Pioneer sa-9800 with slight mains hum?

Here's one other thing you can try while waiting to get some good cleaner and lube for your switches and pots. The hum just recently became noticeable correct? Can you try plugging it into a different outlet? What about trying it at a friend's place that's not in your building? Though the hum could be the beginning of capacitor issues, I'm trying to rule out the "dirty power" issue. So, getting it on a different home circuit might help, even though you've tried turning off other lights etc. Did you replace any major appliances? Did the building manager make other changes to heating/cooling/electrical systems?

If these ideas don't yield any improvement, the issue most likely does lie in your amp. MTF will be able to guide you through some of the voltage troubleshooting to narrow things down, but a rebuild of the power supply and/or protection boards may be in store. To me it seems that the preamp section is doing what it's supposed to, amplifying a low-level signal to send to the power amp boards. In this case it's an unwanted signal (AC or DC somewhere it's not supposed to be) that's now being amplified to audible, annoying levels.

If the rebuild is in order, and you've had no experience soldering and replacing electronic components, hopefully there's a decent repair tech in your area. With a near TOTL amp, you don't really want to go mucking about in it for your first repair attempt. There's a KA-7100 1st recap thread currently in the Kenwood section that will show what can happen if you've never soldered electronic components before.

Not trying to be harsh or scare you off of it, but before you dig into THIS amp, get your feet wet in a "disposable" BPC receiver or amp first, or just something else electronic. Since you didn't know what the Pre-out/Main-in jumpers were until I posted a pic, my confidence level isn't real high that you've had a lot of electronics experience and that you won't do more harm than good trying to chase down a VERY faint hum.
 
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Well i tried that as you said MTF and still the same im afraid.
But i would like to say im very greatful for all the input ive received so far, it means alot that there are other people dedicated to this stuff best forum ever ☺

so.....what next lol.

Your 3 word answer, "still the same"....

I am extremely disappointed. I took all the time to explain the test conditions, and you sacrificed an RCA cable to it.

And all I got was a cryptic "still the same". Same WHAT? I need a matrix of answers to pick apart the signal flow.

I'll try this just one more time. I am about to just "walk away".

EXPLAIN THE BLOOMING SYMPTOMS IN EACH OF THE TEST MODES I DESCRIBED. Fiddle with EVERY blasted switch and control on the front panel in every mode.

The FACT that there is still hum with shorting plugs if you EXPLICITLY did what I said, would prove where and WHERE NOT the hum was being GENERATED INSIDE THE BLOODY UNIT!!!

The balance control can have an effect, or not
the volume control can have an effect, or not
the tone controls, filters and whatnot including the mode switch - is one channel louder than the other, does the mode switch affect this?
Is it louder in phono? and so on and so forth.

EVERYTHING IS A CLUE: POSITIVE OR NEGATIVE.

This is NOT anger, it is frustration.

Next step is to read and post the awr-191 ground referenced power supply voltages found on pins 1 through 13 inclusive, and also pin 15 skipping all other pins for now (especially 16, 17, 18)

as that I've been up 24 hours straight, I'm going to bed.
 
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Hi P-Nut. You have a worthy amp there, and we'd all like to see it healthy again. One of the zillion parts inside has likely failed, so very specific answers are need to home in on the problem. Mark is really good at this - with enough information, he will tell you exactly which part has failed. The cost of the failed part is probably really low, by the way.

Of course, the new part will have to be installed. Do you plan to do that, or do you have a friend who is handy with a soldering iron? During the installation phase, it is even more important to follow directions to the letter - take no shortcuts, do no more than asked, do no less, report back with all information, don't turn the thing on until instructed, etc. You might also have to get or make some basic test gear like a voltmeter and a dim bulb tester.

If you look around this site, you'll see a lot of people seem unable to do this. They are instructed to install a capacitor, then to post a picture so we can check their work. But instead of doing that, they reply with "I replaced the capacitor and plugged it in and turned it on and there was a loud explosion, and sparks flew everywhere, so I got my screwdriver and turned all the trimming resistors fully clockwise, and both my speakers started smoking." That's why Mark can get frustrated.

Here is the link to your service manual.
http://akdatabase.com/AKview/displayimage.php?album=43&pos=91

Twodogs
 
hi two.dogs - i understand what your saying, and i apologise to mark for my lack of explanation.

i will carry out the last test he mentioned and explain it properly, it makes sense about what he's saying and i really do appriciate the help - so i didnt mean to come across as a 'prat' cutting corners or anything.
thanks again
 
I'll try this just one more time. I am about to just "walk away". EXPLAIN THE BLOOMING SYMPTOMS IN EACH OF THE TEST MODES I DESCRIBED. ...if you EXPLICITLY did what I said, would prove where and WHERE NOT the hum was being GENERATED INSIDE THE BLOODY UNIT!!!

This is NOT anger, it is frustration. ...as that I've been up 24 hours straight, I'm going to bed.

I LOVE Mark. He's a true saint...!
 
Right, did checks on the amplifier as follows:
Used short plugs for each of the inputs and here are the results.

