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Old 26th March 2009, 08:43 AM   #31
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Those output transistors are good, they are factory originals. Your pic is good, one can clearly see. The one thing I do notice from that pic is that the bias transistor is not mounted upside down on to the output transistor but at a 90 degree angle. Im not sure on this model but on most its always mounted in line. The reason is that when mounted in line it has larger surface contact with the output transistor which is important for thermal tracking and correct biasing. As it is the metal tab on the back of d600 has very little contact on that d1047. Have a look at the attached pick in this post, its a different model but about all rotels that I have seen are mounted like this. The transistors in question are the ones with the orange wires. After that adjust the bias a little higher than factory spec with the amp warmed up, around 15 mv is good.

Before replacing the zobel resitor test to see if they are ok, before they fail the factory ones tend to turn brown as if burnt, if they are measuring good and look ok leave them be.

After this the amp should be performing close to factory spec, with only maybe the age of the capacitors having any real effect.
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Old 26th March 2009, 08:46 AM   #32
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Here is a pic.
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Old 26th March 2009, 09:00 AM   #33
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Location: Stockholm
homemodder,
how are you?
Quote:
Those output transistors are good, they are factory originals.
It does matter, however.
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Old 26th March 2009, 04:59 PM   #34
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Hi Lumba

Im good, yourself ??


Bart
Drop me a email through link on my profile and Ill point you to a online shop where you can purchase those powersupply caps if you thinking of replacing them, without denting your bank account too much. The manufacturer is the supplier to rotel for those caps. I assume it uses for 4 10000uf caps so it would cost around 55 euros to replace all with same and go up to double the price for superior quality ones.

The zobel resitor is r669 and r670.
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Old 28th March 2009, 05:31 PM   #35
Bartt is offline Bartt  Netherlands
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I checked the zobel resistors and they seem to be fine (+/- 11 ohm). I couldn't mount the bias transistor upside down, because it would have less contact than before. So I turned it straight up (see picture). The wires do make contact though with the small heat sinks. Is that a problem? The're not gonna melt are they?

The heatsink of the output transistors seems to be a bit hotter than before 41 C (left) and 45 C(right). The small heatsinks in between are quite a lot hotter, around 73 C

I've set the bias at 15mV. The left channel got back to 11 later and doesn't deviate more than 10% since. The right channel increased to 18mV and when cooling down for a while to 13mV. The strange thing is that the right channel seems to increasing or decrease during the measuring, while the left channel doesn't: is that normal?
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Old 28th March 2009, 07:43 PM   #36
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MMM maybe we shouldnt turn the bias up that much, i was expecting the temp rise on the outputs but not so big a diffrence on the drivers. Maybe keep it around 12mv max. I sure hope when you say contact you dont mean electrical contact, that could be disaster. I see space is tight there. Something is up with that right channel, but i cannot think what is is. It will vary a bit with voltage and power fluctuations but im not so sure its should be changing like that all the time. In later models rotel improved the vbe multiplier for use with triples, ill have a look and let you know if something can be done without messing with the circuit, maybe a darlington transitor as the temp sense.
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