Actually, the existing drivers are testing good, but I blew one channel of outputs in a botched bias setting procedure and according to most of what I have gleaned, the drivers are now suspect, even though they test good. I may very well not even change them, they would be for a "backup unit" for my office setup. I would really hate to kill my Snells if I ended up using this unit eventually on them. So, should I automatically swap out the drivers? I normally would not flinch, but this particular board is lifting pads like a Made in China ebay purchase...
Always go one stage back from the last stage blown. For a 50 cent part don't even think about it too much, How did you test them in circuit.
From what little I've seen of those crossing lists on the internet; pity the fool that follows them, LOL
I did not think excess bias could kill that OP stage, it's rated for class A. You must not be using EZ hook probes. LOL
From what little I've seen of those crossing lists on the internet; pity the fool that follows them, LOL
I did not think excess bias could kill that OP stage, it's rated for class A. You must not be using EZ hook probes. LOL
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BDent has responded, they have the original devices 2sc3421/2sa1358 in the "Y" grade. I was concerned they would not have the same grade in the two; they seem to have alot of mismatched pairs (one "O", one "Y"). Would the suggested replacements of KSA1220A/KSC2690A still be a good route anyway? I have heard the philosophy of "go with what the original designer intended" but that person did not have these newer devices available and they could perhaps offer better performance. Ft seems a bit higher for the sub devices 175Mhz vs 120Mhz but so is cob 26pF vs 15pF. Note that they will be driving substitutes (NJW0281/NJW0302), not the original outputs (2SC3855/2SA1491), those were not available in matching grade from BDent.
Its up to you weigh all the pluses and minuses. Besides you broke the use "originals only" rule with the output devices? buy all the devices at one place would be an attractive option in my mind. Have you checked with Acme for originals? The design might be at the end of the margins like some designs specifying highest gain transistors. The Fairchild drivers are better parts period.
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