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Old 31st March 2009, 02:30 AM   #1
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Default Need help with older DEI amp

Figure I would post this over in this section to see if I have any luck. Hate to give up on this amp.
Im looking for replacement transistos for this amp. The one person at Digikey Had no cross reference numbers for it.

I have a older DEI amp (2504 series).
I think they are power supply ones since they are close to it. I have a little electronics experience.
There are two different ones that I need. I will list how they read from top to bottom.
9536 NDP 508AEL other 9542 NDP 508AEL

Thanks for any help.
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Old 31st March 2009, 05:49 AM   #2
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Quote:
NDP 508AEL other NDP 508AEL
< part numbers minus the date codes, they are the same device>

NDP = National Semi, and they stopped making those a while back now. In fact to my limited knowledge they have ceased all Mosfet manufacturing.

So they will have to be crossed to something if your serious about bringing that amp back to life. I know of a surplus vendor I will check with him tomorrow for you tom see if he has any leftover NOS parts in his invenory.
He also has product descriptions for these oldies, perhaps we can come back with the info you need to move forward...


I might have some 608's myself...later tomorrow will tell..
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Old 31st March 2009, 10:29 PM   #3
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That would be great.
If I can come up with some kind of replacement would be great.
I didn't want to dump alot into this, Just in case there were other issues with it.
I can see that a few are burnt up. So I figured I would replace the set of 6.
Thanks for your help.
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Old 1st April 2009, 07:39 PM   #4
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35 pieces of NDP-508AEL are available from Advanced Components Electronics.These are NOS unused old stock still in original tube from the maker.
Here is the PDF file link http://pdf.chinaicmart.com/NDB/NDB508A.pdf
Fairchild still makes the device but I can't seem to find any alternate source in the US other then ACE

You can email me thru the DIY mail system and I will share contact info, although they do have a web page with current inventory. Just google them at acecomponents.com
They have a minimum order level in place.
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Old 1st April 2009, 08:57 PM   #5
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Thanks for the help.
I just called them and $60.00 minimum order.
Its not worth it for this thing. Im not sure if thats all thats wrong with this amp to.
I wonder if that spec sheet can be crossed over to something at Digikey?
Thanks
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Old 2nd April 2009, 03:05 AM   #6
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Location: Northern California
The Fets are 19 amp and 80 volt spec'ed.

Nothing really special. IRF-540 might work in its place current and voltage wise. < a little on the overkill side >
Also based on there ratings I would say these are class D outputs not power supply mosfets...BUT I could be wrong, they just seem low powered for SMPS duty.
ACE are good guys, but they run a warehouse operation that serves larger customers, hence the minimum purchase thing. I usually buy large lots in the hundreds and or entire inventory's of items so I never have the minimum issues to deal with. I been buying from them for almost 20 years, through two different owners. They are more like friends then suppliers after all this time lol...

Hope it all works out for you....
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Old 2nd April 2009, 03:08 PM   #7
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Do you think its worth throwing a set of the IRF-540 in to try?

It was funny when I called over there. They knew what I needed, As soon as I started asking he read the number I needed to me. I guess you talked to them. Thanx
Do you run a amp repair Bizz that you order so many?
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Old 2nd April 2009, 05:39 PM   #8
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Join Date: Dec 2005
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I went in and found the parts and looked them up on there computer systems, which I built for them. When I posted I was sure they had them I just had to check stock before i guided you there way.
The parts your looking for are discontinued and i could not find them elsewhere, so I just wanted to be sure for you.

I have been repairing amps for over twenty years in this area, but I am retiring shortly. It has been fun, but fishing has caught my appeal now lol lol lol..I put my time in the trench's, its time to smell the roses and give advice on forums lol lol
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Old 2nd April 2009, 07:06 PM   #9
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Thanks again for going out of your way for me.

Do you think its worth throwing a set of the IRF-540 in to try?
Happy retirement.
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Old 2nd April 2009, 10:57 PM   #10
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Post a pic of the amp inside and I will try to eyeball guess weather they will work for you....They are amply rated to replace the devices that were in there.
The circuitry may not like the upgrade devices. Gate capacitance and what not, may not be suitable for stable operation. Plus there may be other things wrong besides the bad Fets....
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