AUX: hum present with volume on low and on high, when i have the volume on high or flat when i increase the bass knob i can hear the adjustment being made which was never like that before i discovered the hum.
treble only has an effect to where you can identify the hum more when turning the knob to max, tone control has no effect apart from making the hum stand out more when enabled - loudness also has the same sort of effect as tone control.
the bass and treble tune overs switches dont have any kind of effect at all as well as the filters.
this was the same result throughout with tuner and the tape switches.
phono 1 and 2 hum still present with volume on flat obviously i cant hear the hum with volume on max because of the nature of using a phono input ( bg noise forgot what the actual name of it is sorry )
the mode switch has no effect apart from when choosing rev l r or stereo you can hear the hum being changed over ect depending on what option you choose, AGAIN this goes for all the inputs mark asked me test out.
One thing i have noticed is that whilst testing the inputs with volume on high the usual hiss went from left and right to just right then, just moving the volume knob back say 3-4 notches brought the hiss back to both channels - still there but more on the right.
When first powering on from cold i have noticed that after the relay 7 seconds bang on the hum ( as faint as it is ) is more apparent in the left channel then after 2 seconds it moves over to the right as well as the left obviously.
Speakers selection switch from b to a+b for some odd reason seems to switch the hum around from L R to R l, I know it sounds crazy but i notice the smallest of things.
There is no activity on the read out meter regardless of volume selection.
Listening to both transformers im sure the transformer towards the back of the amp sounds a little more high pitched then the other one, could just be me looking for faults could be normal.

The whole test above was tested with 2 pairs of headphones and 1 set of speakers, the hum is stronger through headphones but very quite on the speakers to where i have to have my ear placed right on the woofer/tweeter, HOWEVER i have also noticed when i connected the speakers to the amp is that the hum seems to be just that tiny bit stronger on the left channel than the right channel - and iv'e only just noticed that whilst carrying out the test this afternoon.
Could be something to do with the way the transformers hum?!

I hope the information above is enough and again my apologies to Mark for not giving enough detail :)
 
Afternoon folks, well its the afternoon here anyway
Being advised by the ealier replys to get some caig deoxit, i have provided a picture below cananybody tell me if this is the right type to go for!
One can is the cleaner and i suppose the other is a lubricate type - its located here in the uk for £32 so not too bad i suppose.
Thanks.
 

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Hi guys, not sure why im not getting any replys to my thread but a message for MTF, if its a waste of time me posting on here then just let me know and if so i will delete my acoount as i dont want to waste anymore of your time.
Thanks anyway have a good day.
 
hi peter, i bet he is very busy man ( no intention of coming across rude ) i just thorght maybe i had annoyed him a little too much
I appriciate you letting me know i feel silly now haha.
 
hi peter, i bet he is very busy man ( no intention of coming across rude ) i just thorght maybe i had annoyed him a little too much
I appriciate you letting me know i feel silly now haha.

Believe me, you did not annoy Mark. He is a very generous person to provide his time and knowledge on Pioneer gear - for free. However, you must be patient and you MUST do all steps in the correct order and accurately IF you want your unit to work properly (or at all). It will get done. If I had even a smidgen of the knowledge he has, I would offer it up, but he knows electronics and this vintage Pioneer gear like the back of his hand. Plus, he, like many, does have a life outside of AK. His generosity should NOT be taken for granted, please.
 
Hello, im not taking taking the mickey with anybody and i appriciate your comment - helps me to understand a little more about this unique site which indeed it is.
Like i said previously about annoying Mark - i didnt want to waste his time IF i had peed him off but i DO understand the importance of how busy he must be, obviously im new to the site so im understanding more little by little, reading all the old posts and gosh he's sounds a right clever one
Take care my friend.
 
Here's my two pence...

Do what you can while waiting for responses, it helps the time pass more quickly. So, if you've received your cans of deOxit and Faderlube, go ahead and read the guide to using them...not sure which forum it's on, but it's a sticky. This could (but may not) solve the problem you're starting to notice. It will also start to get you familiar with all the switches and their operation, where certain parts are that you'll be asked to reference, etc. that way, when you get the more specific tasks to accomplish, you'll have more confidence, and you'll have a positive repair, if repair is needed.
 
Hello everybody, just a quick update:
My caig products arrived a few days ago, I followed the instructions and after a few hours I managed to clean all the pots and lube them.
My original problem is still present so i would appreciate any inputs, many thanks again hello from the UK.
 
Pots are NOT the only things that get deoxited, EVERY switch (everything that goes in n out, up n down, back n forth or roundy round) and even the pre-out / amp in external jumpers.

See, occasionally I do answer quickly...

And if I don't see the forum, I certainly can't see the PM's sent.

As to the original problem, headphones reveal hum even with the pre-out / amp-in jumpers (in the back panel's center) pulled?

May be DMM time...
 
Hello Mark and thanks for the reply, well I worked through everything and double checked on what you said and can confirm that all pots switches and rear jacks have been worked on.
I took my time on working through everything too.
Now with the pre main jumpers removed, the hum is not present even with volume on max - it also seems the hum is VERY SLIGHTLY more apparent in the right channel ( with headphone or speakers )
Thanks again look forward to hearing crom you.
 
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