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SA-8800 no right channel on power up.

QSilver

QSilver

Super Member
I've been going through doing a recap of this beast which has gone well - as well as replacing a number of resistors that were looking past their best...

Before the re-cap and after, I have noticed that on first powering the amp on, the left channel works fine but the right channel isn't there at all or is very weak and distorted until you give the volume a boost. Then it kicks in loud and clear and will continue to work if you turn the volume back down. The volume and all other controls have been cleaned with Deoxit. The volume had been crackling a little but that's stopped now.

I've tried looking for the problem and I haven't managed yet as when its on the bench, it doesn't seem to do it as much! My thoughts are that it might be a problem in the tone amp section as that seems to be the last thing after the volume control besides the NSA amplifier.

Are there any places I should check first or am I looking in the wrong place?
 
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Sounds like a protection relay. A classic description of pitted contacts. You have to boost the current through the contacts by increasing the volume to get a signal to pass - once the contact is established all is well.

Look at the top of the relay for any identifying part number.
The Pioneer P/N is ASR-023 a replacement is ? (So far)

Found this quote: :dunno:
Thanks for the information folks. As EchoWars noted, the part number isn't necessarily as informative as needed. For reference sake, the cover also has "Type MS4U" and "24 VDC". The Omron MY4-02-DC24 does look to be a correct replacement part (Mouser part No. 653-MY4-02DC24). I have to agree with markthefixer, if I need to take the unit out to clean or to replace, then there's little point in trying to clean it. As an update, to eliminate the switches and potentiometers from the list of candidate problems, I did a second round of cleaning the potentiometers and switches with Deoxit and then lubricated with fader lube. That seems to have improved things, so I'm going to monitor the relay's performance over time and if the problem persists, I'll replace the relay. Again, many thanks for your assistance.
 
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Thanks guys good idea. I guess that hadn't really crossed my mind. It would probably make sense as sometimes when I was checking if it was a dirty speaker switch, the fluroscan would change its average level. Then when you reconnected the speakers it would drop back again while the problem was there. Thanks for the quote I'll take a look at a replacement relay. As a further diagnosis, could I try tapping the relay or will this not change much?
 
I'll do that next time the problem presents itself. I just have it on quietly at the moment with no problems and it seems that the main heatsink is running at about 50°C according to my IR thermal meter. Is that okay for this model? I know the idle current is 70mV... just thought I would check.
 
I was checking a perfectly running Rotel RX-1603 this weekend. Driving a set of 4 ohm Infinity's at moderate volume with an OAT of 34c and was reading 45c on the heatsinks. Increasing volume to loud, it ran 51c at the heatsink.
 
i cant remember if mine puts out much heat . its been a while since i used it ..it does use lots of electricity at idle so i guess it will get fairly warm .
 
Re the relay, its definitely that. I tried tapping it and the signal came and went so I'll take a look into getting something to replace it with. I'm thinking of trying to get a new Omron of some kind...
 
Thanks for the link. I'll take a look at that and compare with the old relay - will probably pull it out in a few days time to check it out.
 
EchoWars said:
The 8800 should be a MY4-02-DC24.
Click to expand...

Thanks. I was looking at MY4's... I was thinking of going with a MY4IN-D2 seeing how that has a suppression diode built into it which will help with transistor life in the protection circuit. I just need to check that it will fit...
 
Problem with the built-in diode, it may be oriented incorrectly.

The coils are DC...they will engage regardless of the polarity applied to the pins. But the ones with the internal diode are not reversible and depending on how Pioneer decided to wire up the coil, you may burn up a resistor and possibly the relay driver trannie. These devices are great for new design...not so much for retrofitting.

...and D14 on the power supply board is already performing that operation anyway.
 
Yep, I see that D14 is doing its job so I won't bother with that "innovation". The standard MY4 is cheaper anyway so that's a bonus! Thanks for the tip on retrofitting the new one with integrated diode, I will bare that in mind if I ever think of using it in a system again.

EDIT: While I'm getting the new relay, I really should change the trimmers too... I'm looking at the 68k trimmers... is it okay to replace these with 50k or would it be better to go up to 100k. It seems they are the only options I have around the range of 68k...
 
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Any help on replacement trimmers? The closest I can get to 330k is 300k and 68k... I guess the closest I can find is 100k. I just replaced the trimmers on the NSA in a D5000 and these required totally different values which were easy to find.

Would the 300k be okay or when it is set to minimum is the amp seeing 330k or 0? ie is that extra 30k important enough to warrant a larger value?

The same with the 68k too...
 
Need to go through the adjustment procedure, power down, and measure the value of the trimmers to see if a new value will keep you in the necessary range. Problem is that measuring in-circuit can be tricky, and to get an accurate reading a careful desoldering (without disturbing the position of the pot) might be necessary.
 
the pots should be linear . so if sat in the middle they should be half of rated value . if anything else you can only take a guess or do as echo rightly says and remove and test the values as they are now .
if i remember rightly there are 2 pots each side for bias . one to get in ball park and other to finely tune .
 
Yes, I went through the alignment with the amp when I got it. There are a further two pots - one per channel to the DC offset. I was about to look at the schematic and see if I can work out from that how the trimmers behave with the rest of the circuit. Removing these kind of pots without disturbing them can be tricky...

I'll take a look at it on the bench soon and see if I can check the values of the trimmers.
 
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