Nakamichi 500 speaker pop on start

6V6dude

Member
2014-09-09 11:07 am
I press play on my Nak, watch the speakers and the cones pop out as far as they can go, than return and all is fine than. It's somewhat slow as it's almost inaudible. I never noticed that on my big speakers with covers but recently connected small Castle speakers and nearly got a hart attack when I saw it.
It does it only when I press play. What could this possibly be, never had this on anything before, bad cap maybe?
 

Lojzek

Member
2012-02-10 12:12 pm
Croatia
What could this possibly be, never had this on anything before, bad cap maybe?

Your deck is in a need of a good service. Why don't you try downloading
a service manual and go from there. I can see there is free downloadable
manuals for Nakamichi 500. Maybe you'll be able to repair yourself.
After you engage PLAY, it sends an amount of DC voltage to its line out
and then goes away. Can you confirm with a multimeter?
 

6V6dude

Member
2014-09-09 11:07 am
Great idea! I've measured it and getting around 1.5V, being only momentary it's hard to catch it exactly but 1.5V is quiet high I would think. I'm not sure where ground leak resistor would be located to check that. Yes manuals are there but I have no idea what area I should start trouble shooting it.
 

6V6dude

Member
2014-09-09 11:07 am
Right, I see, that makes sense. I'll open it up and see if I can find it. Just had an idea, I better check the chassis is earthed well otherwise ground resistor would be doing nothing. Would be easier fix than looking for bad resistor I think, depending on my luck. I've had ground problems before with amps but not this type yet. I'll report back what I've found if anything, thanks.
 
6V6dude said:
Just had an idea, I better check the chassis is earthed well otherwise ground resistor would be doing nothing.
A ground resistor goes to signal ground, not safety ground. Nothing whatsoever to do with whether the chassis is earthed.

To find any ground leak resistors you need to study the circuit diagram, not look at the insides - a ground leak resistor looks exactly the same as any other resistor on the board. You do that after you have identified them on the circuit diagram.
 

6V6dude

Member
2014-09-09 11:07 am
Looking at it again, sometimes not properly working relay circuit in power board can cause pops in amps.
This Naka 500 has a relay. It engages and plays sound plays immediately on pressing play. There is nothing about it in service manual, but should there be about 1 sec delay before sound comes on after play is pressed in these decks?
If someone has this deck could you please confirm if there is any short delay before sound comes on after pressing play? I don't know so can't look for problem.