Bias Adjust on MA 6100

[tonefoto]

Is there anybody out there that can advise on adjusting bias and dc balance on a Mcintosh MA 6100? I see 4 trimmers and holes to get at them on a pcb behind the faceplate. I can't find anything online about the procedure though. Thanks for any tips or advice. I am new to Mcintosh gear.

 

[clinic-audio]

Hello tonefoto

You are new to MCINTOSH gear and you are right to post your question before to do anything wrong !

1) there is no BIAS and OFFSET adjustement possible on MA6100 . I always read post from users looking for bias adjustments in their units ! adjusting bias will not change the sound of your amplifier so stop to try to touch it .
Bias adjustment should be made only when your amplifier is serviced no other reason. Most important detail for your knowledge, you need a minimum of tool and material to do it correctly which is not the case for final customers (or owners) .
2) to answer to your question : don't touch these adjustments that you can see on the long board behind the front panel . They are factory adjustments about tone treble and bass adjustments and have nothing regarding the bias or offset !
Bias is "automatic" on MA6100 and offset is not ajustable .

 

[c_dk]

You do not want to mess with the tone control gain pots unless you have access to a signal generator.

In fact I do not believe you should try to service a Mac unless you have a distortion analyser and a ocsiliscope.

Are you trying to solve a problem with the MA6100? The circuit deigns that Mac used in their early transitor amps are quite different than those used by the mass market Asian companies. Many of the "rules" written elsewhere in AK forums do not apply to them, and similarly things we do with Macs that do not apply to their contempories.

 

[tonefoto]

You do not want to mess with the tone control gain pots unless you have access to a signal generator.

In fact I do not believe you should try to service a Mac unless you have a distortion analyser and a ocsiliscope.

Are you trying to solve a problem with the MA6100? The circuit deigns that Mac used in their early transitor amps are quite different than those used by the mass market Asian companies. Many of the "rules" written elsewhere in AK forums do not apply to them, and similarly things we do with Macs that do not apply to their contempories.

OK, sounds like I need to read up on Mcintosh then, I'm grateful for the quick response. I just picked up a MA 6100, C26 and MR73. All 3 had the wood cases.. I need to replace the cracked faceplate on my 6100 and C26 and will attempt a thorough cleaning of controls and switches at that point. I imagine removing it could be done without too much trouble or am I assuming too much? Any advice would be appreciated.

 

[c_dk]

Do not throw anything away until you get the new glass, parts must be transferred from the old to the new!

 

[tonefoto]

Do not throw anything away until you get the new glass, parts must be transferred from the old to the new!

It looks like the Service guide for the C26 shows 4 bulbs, I only find three. Is there a guide for removing faceplate assemblies on the MA 6100 and C26?

 

[tonefoto]

It looks like the Service guide for the C26 shows 4 bulbs, I only find three. Is there a guide for removing faceplate assemblies on the MA 6100 and C26?

OK, it appears that i've entered some sort of Dark Arts or Secret Knowledge void re Mcintosh equipment. Just testing the waters...

 

[tonefoto]

I replaced the faceplate successfully by carefully pulling the top and bottom glass frame pieces outward, after removing all faceplate trim and mounting screws of course. Tedious but not to difficult to do, just have to avoid pressing the glass itself to avoid cracking it.