interesting thread, i too have a amplifier that blows the output transistors, noticed the origanal poster was from uk, so hope anyone on here or he can advize,
my harman kardon amp has same brand output sanken, however its a d25560 and underneith b1647,
i bought this amp like this, after putting it in shop, as i couldent be bothered to try and fix as there was 2 channels down, the guy said hes repaired one channel but the other when replaced just gets red hot after 5 mins and then blows again,
to me it sounds as if he couldent be bothered to track the fault and gave it me back, so it cost me 60 pounds just for 1 channel and my amp is only half working,
so i guess im going to try and repair this myself, hope u guys or Frisbee78 might advize.
my harman kardon amp has same brand output sanken, however its a d25560 and underneith b1647,
i bought this amp like this, after putting it in shop, as i couldent be bothered to try and fix as there was 2 channels down, the guy said hes repaired one channel but the other when replaced just gets red hot after 5 mins and then blows again,
to me it sounds as if he couldent be bothered to track the fault and gave it me back, so it cost me 60 pounds just for 1 channel and my amp is only half working,
so i guess im going to try and repair this myself, hope u guys or Frisbee78 might advize.
Sorry man, I scrapped the darn thing. I replaced all transistors and dead resistors on the faulty channel and it burned again... not worth the cost of the parts so I gave up.
Frisbee78, so do u think its worth me trying? also how much did you spend on your amp then? concidering you scrapped it .also where did you buy your parts from mate and resistors transistors etc? as im after some Sanken Output transistors, some resistors, etc.
Member
Joined 2002
Frisbee, your output transistors don't look like genuine Sankens, but rather copies or fakes. These should *always* be suspect for causing failiures.
If you want to purchase genuine Sanken transistors, buy from Profusion PLC. The modern day substitutes are 2SA1695 and 2SC4468.
The drivers may be hard to get as genuine parts also. These were made by Hitachi (now Renesas) and I think they were discontinued a while ago.
Also a bit late now as you've scrapped the amp but you should have checked that little white preset for dirty/open contacts. Depending on how the VBE multiplier is designed, sometimes this pot going open circuit/high resistance can cause the bias current to INCREASE thereby blowing the drivers and output stage.
If you want to purchase genuine Sanken transistors, buy from Profusion PLC. The modern day substitutes are 2SA1695 and 2SC4468.
The drivers may be hard to get as genuine parts also. These were made by Hitachi (now Renesas) and I think they were discontinued a while ago.
Also a bit late now as you've scrapped the amp but you should have checked that little white preset for dirty/open contacts. Depending on how the VBE multiplier is designed, sometimes this pot going open circuit/high resistance can cause the bias current to INCREASE thereby blowing the drivers and output stage.
well im carrying on this thread as i have a harman kardon amp which has same problems ( have made a post about this but currently its under moderation but should be posted hopefully soon)
a repair guy who looked at mine, said the power transistor top side sanken d2560 had blown. he repaced it and said after 2 mins it was getting red hot, and even the fan dident kick in? so i guess theres a problem someware, he dident have time to check anythink else, i also noticed underneith theres another set of power transistors on the heatsink sanken b1647, so i guess theres 2 for each channel, so im going to check hopefully, all i have is a digital meter, have a bit of electrical experience, but hopefull you guys can help, just not 100% sure how you check these.
a repair guy who looked at mine, said the power transistor top side sanken d2560 had blown. he repaced it and said after 2 mins it was getting red hot, and even the fan dident kick in? so i guess theres a problem someware, he dident have time to check anythink else, i also noticed underneith theres another set of power transistors on the heatsink sanken b1647, so i guess theres 2 for each channel, so im going to check hopefully, all i have is a digital meter, have a bit of electrical experience, but hopefull you guys can help, just not 100% sure how you check these.
mrlennon said:
That's up to you if you want to attempt a repair or not... As my amp wasn't worth much more than £50 set myself to spend £15-20 max on the repair, but what you want to spend is up to you. Some people would keep trying until it works regardless of cost... I'm just not one of them... 😉
As for were did I find the parts, I went to http://www.visionaids.co.uk. It's one of the few UK retaillers I found that does the Japanese parts used in our amps but as it's said above, they might not have the best quality... You might want to take a look at Profusion as Jaycee suggested.
Best of luck in your repair.
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