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Old 20th September 2012, 04:11 AM   #81
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OK, do you have a multimeter? if you have one, measure the hfe with it. fine 2 transistor that has same or close hfe, that's the simplest way.
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Old 23rd September 2012, 09:58 AM   #82
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Hi,
so I just ended soldering the JLH boards, wired everything, plugged it in, and.. the fuses burned out..
my configuration:
toroidal transformer with dual 18.6V
the power supply that is suggested on the site, it's output is -25 0 +25
the speakers are 4Ohm (as measured with my multimeter)
the preamp is a tube one, checked with my headphones before so it should be working ok.

the fuses on the power supply, and on one of the JLH boards burned out. I think the front audio panel on my computer burned as well..
i changed the fuses on the power supply and connected the JLH board with intact fuse, and.. the C1 capacitor went smokin'..

any ideas how to debug where the problem might be? one board at a time..
or should i give up DIY and buy a yamaha amp?
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Old 23rd September 2012, 11:04 AM   #83
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You obviously made a mistake somewhere. No pic = no comment. There is no way on earth good advice can be given without seeing the build.

My guess is that you swapped resistors or put transistors in reverse. Or simply a short....
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Old 23rd September 2012, 11:19 AM   #84
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Do NOT connect the speaker before adjust the output to around 0V
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Old 23rd September 2012, 11:20 AM   #85
AndrewT is offline AndrewT  Scotland
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did the light bulb glow dimly or show bright when you powered up?
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Old 23rd September 2012, 12:52 PM   #86
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Quote:
Originally Posted by siliconray View Post
Do NOT connect the speaker before adjust the output to around 0V
ok.. that's one good advice I wasn't aware of.. ok.. I'll give it another try.

everyone, thanks for the replies
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Old 23rd September 2012, 03:45 PM   #87
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I'm running fast out of components..

I've resoldered the board. removed C3 and shorted it as in some previous post. without connecting it to the speakers the output voltage is 25V. tried to play with VR1, VR2, VR3, the output voltage did not change.
any ideas?
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Old 23rd September 2012, 11:51 PM   #88
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if the output is 25V, there must be something wrong: failure parts, unconnected pins, bad transistors, short circuits..you can check the center point voltage stage by stage to find the problems.
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Old 24th September 2012, 12:56 AM   #89
clm811 is offline clm811  United States
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Quote:
Originally Posted by siliconray View Post
I have 4 big toroid transformer which were disassemblyed fron an US made auido equipment, like new. They are 110V and usless for me. I would like to send it to those who want to buy JLH amplifier full kit + Power supply for free

This transformer is ideeeeeeal for Stereo JLH power amplifier (for US and canada DIYers). Spec:

Power: >150W
output1: 24-17-0-17-24
output2: 8V
weight: 2kg

Only 4 available, only one for one person.
Plus $25 for air shipping. PM me if you have interest.
Ray,
You,ve got PM
-Chas
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Old 24th September 2012, 01:27 AM   #90
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Oh...look at the time, it had been sold before our galaxy formed. I had only 4 of it.
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