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Marantz 4270 pops when turning on/off

Richs_Trains

Richs_Trains

Well-Known Member
Hey all,

The 4270 I have in the living room has always popped when I turn it on or off through the speakers. I have read threads about dc voltage and such, and I have recapped the filter caps, power supply board and all 4 amps. I have adjusted both the power supply and the amp boards to the factory spec, there is 0mv dc. The pop still happens, so I tried the trick of putting plugs in the headphone jacks, no change. I have always just turned off the speakers before turning it off and wait till after it turns on to turn on the speakers, and this way there is no pop. It's not loud, but enough to be annoying ... any ideas? Thanks Rich
 
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Hi Rich,
I suspect there is a problem with the protection circuit. The way this unit works is that the protection circuit provides power to the relays after a suitable delay at turn on, and drops the voltage immediately at turn off. (JN10)
The speaker switches then 'allow' the relays to close if this voltage is present. (JN11 and JN12)
From your description, the relays are getting power anytime the relay is on.
My first suspects would be H806 and H807 in the protection circuit.

Tom
 
Last edited:
catrafter said:
My first suspects would be H806 and H807 in the protection circuit.
Click to expand...
Thanks Tom, it's in a wood case in a stack right now, so it will probably be a bit before I pull it out. This shouldn't cause a problem as long as I do what I have been doing, turning off the speakers before turning on/off, should it? Thanks for your help! Rich
 
What you are doing will keep the 'pops' from occurring. However, you need to be aware that if the power amps in your receiver fail, it may damage the speakers.

Tom
 
Hi Catrafter,

On a similar note, I have a recapped Marantz Model Eighteen (18). The original relays appear to work fine and mute on startup for several seconds as designed. The relays have been cleaned with a dollar bill to remove the oxidation. No issues. However, when I turn off the unit, there is a light, low level but audible thump delivered to the speakers. Is that turn off thump 100% normal for the Model Eighteens?
 
monkboughtlunch said:
Hi Catrafter,

On a similar note, I have a recapped Marantz Model Eighteen (18). The original relays appear to work fine and mute on startup for several seconds as designed. The relays have been cleaned with a dollar bill to remove the oxidation. No issues. However, when I turn off the unit, there is a light, low level but audible thump delivered to the speakers. Is that turn off thump 100% normal for the Model Eighteens?
Click to expand...

Hi,
I have no experience with the 18.

Tom
 
catrafter said:
From your description, the relays are getting power anytime the relay is on.
My first suspects would be H806 and H807 in the protection circuit.
Click to expand...
Tom, should I be hearing a relay click on this unit, because I do not. Sounds like you may be right in your 'remote' diagnosis of the protection circuit. I have ordered some 2SC945 and 2SC1318 and hope to check it out when I switch equipment next. Thanks Rich
 
Somebody possibly removed the relay and connected the wires directly if a click can't be heard. It will be interesting to open that baby up!
 
I'm still going with a problem in the speaker protection circuit. Turn the unit's power switch off, and then press the speaker switches. I'm betting there is no delay before the relays click when you push on the power switch.
The speaker switches control the low side of the relay coils, the protection circuit controls the high side.

Tom
 
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