Marantz PM 7200 quiescent currents

[Gasho]

I need information about correct quiescent current of this amp , for A/B and A class running.

 

[jakethemus]

Hi , I know what they are for the pm7200 Ki version.

For the ki the class AB current is 18ma and class A is 90ma. These should be set after the amp has been on for 30 mins. Dont think the non ki would be too much different, maybe slightly lower currents.

 

[Gasho]

18 and 90mA is too low

Maybe you think 180 and 900mA???

Please check.

 

[jakethemus]

It is defintaly 18ma and 90ma, i can email you the page out of the service manual if you like

 

[Gasho]

Ok you can send me service manual , I thak you.

But i am shure that bias is to low. 90mA is used in A/B class amps.

If it runs in A class , current must be over 500mA (probably 900mA in this case).

 

[jakethemus]

Sorry it should have said 18mv and 90mv not mA across the resistors 3335 to 3338 .
Not sure what the actual currents are.
If you let me know your email address i will send you the page which shows how to set the quiescent currents and dc offset.

 

[jakethemus]

Just checked and the resistors are 0.18 ohm so class AB currents would be 100mA and class A is 500mA.

 

[anatech]

Hi Gasho,
Please keep in mind that the "Class A" switch only increases the bias current. The switch should be labeled "Make Run HOT for no reason". At the higher bias current, this is still an AB amp. It just transitions to class B a little later... and runs hot. This is typically rough on the PC board connections.

Besides, there is much more to good sound than the level of bias current. Circuit design and power supply design comes to mind here.

-Chris