2sc2259 replacement

[nosaj]

Hello I have a kenwood super 11 reciever thatI have a 2sc2259 Q7 that is bad.

Juan helped me build a VCA before for a rare chip type.

If I wanted to take 2 regular NPN transistors sharing the emitters to fill the 5 holes which common audio transistors would you choose?
Granted this is just so I can suss out the rest of the power amp for now.

Thanks,
nosaj

2sc2259 specs https://alltransistors.com/crsearch....e=250&caps=SP0

2sc2259 datasheethttp://www.datasheetbank.com/2SC2259...PDF-Mitsubishi

Kenwood super 11 service manualhttps://www.vintageshifi.com/reperto...ice-Manual.pdf

[nickb]

2 x KSC1845 but you'll have to jiggle the leads a little.

[nosaj]

2 x KSC1845 but you'll have to jiggle the leads a little.

Given that what do you thing about a 2n3904 which I do have on hand, specs seem comparable to KSC1845.

Thanks,
nosaj

[nosaj]

Given that what do you thing about a 2n3904 which I do have on hand, specs seem comparable to KSC1845.

Thanks,
nosaj

Looking that over that's gonna be some tricky legwork. 3904 EBC 2259 BCECB

I'm not sure I can finagle that. Only half of the 2259 is dead the left half. I'm thinking about just cutting pins 1 and 2 which I'm hoping will release it from protection and inject signal at pin2 .

Thanks Nickb,
nosaj

[nosaj]

Looking that over that's gonna be some tricky legwork. 3904 EBC 2259 BCECB

I'm not sure I can finagle that. Only half of the 2259 is dead the left half. I'm thinking about just cutting pins 1 and 2 which I'm hoping will release it from protection and inject signal at pin2 .

Thanks Nickb,
nosaj

Snipped leg 2 injected signal at pin2 audio on the left channel transistors. Just need to verify at the speaker jack to make sure it's out of protection mode.

nosaj

[nickb]

Looking that over that's gonna be some tricky legwork. 3904 EBC 2259 BCECB

I'm not sure I can finagle that. Only half of the 2259 is dead the left half. I'm thinking about just cutting pins 1 and 2 which I'm hoping will release it from protection and inject signal at pin2 .

Thanks Nickb,
nosaj

The 2N3904 is only 40V whereas the original was 100V.

The two transistors in the one package have important properties of electrical and thermal matching. Therefore you should replace using matched transistors whose cases are bonded together. Using different transistors is probably not a great solution. I'm sure there are other transistor available with a simple lead out but you still need to couple them together.


The KSC1845 (and KSA992) is something I have a pile of on the shelf that gets substituted for the differential pair in all kinds of SS amps,

[nosaj]

The 2N3904 is only 40V whereas the original was 100V.

The two transistors in the one package have important properties of electrical and thermal matching. Therefore you should replace using matched transistors whose cases are bonded together. Using different transistors is probably not a great solution. I'm sure there are other transistor available with a simple lead out but you still need to couple them together.


The KSC1845 (and KSA992) is something I have a pile of on the shelf that gets substituted for the differential pair in all kinds of SS amps,

I found some originals to replace them with. I was just looking for a solution to finish running through the rest of the signal path. It's still sitting in protection mode but signal is getting to the output transistors now.

nosaj

[nosaj]

I found some originals to replace them with. I was just looking for a solution to finish running through the rest of the signal path. It's still sitting in protection mode but signal is getting to the output transistors now.

nosaj

I clipped pin2 and injected signal which I can hear with an audio probe on the output transistors, but it's not making it to the speaker or headphone jacks. I did pull all the output transistors previously and they tested ok and there is no DC on the jacks.

I'm guessing it's still in protection?

nosaj

[The Dude]

Can you hear the speaker relay engage? Measuring the voltage across D22 (relay coil) would tell you if it's supposed to be engaging or is in protect. There won't be DC (or anything else) on the jacks if the relay is not closing, but there could still be DC coming from one of the amps in front of the relay.

[The Dude]

Also note: This unit has an "adaptor" function which is a pre-amp/power amp loop. If you don't have anything in the loop jacks in the rear, you must have the adaptor button set appropriately on the front panel.

[nosaj]

Can you hear the speaker relay engage? Measuring the voltage across D22 (relay coil) would tell you if it's supposed to be engaging or is in protect. There won't be DC (or anything else) on the jacks if the relay is not closing, but there could still be DC coming from one of the amps in front of the relay.

Getting about 1.9vdc across d22, protect mode will shut off both channels even if it is only one side failing right?

Thanks,
nosaj

Looking at the schematic it says I should see 26.5v, is that in respect to ground or across D22?

[The Dude]

1.9V isn't enough to turn the relay on, so there's likely still a problem with one of the amps. What is the voltage on the base of Q22? I'm betting one of the amps is putting out DC. Look at R83 and R84 feeding the base of Q22. Each of those will pass some DC from a bad amp to the base of Q22 and cause the unit to stay in protect keeping the relay open and DC from reaching speakers.

Edit: The 26.5V is referenced to ground. As long as it's something close, we're good. What's important is the voltage across the relay coil.

[nosaj]

1.9V isn't enough to turn the relay on, so there's likely still a problem with one of the amps. What is the voltage on the base of Q22? I'm betting one of the amps is putting out DC. Look at R83 and R84 feeding the base of Q22. Each of those will pass some DC from a bad amp to the base of Q22 and cause the unit to stay in protect keeping the relay open and DC from reaching speakers.

Edit: The 26.5V is referenced to ground. As long as it's something close, we're good. What's important is the voltage across the relay coil.

Base of Q22 is showing -3.85v .

The 26.5v on the schematic reads 51.2vdc on the amplifier. So I need to run back further to q15, q31, q29 correct?

The outputs were tested out of circuit on a BK transistor tester.

Thanks so much,
nosaj

[The Dude]

Yes, if that's where the DC is coming from. Remember, it doesn't have to be a transistor. I'd first look at any associated resistors in the circuit of the transistor you've already replaced. It's not uncommon for a shorted transistor to take out resistors in the circuit.