AKAI GX 265D transistor replacement

[HendeoNZ]

Hi all,

I've got a little problem with my GX-265D. i can't seem to record in the reverse direction - I've cleaned SW2/3 as much as I can without desoldering them. But in my search I found a bad transistor TR9 (2SC945L) - it should be reading 15v but is only at 10.9v.

My question is can I replace 2SC945L with BC639 - it's the only one I can find in NZ.

Cheers

 

[dr*audio]

Might not be bad. Is the base of TR9 0V? If so, remove TR9 and see if the voltage goes up on the base of TR8. TR9 is supposed to turn off TR8 when it is on. This doesn't have anything to do with not recording in reverse.

 

[HendeoNZ]

Might not be bad. Is the base of TR9 0V? If so, remove TR9 and see if the voltage goes up on the base of TR8. TR9 is supposed to turn off TR8 when it is on. This doesn't have anything to do with not recording in reverse.

Thanks for the reply.

I'll have a look at that. If it's not responsible for recording in reverse. Would you have a idea of where to look? Cheers

 

[dr*audio]

Thanks for the reply.

I'll have a look at that. If it's not responsible for recording in reverse. Would you have a idea of where to look? Cheers

Well, that circuit is the erase oscillator. It is responsible for recording in BOTH directions. If it didn't work you couldn't erase or record at all.
About the only thing it could be is the head switch or the reverse record or erase head. Does it erase in the reverse direction?

 

[HendeoNZ]

Well, that circuit is the erase oscillator. It is responsible for recording in BOTH directions. If it didn't work you couldn't erase or record at all.
About the only thing it could be is the head switch or the reverse record or erase head. Does it erase in the reverse direction?

Cheers for the response, no it doesn't erase in the reverse direction - I'll have a look at the switches again, but is there any way to test the erase/rec heads to see if they're getting power?

Thanks

 

[dr*audio]

Cheers for the response, no it doesn't erase in the reverse direction - I'll have a look at the switches again, but is there any way to test the erase/rec heads to see if they're getting power?

Thanks

It has to be the head switch. You can check with an oscilloscope if the erase and bias signals are getting to the heads. If you don't have a scope, you can check the heads with a meter on Ohms. Then check the resistance across the head switch.

 

[HendeoNZ]

It has to be the head switch. You can check with an oscilloscope if the erase and bias signals are getting to the heads. If you don't have a scope, you can check the heads with a meter on Ohms. Then check the resistance across the head switch.

Thanks - I've got a scope - when probing the heads, can I just attach the ground clamp to the chassis with the heads? Cheers

 

[dr*audio]

Thanks - I've got a scope - when probing the heads, can I just attach the ground clamp to the chassis with the heads? Cheers

Yes. It may be difficult to see the audio signal because the erase signal is very large amplitude and can be picked up by the long ground lead. It may help to bunch up the ground lead to make it as "short" as possible.