mosfet replacements please help!!! |
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jbl_man
Moderator Group Joined: 12 January 2005 Location: London. Status: Offline Points: 11154 |
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Out if interest,what amplifier is this from? Those individual heatsinks look like they would be a dust-trap! |
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Be seeing you.
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young simba sounds
Registered User Joined: 28 October 2011 Location: gloucester Status: Offline Points: 40 |
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out of a please ka2401!!!
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scoops...yes scoops the only SUB for me
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simonp1100
Young Croc Joined: 01 September 2008 Location: Bristol Status: Offline Points: 1103 |
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Sorry i am confused, your asking for the above FET'S yet in the board that you posted a picture of they are BUZ901D & BUZ906D as well as BUZ903D & BUZ908D ????? i am sure these need to be ALL BUZ901D & BUZ906D throughout both channels (the last one i repaired had ALL 906D & 901D). Edited by simonp1100 - 17 May 2017 at 6:47pm |
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ceharden
The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11776 |
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IMO the cost of the replacement FET's will be much more than the value of the amp.
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simonp1100
Young Croc Joined: 01 September 2008 Location: Bristol Status: Offline Points: 1103 |
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young simba sounds
Registered User Joined: 28 October 2011 Location: gloucester Status: Offline Points: 40 |
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thats what was in there, i got another two of these amps all fets are buz903d and 908d but i was just going to put back in what i took out
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scoops...yes scoops the only SUB for me
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young simba sounds
Registered User Joined: 28 October 2011 Location: gloucester Status: Offline Points: 40 |
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in the long run this amp was a spare anyway just incase i needed parts but i thought id have a shot at it to learn on basically so money is not much of an object but rather more of a learning amp
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scoops...yes scoops the only SUB for me
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simonp1100
Young Croc Joined: 01 September 2008 Location: Bristol Status: Offline Points: 1103 |
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I would make sure that you replace all the BUZ906D & BUZ901D with BUZ908D & BUZ903D as the 906D & 901D are rated at 200V devices & the 908D & 903D are rated at 250v devices.
These amplifiers were well known for FET'S exploding hence why they may have changed / up-rated the output FET's due to the high supply rails. Do not mix the two together (either all 200v devices or all 250v devices). Edited by simonp1100 - 17 May 2017 at 7:02pm |
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young simba sounds
Registered User Joined: 28 October 2011 Location: gloucester Status: Offline Points: 40 |
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thanks simon, this must be an older model to the other two then as this one also has different capacitors also not as well built as my other two, i might just put this one to rest lol
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scoops...yes scoops the only SUB for me
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_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
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"Do not mix the two together (either all 200v devices or all 250v devices)."
Does not matter. If the ±V is 100V or less the 200V parts will be fine The difference between the 200V and 250V parts is the 250V parts are obtained on a selection basis. They start out with the same die . The ones that test better than 250V become 250V parts. Then they lower the test spec to 200V, and the ones that pass are sold as 200V parts. Hitachi did the same with the 2SJ48/49/50 series rated at 120/140/160V. |
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djk
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simonp1100
Young Croc Joined: 01 September 2008 Location: Bristol Status: Offline Points: 1103 |
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Because of the past record with these amplifiers having FET's blowing with the 906D & 901D fitted and with the supply rails being OVER 100v, stick with the higher voltage FET's for longer long term reliability. Repaired quite a few of these in the past and have seen many PCB's damaged beyond repair due to FET's blowing and taking out the board as well. By the way these amplifiers were made in Bristol (Flowers hill). Edited by simonp1100 - 18 May 2017 at 5:25am |
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odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5483 |
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Tbh an amplifier with +100V is not a great idea for a learning project anyway. As the FETs are valuable then you're probably better off stripping it for parts or selling intact as spares second hand, then investing in a more sensible amplifier for learning with.
The P3A on ESP audio is a great starter to build, and as long as you have a half decent dual DC power supply then you won't have to build any mains power supplies to be able to have a listen at low levels. If you simulate the design first you will learn a lot as you build it and test it out, mechanical as well as electronic with regards to construction and biasing. It's a good way to start learning vs jumping right in at the deep end with an unknown quantity. |
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