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Old 13th January 2012, 10:27 AM   #1
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Default Marantz PM-40SE No sound.

Hi,
I am going crazy. Received this amplifier as broken. There were plenty of bad joints but after resoldering it does not give a sound. It turns on, LEDs are on but no “click”.
I checked drivers, I tried run it without drivers – no effect. The PSU voltage seems to be ok: +/- 38.4V (for drivers) OK, +24V OK, -18V OK. I do not have 2.9V on pin 9 and 1.3V on pin 8 of TA7317P (protect circuit).
Any ideas?
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Old 13th January 2012, 10:37 AM   #2
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Default schematic

Hi

Do you have a schematic of the amp and a scoop and signal gen.

Regards,

Audiofanatic
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Old 13th January 2012, 10:45 AM   #3
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by Audiofanatic View Post
Hi

Do you have a schematic of the amp and a scoop and signal gen.

Regards,

Audiofanatic
+1

We need to see the circuit.

Have you checked the DC offset voltage at the output (before relay) of each channels power amp. What does it measure ?

Is the output stage drawing current (check by measuring across emitter resistors). What is the current ?
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Old 13th January 2012, 11:18 AM   #4
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Thanks guys,
Diagram herehttps://dl-web.dropbox.com/get/maran...pdf?w=bc6e9674
I did not check offset before relay. I'll measure it and post .
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Old 13th January 2012, 03:47 PM   #5
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The dropbox thing say I don't belong

If the pdf is under 1mb try putting it in a zipped folder and posting directly on the site.

Offset is the first thing to check (with the drivers fitted).
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Old 13th January 2012, 04:09 PM   #6
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Quote:
Originally Posted by Mooly View Post
The dropbox thing say I don't belong

If the pdf is under 1mb try putting it in a zipped folder and posting directly on the site.

Offset is the first thing to check (with the drivers fitted).
Ok.
The schematic is here
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Old 13th January 2012, 04:29 PM   #7
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Resistors 801, 802, 803, 804 in the PSU blow in the PM-66 and cause similar symptoms

Try checking them.


Andy
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Old 13th January 2012, 05:38 PM   #8
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Default Check the resistors

Like mooly said check for DC offset on the output before the relay.
This can be done by measuring the voltage on the resistors R713 and R714. measure both sides of those R's.
The offset must be around 0 volts. If it's more than the protection circuit will never release the relay.

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Last edited by Audiofanatic; 13th January 2012 at 05:39 PM. Reason: wrote the name of my fellow member wrong.
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Old 13th January 2012, 09:04 PM   #9
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Quote:
Originally Posted by Mooly View Post
+1

We need to see the circuit.

Have you checked the DC offset voltage at the output (before relay) of each channels power amp. What does it measure ?

Is the output stage drawing current (check by measuring across emitter resistors). What is the current ?
There is 6mV on both after power up.


Quote:
Originally Posted by poynton View Post
Resistors 801, 802, 803, 804 in the PSU blow in the PM-66 and cause similar symptoms
Try checking them.
Andy
Resistors 801, 802, 803, 804 are checked. I have +24.3V and -17.3V on emiter Q801 and Q802
Quote:
Originally Posted by Audiofanatic View Post
Like mooly said check for DC offset on the output before the relay.
This can be done by measuring the voltage on the resistors R713 and R714. measure both sides of those R's.
The offset must be around 0 volts. If it's more than the protection circuit will never release the relay.

Audiofanatic
Right. It is not around ZERO. It is -14.5V !!!
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Old 14th January 2012, 10:56 AM   #10
Mooly is offline Mooly  United Kingdom
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You need to recheck your readings... look at the circuit

The 6mv (where I said to measure before the relay) are the same points (apart from passing through the large output inductors as R713 and 714. Something amiss in the readings there (unless something drastic has happend like it being dropped and the PCB is cracked).


Measure the DC voltage on the "output" line. That is the line that goes to L751 and L752. It should be around zero. If R713/4 really are at -14.5 then there is physical damage as it is a direct connection between these points.
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