Need help restoring AU-222.

[keli]

Hello, I have a Sansui AU-222 that I just finished a recap on, first time trying to restore an amplifier and so far so good. The recap seems to have solved my issues with the amplifier popping and hissing after a few minutes of use, however I still have issues with the sound.

I can get the amplifier to sound somewhat okay if I dial it in just right but it seems to be rather finicky in regards to input volume, it seems I have to have the input just right, if it is too low the sound is way off, if it is too high it starts to sound too bassy and pops.

My main problem is that in order to get it to a listenable quality I have to turn the bass knob to 0 and the treble knob all the way up i.e. it is just way to bassy and not enough treble. I was hoping that this would be fixed with the recap but that does not seem to be the case. I realize that I probably need to do a bias adjustment, however I do not have the tools for that kind of job, but if I'm lucky I might be able to get someone to help me with that or borrow some tools. I would like to note that one of the main transistors seems to run much hotter that the rest, could this be related to the bias being off?
Overall the amplifier is in a very good state, has minimal wear and tear and is very clean inside.

So I come here for your help in restoring this beautiful amp. Does anyone here have an idea of what might be wrong with it? Will a bias adjustment solve all my problems or do I need to replace some other parts?

Thanks in advance.

 

[keli]

On a related note, I have seen some folks replace the old trimpots with newer ones with the closed plastic housings, should I do that before I get a bias adjustment or are the old trims fine as is?

 

[sanjib]

Welcome to AK!
Did you clean all the switches extensively with Deoxit? What do you mean by input volume? Are you using iPhone or iPad as an input device and you meant the volume of those?
To do bias adjustment you just need a digital multimeter and even a very cheap one will work. For balancing the amp properly you need an oscilloscope but I think there is another way to do it by adjusting the collector voltage of the two output transistors in the middle (one for each channel, collector voltage should be half the collector voltage of the other in the same channel). I never worked on this amp and someone more experienced will chime in here regarding balancing the amp.
Thanks

 

[keli]

All the switches were cleaned with an old can of servisol, should I be using Deoxit instead?
By input volume I meant the volume of the phone that I have plugged into the phono2 of the amplifier. I intend to connect it to a turntable and my computer later on.
Great news, I do own a multimeter, so hopefully that means I should be able to do some adjustment? Hopefully I will be able to dial in a better sound.

 

[sanjib]

All the switches were cleaned with an old can of servisol, should I be using Deoxit instead?
By input volume I meant the volume of the phone that I have plugged into the phono2 of the amplifier. I intend to connect it to a turntable and my computer later on.
Great news, I do own a multimeter, so hopefully that means I should be able to do some adjustment? Hopefully I will be able to dial in a better sound.

Don't use Phono port use AUX or Tape play port to connect your phone and then check. Phono is only for the turntable. Deoxit D5 is better to use.

 

[keli]

Don't use Phono port use AUX or Tape play port to connect your phone and then check. Phono is only for the turntable. Deoxit D5 is better to use.

Okay, thanks for the tip. It certainly seems to be a lot better in regards to not being as sensitive about the input volume when connected to the AUX port. However with that the problem now seems to be reversed, now I can have as much treble as I want but I have to run the bass knob all the way up to get the faintest sliver of bass from the music . I'm going to have to see about getting some of that deoxit though, was having my doubts about the servisol anyways.

 

[sanjib]

Can you give details on what components you changed?

 

[keli]

Can you give details on what components you changed?

I've only replaced all the electrolytic capacitors so far, all of them with the same values as original except for the main filter cap which I've replaced with a 2200uF. I've thought about changing out the trimmers but haven't done that yet. Do you know if there are other components that are usually replaced when restoring this amp?

I've just realized that the only store in the country that sells deoxit has gone out of business, so I might either have to order it online or use some other product. I know that the other electronics store that I frequent sells products from Electrolube i.e. the CCC and CCL stuff as well as others, do you know if those are any good?

I've been playing some more around with the amp and it definitely seems that the buttons need another round of cleaning, they don't really seem to engage properly when switching them to and from, need to jiggle them to get them to work.

 

[sanjib]

You can try a contact cleaner like CCC without any lube first. You may have to do in a couple of cycles and when everything is good you use electronic lube to finish the job. I have used Deoxit D5 and Faderlube with very good results and those two are frequently recommended here. Also, re-check your work particularly the solder joint, polarity of caps, and re-check the values by comparing it with the service manual.

 

[sanjib]

Did you check the sound with a headphone?

