17-05-2020, 07:14 AM
Rob.
I have to agree with Dave, at least don't spend money on heads until you've checked out the circuit.
If you're hearing everything at low volume its most likely the output stage around transistor 9.
Have you already checked out if the supplies are OK?
If so inject an audio signal into the signal path from output to input.
Start with the output jack.
Collector of transistor 9.
Base of transistor 9.
Emitter of transistor 3.
Base of transistor 3.
Collector of transistor 1 or 2 depending on the Chanel used for input, then base.
When your signal disappears check that stage for faults!
Trevor is right that they are reliable, (they were made with good components) but the design of biasing around most of the transistors is really crummy and a bad over value resistor will stop it working. The electrolytic capacitors are early suspects in the tests but mine has Philips ones and the general opinion is that they are normally above suspicion, but never assume anything.
It could just be a broken wire or PCB track.
Sorry Rob I made my previous comments having "assumed" you had already tested the electronics, they would be cheaper to fix than bad tape heads, so....
Thanks,
Amie.
I have to agree with Dave, at least don't spend money on heads until you've checked out the circuit.
If you're hearing everything at low volume its most likely the output stage around transistor 9.
Have you already checked out if the supplies are OK?
If so inject an audio signal into the signal path from output to input.
Start with the output jack.
Collector of transistor 9.
Base of transistor 9.
Emitter of transistor 3.
Base of transistor 3.
Collector of transistor 1 or 2 depending on the Chanel used for input, then base.
When your signal disappears check that stage for faults!
Trevor is right that they are reliable, (they were made with good components) but the design of biasing around most of the transistors is really crummy and a bad over value resistor will stop it working. The electrolytic capacitors are early suspects in the tests but mine has Philips ones and the general opinion is that they are normally above suspicion, but never assume anything.
It could just be a broken wire or PCB track.
Sorry Rob I made my previous comments having "assumed" you had already tested the electronics, they would be cheaper to fix than bad tape heads, so....
Thanks,
Amie.
