Marantz PM-52 - no sound (speakers or headphones)

[danRod93]

Hi!

My PM-52 died some time ago and I never got the time to think about it.

There is no sound coming from either the headphones or the speakers output's. Also, there's no relay click.

I attached some photos of the amp section circuit, hopping it may help identify some problem.

Thanks in advance!

The photos:
Imgur: The most awesome images on the Internet

 

[MAAC0]

First thing:

Look for burned fuses and replace them. If you switch on and they burn there is a short somewhere (burned output drivers ??)

Then try to find out if there is any voltage on the supply rails. If there is an auxiliary stand-by circuit to power the main transformer see if it is being powered and functioning.

If your Protection ?? relay isn't clicking you have no power somewhere or you have DC on the outputs and the protection circuit is working.

If there is power on the rails find out a output point before the relay and measure if there is DC on the output. If there is, the output drivers went kaputt.

 

[anatech]

Hi Dan,
Like MAACO suggested, your protection circuit is engaged. You will probably measure a DC voltage on the emitter resistors of one channel. If you find blown fuses, resist the temptation to replace them and power up unless you have a "variac", or variable AC transformer. It allows you to slowly increase the AC input voltage so that you can limit current flow and do some troubleshooting at partial power.

Question time. We need to know how skilled you are and what equipment you have access to. You're going to need:

• Soldering Station
• Solder Sucker
• Good digital voltmeter
• Variac (don't use the "light bulb current limiter")
• audio oscillator
• Oscilloscope
• 8 R dummy loads. Don't use real speakers for tests
• A THD meter would be nice, but isn't critical

If you need to do work on this amplifier, you need these things. Your amplifier is well worth some care and attention to service properly.

In the event that you don't have the equipment and / or knowledge, consider it wise to take it into a good audio service technician. These folks wouldn't service TVs or video equipment - I'm talking about the actual technician. The shop might. You'll see good equipment on his bench witha parts supply, but on replacement brand parts (ECG, NTE, RCA or similar).

-Chris

 

[jaycee]

This amp uses an STK3062 as the frontend.. they are known for dying.

 

[anatech]

Hi jaycee,
True, but it pays to resolder the pins before condemning the chip out of hand. All STK chips seem to have a reputation for dying. These are available if you look around for them.

-Chris