Faulty Relay in my Marantz Amplifier

[DeMroN]

marantz amplifier circuit diagram

I'm not entirely sure but i think i might have a problem with my relay in my Marantz PM 510 DC Amplifier.

The problem is that when i turn the volume above say 2-3 the relay clicks and one of my channels cuts out for a second.

am i right in thinking that the contacts in the relay are worn or something like that. if so do i have to replace the relay with the same one or can i use a similar one, (as i think they have stopped making the one i have).

The Relay is a:
Matsushita
JC2aD-DC24V
AR34229
7A 250V AC 3V DC
1/10 HP 125V AC 250V AC

any help would be much appreciated.

 

[banjo]

what is speaker protection relay

I do not think this is a bad relay. The relay was included in the circuit to protect your speakers. The amplifier is directly coupled to the speakers without a series output capacitor. If the output stage of the amp develops an imbalance in bias, a net DC voltage would be applied across the speaker quickly destroying it. There is a monitoring circuit that watches the net DC voltage to the speakers and drops out the relay if a problem is detected.
It sounds like this monitoring circuit is being energized whenever you crank up the volume.
Is the volume control a mechanical pot? That is, are you turning a knob? If so, then perhaps the pot is just noisy and needs cleaning or replacement.
If your volume control is electronic, ie push buttons, then the monitoring circuit is too sensitive or the amp is devloping a bias problem.

 

[BJRONLINE]

amplifier problem clicks volume

Just curious what you found wrong with your amp. I have isolated my Sony product to the exact same component. It is about fifteen years old and uses a turn style volume control. The relay clicks off seconds after powering with no volume or even unpluged from all components.

Really hoping to salvage this component. Any suggestions?

 

[Verba]

marantz 2330 speaker relay

I think banjo is right, there is no direct influence of the volume on this relay, it turns off the output stage in case of overvoltage and/or overcurrent.
I would say, some dead capacitor or transistor - looks like it takes time to the FB circuit to set the right voltage at the output.
Or may be indeed, the reason is the knob, that gets disconnected, but it doesn't explain the start-up failure

 

[Lancey6969]

jc2ad-dc24v ac250v 7a

I'd suggest resoldering the output stages and power supply PCB... most likely that will fix it. If not, you'll need to use a 'scope to monitor the output stage biasing and/or the protection circuit to isolate the faulty part. Bet its not the relay.

 

[banjo]

relay matsushita jc2ad-dc24v

Here is a quick check. Find the relay and identify the terminals. Two terminals are the coil, ignore those. The remaining terminals go to the speakers and to the output stage of the amp. When the relay drops out and no audio output by tuning the radio between channels and reducing the volume to zero, measure the DC voltage from the relay terminals to ground. The speaker side should have zero voltages as the relay is open. The audio output side should also have zero volts, if it is working properly.

If the audio output side is non-zero, then the speaker protect circuit is working and you need to troubleshoot the output stage. Often the cause is blown output transistors. This will often burn up biasing resistors and some of the small driver transistors. If only one channel is bad, you can use the other channel for measurements of resistor values, etc.

If the output voltage is zero, then the speaker protect circuit is defective and you need to troubleshoot that section.

---- Steve

 

[leftyretro]

marantz dc at output of one channel

In these vintage DC amplifiers there are usually two adjustment pots for each channel (four in all). One sets the no signal idle current, usually around 20-50ma and the other adjusts the DC offset to zero volts. If the offset adjustment drifts then it can trigger the protection circuit that drives the speaker protection relay. Check with Audiokarma.org, that is a forum that has tons of people that can help you with the adjustments needed and their procedure.

Lefty