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Hitachi SR 603 Transistor Question

Isaac C.

Isaac C.

Cat Hoarder
Hello everyone, I have a Hitachi SR 603 that I purchased a few months ago that has a hissing noise that gets louder as the volume is increased. For the longest time I thought it was noise from my turntable, but it is there regardless of what input is selected. It wasn't until today that I realized the receiver has two of the notorious 2SC458 transistors. I replaced them with two 2SC2240 from a NAD parts receiver that I have. Now the left channel sounds bad and the right channel doesn't work. Im going to order some new transistors since the 2SC2240s do not work. What are some alternatives? It appears that the 2SC2240s and KSC1845s are now obsolete. I have two 2SC1815s from another parts circuit board that I could try, but I do not know if they work.
 
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Isaac C. said:
. I replaced them with two 2SC2240 from a NAD parts receiver that I have. Now the left channel sounds bad and the right channel doesn't work.
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If the 2SC458's were the outhouse shaped (2SC458LG) TO-92 style it is easy to confuse the pin out on them when replacing with the 2SC2240's.
 
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avionic said:
If the 2SC458's were the outhouse shaped (2SC458LG) TO-92 style it is easy to confuse the pin out on them when replacing with the 2SC2240's.
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The Hitachi 2SC458s were Base, Collector, Emitter, and the 2240s were ECB so I made sure to flip it around. The 2240s might have been duds. Thanks for the mouser links, thats my favorite place to order from.

If they 2240s were duds would it have messed anything up? I only turned it on for a minute to test it after installing them.
 
Isaac C. said:
Is that transistor related, or am I wrong?
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Could be... The 2SC458's in this unit are for the protect circuitry Q501 and 503. And would have nothing to do with your hissing noise. The just control the protect relay coil voltage.
 
Hissing in both channels suggests something in common with both channels......Power supply..
 
Ok, thanks for the help. Once I replace those transistors, should I be using the receiver if the issue is in the power supply?

Since these transistors simply act as a switch in the protection circuit, would I be fine to put the SC458s back in, or should I replace them while I am at it?
 
avionic said:
deleted --rhetorical question..:biggrin:

Just how loud is this noise?
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Its noticeable a couple feet away at volume of 2 (max is 10) when nothing is playing. I just don't want to use it if there is a component going bad that could cause further damage.
 
Did you get back to the original problem with the old 2SC458's? Actually these two should have just messed with the relay clicking or not clicking.
 
Look your solder connections over for Q801 and Q802 2SD478 and 2SB568 in the power supply.
 
avionic said:
Look your solder connections over for Q801 and Q802 2SD478 and 2SB568 in the power supply.
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Tommorow if I get a chance I'll resolder those back in. Actually I might have been exaggerating a little bit unintentionally, if you put your ear about 6 inches away you can hear a "hsssss" at about 2 volume, full volume you can hear it a few a couple feet away. Besides that, the sound quality is phenomenal for what it is. I just know my Lafayette is dead quiet when nothing is playing, it might be inherent noise to the Hitachi. The DC offset in the Hitachi was only 4mv in each channel.
 
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