Marantz 2245 has no sound

[Raccoon1400]

Racoon1400 I'm not sure exactly about the bias but I will be sure to ask, but I would think they would know to check if it is a typical issue with most Analog systems but then again I'm sure they arent Marantz experts but what do I know. I'll give them a couple more days to work on it and hopefully they figure out the issue, after all any technician with the proper documentation and equipment should figure this out right?

Anyone who is at all familiar with power amps should jump straight to checking the bias if one channel is running hot.

 

[disisme]

Anyone who is at all familiar with power amps should jump straight to checking the bias if one channel is running hot.

Actually they didn't say it was Hot but left side was warm and right side cold.

 

[Raccoon1400]

Actually they didn't say it was Hot but left side was warm and right side cold.

Still would check the bias, especially if it got warm fast. The heatsinks shouldn't get noticeably warm until it has been on for a while or has been outputting a lot of power.

 

[disisme]

So it seems I will be picking up the receiver today after work, they couldn't figure out the problem, they wanted me to drop it off to another guy but I told them I would prefer to just take it home for now.
I'm really hoping you smart guys here can guide me on trouble shooting myself. I have a good voltmeter, solder wick and a good solder iron. I'm not familiar with fixing electronics but I can do what I'm guided to do.
What should I check check first off?
Thanks
Lynn

 

[disisme]

Just wondering should I start this thread over in another area like diy ?
Thanks

 

[Steven Tate]

Just wondering should I start this thread over in another area like diy ?
Thanks

You are in the right place. I'm not the one to guide you through the diagnostics, but there are many on the Marantz forum that can help you. If you don't have one and you want to try this yourself, you need at a minimum a Dim Bulb Tester and decent Digital Multimeter. The first thing I would do is fire it up with the Dim Bulb Tester and make sure the bulb dims indicating (hopefully) no major shorts. If it passed that, I would probably pull the output transistors and test them according to Echowars tutorial here:

http://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

If they pass, I would measure the DC offset at the speaker terminals and the bias (idle current) according to the service manual. To do this without blowing things up, you MUST have some mini-grabber clips for your DMM that you can place on the proper test points with the unit turned off, turn on, take a reading, and turn off before removing the test leads. Knowing those readings (in mV DC) will be a good first piece of information to have. There are a lot of guys who know much more than me that may have a better first few steps. If so, hopefully they will chime in. Good luck!

 

[disisme]

Ok first thing I'll do is make the dim bulb tester.

 

[Steven Tate]

Ok first thing I'll do is make the dim bulb tester.

Here is a really good plan for one.

http://www.audiokarma.org/forums/index.php?threads/compact-dim-bulb-tester-wiring.465423/

 

[disisme]

Thanks Steven Tate I made one up.

This is with the DBT switched to on


This is with DBT switched to off


What does it mean? I'm using a 100 watt lite bulb,if that matters.

Thanks
Lynn

 

[Bassblaster]

Appears to be a short in the output stage.

 

[Steven Tate]

^^^^^yep. If the light stays bright more than 2-3 seconds when you turn it on, something is shorted (assuming the DBT is wired correctly). If you have another unit, you might plug it into the DBT and see if the bulb dims like it should. To look for a short, start by pulling the output transistors and try again, or better yet, pull them and test them per Echowars' thread. Like Bassblaster said, there is a good chance you have blown outputs. If so, the question is why. That will require mentors above my pay grade.

P.S. If you pull the outputs, take a photo or take notes on which one goes where. Nothing worse than getting them out and not having that record. They are not reversible between the top and bottom.
Steve

 

[disisme]

Ok I just did as Steven Tate suggested and now I see. I plugged in the amp and it went dim and as I turned the volume up the bulb went briter.
I had the Marantz connected up direct to the power bypassing the DBT , it was on for maybe 10 minutes, the left heat sink got warm and right side ice cold.
Are the output transistors the two transistors on the left and right heatsink?
These guys

Sorry its going to take me a bit to get use to the names and purposes of the electronic pieces.

I'll spend some time and read up on Echowars thread. Working shift work is going to slow down progress.

 

[disisme]

Also there were some good suggestions on bias setting , I'll have to read back at all the suggestions now that I have the unit home.

 

[Bassblaster]

Yes those are your outputs, one is PNP the other in NPN. dont get them mixed up or you will see smoke

 

[disisme]

ok thanks Bassblaster, got lots of reading to do.

 

[disisme]

Just had a thought,yesterday I purchased a Marantz 2238B , works great. Can this 2238B help in any way in troubleshooting the 2245?

 

[Steven Tate]

I don't think it will be of any help. Very different design. When you remove the outputs to test them, there will be thin mica insulators under them with thermal compound on both sides. Carefully remove them without bending - they are brittle. If they are intact, you can clean them with isopropyl alcohol and reuse them. When you reinstall, you need a thin coating of good thermal compound like Dow 340 heat sink compound on both sides of the insulator. Do not use computer CPU compound. It is conductive and will make bad things happen.

 

[Raccoon1400]

Check the fuses on the plate mounted to the heatsink I mentioned earlier if you haven't already. If you can't see the filament you can use your ohm meter.

 

[disisme]

Check the fuses on the plate mounted to the heatsink I mentioned earlier if you haven't already. If you can't see the filament you can use your ohm meter.

Yes I checked them last nite and get an audible beep on all four, on one I could not see the filament which is why I checked with meter. Just to be sure, what should my voltmeter me set at in ohms?
Thanks
Lynn

 

[KutzlerTrans]

It scares me if someone was in there swapping parts and didn"t even check the dc offset and idle current first.

Your getting good advice

You MUST use good mica insulators on each output. There should not be any continuity between the output transistors and the heatsink.

How hot are the driver transistors getting?? Use a point and shoot LED temperature gun.
Adjust the bias first.
If your dc offset is good, then the relay should click.
If the drivers are getting over 85-90 degrees at an idle, or climbing, shut it down and let it cool a bit.
Make sure to verify if the transistor numbers match from one amp to the other.
That will verify whether or not someone may have put the wrong transistors in.
Also make sure any parts(thermistors) glued to the heat sinks are still attached.

You have a good group of guys helping you here. Your job is to be very carefull when checking voltages and removing and replacing parts.
Make sure your volt meter is accurate. Remember to subtract the ohm lost through your test leads when checking resistance.
Using mini clips and attaching and removing them only after shut down is the correct way to test voltages.
If you must use a pointed test probe, cover the probe with tape all the way to the tip, obviously keeping the very tip open. It is way too easy to short out stuff by not paying attention.
Where safety glasses when powering it up with your head in there. If a cap blows up, youll be glad you did.
Everyone here can tell you stories of stupid mistakes we don't want you to make.
I made lots of them.