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Dead Marantz 2270

Seem to be wasting a lot of time troubleshooting the relay circuitry, when the output of the amp still has not been checked and has better than an 80-20 chance of being the root problem.
 
EW,

I thought I did that by checking the DC offset. If not how do I check for output?

BTW, it is not that wastful because I was replacing the caps for the 1st time in my life. Took me about an hour and $1 of caps.
 
Been following this thread with interest as I am soon to jump into component replacement myself. Here's a couple points to consider Hotgas, and others correct me if I'm out of line. The purpose of the protection relay is to prevent "bad" voltage from reaching the speaker terminals. We are talking about DC voltage high enough to kill your speakers. If your protection relay is not clicking in, you have 2 possible problems (in very general terms). First, the protection circuit is out of wack in the way it senses, or reacts to what it senses, or, secondly the protection circuit works and is not clicking in because it is sensing a dangerous voltage present. Logically, the first step, even if you want to take a shot at replacing some parts later, would be to find out what voltage the protection circuit is "seeing". If that voltage is acceptable, then the protection circuit components are probably to blame. Hotgas, you've already replaced more caps than I ever have. More power to ya. :thmbsp: I'll be learning that soon :yes:
 
The cow and the cat both killed me. The HP is soooooo true. Good link.
 
hotgas said:
EW,
I thought I did that by checking the DC offset. If not how do I check for output?
Click to expand...
Can't do this in the traditional way since the relay is not closing. Need to look at the output of the amp before the relay. I don't have a scat for that amp, and without it I couldn't begin to tell you where to look, except at the relay itself. Find the 'common' terminals.
 
I think I need some education on how this particular relay works.

It seems to me the voltage on blue (pin3) and yellow(pin 4) comes straight from power supply transformer and the voltage from pin1 and pin2 comes from the relay PCB circuitry. When this voltage 1-2 is high enough it should trigger the relay to make contact so that there is some voltage drop between pin 5 and 6. As there is ZERO volt across 5 and 6 it means either the relay is bad or the voltages across these pin 1,2,3,4 are not good.

Does anyone have specs on the relay?
 
These are almost always 24V relays, coil resistance of around 640 ohms.

One side of the relay coil is usually at some voltage, like 30 to 40 volts. The other side is connected to a transistor that controls whether the relay gets turned on or off.

Here's a semi-typical setup. Don't let the whole circuit confuse you...note that at the top right is the relay. Current runs through the relay, drops voltage across the series resistor under it, and flows through the transistor when it is on. When the transistor is off, you will still measure voltage on the relay coil, but until the transistor is turned on there is no path for current flow, so you will measure the supply voltage on both sides of the relay coil.

http://audiokarma.org/forums/showpost.php?p=41213&postcount=3
 
Referring to the first pic, measure the voltage at J816/814 (one channel) and J815/813 (other channel). If it ain't zero or close to it on each, that's the problem.
 
Did not have time to look into this problem last night. Hopefully by the end of the week I'll try to tackle it one more time.

So, EW, if the voltage across J816/814 (one channel) and J815/813 is not zero then what is the culprit?
 
At about 1.5 to 2V or somewhere in there, the protection circuitry will sense a fault condition in the amp, and will not allow the relay to close. The problem will be somewhere in the amplifier section.

You can use the DC offset trimpots and try to zero it, but if it's a long ways off you won't be able to, which will mean a burnt transistor or resistor or some such thing in the amp section.
 
Where do we stand on this one? I have not seen an update recently. I was following this thread with great intrest. Please keep it up. :thmbsp:

Thanks,
Todd
 
I've been sick in the last few days so have not test it yet. Hopefully in the next couple days I feel better then will continue the work and let people know the progress.
 
I am back on this topic. To tell the truth I gave up and brought it to my tech today. When he looked at it he told me he serviced this kind of Marantz roughly for >100 units in the 1980's when many people were more willingful to pay him top dollars for repair. When I told him about the relay issue he said there was usually nothing wrong with the relay. He measured the output transistor resistance (without taking the part out of the circuit) from the base to emiter and base to collector and told me the output transistor shot. To his experience this Marantz kills all the output transistors in both channels.
He doesn't want to repair it because he said it is too difficult and too labor intensive to find the transistors, drivers, other parts and after putting all the correct parts together he must balance it (I don't understand this part!)

So, I don't know what to do next. Should I order the parts (where?) and then replace them myself then bring the Marantz to him for balancing? Or is there something not right about his reasoning? :dunno: I may need to use this Marantz as an introduction to electronics repair :) but I found it is too time consuming. It is fun if I find an easy fix but after a few hours of struggling I am now so .. tired and need a rest. :sigh:
 
He doesn't want to repair it because he said it is too difficult and too labor intensive to find the transistors, drivers, other parts and after putting all the correct parts together he must balance it (I don't understand this part!)
Click to expand...
He's on crack...look for the telltail glass pipe and whores hanging around the back door trying to bum a hit or two. :smoke:

Forget this guy...

Pack it up and send it to me or dr*audio. I'd really like to steer you in the right direction, but it is very very time consuming on the net and I'm behind on most of my projects anyway.

Unless the thing has caught fire, I can fix it (and so can any other tech who is properly toilet-trained).
 
You are right Echo!!

What kind of tech is that?
I laughed my sock's off.

In the meantime i will going to balance the DC-offset on my SM-7 :D :D
 
You guys crack me up. So balancing means adjusting DC offset? :scratch2:

I now understand my tech more. He is a guy who likes to repair moderm electronics more than old ones. The reason is parts are more readily available and people are more willingful to pay for it. I think I'll keep him to do free diagnostic :) and simple repair only.

EW, I may need to send it to you as I am curious to understand what goes wrong. I am travelling again tomorow so I'll look into sending it to you sometime next week.

Case closed guys .............
 
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