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Sony Vfet Illustrated build guide
Sony Vfet Illustrated build guide
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Old 8th March 2017, 12:04 PM   #121
alvinlim is offline alvinlim  Malaysia
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I don't disagree with the article . All I am saying is that if you move it an inch higher, the temperature difference will probably be less than 1 degree Celsius.


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Old 8th March 2017, 12:06 PM   #122
henryve is offline henryve  South Africa
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Currently it looks like it will be 5mm higher than the centerline. So it should not make a big difference.

Last edited by henryve; 8th March 2017 at 12:23 PM.
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Old 8th March 2017, 02:09 PM   #123
jerry g is offline jerry g  Uzbekistan
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Looking at my left and right channels, from the front without the front panel in place, one is a few mm higher than the other. Further inspection reveals that the heat sinks are asymmetrical top to bottom.....you might check this out and gain a bit of height by reversing the heat sinks. for me, I'm going to leave well enough alone.
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Old 8th March 2017, 02:11 PM   #124
6L6 is offline 6L6  United States
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Sony Vfet Illustrated build guide
This amp doesn't get all that hot, (compared to, say, an Aleph) don't worry about heatsink orientation.
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Old 8th March 2017, 04:11 PM   #125
henryve is offline henryve  South Africa
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Quote:
Originally Posted by jerry g View Post
Looking at my left and right channels, from the front without the front panel in place, one is a few mm higher than the other. Further inspection reveals that the heat sinks are asymmetrical top to bottom.....you might check this out and gain a bit of height by reversing the heat sinks. for me, I'm going to leave well enough alone.
My heatsinks are not the store pre-drilled sinks you can get with the 5U/400 and 4U/300 Deluxe cases. I some odd way one cannot order pre-drilled UMS heatsinks that fits the 4U/400 case. So I can drill my own sinks whenever I am happy with my layout.
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Old 2nd April 2017, 12:57 AM   #126
PJN is offline PJN  United States
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Finished my build today but have a strange problem with one (R) channel. I installed the VFETS and started out with about 30 mV across R32 before I started adjusting bias using a 1 amp fuse on the PSU and hooking up only one side at a time as Nelson suggested in his instructions. I biased up both channels to 100 mV and ~ 3 mV offset (after they had heated up for ~ 1 hr with lid on for each channel). They both biased up pretty easily and both the heat sinks got only moderately warm. I then hooked it up to some relatively cheap speakers for a test drive. No hum, no noise, silent but the right channel volume fades out and goes silent after ~ 2 seconds, the left channel is fine and sounds great. If I disconnect the source from the right channel and connect it again it plays and fades out in ~ 2 sec. There is no noise from the right channel. During the built both boards passed the resistor test (part 1) and the voltage tests (part 2) in Nelson's instructions. The parts were from the DIY Audio supplemental kit. Does anyone have any thoughts or ideas on where I should start looking ?
Attached Images
File Type: jpg Front VFET(1)(1).JPG (304.4 KB, 724 views)
File Type: jpg Internals VFET(1)(1).JPG (411.8 KB, 733 views)
File Type: jpg Close up.JPG (385.2 KB, 680 views)
File Type: jpg Rear VFET(1)(1).JPG (282.5 KB, 649 views)
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Old 2nd April 2017, 08:41 AM   #127
qwertyl is offline qwertyl  United Kingdom
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Quote:
Originally Posted by PJN View Post
Finished my build today but have a strange problem with one (R) channel. I installed the VFETS and started out with about 30 mV across R32 before I started adjusting bias using a 1 amp fuse on the PSU and hooking up only one side at a time as Nelson suggested in his instructions. I biased up both channels to 100 mV and ~ 3 mV offset (after they had heated up for ~ 1 hr with lid on for each channel). They both biased up pretty easily and both the heat sinks got only moderately warm. I then hooked it up to some relatively cheap speakers for a test drive. No hum, no noise, silent but the right channel volume fades out and goes silent after ~ 2 seconds, the left channel is fine and sounds great. If I disconnect the source from the right channel and connect it again it plays and fades out in ~ 2 sec. There is no noise from the right channel. During the built both boards passed the resistor test (part 1) and the voltage tests (part 2) in Nelson's instructions. The parts were from the DIY Audio supplemental kit. Does anyone have any thoughts or ideas on where I should start looking ?
It may be unrelated, but I think these rectifier diodes need some heatsinkig, mine are getting pretty hot...
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Old 2nd April 2017, 02:22 PM   #128
Botte is offline Botte  United States
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Quote:
Originally Posted by PJN View Post
Finished my build today but have a strange problem with one (R) channel. I installed the VFETS and started out with about 30 mV across R32 before I started adjusting bias using a 1 amp fuse on the PSU and hooking up only one side at a time as Nelson suggested in his instructions. I biased up both channels to 100 mV and ~ 3 mV offset (after they had heated up for ~ 1 hr with lid on for each channel). They both biased up pretty easily and both the heat sinks got only moderately warm. I then hooked it up to some relatively cheap speakers for a test drive. No hum, no noise, silent but the right channel volume fades out and goes silent after ~ 2 seconds, the left channel is fine and sounds great. If I disconnect the source from the right channel and connect it again it plays and fades out in ~ 2 sec. There is no noise from the right channel. During the built both boards passed the resistor test (part 1) and the voltage tests (part 2) in Nelson's instructions. The parts were from the DIY Audio supplemental kit. Does anyone have any thoughts or ideas on where I should start looking ?
What is the voltage at T18?

It should be ~0V +-200mV when all warmed up.
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Old 2nd April 2017, 05:34 PM   #129
PJN is offline PJN  United States
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Today I let the amp warm up for ~ 30 -40 minutes and took some voltage readings to compare the working channel to the non-working one (right channel). Nothing really stands out as being different between the two. I have attached a copy of the readings. I also tested the continuity of the input cables from the jacks back to the board, no surprises there either. I am wondering if the input JFEts (2SJ74/2SJ170) are the problem. Is there anyway I can check them mounted in the board ?

Thanks

Paul
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File Type: jpg Readings.jpg (275.9 KB, 585 views)
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Old 2nd April 2017, 06:16 PM   #130
Botte is offline Botte  United States
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Quote:
Originally Posted by PJN View Post
Today I let the amp warm up for ~ 30 -40 minutes and took some voltage readings to compare the working channel to the non-working one (right channel). Nothing really stands out as being different between the two. I have attached a copy of the readings. I also tested the continuity of the input cables from the jacks back to the board, no surprises there either. I am wondering if the input JFEts (2SJ74/2SJ170) are the problem. Is there anyway I can check them mounted in the board ?

Thanks

Paul
Check R4?
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