2SA1102 vs 2SA1104 with 2SC2577

[svkr2k]

Dear forum members,

I have a Kenwood amplifier that has 2SA1102/2SC2577 pair for the output stage.
I could not find a replacement for 2SA1102. But, I have got 2SA1104. The specifications looks similar.

I request the experts here to advice me if 2SA1104 can be used in circuit where 2SA1102 was used? (i.e., can it be replaced without doing any modifications to the amplifier circuit? can it work along with 2SC2577 as compilemtary pair ?

(Please note : One thing that worries me is that the Collecter-Emitter saturation voltage is different for the two transistors.)

Thanks in advance for your help.
Regards,
Rajesh Seenivasan.

[embrown057]

I'm not sure where you live but they are still around:
2SA1102
Search results for 2SA1102

Or you could use the 2SA1693/C4466 that is if they are in your area.

[svkr2k]

I live in India. It is not very easy to get discontinued sanken components. So, I'm trying to explore alternatives. kindly let me know your opinion on 2sa1104 and 2sc2577 working together. should there be modifications in the circuit to make it work? the amp model is KA-32. Circuit diagram is available for free in several websites.

[svkr2k]

can we use 2SA 1693/C4466 instead of 2sa1102/2sc2577 without doing any other modifications to the circuit in ka-32 amp ?

[sakis]

first of all you cannot replace one transistor only ...they need to be replace as pairs Obviously if the new pair has some difference than the old one in a sonic signature level you will also need to replace the other working Chanel also for symmetry reasons.

now here is a couple of serious issues

one :
unit of that age beyond checking all parts very very carefully will need most of small electrolytics inside to be replaced .... expect most of them to be dead . This can teake you to stability issues and/or sound quality issues .

two and more important
the Kenwood KA-32 doesn't feature a bias trim .... if the new transistors operate with high or lower bias this will eventually blow your amp or play with distortion ...Expecting new transistors to operate in the same bias is very wrong practice .


you need to figure out the bias scheme from the schematic and where a fixed resistor exists you need to replace it with a trimmer so bias from now on is adjustable ...

After that you may use any complementary pair for audio amplifier like the well known combo 1943-5200 and you are done .

Schematic is available if you like to have it email me

Kind regards
Sakis