I picked up a Azure 340a which I am trying to get working.
It has a problem with the right channel: There is a hum which gets louder when you change the volume, the audio you can hardly hear at all.
Left channel works fine.
On the record out all you can hear on the right channel is the hum.
I replaced U9 in the board and I have tested C45 & C46 which seem OK. However I only have -10v not -15v on the OPAMP supply rail, +15v appears fine.
LK1 & LK4 also seem to be around 36v & -36v instead of 28v & -28v reverenced to LK2.
C24 & C27 seem OK.
Can anyone give me any pointers? I only have a very basic understanding of electronics.
I have uploaded the service manual here: http://docdro.id/d7hHVKS
It has a problem with the right channel: There is a hum which gets louder when you change the volume, the audio you can hardly hear at all.
Left channel works fine.
On the record out all you can hear on the right channel is the hum.
I replaced U9 in the board and I have tested C45 & C46 which seem OK. However I only have -10v not -15v on the OPAMP supply rail, +15v appears fine.
LK1 & LK4 also seem to be around 36v & -36v instead of 28v & -28v reverenced to LK2.
C24 & C27 seem OK.
Can anyone give me any pointers? I only have a very basic understanding of electronics.
I have uploaded the service manual here: http://docdro.id/d7hHVKS
Appears to be associated with the input selector circuit and U4 TC9163,
if the tape out signal is bad. Check related solder joints and traces first.
All the power supplies are common to both channels, so they aren't causing
the hum, if it's only in one channel.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.