Bias adjustment Luxman R-404 Receiver?

[jefferylhenr]

I was gifted a very nice and clean R-404 receiver. Is their a bias adjustment? Can’t find a manual for the 404, but there is one for the 405. The 405 manual indicates 15mv. Anyone know for certain what it should be for the 404?

 

[cademan]

Just curious in why you think you need to adjust the bias (assuming it has an adjustment)?

 

[jhjove]

I was gifted a very nice and clean R-404 receiver. Is their a bias adjustment? Can’t find a manual for the 404, but there is one for the 405. The 405 manual indicates 15mv. Anyone know for certain what it should be for the 404?View attachment 2565464

I can't say for certain about this 404 (I have a 105; the black-front-panel version of the 405).
Anyway came here to say if you're gonna keep this 404 it may use an STK module for the driver stage, add a heatsink to hopefully extend it's life.
I did on my 105.
That's all.

 

[idf.bts]

What do you need from the 404 manual? I might be able to help.

 

[jefferylhenr]

What do you need from the 404 manual? I might be able to help.

Procedure and voltage for bias or dc offset if any

 

[jefferylhenr]

Just curious in why you think you need to adjust the bias (assuming it has an adjustment)?

I have a checklist and process that I go through with any vintage pieces I go through before i sell or gift. Throughly clean, visual, go through test points, check bias and dc offset. Ie basic health and hygiene. Along with confirmation of functionality including scoping the outputs with a test signal.

 

[dr*audio]

1. Locate the white ceramic emitter resistors for the power amp stage.
2. Find the resistance value marked on them.
3. Your goal is to adjust the bias to 20mA by measuring the voltage drop across one resistor. By Ohm's Law, multiply .020 X the resistance to get the voltage. Adjust for that voltage.

 

[idf.bts]

I have a checklist and process that I go through with any vintage pieces I go through before i sell or gift. Throughly clean, visual, go through test points, check bias and dc offset. Ie basic health and hygiene. Along with confirmation of functionality including scoping the outputs with a test signal.

This should help with the bias.

If you need tuner adjustment, let me know but I think its the same as the 405. They are almost identical. I recall it was a different IC chip and it changed the board a good bit but otherwise its the same.

 

[jefferylhenr]

Thank you for the guide. I have the 405 manual but didn’t know it was the same and didn’t want to assume.

 

[idf.bts]

Thank you for the guide. I have the 405 manual but didn’t know it was the same and didn’t want to assume.

Its almost the same, mostly that IC.

You're safe with the 405 manual unless you have to do a trace. I don't have the manual but I can ask for pages.