AU-317 1 channel noisy on bass

Hi there, I managed to replace some resistors to get my 317 working some weeks ago with the help of the forum.

Now, for some days, my left speaker is noisy, distorted. Especially when basses are played, it's horrible.

It's from any input: pc from a midi device, TU-217 tuner on tuner input, and what I use to test: a vinyl-player on the phono in with a Daft Punk Alive album (cause there's enough of bass to test).

What I did: opened it and put contact cleaner on the switches, from the inside, turned them slowly and on moderate speed to help the cleaning. This helped to get rid of the crackles on the balance (especially around the dead-point on +-0 ). Overall it helped a bit, but compared to the right speaker, the left is unacceptable.

What can I measure inside the amp? (i have the plans from the internet and have "basic" eletronics skills, a multimeter and some spare resistors.)

 

Is your AU-317 the first version or the II version? From the title I read "one channel noisy on bass", but yours can be the I version. If it's the first version, you can first test/check if the problem is in the preamp or in the poweramp section as the first version has the RCA connectors at back the unit.

 

all the 317s i have looked at needed the transistors replacing in the phono and tone circuits, the original 317 has preout connections try another power amp to see if problem is in the pre or power amp section

 

i guess it's the II version. I only have Sansui RA-500 reverbation amp to which i can't connect speakers directly. I go from (or without, doesn't matter) the RA-500 to the AU-317 II phono. I also tried the tuner in, but as I'm using a vinyl player, i had no "power".
Do you know which transistors are to be replaced ? Or how i can test them?
Mine looks like this on the back:

 

got these plans:
https://elektrotanya.com/sansui_au-117-ii_217-ii_317-ii_sm.pdf/download.html

for the left channel are those TR17 and TR19 ?

In the plans TP01 and TP03 are measure points (it says >volt meter<), what voltage is to be expected there ? (DC i guess? )


I also tested other inputs, tuner with a tuner e.g and the noise is always on the left channel

 

Update:
I mesured the pins from 8 transistors (4 of them are the fat ones connected to the cooling rips)

TR15
red C- black B : 740
red C - black E : 560

TR13
black C - red E 560
black C -red B 750

TR14
black C - red B 750
black C - red E 578

TR16
red C - black B 725
red C - black E 557


TR19
black on B 551
black on E 715

TR17
red on B 576
red on E 619

TR18
red on B 575
red on E 619

TR20
black on B 550
black on E 725

used my digital multimeter, diode setting. Those are the values i get. They don't seem to spread a lot. What can I test next ?

@inductor any idea?

 

that wont determine whats wrong, i am refering to the small to92 transistors on the preamp and tone pcbs, for noise and crackles i just replace them all, sounds like you need to get it to a repair tech ?

 

don't know what transistor you refer to,
they have definitions like "2SA992" "2SA991" see page 8 of the manual here: https://elektrotanya.com/sansui_au-117-ii_217-ii_317-ii_sm.pdf/download.html

i can replace them myself, I just need to get from the internet / local shop soldering is not a problem. I'd just like to make sure they are dead / faulty before replacing 10 transistors ^^

 

perhaps @Hyperion knows more ?

 

yes maybe he does

 

inductor is correct - it isn't easy to check the transistors for failure due to noise, it is best just to change the suspect ones - these will most likely be the ones in the pre-amp. The transistors are cheap - why not change them all? - BTW I suggest you don't buy the new transistors from auction site sellers, as this is just asking for counterfeit/substandard device issues.

 

hi, thx for the answer. I was already making a list of all transistors and trying to buy all of those new.
There are a few I can't find on my german electronics site (pretty big: reichelt.de).
2SD357 no alternative found
2SC1951 -> some forumpost suggested that a BC550c would do it too
2SA981 no alternative found

The following transistors couldn't be found directly, but alternatives were found after researching some sites (perhaps someone can confirm)
2SA917 alt: 2SA970
2SA991 alt: BC560C
2SB527 alt: sa1111
2SB560MP alt: 2SA1013
2SC1313 alt: BC550C
2SC2261 alt: SC4467 ( orig: 180/120, 8A, 80W , altenative: Ucbo:160/120V, Ic 8A, Ptot 80W, fT 20Mhz )

if someone knows a shop that delivers to Europe / Luxembourg for less than 10eur/$/£ , that has them in stock, tell me


and while I'm ordering: should I also order some capacitors ? mine all look fine, just as I'm already ordering....(won't replace them now, but having them in stock is a good idea i guess)

 

@Jigo
That is an odd looking list of substitutes, I was joking quite a lot when I said change them all, sorry - you only need to change the noisy ones, just change the ones in the pre-amp for now.

But a). refer to an AU-317 restoration thread for information about any required component replacement.

This is the only one I can find quickly
http://audiokarma.org/forums/index.php?threads/sansui-au-317-recap.666630/#post-8889181

and b). use the transistor substitutes thread to find your replacements, Some of the transistors you have listed haven't been made for decades - and will almost certainly be counterfeit or substandard.
Here
http://audiokarma.org/forums/index.php?threads/once-more-sansui-transistor-substitutions.583009/

 

ok thx for those threads.
in fact, the transistors I found are available at the shop.

I just tried only 1 transistor from the substitutes list, and it's not available in the shop.
As you are from the UK, where do you look for transistors etc? I guess not from the USA?

 

Mostly
www.mouser.co.uk
www.farnell.co.uk
www.hificollective.co.uk

Sometimes
www.rsonline.co.uk
www.digikey.co.uk

There is often a local site where you are located in Europe - I am certain this is the case for Farnell for example.

Also just for info - there is a "known troublemaker" thread/link with a list of noisy/failing transistors - and their modern replacements.

found it...
http://www.audiokarma.org/forums/in...ilure-prone-whatever-and-replacements.731653/

 

I live in Luxembourg, I only know 2 shops which sell electronics stuff I'll take a look at your shops, shipping shouldn't be too high

 

Try also Reichelt, in Germany...

https://m.reichelt.de/Japan-Transis...wQATMAAA7Uiecf2801f5942731a3d482b3cca01fdb5c7

 

that's where i was looking I wrote it in one of the last posts.

In fact, as I'm pretty "new" into amps: what section on the plans is the "pre amp" section ? I got the different boards entitled power amp, tone circuit board, mic amp, equalizer circuit board...I'm really confused

 

As per the schematic - Board F-2752 - Control Amp

 

so....i changed 8 transistors. But i initially made a mistake:
as i had to buy BC 560C transitors instead of the not-available SA991, I didn't see that those were CBE and not BCE ..2nd fault: i thought that transitor 7 and 8 were those, but was wrong...
so what happened:
Tr01 and 02 are correct.
Tr03-06 were wrong inserted, CBE instead BCE
and Tr07 was wrong inserted.
TR08 was right.
Plus i first soldered out a diode, as i miscounted the pins...DR01 , later on to that

I switched it on, and the relais didn't even click. I found out that the transistors were wrong, resoldered them.

Relais clicks, yeah, but no sound output whatsoever. Muted like a dead body.

Plus: The DR01 Diode is a MV12 Diode, it has a "red" and a "black" half. Which color is the output ? Black? I resoldered it from the other side as i had more space.

On the schematics, the diode sign has 2 triangles followed by a ¦

is it at the " ¦ " side where "black" belongs?

(see picture taken at 2nd page)