The discoloration on the left comes from hot running, on the edge of normal, and likely eliminated if they were on longer legs.
The parts next to the output transistor, that's a catastrophic failure, likely failed op transistor taking out the other parts.
Those sanken op transistors are common, relatively cheap and the other parts are pennies, 1/4 watt metal films and diode.
The parts next to the output transistor, that's a catastrophic failure, likely failed op transistor taking out the other parts.
Those sanken op transistors are common, relatively cheap and the other parts are pennies, 1/4 watt metal films and diode.
Original Sankens in those large MT200 cases are not really common since they are now obsolete. However, the supply market is and has been overflowing with fake copies of 2SC2922 and 2SA1216 pairs for many years. Most look identical in almost all respects including batch marking and brand logo. but often the grade mark (bottom line) is missing, wrong or does not match your requirement. The originals are also quite heavy due to large copper heat spreader plates inside but fakes are often lightweight, so there are some indicators that may help.
Yes, you can indeed buy originals too if you also research the supplier's credentials as an honest trader. You need proof that his product is different to all the fakes out there and it is a compatible grade to your existing original semis. Typical asking prices of genuine, new product are now US $25 each in small quantities.
Sometimes the parts offered will be used ones (pulls) which may be fine and affordable but still not with any formal guarantee. If cheap, you will surely have the common sense to know that you are being lied to. Otherwise, you may just have to wait until you hear the disappointing sound of fake LAPTs.
The Audiolab 8000 models rely on these particular LAPT semis for good sound. Without them, it is a waste of time and money trying to restore a mess like that without knowing exactly what to do and what to buy as replacements. You also won't know how much it will cost and where to source good quality components ahead of any attempt at restoration. One could mess about, trying hard with cheap parts, following suggestions that may be sensible, unwise or dead wrong but do the job right the first time and you won't be disappointed.
Yes, you can indeed buy originals too if you also research the supplier's credentials as an honest trader. You need proof that his product is different to all the fakes out there and it is a compatible grade to your existing original semis. Typical asking prices of genuine, new product are now US $25 each in small quantities.
Sometimes the parts offered will be used ones (pulls) which may be fine and affordable but still not with any formal guarantee. If cheap, you will surely have the common sense to know that you are being lied to. Otherwise, you may just have to wait until you hear the disappointing sound of fake LAPTs.
The Audiolab 8000 models rely on these particular LAPT semis for good sound. Without them, it is a waste of time and money trying to restore a mess like that without knowing exactly what to do and what to buy as replacements. You also won't know how much it will cost and where to source good quality components ahead of any attempt at restoration. One could mess about, trying hard with cheap parts, following suggestions that may be sensible, unwise or dead wrong but do the job right the first time and you won't be disappointed.
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Of course we are not talking old radios don't you get the analogy ?
Okay change that to overheated metal film resistors in power amps ,usually overheating from the middle of the resistor towards both ends going open circuit that's not "burning out " just overheating .
They are more like fuses in many cases.
"poor attempt at sounding witty " ---eh !!!
I was putting another analogy as regards the overheating which was actually IN the dictionary definition --if you read it online dictionary ,so get up the same dictionary and check out if I am telling the truth .
So you are saying its "okay " for a audio design engineer or should I say the company he works for allowing low wattage resistors to heat to such an extent they cause burning to the PCB ?
I repeat show me which UK design engineers --of note and include an Italian and others who write and have written many audio articles of note and fame for that matter in Electronics World getting much approval from others of the same ilk who say its acceptable for that to happen ?
Always high quality with large safety margins are advised in resistors ,read their design strategy , not one has had his design criticized for under-performing resistors which browned their PCB,s under NORMAL use.
No this is down to penny pinching .
I would think the majority of all these posts will put the op off... it's not helping him fix the amp or gain an understanding of what has happened here.
Just sayin' 🙂
We need to see the circuit diagram for this variant and the resistors that have failed highlighted so that any possible failure modes can be identified and possible scenarios and remedial action taken.
Just sayin' 🙂
We need to see the circuit diagram for this variant and the resistors that have failed highlighted so that any possible failure modes can be identified and possible scenarios and remedial action taken.
I didn't start this but I will take your advice and will resist replying to any criticism on this matter directed at me.
Well I must admit... I didn’t realise that I would generate so much historical and design analyses and comment.
I AM a newbie. It is a nice amp. The headphone socket works (but neither channel). Donkey years ago I did electronics courses on my B. Eng. Repairs can really only follow logical processes. E.g.... what is broken? What parts need replacing?
The clever stuff is.... how could this happen ? And why did it affect this part of the board?
The posters, who have kindly taken the trouble to help me above, have pointed me into my first steps of things to look at/test/be aware of this too , etc.
For that, I thank you all.
The learning curve is steeper than I expected. But I’m not afraid of heights.
I AM a newbie. It is a nice amp. The headphone socket works (but neither channel). Donkey years ago I did electronics courses on my B. Eng. Repairs can really only follow logical processes. E.g.... what is broken? What parts need replacing?
The clever stuff is.... how could this happen ? And why did it affect this part of the board?
The posters, who have kindly taken the trouble to help me above, have pointed me into my first steps of things to look at/test/be aware of this too , etc.
For that, I thank you all.
The learning curve is steeper than I expected. But I’m not afraid of heights.
Hi there,
I’ve taken a pause. I’ve removed the two burnt out resistors, but have only just (Today) downloaded the 207 service manual. So I need to read that. Compare circuit diagrams, and see what to test.
At least I found my multimeter in the cellar. Changed the battery and It works!
I also need to get the parts to build the dim bulb tester.
But thanks for asking!
It’ll be a few days before I know more. Life gets in the way of fun projects, I’ve noticed.
I’ve taken a pause. I’ve removed the two burnt out resistors, but have only just (Today) downloaded the 207 service manual. So I need to read that. Compare circuit diagrams, and see what to test.
At least I found my multimeter in the cellar. Changed the battery and It works!
I also need to get the parts to build the dim bulb tester.
But thanks for asking!
It’ll be a few days before I know more. Life gets in the way of fun projects, I’ve noticed.