Marantz 2216B rebuild

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The only way this will make some kind of sense to me is if you right down the voltages on all the transistor junctions as measured from ground. Use this form and layout and do a copy and paste with the results typed in:

Q714
E =
B =
C =

Q712
E =
B =
C =

Q710
E=
B =
C =

Q708
E =
B =
C =

Q706
E =
B =
C =

Q704
E =
B =
C =

Q702 'left'
E =
B =
C

Q702 'right'
E =
B =
C =
 

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Hi Mooly, here are the results looks like one of the 702 is shorted i have to order more of the A992 to replace that one
Q714
E = - 1.3
B =- 1.1
C = 2.15

Q712
E =- 1.9
B = -1.9
C =- 2.1

Q710
E= .16
B = -.4
C = 2.1

Q708
E = -1.7
B = 02
C = -1.9

Q706
E = .25
B = .27
C = .26

Q704
E = - 1.9
B = -1.9
C = 2.7

Q702 'left'
E = -1.7
B = -1.3
C = -1.9

Q702 'right'
E = -1.7
B = 0
C =- 2.5
 
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So it looks like you have almost a short somewhere across the rails or the output devices are conducting heavily. Both supply rails are pretty much non existent.

Here's what you do, and in this order.

1/ Apply a wire link across Q706 linking C and E. This links the two driver transistor bases together and forces a zero bias condition.

Retest and see if the supply voltages have come up, and if the bulb tester goes dim.

If that happens and all seems OK then we have a bias problem that is causing the outputs to conduct heavily.

Assuming it does not and the rails are still low and the bulb is still lit then leave the link in place and do the following.

2/ Remove both output transistors.

Retest and ensure the bulb is now out and that nothing gets hot. If R726 and R728 now overheat then that shows there was an existing problem with the driver transistors.

Lets take it to that point and see what you get :)
 
Hi Mooly, I jumped the Q706 at C and E and the bulb stayed lit I then removed the 2 output transistors Q712 and Q714 and the bulb went out nothing seem to get hot. The traces are really bad now how do I correct this??? Let me ask you everything was OK what i mean by OK is that the left channel was out when i replaced the dual transistors Q701 and Q702 the left channel came to life everything worked great that is until i replaced the 1384 and 684 and shorted the 2 output transistors and everything went BAD
Pat
 
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The only way to repair the print is to run fine bare wire over it. If the board has lacquer/solder resist then you need to carefully scrape that off first at points on either side of any breaks in the print.

So it looks like there is a problem with either the outputs and/or the drivers.

With the outputs still removed and the link still in place, the DC voltages should be correct so we need to check this.

1/ Measure the DC voltage on the output (at the junction of the 0.22 ohm resistors). It should be close to zero.

2/ There should be no voltage across the two 150 ohm resistors R726 and R728
 
Hi All, And Happy New Years. Well i finally got the switch for the 2216b and while i was waiting i started to fix up the bad traces and replaced some of the eyelet and low and behold when i replaced the power switch and turned on the unit everything was fine the unit sounds great the bias is spot on, i guess i had some issues with the traces and that seemed to fix my problem. I have bin running the unit for a couple of days and everything is OK. I would like to thank you all for all your help

Pat
PS on to the next project
 
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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.