McIntosh MA6300 bias adjustment

[Ingenieur]

I've had it for 12 years so I thought a check was in order.
Blew all dust out
Cleaned heat sinks
Cleaned most connections and Vol and Bal pots.

They make adjustment easy, 2 pins to clip meter to, the pots are on top, adjust to 20-25 mV with unit cold.

One channel was way high, ~60 mV.
The other good.
Adjusted both ~22.5 mV.

 

[JeyElDee]

I still have a MA6300 and sometimes one channel went out occasionaly. An easy replacement of one relay (<50 Euro) solved it. Though the bias of a MA6600 I owned (and sold) had to be re-set as one side of the amp came unreasonably hot. Luckily working on a McIntosh is very straight forward as the lay-out is well done.
I consider the MA6300 one of the best integrated amps they ever made with good power and lower internal resistance (higher Damping Factor) than the usual ones with transformers. I still use it as power amp (directly power amp in) with a Topping D70S as préamp, driving a pair of JBL Ti10k. Superb sound, power, musicality and transparancy while remaining fun.

 

[MarkF]

I still have a MA6300 and sometimes one channel went out occasionaly. An easy replacement of one relay (<50 Euro) solved it. Though the bias of a MA6600 I owned (and sold) had to be re-set as one side of the amp came unreasonably hot. Luckily working on a McIntosh is very straight forward as the lay-out is well done.
I consider the MA6300 one of the best integrated amps they ever made with good power and lower internal resistance (higher Damping Factor) than the usual ones with transformers. I still use it as power amp (directly power amp in) with a Topping D70S as préamp, driving a pair of JBL Ti10k. Superb sound, power, musicality and transparancy while remaining fun.

I have a MA6300 which I purchased in 2007. For the last 5 years or so 1 channel will cut out at least a few times per day. It could be either channel. I just took it to an authorized service center. When I dropped it off I told the tech that I read about a relay problem with the MA6300 causing this problem. He said it’s not a relay. Fast forward 1 week. I picked it up and he said the problem was the volume control and he had rebuilt all switches and controls. Shortly after getting it reconnected the problem happened again. It’s still happening every day. Who did you have do the repair?

 

[JeyElDee]

. Who did you have do the repair?

I went to a local dealer that does repairs for a few decades now. https://staelenshifi.be/ And the guy opened the amp, knocked on the relay while one channel was not playing, hence the problem was found. He ordered it from McIntosh and replaced both relays himself. Now the amp is still playing perfectly. Price was 50 Euro.

 

[MarkF]

Thanks.

 

[MarkF]

Took my MA6300 to a different non-authorized repair shop and gave them all of my research on the channel cutting out problem including a picture of the suspect relay and the schematic indicating the exact part. They ordered the replacement relay from McIntosh and installed it. Problem solved.