AU-505 no slouch!

[richardpp]

Hi,

I think I'm beginning to get what it is about Sansui amps that so many of you on the forum know so well, already. They're great!

I recently bought an AU-505, having kept an eye out for some time for something reasonably priced and, as the seller knew not if the amp was working, it was priced accordingly.

After some preliminary tests and a check under the bonnet (where everything looked like new), I plugged the amp in and in due course connected my best speakers.

What a delight to hear! I would have to say in every respect, this is a wonderful amp. All controls and switches work beautifully.

If my AU-20000 ever has to go in for repair, I would be very happy for the AU-505 to take its place. This amp ain't no slouch!

 

[mroboto]

Here is my restored AU-505 with a partlist

http://audiokarma.org/forums/showthread.php?t=368406

 

[datafone]

Got rid of one of these a while back, should have kept it!

Nice little amps, and that one you have is very clean

 

[richardpp]

When I bought this amp I had in mind to restore it, but seeing it's original condition and hearing it play I'm just very happy to enjoy it.

mroboto, your recap looks like fine work and your post will make a good reference for me in the future, thankyou. I wonder, were you able to make a judgement on sound quality before and after the recap?

 

[mroboto]

In fact, i don't have listened to it a lot before the recap, So it's hard to make a fair judgement, sounded very good before, it compares, but maybe it's beter after with cleaner bass, but now, he have a better troublefree life expectancy.

 

[stereofun]

Dont have the 505 but two 555a's and a 777a. They are simple designs, cap coupled, single rail voltage and no differential amp - yet they sound downright amazing and with a decent punch.

Less is sometimes more if you don't need nosebleed level power but just unprocessed musicality. Congrats on this fine piece.

 

[richardpp]

I didn't know much about the AU-505 beforehand, that it was cap-coupled, etc. Nice to have something different to work on.

It really does have some punch I wasn't expecting, the test speakers nearly popped their cones when I flicked the 'loudness' switch on!

 

[richardpp]

Got rid of one of these a while back, should have kept it!

Nice little amps, and that one you have is very clean

Hi datafone, how's things in Brizzy!

The amp is certainly very clean and original, remarkable given it's age of forty years.

I can just hear a slight persistent crackle from one channel.

 

[skippy124]

Crackle is likely to be due to a noisy 2SC871 or 2SC871R, or possibly a dirty control (it took me couple of cleaning cycles to get rid of control noise in my 505).

You could try the freeze spray diagnosis method to see if you can localise the noisy transistor.

Cheers

John

 

[richardpp]

Thanks John,

Much appreciated!

Richard

 

[skippy124]

If it does turn out to be a noisy 2SC871, you can replace with either 2SC2240 (can be hard to get, let me know if you have trouble, I have a stash of these), or a BC549 or BC550. The BC549/BC550 have a different pin out than the 2SC871, this needs to be taken into account if you use either of these s replacement.

Cheers

John

 

[richardpp]

That's great, John. I do have some 'garden variety' BC549's at hand. Though, thanks for the offer of the 2SC2240's, are they a better choice? Knowing what can be replaced with available stock is invaluable, especially when you get info on the pin outs to keep you covered, (Skip, to the rescue )

On cleaning, I've been thinking of investing in the Deoxit products as they are highly regarded on the forum, they just seem a little pricey here in Oz. I have some cleaner/lubricant but it probably lacks the deoxidising capability of Deoxit.

I look forward to getting the amp back to good health, soon! Thanks again for your help and all who have posted.

 

[skippy124]

Hi Richard,

The BC549's will work fine, as will the 2SC2240's, there would be no difference in the outcome. The only real benefit of using the 2240's is that they are the same pin out (as far as I am aware) to the originals so there is no need to be "creative" with lead orientation.

The toggle controls are the hardest to get noise free in the 505, it is possible to get some deoxit or contact cleaner inside of these, but it they remain noisy then the only way to properly fix it is to dismantle the switch and get the deoxit onto the internal contacts - this is fiddly and you have to be careful not to damage the sliding contacts, lose them or incorrectly re assemble the switch.

Happy to post over a dozen or so 2SC2240's to you - send me a PM.

Cheers

John

 

[richardpp]

AU-505 replacement transistors

Hi John,

I tried the 'freeze spray' as you suggested and sure enough found a noisy 2SC871 transistor on the Filter Block. The 2SC2240's you kindly sent me fitted in reverse order pinout, still very neat. Now there is no sign of crackle and the amp sounds great. I'm really enjoying it. Thanks very much!

Cheers,
Richard

 

[skippy124]

Happy to be able to help!! and very happy to hear that your 505 is now behaving properly. And good pick on the orientation of the 2240's compared to the 871's, I knew that they were both collector in the centre, but couldn't be sure that they exactly the same pin outs.

Cheers

John

 

[richardpp]

Well, I must admit I found out the hard way! :nono:

The extra two you sent as spares gave me the insurance that all is now well. :yes:

 

[rjag46]

sui

Got one and love it !!!!!!!!!!!

 

[stereofun]

No it aint no slouch for sure! Finally got around to recap and mod one I picked up two weeks ago. Will share some pics in separate thread. The 505 has no right to sounds this good for its bottom of the totem pole status. I think the engineers pulled a trick on us :tresbon:

 

[richardpp]

Wow, didn't take you long to do the recap and mod. Looking forward to the pics.

 

[Kingfisher]

The 505 has no right to sounds this good for its bottom of the totem pole status. I think the engineers pulled a trick on us :tresbon:

No, they didn't...the 505 is not the lowest on the totem pole. The AU-101 is. It might be above the AU-222 also, but I haven't tried comparing specs yet.