Pioneer VSA 805S Probs - Schematic wanted

Omegasteffy · 10th August 2006, 10:05 AM

Hi, im am trying to repair an older Pioneer surround amplifier (VSA-805S) and are in need of a schematic. I would be happy if anyone were able to email it or link to it.
The problem is that the Left channel does not work if it is loaded and a signal is applied. If i connect a speaker the amplifier will report "Overload" and enter standby mode, once i turn the volume knob.
I tried to measure voltage at the Collector of the NPN output transistor and the at the driver. Here the supply drop from 47 V to 44.3 V before the amplifier report overload.

The power amplifiers are mounted on a pair of prints which are sperated from the remaining amplifier (signal processing, control and PSU). There is a overload line from the power amplifier which seems to be digitally controlled. A negative pulse occur on the overload line before the amplifier goes into standby.

I think it could ease the the repair a lot if anyone had a schematic or a service manual.

PS. On the amplifier modules there are made room for an extra output transistors and i guess that the same modules might are used for larger surround amplifiers from the same year 1996. I am not aware of which models this might be.

Leolabs · 11th August 2006, 01:20 AM

Try to check for shorted semiconductors and dry sloder joints.

Omegasteffy · 11th August 2006, 09:40 AM

I will try to resolder any doubtful solderings.

Yesterday i found a bad connection on the emitter resistor of the left channels power transistor. It is a shared power resistor and i resoldered all three pins. Thereby forgot to note whether it was the positive or negative part where the connection was gone loose.

Omegasteffy · 11th August 2006, 10:51 AM

Uff! It seems i might have found the flaw. It tried testing with a variable power resistor and it did not seem like it got overloaded until i went down to approx 2 ohm. I tried swiching speakers and now it seems to output sinus tones just fine. I guees i fried the speaker before i found the bad emitter resistor connection or maybee the speaker was already fried. So i think have spent a few days wondering why the amplifier did not work with this speaker, when the problem actually was the speaker

.
I will bring it home from the lab and test with music and other speakers.

10th August 2006, 10:05 AM	#1
Omegasteffy diyAudio Member Join Date: Jun 2005 Location: jutland	Pioneer VSA 805S Probs - Schematic wanted Hi, im am trying to repair an older Pioneer surround amplifier (VSA-805S) and are in need of a schematic. I would be happy if anyone were able to email it or link to it. The problem is that the Left channel does not work if it is loaded and a signal is applied. If i connect a speaker the amplifier will report "Overload" and enter standby mode, once i turn the volume knob. I tried to measure voltage at the Collector of the NPN output transistor and the at the driver. Here the supply drop from 47 V to 44.3 V before the amplifier report overload. The power amplifiers are mounted on a pair of prints which are sperated from the remaining amplifier (signal processing, control and PSU). There is a overload line from the power amplifier which seems to be digitally controlled. A negative pulse occur on the overload line before the amplifier goes into standby. I think it could ease the the repair a lot if anyone had a schematic or a service manual. PS. On the amplifier modules there are made room for an extra output transistors and i guess that the same modules might are used for larger surround amplifiers from the same year 1996. I am not aware of which models this might be.

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11th August 2006, 01:20 AM	#2
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Try to check for shorted semiconductors and dry sloder joints.

11th August 2006, 09:40 AM	#3
Omegasteffy diyAudio Member Join Date: Jun 2005 Location: jutland	I will try to resolder any doubtful solderings. Yesterday i found a bad connection on the emitter resistor of the left channels power transistor. It is a shared power resistor and i resoldered all three pins. Thereby forgot to note whether it was the positive or negative part where the connection was gone loose.

11th August 2006, 10:51 AM	#4
Omegasteffy diyAudio Member Join Date: Jun 2005 Location: jutland	Uff! It seems i might have found the flaw. It tried testing with a variable power resistor and it did not seem like it got overloaded until i went down to approx 2 ohm. I tried swiching speakers and now it seems to output sinus tones just fine. I guees i fried the speaker before i found the bad emitter resistor connection or maybee the speaker was already fried. So i think have spent a few days wondering why the amplifier did not work with this speaker, when the problem actually was the speaker . I will bring it home from the lab and test with music and other speakers.

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