AU-317 running warm?
- Thread starter h3ll0
- Start date
stereofun
Super Member
I am in the "take a bias reading" camp. It is real easy and something that is always a good idea with any "new" amp. Heat is mostly generated by resistors or transistors, not caps.
Bias is like the rpm of an idling engine - it prevents the transistor from switching off for the period of time the other half of the waveform is being conducted. By keeping some rpm going it is instantly ready to "drive" it's half waveform at its turn. Set too low and it will be too slow to get up to speed (cross over distortion) - set too high and its like an engine idling at 4000 rpm just generating excess heat while parked. But the idle setting, has nothing to do with how hard the speeder eventually is pressed down to drive its half cycle - aka - how loud it plays.
Bias is like the rpm of an idling engine - it prevents the transistor from switching off for the period of time the other half of the waveform is being conducted. By keeping some rpm going it is instantly ready to "drive" it's half waveform at its turn. Set too low and it will be too slow to get up to speed (cross over distortion) - set too high and its like an engine idling at 4000 rpm just generating excess heat while parked. But the idle setting, has nothing to do with how hard the speeder eventually is pressed down to drive its half cycle - aka - how loud it plays.
Last edited:
My experience with the glue (there are few different formulations of the same thing) is that acetone merely softens the glue. After 10 or 15 minutes the glue is softened and looses its grip just enough that you can scrape it off, thus it is about timing as vigman says - but also patience.
The key here is use a 'blunt' scraper preferably not metal. The kind of thing that skippy124 uses is just about perfect in my opinion, (fibreglass PCB material). I use a combination of a blunt pen knife, a hard plastic scraper and, would you believe, snipe nose pliers !!!
I also feel that using Q-Tips is almost ridiculously fussy for removing this stuff (sorry guys), I use a small artists paint brush, and apply more to refresh the application every 5 minutes or so for the toughest of those formulations. :yes:
Last edited:
Karl vd Berg
Super Member
I'm in this camp, too. Bias value drifts easily in a vintage amp and due to a variety of things (including room temperature at a more paranoid level). Anything can affect bias, from faulty components to old trim pots behind it.
I always replace the old pots in any amp: http://www.audiokarma.org/forums/showpost.php?p=7527661&postcount=36
There's an old article about it if the OP is interessed:
http://www.tnt-audio.com/clinica/bias_e.html
..
Last edited:
vigman
SUBSCRIBER
John, I use q tips ( old skool wood,long shaft ) cause I got's a million of em.. but all my artist brushes... have gone... somewhere....and never have replaced em... and Ipod plastic opener works well too as a scraper....
But this is all MUTE if the OP isn't going to replace the caps...
I still think the " stain " is from a cap venting.... from a while back....
But this is all MUTE if the OP isn't going to replace the caps...
I still think the " stain " is from a cap venting.... from a while back....
There is no such thing as a dedicated bias measuring tool. The tool needed for this would be a common DMM. Instructions for reading/adjusting bias are included in the Service Manual which is available here in the AK database for free. Here is the link: AK database page w/ AU-317 SM
Adjustments would be made using a small screwdriver. Ideally it would have a plastic blade, but if not you could put electrical tape on the blade to insulate it all except for the tip. Same thing for the DMM probes. If you do any work inside the amp be careful not to short anything out. Reading bias and adjusting it is done with the amp powered up
Adjusting the bias may or may not cool down the amp, but it would be a good thing to have properly set if you feel up to it.
Adjustments would be made using a small screwdriver. Ideally it would have a plastic blade, but if not you could put electrical tape on the blade to insulate it all except for the tip. Same thing for the DMM probes. If you do any work inside the amp be careful not to short anything out. Reading bias and adjusting it is done with the amp powered up
Adjusting the bias may or may not cool down the amp, but it would be a good thing to have properly set if you feel up to it.
Last edited:
h3ll0
Active Member
So I just need a mutimeter and some probes? Well I could do that.
I guess I'll give the amp to a repair shop to replace those two caps and resistors as a full recap would cost over $100 just for the caps.
Overall the warmth is coming from the area AUD101 pointed out and thats normal.
Last edited:
Multimeters come with probes. Maybe "probes" isn't the right term IDK, but they always have their own leads or whatever...
Yes, you could do that. Be aware that the amp needs to be warmed up, volume set all the way down, no inputs connected, loudness button not activated, balance centered, etc. Also, the bias reading you see may be steady and stable or it may fluctuate. After you make an adjustment give the amp a few minutes to settle then take another reading. If you are uncertain about anything just post back here.
Bias setting too high means that the main output transistors are generating unnecessary heat. Bias too low means that there would be some amount of crossover distortion. Whether (or at what point) that distortion would be audible I don't know, but any audiophile would cringe at the thought of having any...
Yes, you could do that. Be aware that the amp needs to be warmed up, volume set all the way down, no inputs connected, loudness button not activated, balance centered, etc. Also, the bias reading you see may be steady and stable or it may fluctuate. After you make an adjustment give the amp a few minutes to settle then take another reading. If you are uncertain about anything just post back here.
Bias setting too high means that the main output transistors are generating unnecessary heat. Bias too low means that there would be some amount of crossover distortion. Whether (or at what point) that distortion would be audible I don't know, but any audiophile would cringe at the thought of having any...
Karl vd Berg
Super Member
If I remember well, there's someone from Kelowna, BC who's an AK member.
Just put an ad in the Vintage Solid State forum asking for a help in your area. Although reading a service manual could be "easy", set bias and DC offset you still need to take a lot of care while working in an operating amplifier... And you'd learn how to do and understand a bit more for the next times...
