Hi Sakis,
I actually followed your advice all the way but than I didn't get any answers to my new posts so I continued searching and managed to get there eventually. Same concerning the Marantz 1122DC I was working on where I did exactly as you said. When you say this do you refer to some answers in particular that I might have skipped ?
I'm very thankful of all the help I get here, sometimes it happens that someone suggests something that I have already checked or done and so I don't necessarily mention it in my replies...
I actually followed your advice all the way but than I didn't get any answers to my new posts so I continued searching and managed to get there eventually. Same concerning the Marantz 1122DC I was working on where I did exactly as you said. When you say this do you refer to some answers in particular that I might have skipped ?
I'm very thankful of all the help I get here, sometimes it happens that someone suggests something that I have already checked or done and so I don't necessarily mention it in my replies...
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2 pointers that you will find in my writing more than often :
1) many of the transistors present mechanical type of failure and as a a basis you may check them OK with a DVM but actually expect them to fail under voltage
2)There is an urban myth personally i could better call it Audiokarma myth that all output transistors in Japanese amplifier can be replaced with 21193 driven also from 150xx drivers .... That is false and there is many times the problem that if your criteria is how rugged is the output transistor and driver this is not enough for first to operate is some Japanese amplifier and farther more to produce equal sound or settings with the originals ....
1) many of the transistors present mechanical type of failure and as a a basis you may check them OK with a DVM but actually expect them to fail under voltage
2)There is an urban myth personally i could better call it Audiokarma myth that all output transistors in Japanese amplifier can be replaced with 21193 driven also from 150xx drivers .... That is false and there is many times the problem that if your criteria is how rugged is the output transistor and driver this is not enough for first to operate is some Japanese amplifier and farther more to produce equal sound or settings with the originals ....
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1) indeed you did that is also why I suspected just testing them with a multimeter wasn't going to be enough.
2) duly noted, In this particular amp I went with the originals for the outputs and I will replace the drivers by some 2sa1930/2sc5171 (now just some original ones from another pioneer amp that I removed to test) as suggested in some other threads about the SA-7800. I have learned not to trust simple cross reference tools but refer to what I can find here or on audiokarma and if possible get "live" advise".
Is there a way (other than experience) to know what transistor would be best if not just by comparing the specs ?
2) duly noted, In this particular amp I went with the originals for the outputs and I will replace the drivers by some 2sa1930/2sc5171 (now just some original ones from another pioneer amp that I removed to test) as suggested in some other threads about the SA-7800. I have learned not to trust simple cross reference tools but refer to what I can find here or on audiokarma and if possible get "live" advise".
Is there a way (other than experience) to know what transistor would be best if not just by comparing the specs ?
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The unfortunate problem is that no one is manufacturing high speed T0-3 case output transistors any more.
Almost any Japanese numbered (2SA/SB, 2SC/2SD) TO-3 outputs that one is likely to find on the internet are guaranteed to be Chinese fakes.
Sadly, we are stuck with MJ21195/96.
you need to be as close is possible in 3 points
1-capacitance since this will stress previous stages and need other type of compensation.
2-speed which will either decrease the performance of the amplifier if less or drive it to oscillation if far more than the original.
3-Also important is if the base of the transistor can be driven the same way like the original since this will also stress the previous stages.
1-capacitance since this will stress previous stages and need other type of compensation.
2-speed which will either decrease the performance of the amplifier if less or drive it to oscillation if far more than the original.
3-Also important is if the base of the transistor can be driven the same way like the original since this will also stress the previous stages.
you are wrong
you need to search more carefully or examine alternative sources when you repair 1500 audio devices per year then you need to find proper suppliers
For example we often shop from a local YAMAHA dealer ....expect to pay them like diamonds but yes what you will get is the original Japanese thingy ....Practice is the same you can check other local distributors
I had the great fortune about six years ago to buy out the inventory of a competing stereo repair shop that had closed down. I have just a few sets of original Japanese TO-3 devices left, and I dread trying to find real ones when these are gone.
I flat out refuse to pay $20-$30 apiece for them.
I flat out refuse to pay $20-$30 apiece for them.
Ok I got the first 2 points but what exactly do you mean by " if the base of the transistor can be driven the same way like the original"
Concerning the outputs, I'm not a professional (maybe one day who knows) so giving a fortune for parts is not really an option even if I always try to get the best possible option.
Concerning the outputs, I'm not a professional (maybe one day who knows) so giving a fortune for parts is not really an option even if I always try to get the best possible option.
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Did exactly the same but i was far more lucky than you Got my self hundreds of them and many many totally obsolete things like 2SK117 or 2SK34
all original
Another sad thing is that many older techs are passing away, and their families, as often as not, have a tendency to view their horde of electronics parts as "old junk", and throw them in the trash.
Depaj, most vintage receivers/amps over 60 watts per channel or so use four output transistors per channel, so you're looking at $80-$120+ for one channel's worth of outputs. Most customers are total cheapskates, and trying to sell them on a $250 repair, plus take care of 40 years of deferred maintenance can be pretty tough.
