Hi,
Please can anyone help with some advice?
My Rotel RA-913 integrated amp has 4 2SA1403A TO3 outputs.
One is blown.
Should I:
- Try to buy an original one from a used parts vendor?
- Replace with a new version?
- Replace all 4 transistors with new versions?
And which currently manufactured transistor should I buy?
Please can anyone help with some advice?
My Rotel RA-913 integrated amp has 4 2SA1403A TO3 outputs.
One is blown.
Should I:
- Try to buy an original one from a used parts vendor?
- Replace with a new version?
- Replace all 4 transistors with new versions?
And which currently manufactured transistor should I buy?
It was originally used as a CRT video amplifier BJT .
While its available in the usual Chinese ( or thereabouts ) sources I would go for a genuine -NOS replaced --if you can find a genuine one ?
The set up instructions are pretty specific so a replacement should be near the original if you cant get an original.
The circuit is designed for that type so sticking heavy current modern devices is not advised, need to be at least near the 2SA1403A.
The TO3 version was later changed to a TO126 so I don't know if you can a replacement unless its genuine NOS.
Otherwise you would need to change all four to modern plastic types of near the same spec. which even here more modern versions originate from China .
While its available in the usual Chinese ( or thereabouts ) sources I would go for a genuine -NOS replaced --if you can find a genuine one ?
The set up instructions are pretty specific so a replacement should be near the original if you cant get an original.
The circuit is designed for that type so sticking heavy current modern devices is not advised, need to be at least near the 2SA1403A.
The TO3 version was later changed to a TO126 so I don't know if you can a replacement unless its genuine NOS.
Otherwise you would need to change all four to modern plastic types of near the same spec. which even here more modern versions originate from China .
Thanks Duncan, appreciate your attention and the advice.
So putting in some MJ15003G or MJ21194 might well 'work' ..but not happily?
So putting in some MJ15003G or MJ21194 might well 'work' ..but not happily?
The original BJT was biased at a much lower current than the ones you mention as well as the big difference in wattage .
What you need are "lightweight " types in relation to current , the reason for using a CRT video BJT was for the speed required due to old fashioned internal design, so a modern ,fast type with no more than 1 amp /10 watt or so is required unless you change the design .
If you put the ones you posted in --yes it might work but as you say not very well
What you need are "lightweight " types in relation to current , the reason for using a CRT video BJT was for the speed required due to old fashioned internal design, so a modern ,fast type with no more than 1 amp /10 watt or so is required unless you change the design .
If you put the ones you posted in --yes it might work but as you say not very well
Thanks again.
Two questions.. are there any dealers who supply used pieces from original amps etc?
And, I'd have no idea how to look up or judge the eligibility of a modern piece. If you could suggest a product it would be an enormous help.. but fully understand if it's a chore too far.
Best wishes.
Two questions.. are there any dealers who supply used pieces from original amps etc?
And, I'd have no idea how to look up or judge the eligibility of a modern piece. If you could suggest a product it would be an enormous help.. but fully understand if it's a chore too far.
Best wishes.
Dont know any dealers off hand but must be some in the USA .
I will get back in the morning as getting one near the original means running through equivalent books and the spec. is not very standard.
BD 385----- BD390 are quite near --if you can get them --all 50ma bias some easier to work with in your original circuit .
Mouser says not stocked but can be made available .
I will get back in the morning as getting one near the original means running through equivalent books and the spec. is not very standard.
BD 385----- BD390 are quite near --if you can get them --all 50ma bias some easier to work with in your original circuit .
Mouser says not stocked but can be made available .
I did mention Chinese ( or thereabouts ) were available , it depends what you think of their imports ?
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2SC1403A
- параметры, поиск аналогов, даташиты транзистора - Справочник транзисторов
VCEO Collector-Emitter Voltage 100 V
IC Collector Current-Continuous 8 A
PC Collector Power Dissipation
@ TC=25℃
70 W
hFE DC current gain IC=3A ; VCE=4V 30
fT Transition frequency IC=0.5A ; VCE=10V 10 MHz
- параметры, поиск аналогов, даташиты транзистора - Справочник транзисторов
VCEO Collector-Emitter Voltage 100 V
IC Collector Current-Continuous 8 A
PC Collector Power Dissipation
@ TC=25℃
70 W
hFE DC current gain IC=3A ; VCE=4V 30
fT Transition frequency IC=0.5A ; VCE=10V 10 MHz
Last edited:
Dear Karl vd Berg,
Thank you for pointing out my annoyingly silly typo!
Yes, it's a suitable replacement for a 2SC1403A that I require (please note, C not A).
My apologies to anyone who has scratched their head excessively..
Suggestions continue to be very welcome.
Thank you for pointing out my annoyingly silly typo!
Yes, it's a suitable replacement for a 2SC1403A that I require (please note, C not A).
My apologies to anyone who has scratched their head excessively..
Suggestions continue to be very welcome.
Thanks very much OldDIY.
Have you ever ordered from them? I was directed to a Chinese website which showed the transistor as listed but I couldn't see how to order it.
Have you ever ordered from them? I was directed to a Chinese website which showed the transistor as listed but I couldn't see how to order it.
Another option is the MJ4502G. Also a good equivalent. I use the complementary MJ802 in my Bedini 25.25
Adjusting bias on the Rotel RA-913 which is now working!
So, an adjusting bias question...
Service manual says:
"adjust to 7.5mV"
AND
"adjust to 20mV"
DC offset reads:
3mV Left
6mV Right.
I’ve just replaced all four output transistors with:
MJ15022 (formerly 2SC1403A)
and the drivers on left channel with:
KSA1381 and KSC3503
Naturally still feeling cautious given that I’ve only just got the amp working again.
Currently at bias is 7.5mV on both channels.
Please could anyone advise on most appropriate bias to adjust to?
So, an adjusting bias question...
Service manual says:
"adjust to 7.5mV"
AND
"adjust to 20mV"
DC offset reads:
3mV Left
6mV Right.
I’ve just replaced all four output transistors with:
MJ15022 (formerly 2SC1403A)
and the drivers on left channel with:
KSA1381 and KSC3503
Naturally still feeling cautious given that I’ve only just got the amp working again.
Currently at bias is 7.5mV on both channels.
Please could anyone advise on most appropriate bias to adjust to?
