Sadly, you are looking at history there. Sanyo's 2SC/2SA types and Philips/Siemens BF4xx type parts were all developed for old picture tube type TVs. Look at availability and the seller's credentials as the prime indicators of suitable replacements. Those parts were obsolete long ago and Fairchild then made single KSC/KSA replacements as a "one size fits all". Both Sanyo Semiconductor and Fairchild Semiconductor are now owned by On Semi so theirs are the appropriate datasheets and selling agencies to check.
Unless you are prepared to buy stock quantities of obsolete or NOS parts, don't buy those which you may find on Ebay etc. in China or various electronic parts traders around the globe. Buy from authorised sellers of genuine parts. Otherwise, you are stuffed again when if they turn out to be fakes, there is a meltdown or you need to buy more for other purposes.
Yes, they should be drop-in replacements but I have only performed the surgery once for another ETI 5000 owner and checked with another repairer in correspondence. AFAIK, three examples still work after at least 7 years but it may not be so for all builds, perhaps where the capacitance of different PCBs and wiring layouts provokes instability. You cannot guarantee DIY results with that, only make suggestions.
I bought my Sanyos long time ago, Fairchild's ksa1142, ksa992 and ksc3503 are still available, unfortunately ksc2682 is now obsolete. B+D Enterprises still has Sanyo's 2sa1209 and 2sc2911 but they are expensive. Also, apparently, digipart has them. You can write to both and ask if these are genuine Sanyos.
In the 1980s there was some problem with BF availability in Australia so kit makers such as Jaycar later supplied their kits with mje340/350. I got such a kit but I managed to get BFs and used these. I don't have this amp anymore.
Several years ago I got another eti5000 amp and preamp, rebuilt eti477 as well as my original eti5000 preamp. From the latter I kept only the case and its display.
Anyway, my current eti477 has single filter at the input (820/1nF), no cap on 22k nfb resistor, non-inductive 220 ohm resistors in gates, 470pF caps gate to source, non-inductive 0.15 ohm source resistors, 10 ohm caddock in zoebel and "non-inductive" cap, Sanyos in VAS and 220pF there and no oscillations with ancient but genuine Hitachis.
cheers,
In the 1980s there was some problem with BF availability in Australia so kit makers such as Jaycar later supplied their kits with mje340/350. I got such a kit but I managed to get BFs and used these. I don't have this amp anymore.
Several years ago I got another eti5000 amp and preamp, rebuilt eti477 as well as my original eti5000 preamp. From the latter I kept only the case and its display.
Anyway, my current eti477 has single filter at the input (820/1nF), no cap on 22k nfb resistor, non-inductive 220 ohm resistors in gates, 470pF caps gate to source, non-inductive 0.15 ohm source resistors, 10 ohm caddock in zoebel and "non-inductive" cap, Sanyos in VAS and 220pF there and no oscillations with ancient but genuine Hitachis.
cheers,
So to drum up this old post. I recently bought a TA-477 kit on ebay. sadly only one channel but the kit is brand new and the 4 mosfets alone are worth more then what i paid for the whole kit. I thought it would be fun to build this old kit. something to do now that the motorcycles are put away and winter is approaching here in MinneSNOWta.
reading through this old post is interesting. If anyone has any other tips to make this amp very reliable. I would be interested to know! I have yet to dig into my kit to see what transistors my kit came with as it just arrived this morning. but. let the discussion begin. My goal is not ultimate fidelity, but stability and reliability as i will be using this as a General Purpose shop amplifier and it may be driving any load on any given day. speakers, transformers backwards, light bulbs who knows...
reading through this old post is interesting. If anyone has any other tips to make this amp very reliable. I would be interested to know! I have yet to dig into my kit to see what transistors my kit came with as it just arrived this morning. but. let the discussion begin. My goal is not ultimate fidelity, but stability and reliability as i will be using this as a General Purpose shop amplifier and it may be driving any load on any given day. speakers, transformers backwards, light bulbs who knows...
Because the original driver semis are now obsolete or quite expensive and difficult to find as genuine parts, I looked at the more recent and very successful work with lateral Mosfet amplifiers by Mike J Renardson of UK's Manchester University. If you're new to lateral Mosfet designs, his articles are eye-openers and quite informative regarding general design requirements and even the challenge of feed-forward compensation for those with an interest.
His VAS designs are not the same as the ETI477 module, the ETI5000 amp nor other Mosfet designs generally but they all still require similar fast, medium power transistors with very low Cob. I suggest you have a careful read for the information there and note the exemplary figures he gets for his MJR-7 design in particular.
Audio Amplifier Design
The amplifiers at the site are now fitted with On Semi/Fairchild's video drivers KSC3503/KSA1381 or KSC2690/KSA1209, without other changes as far as I can see. The archived material shows older versions and semis for comparison. The above types are current production and at reasonable cost from most On-Semi agencies. I think that's much better than crossing fingers and trusting in possible fakes and having nagging doubts.
His VAS designs are not the same as the ETI477 module, the ETI5000 amp nor other Mosfet designs generally but they all still require similar fast, medium power transistors with very low Cob. I suggest you have a careful read for the information there and note the exemplary figures he gets for his MJR-7 design in particular.
Audio Amplifier Design
The amplifiers at the site are now fitted with On Semi/Fairchild's video drivers KSC3503/KSA1381 or KSC2690/KSA1209, without other changes as far as I can see. The archived material shows older versions and semis for comparison. The above types are current production and at reasonable cost from most On-Semi agencies. I think that's much better than crossing fingers and trusting in possible fakes and having nagging doubts.
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