 

[tom_tm]

I've just done an AU-222 restoration. My amp now sounds amazing. Replace all 4 trimmers. Very important. If you are getting hiss, it's likely that you also need to replace the small signal transistors too, as they often fail and go hissy. This is no easy task as they are nigh impossible to find the originals. However, the 2SC815's can be replaced with KSC1815, 2SA539 with KSA1015, 2SC733 with KSC1845. It took me *months* to figure out these replacements! 2SC2240, if you can find them, are better replacements than the KSC1815, but you can also get these in SMT versions. They are 2SC3324-GR. The power transistors can be replaced with MJ15022.

I also used ELNA Silmic II's for e-cap replacement, but they can take ages to settle in. General consensus is to use Panasonic FC's (I used FC's for the PSU cap replacement), although Nichicons will work just fine too. The 1µF and 3.3µF's should be replaced with film capacitors, such as this one which came highly recommended by @AnalogueBen https://www.mouser.co.uk/ProductDetail/KEMET/F612JT105J100R?qs=CBysBIMljtjhOXtn2%2BSVug==

I should also add, get a can of freeze spray. I believe that this is almost as good as having a good scope and/or multimeter. Saved me hours trying to locate a noisy transistor. Also I too had 'popping' in the left channel. It initially went away after a recap, but then returned again. The popping is certainly caused by bad transistors. It was one of the 815's that had gone bad. And it was the freeze spray that helped me locate it.

 

[slimecity]

I've just done an AU-222 restoration. My amp now sounds amazing. Replace all 4 trimmers. Very important. If you are getting hiss, it's likely that you also need to replace the small signal transistors too, as they often fail and go hissy. This is no easy task as they are nigh impossible to find the originals. However, the 2SC815's can be replaced with KSC1815, 2SA539 with KSA1015, 2SC733 with KSC1845. It took me *months* to figure out these replacements! 2SC2240, if you can find them, are better replacements than the KSC1815, but you can also get these in SMT versions. They are 2SC3324-GR. The power transistors can be replaced with MJ15022.

I second this. This is pretty likely to have been your original issue if you had popping & hissing after a few minutes of use.

The freezespray method will be best to diagnose any dying transistors, rather than replacing the whole lot in one go.....

 

[tom_tm]

In fact in many ways I wished I had used the freeze spray method before I did a recap. Those old ELNA caps sounded pretty damn good compared to the modern ones. I guess I'm just going to have to wait another 50 years before the new ELNA's sound as good as the old. Oh well. Here's hoping I find another trashed 222 again. ;-)

 

[keli]

I've just done an AU-222 restoration. My amp now sounds amazing. Replace all 4 trimmers. Very important. If you are getting hiss, it's likely that you also need to replace the small signal transistors too, as they often fail and go hissy. This is no easy task as they are nigh impossible to find the originals. However, the 2SC815's can be replaced with KSC1815, 2SA539 with KSA1015, 2SC733 with KSC1845. It took me *months* to figure out these replacements! 2SC2240, if you can find them, are better replacements than the KSC1815, but you can also get these in SMT versions. They are 2SC3324-GR. The power transistors can be replaced with MJ15022.

I also used ELNA Silmic II's for e-cap replacement, but they can take ages to settle in. General consensus is to use Panasonic FC's (I used FC's for the PSU cap replacement), although Nichicons will work just fine too. The 1µF and 3.3µF's should be replaced with film capacitors, such as this one which came highly recommended by @AnalogueBen https://www.mouser.co.uk/ProductDetail/KEMET/F612JT105J100R?qs=CBysBIMljtjhOXtn2%2BSVug==

I should also add, get a can of freeze spray. I believe that this is almost as good as having a good scope and/or multimeter. Saved me hours trying to locate a noisy transistor. Also I too had 'popping' in the left channel. It initially went away after a recap, but then returned again. The popping is certainly caused by bad transistors. It was one of the 815's that had gone bad. And it was the freeze spray that helped me locate it.

Yes, it would certainly seem like there is more for me to do for this amp, I attempted to do a biasing after finally finding my multimeter (got lost behind a closet) and it seems that I am unable to get it up to the correct amperage by adjusting the trimmers. So possibly some problem with the board itself or the trimmers, although I measured them and they seem to be alright but I still don't trust them. I tried getting new trimmers from my local electronics supplier but they did not have them in stock, so I will probably need to order online (any particular brand or type you reccommend?). I'm going to have to take a closer look at those transistors as well when I find the time.