I changed all cap. I'm happy for the result. It's just like new amp.
if so; use mkp cap for C319&C320,
if so; use mkp cap for C319&C320,
If R281 is very hot and if you don't use 12 volt output/J302, Disconnect D123. It will close. In my NAD it was burn. It use many current and not necessary (for me 🙂
Q155&Q158 are very hot in my NAD C352. On series 33 ohm resistors current is less than 0.1 A. Q155&Q158 must be cool in that current😕
All performance are good for NAD. There is no fault.
Also, preamplificators some transistors are very hot. But, it's working. I couldn't find the problem 😡
All performance are good for NAD. There is no fault.
Also, preamplificators some transistors are very hot. But, it's working. I couldn't find the problem 😡
Hi mdardeniz,
Maybe the hot transistors in your preamps would work as well or better at a lower bias point. It's a pretty straight-forward circuit, each module giving a modest ~5dBV gain. But lot-to-lot differences in transistors could explain different operating points.
Likely a 20 or 25% reduction in current in the preamp output stages, Q605 & Q607 and Q606 & Q608, wouldn't change the sound even a small amount.
Then your Q155 & Q158 could have a happier, longer life as well. 😀
Regards
Maybe the hot transistors in your preamps would work as well or better at a lower bias point. It's a pretty straight-forward circuit, each module giving a modest ~5dBV gain. But lot-to-lot differences in transistors could explain different operating points.
Likely a 20 or 25% reduction in current in the preamp output stages, Q605 & Q607 and Q606 & Q608, wouldn't change the sound even a small amount.
Then your Q155 & Q158 could have a happier, longer life as well. 😀
Regards
Unless I've bodged the arithmetic, each preamp module output transistor (Q605 through Q608) should only be carrying about 13mA, which is about 200mW to dispatch. Plenty warm, surely, but not what I'd usually call hot.
Cheers
Cheers
4 preamplificator, 4x13=52ma. I measured current on Q155 is nearly 86ma (2.83v/33ohm). So, current is normal. But, with that current Q155 very hot (60C?) and "Lynyrd" says not hot 🙂
Ice 0.1A is normal for 2SD669 (on board there is SC2690A). It drops nearly 41 volt to 18V. It couldn't be that much hot? Am I wrong?
Ice 0.1A is normal for 2SD669 (on board there is SC2690A). It drops nearly 41 volt to 18V. It couldn't be that much hot? Am I wrong?
Sorry, I didn't realize the output voltage from BR101 was that high. 😱
23V at 86mA is around 2W, so unless it has a fairly decent little heat sink, 60°C might not be unreasonable. But now that we know you have 20 *extra* volts to *play with*, maybe additional resistance in the Collector supply would be worth considering. As long as the current demand doesn't increase dramatically with signal, should be OK to add up to 100 ohms, or so at least.
That, or adding any size heat sink that will fit physically.
Regards
23V at 86mA is around 2W, so unless it has a fairly decent little heat sink, 60°C might not be unreasonable. But now that we know you have 20 *extra* volts to *play with*, maybe additional resistance in the Collector supply would be worth considering. As long as the current demand doesn't increase dramatically with signal, should be OK to add up to 100 ohms, or so at least.
That, or adding any size heat sink that will fit physically.
Regards
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Himm 🙂 I will think about to decrease voltage as you said. Good idea and good to test.
