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★★ Free PCB for JLH 2005 Class-A Amplifier
★★ Free PCB for JLH 2005 Class-A Amplifier
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Old 5th September 2017, 06:34 PM   #301
speedless is offline speedless  Denmark
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Location: just short of paradise
Default Help with jhl2005

Hi

Any one know where I can find some info on the jhl 2005 amp.
I buid them allmost 4 years ago and of cause lost all the "paperworks"
Adjustment procedure would be most welcome and maybe a scematic .
I have one pair built and they where actually adjusted and testet.
Sounded real class a but to weak for my speakers at the time.
Power transistors was then reused for a bigger amp.
So I need to adjust for new power transistors.
I allmost sure I found the info here and printed it out for my "book of builds" but cant find it.
Right now im completing a tri-amp system,3 way active inline filter and I think this little amp will be fine for the highs.
I have everything needed;
PSU,Cap multipliers,enclosure,connecters,heatsinks.
It seems like siliconrays site is gone. (R.I.P) .No help there.
Hope someone here can inlighten my old dusty memory.

Jan

PS.I got 2 pairs of pcbs.
1 pair free for best answer.
The other pair,well try to PM
No free shipping
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Old 6th September 2017, 11:41 AM   #302
polsol is offline polsol  South Africa
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Location: Cape Town
Here's a (PDF) scan of the JLH 15W schematic I have. Can't find the original so I have attached my file copy. It's a bit messy with the 'setup' annotations but the comments might be of help to you.
Cheers
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File Type: pdf 15W Class A schematic.pdf (286.4 KB, 45 views)
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Old 6th September 2017, 01:41 PM   #303
speedless is offline speedless  Denmark
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Hi
Thanks Tony
Another piece in the puzzle in place.
Thats exactly what I need.
Your notes on adjustment are clear and concise.
Just one question:Output,open or with load under adjustment ?
If you want a free pair of pcbs,send a PM

Jan
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Old 6th September 2017, 02:18 PM   #304
e_fortier is offline e_fortier  Canada
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★★ Free PCB for JLH 2005 Class-A Amplifier
This will answer all your questions...see attached file and text below.

VR1,2 and VR3 adjustment
1. VR2 = Bias... - Set to 330mv across R10 330mOhm ( Equals 1A Bias Current... )
2. Power the amp to Full Heat ( app. one hour of operation ), and udjust VR1 to 0.00 Volt DC Across the output terminals ( With input shorted / No load )
3. Turn off the Amp, and allow to cool off. Re-adjust in cold state DC Offset to almost 0.00 with VR3.
4. Wait for full heat, and repeat adjustment of VR1 , VR3 until you're satisfied with the difference in cold and hot state. It should be possible to obtain app. +/- 30 mV DC offset - Which is quite OK. ...I have 16mV and 20mV.

BR,
Eric
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File Type: gif JLH-2005-10W schem.gif (42.0 KB, 63 views)
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Old 6th September 2017, 03:12 PM   #305
speedless is offline speedless  Denmark
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Hi
Thanks Eric.
Its all clear to me now.Im recalling the procedure.
If you want a free pair of pcbs,send a PM

Jan
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Old 6th September 2017, 03:19 PM   #306
polsol is offline polsol  South Africa
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Hi Jan,
Basically as per what Eric said above, Input shorted, no load output.
As per the notes on the schematic, I'm running at around 580mV across R10 (0.33 ohms) giving about 1.9 Amp bias current. Supply voltage is around 20V.
Runs at about 40C above ambient with the heat sinks used.
More info of the build on pages 29 and 30 of this thread under my name.

Cheers

Thanks for the offer of the PCB's Eric but no real use for them at this time. I'm sure they will go to a worthy enthusiast - or you'll find you need them at a later stage.
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Old 6th September 2017, 03:31 PM   #307
polsol is offline polsol  South Africa
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BTW Jan, the drivers get very hot which is why I kept the quiescent current down to a little less than 2 amps. There's little room for any heat sinking either so I used LED heat sinks on the drivers. Also upgraded R10 to a higher wattage for the same reason.
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Old 6th September 2017, 08:30 PM   #308
speedless is offline speedless  Denmark
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Hi
This is embarrasing,I just found out I actually posted in this tread some years ago.
My memory is failing me,sigh
Any way thanks for your help.
Jan
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Old 6th September 2017, 08:47 PM   #309
e_fortier is offline e_fortier  Canada
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★★ Free PCB for JLH 2005 Class-A Amplifier
Hi Jan

We are all some how getting older...lol

Would you happen to have the headphone pcb ?

If not, I guess the power amp could be used as a HA with some changes

BR
Eric
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Old 6th September 2017, 11:35 PM   #310
Lo_Tse is offline Lo_Tse  Canada
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Join Date: Dec 2006
Quote:
Originally Posted by speedless View Post
Hi

Any one know where I can find some info on the jhl 2005 amp.
I buid them allmost 4 years ago and of cause lost all the "paperworks"
Adjustment procedure would be most welcome and maybe a scematic .
I have one pair built and they where actually adjusted and testet.
Sounded real class a but to weak for my speakers at the time.
Power transistors was then reused for a bigger amp.
So I need to adjust for new power transistors.
I allmost sure I found the info here and printed it out for my "book of builds" but cant find it.
Right now im completing a tri-amp system,3 way active inline filter and I think this little amp will be fine for the highs.
I have everything needed;
PSU,Cap multipliers,enclosure,connecters,heatsinks.
It seems like siliconrays site is gone. (R.I.P) .No help there.
Hope someone here can inlighten my old dusty memory.

Jan

PS.I got 2 pairs of pcbs.
1 pair free for best answer.
The other pair,well try to PM
No free shipping
In case you want more info on the amp, try this link:

The Class-A Amplifier Site

Regards,
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