Kenwood Basic M2 Amplifier

[Neal]

Picked up the 200 watt per channel amp for $5 at garage sale and works great. Downloaded the service manual and wanted to check the adjustments. All is good except for the idle current, specs call for 13mv+/- 8mv.
Both channels start out @ 3 or 4 mv and very slowly work there way up to 19 to 19 mv after about 10 to 15 minutes and seem to stabalize at this point.

Does anyone have an idea if this is normal. Even though it is in spec it seems odd.

I wanted to attach the pdf manual, but not sure how

Thanks
Neal

 

[shimniok]

I'm no expert but I think that is normal for bias to increase and stabilize as things warm up. I think what's important is that the value is stabilizing and is in spec, albeit on the hot side.

 

[Neal]

I can adjust it down to 13mv with the adj pots, just was not sure if taking 15 minutes to stabalize was normal. But I guess that makes sense.

 

[Neal]

Also, does anyone know what the "sensor" conections on the back next to channel "A" speaker output is for?
They are the same connectors as is used for the speaker wires. The manual does not address these sensor connectors.

 

[Neal]

Found it!
It's just a sense line as in long power supply runs.

Only to to take care of line drop going to speaker.

All is well

 

[Nigel Goodwin]

I can adjust it down to 13mv with the adj pots, just was not sure if taking 15 minutes to stabalize was normal. But I guess that makes sense.

Yes, perfectly normal, which is why instructions for setting it tell you to let the amp warm up first.