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Old 16th November 2004, 12:19 PM   #1
Giaime is offline Giaime  Italy
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Question Schematics needed for a Marantz 1020

I have an old Marantz 1020 solid-state integrate amplifier. It sounds good, however someone during a party short-circuited the left channels outputs, and now the left channel only hisses a little, but no sound. I think I must replace the output transistors. Can someone help or send me the schematics? I found these only for the 1030 which has a different type of output transistors (I think).
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Old 18th November 2004, 03:17 PM   #2
Giaime is offline Giaime  Italy
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Excuse me for the wrong post, I got the amplifier today and it is a Marantz 1060.... sorry again. I still need the schematics! Is there someone that owns one or have serviced one?
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Old 18th November 2004, 04:30 PM   #3
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Try this:

1060 schematics

I have fixed many 1060's. They are nice amplifiers when they're working. The power amplifiers seem to be fussy now at an average age of over 30.

Good luck.
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Old 18th November 2004, 08:00 PM   #4
Giaime is offline Giaime  Italy
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Hello sllydderrr! Thank you for posting the schematics. If you have fixed many, maybe you can help me: before my friend sent me this amp, it was working, only one channel, I suppose I had to change the output transistors (hard to find, btw). Now when I plug to the mains outlet and I press the power on, the lamp doesn't glow! I have cheked all the fuses and the wiring, and that's perfect, no signs of corrosion, overheat, broken wires, bad solder joints. I measure 0 volts between the fuses and the cabinet, but the 230V does reach the two outlets in the back. What's that? How can I do? I'm a little unexperienced in solid-state pc-board stuff....

Please help me!
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Old 18th November 2004, 08:18 PM   #5
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Hello Giaime,

I can't take credit for the schematics, they are not mine. I just knew where to find them.

With regard to your problem... did you check for continuity on both sides of the power switch? On both sides of the fuse holder? The switches have a tendency to die unexpectedly.

I'm assuming that the lamp didn't burn out in the meantime?

I honestly don't know what else could cause your new problem. Usually it is something almost TOO simple

sllydderrr
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Old 18th November 2004, 09:05 PM   #6
Giaime is offline Giaime  Italy
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In fact, it was too simple. The smallest fuse holder wasn't making good contact with the fuse. Now the amp works for the right channel, but the left one simply hums. I believe that the right channel transistors are the two right ones (seeing them under the cover, from upside), and the left channels transistors are the left ones. Well, I read the voltages on them and on the right side I see many 30VDC and a 0,6VDC, on the left ones I see only 70VDC! That's strange, something is happened down there. If the voltages are high, there's usually an open device, but I'm not much experienced. Someone's able to help?
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Old 20th November 2004, 11:32 AM   #7
Giaime is offline Giaime  Italy
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Hey! I'm waiting for help... Please!
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Old 20th November 2004, 01:35 PM   #8
Giaime is offline Giaime  Italy
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Hello! I submit an update: I desoldered the output transistors' leads from the PCB, and checked the transistors with the directions of this site:

http://www.elexp.com/t_test.htm

I know that the Marantz' are NPN BJT, and I measured them with a DMM that has the diode check. I put the negative lead of the DMM in the base (at least what I suppose to be), the positive at the collector and measured 2 ohm. I started trying every connection possible, B-C, B-E, C-E, I swapped the leads of the DMM and all the readings are the same: 2ohm. I suppose this is a short, and it's the leftmost transistor.

The other left channel transistor, the middle-left one is inexplainable. All the four transistors are marked the same number, 2sc897 Hitachi. But this one wants the base with the positive DMM lead to read a value of 200mV! So it should be PNP. But they are all marked the same!
The other strangeness is that either polarity I put between C and E, I read 0 ohm. Should it be another short?

I searched the web to find a 2SC897 substitute, and I find the MJ15001. Are there others? I need a modern, ready-to-buy one, because strange and old transistors are very HARD to find here in Italy!

Please Help Me!!!!!!!!!!!!!!!!!!!!
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Old 20th November 2004, 07:10 PM   #9
Giaime is offline Giaime  Italy
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Guys, please, GIMME HELP!
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Old 21st November 2004, 01:12 AM   #10
jaycee is offline jaycee  United Kingdom
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You could most likely use any TO-3 package transistor suitable for audio use. MJ15024/25, MJ21193/94 spring to mind.
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