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Marantz 2270 Slow to Click in...sometimes

As you set higher bias, better performance at low volume settings would be expected. The bias value determines the transition from class A to class B. More bias, higher class A operation, and more power wasted in heat.
 
Thank you for that quick reply! Admittedly, I don't get to open this up often since I live in an apartment, so better performance at low volume actually sounds appealing to me. However, is it dangerous in this case? Especially given the inability to adjust it downward?
 
No, it should not be dangerous. Read the heat sink temperature after 30 min idle. That will give us a better picture.
 
I'd say 1" away of the output transistors would be fine. Apply a dab of silicon grease on the heat sink and place the thermometer sensor in it so it makes good contact.
 
Looks like real fine. If anything, correct slightly the bias value so both have exactly the same. You may go up to 104F without wasting a lot of power.
 
adjust by mv at test points ..
proper way is use distortion analyser but not everyone has one .. the figures were decided by the manufacturer when new and often set a little bit low for safety ..
well thats what i read somewhere ...
 
Pete's sharp... I'd trust a good warm up if you're in some old wine or coal cell in the Uk.. :D kisses, too.
but good idea if you can get the unit up in room temp constant to test. Not wwII ya know.
 
i always set after gentle warm up then monitor as i crank it up . when it seems stable i leave it running flat out for a good side of the test cd i use .. then if it survives that and it will i know that by now i will run it for a few hours at half power .. on the occasion i might go and crank it up for a few minutes ... nothing like a good old stress test ..
then cool overnight and test again from cold .. this test seems more important than the first test and seems to sometimes reveal things that never showed up the day before .
 
grailseeker said:
Thanks for the reply! I appreciate it! Can/should I adjust based on temperature?
Click to expand...

It is safe and you may perfectly do it, to adjust bias based on tempearture (whoever think it's not please elaborate). Since you'll be dealing with mild tempeartures there's no risk in that. Bias will be higher than what it is now, but not much. As said, more bias would only bring you better audio quality at low volume settings.
 
Yes, since I had no room to bias downward, I had to match the cooler side to the warmer side, which came in at 26.5mV, yielding 88.7°F on each side.
I'm afraid I'm not in a position to play the 2270 very loud, but at 25% volume the temperature is around 95°F.

Does that sound reasonable?
 
Excellent! And sound good it does!
I will say, now that I have put it back together and wrapped it in its wooden sleeve, I notice the left side feels physically warmer to the touch than the right. Not by a lot, but enough to notice. Is that normal? I don't think I would have taken note of it one way or another before since I was mostly focused on the relay.

In any case I'd like to thank everyone again for the wonderful support and guidance. I learned a lot! :)
 
Sure sounds nice :)

Both channels should heat up to the same extent. A noticeable difference, even a small one, means bias value is not the same on both. You may correct measuring the least warm one and replicating the value on the warmer one.

Keep in mind, your Marantz has a automatic bias correction based on temperature (there are components reading the heatsinks temperature. Be very slow and patient when adjusting bias. After each change give time (several minutes) for temperature change as bias will be slightly altered by the circuit in charge.
 
Ah ok, thank you for the information!
Indeed, after studying its habits for the last couple days, the left side is a bit warmer.
That means in my case, I will have to further increase the cooler side to make them match, because the warm side is already turned down fully.
Which makes me wonder: How can I make those calculations from comment #56 and know whether or not the adjustments I make are still within acceptable ranges?
Keep in mind, your Marantz has a automatic bias correction based on temperature (there are components reading the heatsinks temperature. Be very slow and patient when adjusting bias. After each change give time (several minutes) for temperature change as bias will be slightly altered by the circuit in charge.
Click to expand...

Also, I was wondering more about the automatic bias correction. Where can I find out more about that and in what fashion should I be accounting for it?

Thanks a million! :)
 
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grailseeker said:
Ah ok, thank you for the information!
How can I make those calculations from comment #56 and know whether or not the adjustments I make are still within acceptable ranges?
Click to expand...

Ohm´s and Watt's laws.

Rail voltage: +/-47V
Bias voltage drop: 26.5mV
Emiter resistors: 0.2 ohm

Through Ohm's law: I = 26.5mV/0.2ohm = 132.5mA
By Watt's law, power through the output device: P = 47V x 132.5mA = 6.2W

Replicate this for the negative rail.

Total channel bias power: 12.4W

In regard to the temperature bias compensation, you'll find a suscint description in the service manual. PDF's page 7.
 
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