Hi,
If anyone knows, or already been done that, what transistor replacement is recommended for AKAI AA-1030 amplifier, instead 2SD428 / 2SB558 ?
I already try with MJ15022 / MJ15023, but this replacement aren't perfect function.
There is sound distortion and TR5 (2SC1625) is overheating a lot.
TNX
If anyone knows, or already been done that, what transistor replacement is recommended for AKAI AA-1030 amplifier, instead 2SD428 / 2SB558 ?
I already try with MJ15022 / MJ15023, but this replacement aren't perfect function.
There is sound distortion and TR5 (2SC1625) is overheating a lot.
TNX
With any change of component the circuit must be altered to suit. I would use 2n3055 and MJ2955 as they are similar and have reasonable Hfe. of min 40. MJ15022 can be as low as 5!
this one bad channel is totally malfunction.
till waiting new 2n3055/MJ2955 transistors, for testing I moved transistors pair 2SD428/2SB558 from good working channel.
So i got the resistor R13 get heating & burned... I replace it and do some resistance measurement :
C7:
good channel = 18,8 M Ohms
bad channel = 11,7 M Ohms
R10:
good channel = 4,3 k Ohms
bad channel = 2,5 k Ohms and slowly rising to 4 k Ohms
R11:
good channel = 3,3 k Ohms
bad channel = 2 k Ohms and slowly rising to 3 k Ohms
any idea ?
tnx
till waiting new 2n3055/MJ2955 transistors, for testing I moved transistors pair 2SD428/2SB558 from good working channel.
So i got the resistor R13 get heating & burned... I replace it and do some resistance measurement :
C7:
good channel = 18,8 M Ohms
bad channel = 11,7 M Ohms
R10:
good channel = 4,3 k Ohms
bad channel = 2,5 k Ohms and slowly rising to 4 k Ohms
R11:
good channel = 3,3 k Ohms
bad channel = 2 k Ohms and slowly rising to 3 k Ohms
any idea ?
tnx
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Last edited:
aditionally,
resistance measurement without this transistors:
good channel - 13 M Ohms
bad channel - 50 k Ohms
Then there is something else wrong with it. Short the base of Q5 to the base of Q6. If that clears the heating problem, the bias stack is bad. If it doesn't, change Q5 and Q6.
15022's will work just about anywhere an old TO-3 was used. Unless it was germanium.
still looking what is wrong with non-working channel.
without installed those transistors on both channel, 10 seconds after power on, TR6 (2SA815) are heating a lot on a bad channel.
and there is 13V on this transistor on bad channel.
0,5V is on same transistor on good channel, like it is in service manual.
without installed those transistors on both channel, 10 seconds after power on, TR6 (2SA815) are heating a lot on a bad channel.
and there is 13V on this transistor on bad channel.
0,5V is on same transistor on good channel, like it is in service manual.
Last edited:
Hello,
Here is some updates...
I checked all transistors on bad channel and TR5 (2SC1625) was bad with resistance in kOhms.
BD241C was the only similar I had available for testing.
With BC214C all voltages become OK... still without 2SD428 / 2SB558.
When putting them back in this channel work OK, but R14 is overheating.
So I have to find good and available replacement for 2SC1625 & 2SA815.
Here is some updates...
I checked all transistors on bad channel and TR5 (2SC1625) was bad with resistance in kOhms.
BD241C was the only similar I had available for testing.
With BC214C all voltages become OK... still without 2SD428 / 2SB558.
When putting them back in this channel work OK, but R14 is overheating.
So I have to find good and available replacement for 2SC1625 & 2SA815.
new update...
Transistors 2SC1625/2SA815 were replaced with TIP41C/TIP42C, and transistors 2SD428/2SB558 were replaced with 2N3055/MJ2955.
Everything work fine.
Transistors 2SC1625/2SA815 were replaced with TIP41C/TIP42C, and transistors 2SD428/2SB558 were replaced with 2N3055/MJ2955.
Everything work fine.
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