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Sansui AU-222 Restoration by Total Novice


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13 minutes ago, aussievintage said:

 

I am wondering if one or more transistors were damaged when you had them soldered incorrectly and powered the amp on.     

Thank you for the info and Very likely. Is there a way to check if the transistors are damaged before replacing all of them with new one?

I have digital multimeter but not sure if I can use it to check if it works or not. 

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1 hour ago, Spider27 said:

Thank you for the info and Very likely. Is there a way to check if the transistors are damaged before replacing all of them with new one?

I have digital multimeter but not sure if I can use it to check if it works or not. 

 

Not with any equipment I own.  I did read about "in-circuit" testers,  but...           Some digital multimeters can test transistors.  Honestly though, they are cheap.  If you desolder one (for the second time) I would replace it with a new one.

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1 hour ago, Spider27 said:

Is there a way to check if the transistors are damaged before replacing all of them with new one?

I have digital multimeter but not sure if I can use it to check if it works or not. 

Generally the transistors don't conduct when incorrectly inserted so you might be lucky. You can try testing in circuit, looking for a short between b-e or c-e or.. using either resistance/ohms function but the diode test feature is better. Attached graphic shows the 6 combinations to be tested with expected results OL (open loop) or 650mV(or there abouts), red/black give meter probe orientation. Graphic curtesy markthefixer from audiokarma.

 

EDIT: I should add that some faulty transistors need a few "amps" before they fail, bottom line, a transistor that passess diode test may still be faulty since your MM does not deliver the necessary mA. Conversely anything that fails diode test is certainly faulty.

 

EDIT 2:If you find a suspect transistor then you need to remove and test out of circuit in which case you might as well replace as per aussievintage

DiodeTest.JPG

Edited by mbz
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I actually watched this video to understand how transistor works and how to do diode test.

Checked all of transistors that I could see and they seem all pass the test. 

 

TR807 and TR808 did not pass the initial test so I was excited that I found the defect ones. However, I found that those two are PNP type when all others are NPN so had to do opposite and they also passed the test. ?

 

I got some extra brand new BC550 transitors and will replace all 4 of them later today to see if it helps.

 

 

Edited by Spider27
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Just completed replacing BC550 transistors with new ones. And, sound output is now back to normal. ?

 

The crackling noises are still there though. I guess that these crackling noises are coming from old caps. Hope it is not noisy transistors but caps because do not want to replace same transistors again....

 

Edited by Spider27
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1 minute ago, aussievintage said:

Or a more thorough clean of every switch pot and socket/plug is necessary.

I am not sure about the pots and switch because they are cleaned quite thoroughly.

When I test turning every switch & knobs up and down, it does not affect crackling noise at all. Doesn't it affect crackling noise when switch/knobs are turned up and down if pots and switches are dirty??

 

4 minutes ago, aussievintage said:

 

Glad my guess was right for a change :)   

YES.. Thank you.?

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22 hours ago, Spider27 said:

I got the transistor from JayCar and here is the link for datasheet.

Soory, I don't consider the car place as a reliable source of silicon. Also their Serv**ol "Clean and Lube" does very little cleaning, reasonable as a lube. Both Mouser and Digikey have free shipping to AU for orders over AUD60-, delivery in 3 days max(!) For small orders RS. I'm undecided about ele14 though did buy a power supply from them, seems to be of suitable quality.

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5 hours ago, PKay said:

Thanks for the suggestion. I happen to have DeOxIt D100L which is brush type. I applied all of joints and gap inside pots but does not make any difference. However, it is not spray type so could not reach deep inside the pot so it may make a positive difference with spray can type.

 

When I pass the city next time, will get one to try. However, I feel that it is more likely transistor or solder joint. The reason for this assumption is that the crackling noise is now on the left channel when it was on the right before replacing the signal transistors.  

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  • 2 weeks later...

Been away from this project and just coming back and placing my order to element14 to purchase required capacitors.

 

@pete_mac  By any chance, would you be kindly spare just a few sec to have a look at below linked list look okay to you?

 

First time ordering for capacitors and I think that I found them ok and just want to double check if possible. :) 

Part List-1.png

Part List-2.png

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Hi mate,

 

I'll see if I can have a look tomorrow afternoon or evening... I'll be burning the midnight oil tonight on an urgent report.

 

EDIT: I won't be able to comment on the suitability on capacitors from a physical sizing perspective, as I don't have any details regarding the dimensions of the original caps. I'll have to take your word for it. ;)

Edited by pete_mac
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On 04/04/2020 at 4:46 PM, Spider27 said:

...Maybe i am too novice after all and not cut out for this task ? (my self-confidence level is dropping down rapidly now)...

I've been reading this thread and have a degree of admiration that you are tackling this - I feel it's one step beyond my novice skills!  I'm pleased to see you have persisted through this challenge,  as this is what develops competence and knowledge.  Good luck with the rest of the restoration. 

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1 minute ago, audiofeline said:

I've been reading this thread and have a degree of admiration that you are tackling this - I feel it's one step beyond my novice skills!  I'm pleased to see you have persisted through this challenge,  as this is what develops competence and knowledge.  Good luck with the rest of the restoration. 

Thank you for your kind word and encouragement. If COVID-19 lockdown was not in place, I would have been given up already.  Since I have some spare time, I am doing this but it is still not progressing into positive way or improving from current status as yet ?

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29 minutes ago, Batty said:

Will we see this in the classifieds soon Spider?

I am not evening thinking that far. My sole focus is making this work without crackling noise coming and going which is very annoying and unpleasant whenever I power it on and try to listen.

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2 minutes ago, Batty said:

Good, man, I hoped you wouldn't give up on this.

 

We will see the outcome either making it work and enjoy listening with it with big smile or fail miserably and wasting money and time on this and weeping at the corner of my room soon....

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On 17/04/2020 at 2:23 PM, pete_mac said:

Sorry @Spider27… still working on that darn report. Let me see what I can do later tonight. :)

Hi Peter. Have you had a chance to check those 9 capacitors by any chance?  No urgency... It just has been 7 days waiting and not sure if I just should proceed placing an order to see how it goes or wait for your confirmation before proceeding. 

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9 minutes ago, Spider27 said:

Hi Peter. Have you had a chance to check those 9 capacitors by any chance?  No urgency... It just has been 7 days waiting and not sure if I just should proceed placing an order to see how it goes or wait for your confirmation before proceeding. 

 

No closer unfortunately - work has been consistently busy.

 

Provided that you have double-checked your list against what is actually physically installed in your amp (there can be variations during production runs and improvements to the design over time) then you should be OK. This also gives you the opportunity to measure the diameter of the current caps and ensure there is space for the new caps that you've chosen, and to get a feel for the lead spacing of the original capacitors vs the ones you've chosen (I have no way of doing this remotely). I'd particularly check the 3.3uf film cap - is it a 5mm lead spacing? If not, it definitely won't fit.

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