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FS Toshiba Tranistors 2SD424 & 2SB554

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These are not fakes. Here are some pics. I know there are a lot of counterfeits out there, but these are not them:)

An externally hosted image should be here but it was not working when we last tested it.




I have 500 total. I will be selling matching sets soon.
Thanks again

ben62670 is my screeen name on Ebay, and Polk Audio
Looking for 2SD424 and 2SB554

Hi folks,

I have just subscribed to diyaudio.

After a long absence from bench-top experimenting I'm making some tentative steps toward setting up a very small home workshop. First up for some work is my old Aragon 4004 which needs replacement outputs - namely 2SD424 and 2SB554 matched pairs. I did send a message to ben62670 to see if he had some left but I then traced another thread where he mentioned his stock was out. Apologies for the double-query ben62670.

So I would like to throw the question out to see if anyone knows of sources of decent pairs. I'm well aware that inferior product is out there on the web so I'm willing to wait for a good lead.

All the best

Hi Don,

Welcome to the forum. Glad you're here!

I happened to see your post and thought you might find the following info useful as the gent who did his was very thorough:

• Ver Tema - Reparación, modificación y actualización Aragon 4004 MK II

The short answer is use MJ21193G & MJ21194G as replacement output transistors. You will find as long as they're from the same lots that their device to device tolerance is much closer and matching should be close enough to not be required.

If you dig deep enough, you will find that the design of the above devices was "borrowed" from Toshiba and improved on by ON-Semi. ;)

I too am rebuilding one and am using the above outputs in mine.

You might consider starting a new thread dedicated to the restoration process of your amp so others will be able to find it easily.

Kind regards,

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Hi Steve

Many thanks indeed for your quick reply. Much appreciated. I did use the search engine to look for "Aragon 4004" but I didn't pick up the threads you suggested here. Put it down to my apprenticeship on the forum..

The MJ1193G and 1194G sound good. In fact the schematic of the Amp I have shows the MJE15003 and MJE 15004. If you are restoring an Aragon as well there are definite advantages in my using the same transistors so that there's an opportunity to compare notes. I haven't yet obtained the gain characteristics of the transistors from data sheets. I'll try to get some of those here but, failing that, I may need to ask if I can pick up some via one of the members of the forum.

As you suggested, I ought to start a thread entitled "Aragaon 2004 restoration."

I have been fortunate enough to get in touch with a Mondial tech who sent me the main schematics as well as the parts list and positions of components for a 2002 upgrade to the Mark 2. I also picked up a biasing procedure which, I think, is elsewhere on this forum.

I notice that on all of the output transistors the thermal grease is very dry and patchy so it would not surprise me that the outputs would suffer from heat build-up and eventually fail. Therefore, I'll be removing all of the outputs and re-applying some new thermal grease, taking care not to bend and break the insulating thermal pads the go between the transistors and the heat sinks. There are materials such as the Unigrease product (Unigrease 3000) which I'm considering.

I wonder also if problems in optimising biasing (different mV reading on different channels) might be due to local temperature differences in the transistors. I haven't really investigated that as yet.

I'll set up a thread shortly.

Yours appreciatively

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