Setton AS1100 bias current adjustment help.

[Craig Skeet]

Hi has anyone serviced/ repaired a Setton AS 1100?
I'm currently repairing and restoring this amp that has a few issues.
The service manual suggests that the left bias current is set to 30 mA and the right to 70 mA
Surely this can't be correct.
Is this a misprint?
Does anyone one what the correct bias current should be?
I can't find anything on the AK or the net about this.
There seems to only be one copy of the service manual available on the net (several versions of the same bad copy with bits on the he edges cut off).
Any help would be greatly appreciated.

 

[mroboto]

30 mA sounds more logical to me, try both channels at 30 mA and if it works fine, call it good.

In French I found this: https://www.google.com/search?q=Setton+AS-1100+repos+site:vintage-audio-laser.fr

With keyword "Repos" for "Courant de repos" (BIAS)

 

[Craig Skeet]

That's really helpful. Thanks for your reply.
I've got another problem now!
I'll start a new post.

 

[Craig Skeet]

30 mA sounds more logical to me, try both channels at 30 mA and if it works fine, call it good.

In French I found this: https://www.google.com/search?q=Setton+AS-1100+repos+site:vintage-audio-laser.fr

With keyword "Repos" for "Courant de repos" (BIAS)

Just seen your edit and checked out that post. Translated it with google and it's exactly what I needed. It shows the recommended mV value across the emitter resistors. Much better than measuring the bias current, especially when the service manual is so unclear.
Many thanks for your stellar detective work.
Do you speak French?
There must be so much information in other languages that we just don't find.

 

[mroboto]

Glad this can help you.

Yes, my primary language is French.

 

[Craig Skeet]

The French forum post says measure the voltage across both cement emitter resistors on each side of the main amp. (they are in series).
Adjust VR on each side for 30 mV.
No need unsoldering the wire on pin 3 and measuring the current.
The amp seems healthy with this adjustment. Great sound, stable, warm, but not hot (heat sink around degrees C).

 

[UncleAng]

The service manual suggests that the left bias current is set to 30 mA and the right to 70 mA

Never heard of any amp having different bias adjustments.... both channels should be the same; and 30 mA sounds right.

 

[painttoad]

Hi has anyone serviced/ repaired a Setton AS 1100?

i'm not sure if it has what info you need but you might find this informative anyway.

 

[Craig Skeet]

i'm not sure if it has what info you need but you might find this informative anyway.

Thanks,
I did see this, but he doesn't mention the misprint in the service manual. He did message me back and suggested 30mV left and right as others have suggested.
XRayTony's videos are an excellent source of information and learning. I highly recommend them