Depaj, most vintage receivers/amps over 60 watts per channel or so use four output transistors per channel, so you're looking at $80-$120+ for one channel's worth of outputs. Most customers are total cheapskates, and trying to sell them on a $250 repair, plus take care of 40 years of deferred maintenance can be pretty tough.
I've noticed, that's is how I got a hold on some amps (luckily some people sell them for a fair price or even donate them).
I've been working on a lot of less powerful amps and most of the 60W+ had a good output stage. A marantz 1122dc that has its own thread here didn't have though and east electronics suggested to replace the 4 per channel by one more rugged pair, this works great on this amp and was a rather "cheap" option, is that an option for most amps using this configuration ? Are there any makes of recent transistors equivalents that you would recommend (I've heard a lot about fairchild).
I've been working on a lot of less powerful amps and most of the 60W+ had a good output stage. A marantz 1122dc that has its own thread here didn't have though and east electronics suggested to replace the 4 per channel by one more rugged pair, this works great on this amp and was a rather "cheap" option, is that an option for most amps using this configuration ? Are there any makes of recent transistors equivalents that you would recommend (I've heard a lot about fairchild).
There are plenty of options for plastic cased transistors. Unfortunately for us, the only new mfg. TO-3 transistors worth considering are the MJ21195/96, or MJ 21xxx for lower power applications.
ST Micro was making a nice, robust, high-speed TO-3 pair up until just a few years ago, but they are now all gone as well.🙁
ST Micro was making a nice, robust, high-speed TO-3 pair up until just a few years ago, but they are now all gone as well.🙁
4 pairs of 4467 -1694 original will cost no more than 10-15 euro or USD.
You can get 1943 and 5200 at almost the same or a bit higher cost ....
Servicing an amplifier of that era is a subject of knowing what to do what to change and it can actually both be done very fast and very effectively .
Repair 10 of each model and then you know what to do and where to look .
Problem is that after all these guys passing away as you said unfortunately it seems that only source of knowledge is internet and like many other issues internet is notorious place for the creation of urban myths ....
I think that i should be probably one of the very few guys world wide that really shares real knowledge on repairs rather than a personal opinion that you see way too often in places like Audiokarma .
Let us not forget that i have the benefit of numbers Repairing so many times the same models lets you know all the little dirty secrets inside ...fails in consumer audio are epidemic ...
Kindest regards
Sakis
Not really... 1122 and some Pioneer amps that use similar configuration in the output like 4 small barely TO220 semis to produce 70-80W originates from the commitment of the companies to use NEC transistors
Other than that is a very poor choice and even worst a horrible implementation IE semis hardwired from the board with flat triplets of cable
so using 2 proper and bigger semis rearrange wiring in a better way is actually a huge upgrade not just a quick fix
Remember that hardwiring transistors with flat cables eventually you will have the base cable modulated by the other two that carry the hard load this will inject the signal with all forms of inductance or "crosstalk" which will also produce very weird clip conditions and or oscillation ....
So dear Depaj in the near feature you should advance your testing methods and instruments and you will understand that a lot of juice of the sound and the stability is hidden inside small mistakes like the above mentioned ....
Kind regards
Sakis
4467/1694 and 1943/5200 aren't TO-3 transistors. You can get those from Mouser or Digi-Key. There is no shortage whatsoever for authentic high- quality plastic case transistors.
It's the good TO-3s that are hard to source. Yes, I do realize that with a little work, a plastic cased transistor can sub for a TO-3, but most times I would rather not do that.
It's the good TO-3s that are hard to source. Yes, I do realize that with a little work, a plastic cased transistor can sub for a TO-3, but most times I would rather not do that.
Trust me we do that every day ...some time is even faster than installing cans and the all related hardware of the cans
Yeah, I've subbed TO-220s in place of TO-66 and TO-3P/TO-247 in place of TO-3. It worked, but it looked pretty hokey.
Sorry audiopackrat, I didn't see you were talking about to-3 cases in particular so Just a simple missunderstanding.
Sakis, I think you missunderstood my question, you seem to disagree with me but than say the exact same thing I said before... I Just wanted to know if what I did on the marantz is also a good option for other amps with parallelled output transistors, from what you sais I understand the answer is yes.
Sakis, I think you missunderstood my question, you seem to disagree with me but than say the exact same thing I said before... I Just wanted to know if what I did on the marantz is also a good option for other amps with parallelled output transistors, from what you sais I understand the answer is yes.
Yes looks is something a good tech should also take care off The average user will pop the hatch to see what he paid for ...
Don't feel bad, Depaj, I just realized that the Pioneer SA-7800 doesn't even use TO-3s.😱
I have one sitting out in my shop that needs repaired. Not when I will get to it though. However, I don't think that I would replace four ouput transistors with two on that amp. It is a non-switching amp, and tweeking the design could be trouble.
I have one sitting out in my shop that needs repaired. Not when I will get to it though. However, I don't think that I would replace four ouput transistors with two on that amp. It is a non-switching amp, and tweeking the design could be trouble.