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Pioneer SA-9500

Bobyoung53

Bobyoung53

New Member
I just got it up and running today, ran great the first few hours, nice and loud, then a relay tripped for a second, sound went dead but came right back, I detected no heat, nothing overheating, no heat from the output stage at all. The speakers I'm using are so so 6 ohm Pioneer speakers. The problem is I shut if off for a while and use it again and the interval between the relay kicking off and shutting the sound gown are gradually getting shorter and shorter, until right now they relay won't even kick on after a few seconds sometimes, the sound is dead for varying lengths of time. I'll check it tomorrow and see if after having been off all night it will function for several hours again like if first did today and at a decent volume, I suspect not though, volume seemed to have nothing to do with setting it off and /i had it fairly loud today for a good hour,
Any advice would be appreciated, It sounds good when working, also I know if can run down to 4 ohms and these are 6 ohm speakers, could the impedance of these have anything to do with this problem? In other words for these amps to be run at 4 ohms does it need to be 2 pairs of 8 ohms speakers into both A&B or am I overthinking it, are the A&B outputs paralleled or not?
 
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spiette said:
When the speaker switch is in the A+B position the two are connected in parallel.

View attachment 2274249
Click to expand...


OK thank you, that is what I would have thought, so having a 6 ohm load on one output should not be triggering the protection relay as they are good down to 4 ohms. Any ideas of what is triggering thi relay anyone?I smell nothing and there is no heat at all coming from the output section, the heat sinks are not even warm.
 
My SA-9500 is sitting on a shelf because the protection circuit failed and wouldn't switch on the relay. I didn't get to dig into it before life got in the way.
From what I've read it's a common fault due to either failing transistors or a cap in the circuit but it could be doing exactly what it was designed to do so start with the basics.

There are several good troubleshooting threads here on this model. If your comfortable with a voltmeter and a soldering iron you should have it working fine in no time.

The first thing I would look at is the DC bias voltage on each channel before opening the case up. Once you do the next stop is measure the voltages on the power supply board.
 
spiette said:
My SA-9500 is sitting on a shelf because the protection circuit failed and wouldn't switch on the relay. I didn't get to dig into it before life got in the way.
From what I've read it's a common fault due to either failing transistors or a cap in the circuit but it could be doing exactly what it was designed to do so start with the basics.

There are several good troubleshooting threads here on this model. If your comfortable with a voltmeter and a soldering iron you should have it working fine in no time.

The first thing I would look at is the DC bias voltage on each channel before opening the case up. Once you do the next stop is measure the voltages on the power supply board.
Click to expand...


OK thanks, It stopped doing it yesterday and it's been on for hours both yesterday and today. I did turn the speaker switch back and forth several times and also made sure the speakers wires were making good contact on the amp and it seems to have straightened out. I can hear it switching on after a few seconds, it does pop a little bit when it's turned off though. I've read that's not good.
 
You have only one pair of speakers connected, at 6Ω, right?
Popping at power off usually means the protection circuit is not dropping the relay soon enough after ac loss.
I suspect you have a tired old protection circuit that could use a rebuild. Has anything been done to this unit, as far as servicing it?
 
That pop

get the amp going, warmed up etc...
THEN turn down the sound to zero, and measure the DC offset at either the speaker terminals in back, or at the speakers themselves.

Report back the values for the two channels.

Another - NOT easy test - is to find the lamp fuse (by tracing the blue transformer wires)
on the (vertical!!) AWR-074 board that has the (red transformer wires) rectifiers for the 18,000 uF caps.
Open and close the lamp fuse like a knife switch, when the fuse is open, the protect should
disconnect the speakers. IF it does so, even with a small pop, it IS working correctly and the
DC offset at the amplifier output should be addressed further.

IF the protect is NOT disconnecting the speakers when the lamps are turned off, it is probably
NOT doing DC protect or over-current functions (they are all related) either!!
 
merlynski said:
You have only one pair of speakers connected, at 6Ω, right?
Popping at power off usually means the protection circuit is not dropping the relay soon enough after ac loss.
I suspect you have a tired old protection circuit that could use a rebuild. Has anything been done to this unit, as far as servicing it?
Click to expand...


I have no idea if it was ever serviced but I doubt it. Yes one pair of 6 ohm speakers. I think I'm going to change these speakers, I just bought them, obviously nothing to do with the popping, just don't like them.
 
markthefixer said:
That pop

get the amp going, warmed up etc...
THEN turn down the sound to zero, and measure the DC offset at either the speaker terminals in back, or at the speakers themselves.

Report back the values for the two channels.

Another - NOT easy test - is to find the lamp fuse (by tracing the blue transformer wires)
on the (vertical!!) AWR-074 board that has the (red transformer wires) rectifiers for the 18,000 uF caps.
Open and close the lamp fuse like a knife switch, when the fuse is open, the protect should
disconnect the speakers. IF it does so, even with a small pop, it IS working correctly and the
DC offset at the amplifier output should be addressed further.

IF the protect is NOT disconnecting the speakers when the lamps are turned off, it is probably
NOT doing DC protect or over-current functions (they are all related) either!!
Click to expand...

OK thanks, 22.6 mV right channel and 19.3 mV on the left channel. I'll have to take it apart for the lamp fuse test and won't have time until I finish working on my Ampeg SVT which hopefully won't be long as it's got to be ready for Friday.
 
Bobyoung53 said:
OK thanks, 22.6 mV right channel and 19.3 mV on the left channel. I'll have to take it apart for the lamp fuse test and won't have time until I finish working on my Ampeg SVT which hopefully won't be long as it's got to be ready for Friday.
Click to expand...
Those numbers are not bad, but it is adjustable on the SA-9500. If it was mine, and in place in a system, I would not pull it to adjust it. YMMV.
 
merlynski said:
Those numbers are not bad, but it is adjustable on the SA-9500. If it was mine, and in place in a system, I would not pull it to adjust it. YMMV.
Click to expand...


Two questions although I think you already answered the first one:

1. Will it hurt it to leave it like that?

2. Will it sound better if I adjust them?

It's just sitting on top of some shelves.
 
As for DC offset:

1. It will not hurt it to leave it like that. IMHO that is not enough offset to cause any problem.

2. It probably will not sound any different is you adjust it. This is a judgement call and is very subjective.

Lastly, the pop at power off may indicate a slowly growing problem, but IMHO, it is with the Protection circuit, not the power amp / DC offset.
 
merlynski said:
As for DC offset:

1. It will not hurt it to leave it like that. IMHO that is not enough offset to cause any problem.

2. It probably will not sound any different is you adjust it. This is a judgement call and is very subjective.

Lastly, the pop at power off may indicate a slowly growing problem, but IMHO, it is with the Protection circuit, not the power amp / DC offset.
Click to expand...


OK thanks, the relay clicks off at about the same time as the pop, in fact it sounds like it may be clicking off mid pop, in other words it cuts it off, it's not very loud, the relay click is just as loud as the pop.
 
FWIW, just to be OCD, if the pop gets louder or longer so you have a large enough pop it can damage speakers. If it is no louder than the relay it just needs monitored.
It can be fixed if you want. :cool:
 
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