I almost positive the I have developed the dreaded hissy channel problem. When I record stuff the left channel is hissy and it is seems to be going on the recordings too. the right channel sound fine but the left hissy. I can record on least. is it normal for on channel to be noise and the other one fine?
I am listen to a tape that was made a while ago on this unit and it and seem to have the same thing.
Also seem to change with point on tape?

Please help.

I would eliminate all the other factors first - noisy source, cables, output level knob, etc. The transistors that get noisy are 2SC458s - I think there are either 3 or 6 per channel in the GX-255. Maybe it is 3 per channel for record and 3 per channel for playback.

I used 2SC1815(Y) to replace them.

The 2SC458 will sound better, but the 2SC1815 will do.
The new 458's are better than the ones from the 1970's. ;)
But they are hard to find. I orderd 500 pcs from this site: http://www.ceitron.com/

If you have the deck opened you can easily replace the capacitors of the record and playback amps as well.

Is that site legit?
On the bay the have some vintage ones for cheap. Is it hard to replace them?
I am 99.9% sure the transistors are bad its hissy if the record volume goes up more then 50 percent and its a deep sound hiss. Plus play back is noisy in one channel only.

Should I look for new ones? or get some NOS off of the bay?

I would avoid old ones from the bay.

Thank you I will try to look for new ones.
Are they soldered in?
IS replacing them hard?

I used On-Semi MPSA18RLRAg's to replace 2SC458's in my Akai GX-267D. The pin layout is different, but otherwise work great. Recommended by dr*audio here. :thmbsp:

They are soldered in.

Hard to replace?

Hard to replace?

Not if you're handy with a soldering iron and solder wick. I did two of the 4 transistors on my GX-267D with guidance from a member here and it came out great. If you've never done it before, I'd pickup a junker deck somehwere (anything, bad power supply, SA tape deck...) and practice de-soldering components. Then re-solder a few back in. It's easier than it sounds.