
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