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Toshiba GT20D101/102 replacements?

No it’s the one from DIY Audio alright. I haven’t done it yet, but that one will make my work easier!
 
I mentioned them up thread, they're as good as any.... More important than precise choice of mosfet (within reason!) is biasing them correctly and having the amp compensated properly.

No further errors then on the schematic...
 
S-Man said:
They were supposed to have the ease of drive of mosfets and the current gain of bipolars. Tosh had to do some engineering to avoid the latchup issues with IGBTs (which paved the way for modern IGBTs which are used in nearly all modern power electronics!).
They do have some issues: pole-splitting behaviour with low impedance loads, which means they have to be over compensated compared to mosfets. I can't remember if they need thermal compensation - I probably ought to read the apps note Jez mentioned again. I worked with Steve Langdon (I think Steve's name is on the AN) at Tosh when JLH did the IGBT testing. Wish I had loaded up on all the JFETs and bipolar audio devices at the time, instead of just getting a few for my own use. Wish I had met JLH as well!!

As far as replacements go - how about some of the Fairchild mosfets that the diyaudio chaps rave about?

I might have a couple of lightly used pairs of the IGBTs somewhere.


BTW, during "allocation" of semiconductors IGBT stands for "Ignore Great Britain Totally"! :D
Click to expand...


It’s only the lateral power MOSFETS and the quite rare no longer manufactured static induction transistors from Sony and Yamaha that have a benign temperature bias current relationship. With VMOS you have to have low gain devices with gfs less than about 3-4S, Toshiba did this with the 2SJ200 2SK1530 etc and hitachi with 2SJ118/2SK413 and it’s possible to design good amplifiers with these. If power is not a big issue then IRF520/IRF9530 are a good choice and are virtually free as opposed to the other devices.
 
The IGBT transistors I received. Genuine Toshibas, perhaps a third, later batch – the first ones were black/green, the second series had white silk screening and these ones are etched.

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How do I know? The thing lives!
I had to replace more than twenty components: many diodes, transistors and resistors were fried. Plus a few Philips caps almost having transformed into pure resistors…

The LFD is borrowed from Philips. Is is in fact a CD player display!


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Yes. Even idle current (100 mA) and offset (9 mV) were in order at first switch-on. Drivers are hot (no heat sinks) but output transistors stay lukewarm.
 
Cracked it. Some stupid idiot had done this:

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Yes, really. That explains everything that happened to this poor amp, probably :p
 
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