Last edited:
pete_mac
Super Member
The cost price of every cap inside the AU-317 should be less than $30 for all caps excluding the filter caps, and around $60 if you decided to fit the correct Nichicon Gold Tunes filter caps from Partsconnexion.
h3ll0
Active Member
If you take into account that I live in kelowna and that there is only one place that stocks capacitors and doesn't have most of them and the cost of shipping and tax from a place like partsconnxtion or digikey the cost becomes around $100.
I wanted 2 10uF 50V bipolar caps at $0.67 each and shipping was $11 from parts connexion. For digikey for most of the caps on a AU317 it was $20 for shipping.
Grand total was $65 at partsconnection and $32 at digikey and $15 at element 14.
Attachments
Last edited:
To be fair, I think the OP has had a lot of info coming at him fast, lol. There is a lot to learn when you're starting from scratch.
IMHO baby steps... try setting bias and see how that goes. DC offset is right there at the same skill level, and also in the SM and same tools required.
FYI Digikey has free shipping on prepaid orders to the US and Canada:
http://dkc1.digikey.com/us/en/mkt/terms.html#Pay
See sub-heading II-6
IMHO baby steps... try setting bias and see how that goes. DC offset is right there at the same skill level, and also in the SM and same tools required.
FYI Digikey has free shipping on prepaid orders to the US and Canada:
http://dkc1.digikey.com/us/en/mkt/terms.html#Pay
See sub-heading II-6
h3ll0
Active Member
Thanks for the link, and ya I have a lot of info coming at me fast as I just bought a nice amp for $100 and EPI M50 speakers thinking "this is going to be a nice first system" and instead I have people on forums telling me to replace this re-cap that and I don't see anything wrong with the amp other than maybe a cap that need to be replaced and a bias adjustment.
As of right now I'm listening to the system no cracks, pops, hiss, distortion, or problems and a lot of what people are telling me is a "what if" "maybe" situation. I'm trying to ask for help but I feel that the info I feel is the most helpful is from roger2, AUD101, hyperion,skippy and karl vd berg. I not saying that any of the other info is bad, just like I said before its a maybe.
So I will check the bias as I have a friend thats an audio engineer and has a multimeter. I will also have him replace the cap and resistor vigman thinks is leaking, but I don't think the amp needs a FULL recap. I know everone is just trying to help but it is confusing me.
Attachments
Last edited:
vigman
SUBSCRIBER
Sorry H if this is all a bit much… ( as I know it can be )…. Sansui built this stuff to last.. but nothing lasts forever, especially in the world of electronics. This was " released "in 1978 call it older than 35 years old. Heat , time, corrosion breakdown of chemicals all have an additive effect on performance ( or lack there of ) . Yes I get your only into it for 100 bucks.. Throwing another 100- 200+ at it , seems to make no sense, especially when it's working " fine ". Car batteries & capacitors are similar ( like a shark & goldfish ) You wouldn't have a " daily driver" car with a 1978 Die Hard in it? So when a power supply goes, it goes UGLY.. and takes out other components which are getting harder to get.. and these are really sweet units from the AU117 to the AU 20K.. So my apologies if I have flooded you with to much info.. it's all about keeping em running and as CLOSE to new spec as possible.. and making you aware of the issues...Oh and it's not a MAYBE.. it's a how soon… Either way we will all be here to help you what ever you decide to do
Attachments
pete_mac
Super Member
Nicely said! :thmbsp:
If you were indeed keen on proceeding with this kind of work, post beer and I'm 100% certain that we could find you a solution which would see you sourcing most of the caps from the one source (or two at most).
My fully restored 317 is my daily-driver workhorse for my PC, and apart from the Nichicon filter caps and bipolars, the rest of the amp features Panasonic FC, FM and ECQV caps. These or the Nichicon PW/HE can be used throughout the amp and it will sound brilliant! I'd not hesitate to use my 317 in my main rig if push came to shove.
As vigman rightly said
thmbsp we're sorry for throwing a lot of info at you, but the beauty of this forum is that help is only a question away. 
h3ll0
Active Member
Nicely said! :thmbsp:
If you were indeed keen on proceeding with this kind of work, post beer and I'm 100% certain that we could find you a solution which would see you sourcing most of the caps from the one source (or two at most).
My fully restored 317 is my daily-driver workhorse for my PC, and apart from the Nichicon filter caps and bipolars, the rest of the amp features Panasonic FC, FM and ECQV caps. These or the Nichicon PW/HE can be used throughout the amp and it will sound brilliant! I'd not hesitate to use my 317 in my main rig if push came to shove.
As vigman rightly said
Like I said I'm just confused as its like a poll with a thousand different options and no one can just pick one. I will do a full recap when I have the money, but as for right now I'll check the bias and the replace that cap and resistor along with the crossover cap in my EPI M50 speakers.
I'm a 16 year old kid without a job (yet) and I'm hoping to get one this summer.
What I was referring to when I said maybe, was the source of the heat being from that heatsink because after a closer evaluation the heat was coming from the area AUD101 pointed out. I know that good things can't last forever unless you take care of them but when your outta money it sucks.
Attachments
h3ll0
Active Member
I found a place in town (wytek) that stock some the caps I want to replace at the moment. So I put 6X 470uF 63V caps and 2x 2.7K 2 watt resistor on hold for a total of $9. Going there tomorrow to check it out.Nicely said! :thmbsp:
If you were indeed keen on proceeding with this kind of work, post beer and I'm 100% certain that we could find you a solution which would see you sourcing most of the caps from the one source (or two at most).
I think the reason the amp was also warm was my room was 28C-30C or 82F-86F as my A/C is broken at the moment. Right now my room is 75F and the amp is cool.
Last edited:
Similar threads
