Re: Marantz PM-66SE Burns Transistors
Only thing that goes to the amplifier board is that three pole transformer cable. Nothing else.
Q752 stays cool as well as R752 and it is very good looking, like a new and reads 10 kohm.
As I have told before, there is something "going on" on that board. Sometimes voltages are steady and stable, sometimes some voltages fluctuates all over the place and so on......
Announcement
Collapse
No announcement yet.
User Profile
Collapse
-
Last edited by hyva_ana; 03-09-2023, 12:16 PM.
-
Re: Marantz PM-66SE Burns Transistors
Here are some voltages:
[url]https://www.badcaps.net/forum/picture.php?albumid=308&pictureid=968[/url]
Now all the voltages were pretty stable, unlike on earlier measurements. Things really seem to change on this amp board...
I don't know much of these, but I just wonder those QN03 voltages, or especially collector voltage.Re: Marantz PM-66SE Burns Transistor...<br /> <br />
Leave a comment:
-
-
Re: Marantz PM-66SE Burns Transistors
Q752: B and C; voltage rises to about 26V for a little while and then rapidly drops to about 10 V, then it drops more slower towards zero - the lower it get's the slower it drops. But, when I cut the power off, the voltages rises rapidly to about 15V, and then drops to zero within couple of seconds. This same thing applies to Q702 collector.
Q752: E -25.6V
When I measured voltages again from Q752 E, it goes first to about +22V, then it rapidly drops to couple of volts and then slowly to zero and from there to negative...
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
Those are not shorted.
Q801: B 24.4V; C 41.0V; E 23.8V
Q802: B -18.0V; C -40.3V; E -17.5V...
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
Back again.
What exactly you mean by this: are you shorting the inputs to 0v during testing?
Q754 B-E: 0.62V. Q756 B-E: 0.58V
Components that warms up: Q763, Q764 (1k resistors between B-E), Q756, Q760, Q704, Q703 (warmest), Q728, R732.
R762 is in its place and not even getting warm.
Q702 B: 22.6v; C: 18.6V; E: 23.2V
Q704 B: -16.7V; C: 13.9V; E: -17.2V
Those are readings when I'm driving that board with two in series connected BPS, with...
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
I'm taking a few days off from this project. I'll get back to it soon.
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
Now those transistors are back in their places, except Q757-Q764.
Q754 @B 17.8V, Q756 @B 14.5V
Q758 @B 17.8V, Q760 @B 14.5V
I don't know if I'm just too tired or what, but I could almost swear that when little earlier I measured those bases of Q754 and Q756, the voltages were negative, and now those are positive...
But now, state is steady.Last edited by hyva_ana; 02-14-2023, 11:20 AM.
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
And now:
QN01, QN02, QN03
Q701, Q702, Q703, Q704
Q801, Q802
This means that whole board is stripped out of transistors, and none of them is faulty (or at least not shorted). How close these small transistors (2SC2240 and 2SA970) should be each other in terms of gain?
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
Now I tested all of these transistors:
Q757, Q758
Q753, Q754
Q751, Q752
Q755, Q756
Q759, Q760
All of those are good and in right position.Last edited by hyva_ana; 02-13-2023, 12:12 PM.
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
Q754, first rises to about -12V then starts dropping.
Q756, first rises almost -17V then starts dropping.
I have to build that light bulb current limiter.
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
I removed those output transistors and soldered 1kohm resistors between base and emitter places. Now resistors "in" Q762 and Q764 gets burning hot after couple of seconds when I turn the power on, and same goes to Q759 but it warms slightly slower - anyway, temperature in it rises so much, that I must shut power off after a few seconds.
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
And these are the output transistors?...
Leave a comment:
-
-
Re: Marantz PM-66SE Burns Transistors
Voltage is -0.9V
I'm pretty new to audio amplifiers, so what do you exactly mean by "add resistors from where the bases and emitters connect"?
And, I have not connected any other thing than transformer leads in to it....Last edited by hyva_ana; 02-12-2023, 01:32 PM.
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
I'm not sure what you mean, but in front panel is a plate which says "KI Signature", so maybe it's KI model?
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
No it's not. Just removed it from the board and measured....
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
R806 and D804 gets hot. From transformer comes 32.8 VAC. After bridge rectifier comes + / - 44.8 VDC. All of the voltages are higher than printed on the schematic.
Voltages from QN02:
B C E
-22.1V ; 44.7V ; -22.1V, so far away from what those should be.Last edited by hyva_ana; 02-12-2023, 10:15 AM.
Leave a comment:
-
Re: Marantz PM-66SE Burns Transistors
Yes. screwed down to the heatsinks and properly insulated. Caps inserted as they should be.
I have not found any shorted transistors and all transistors I have changed are likewise.
About voltages, they seem to be all over the place:
B; C; E
Q802 -18.5 V ; -43.4 V ; -18.0 V
Q801 25.1 V ; 44.3 V ; 24.6 V
Diodes:
Cathode; Anode
D805 0 V ; -18.7 V
D804 25.2 V ; 0 V
D803 -18.8 V ; -18.5 V
D806 ~32.9 V ; ~8 V
D802...
Leave a comment:
No activity results to display
Show More
Leave a comment: