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JLH Mosfet Power amplifier construction thread
JLH Mosfet Power amplifier construction thread
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Old 11th April 2020, 09:45 AM   #51
2 in 1 is offline 2 in 1
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Thank you jamesfeline. I am excited and waiting.
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Old 17th April 2020, 12:50 PM   #52
tonewheelkev is offline tonewheelkev  Europe
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OK...back again with an update on my JLH Monoblocks project!!
Finally got a matching pair of transformers from Tiger-Toroids here in the UK.
Replaced all the electrolytics....and here in my solitude, am finally getting onto the last stage of getting these babies goin' again.....OR so I thought!!


Setting up the 50/55v rails on the PSUs, went swimmingly...until I got to the final -55v setting on one of the monoblocks! Essentially, adjusting RV4 does nothing...voltage continues to read 70v approx....so some work to do here.
Post #6 of this thread has the relevant circuit diagram (from Paul Kemble's page I think!)
Any thoughts out there on my next step please??
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Old 17th April 2020, 04:44 PM   #53
jamesfeline is offline jamesfeline  Togo
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Hello
sometimes you may have to put a small load on the power supply to set up probably I use a couple of low current lamps or load resistors to give the PSU some load .. assuming no faults of course
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Old 17th April 2020, 05:01 PM   #54
tonewheelkev is offline tonewheelkev  Europe
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Quote:
Originally Posted by jamesfeline View Post
Hello
sometimes you may have to put a small load on the power supply to set up probably I use a couple of low current lamps or load resistors to give the PSU some load .. assuming no faults of course
Aaaagghhh....read about this in the manual...but didn't realise just how the failure of the rail setup 'manifested' itself!!
So...could be that it's going to be a simple fix.....here's hoping!!
Thanks James
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Old 18th April 2020, 03:51 PM   #55
tonewheelkev is offline tonewheelkev  Europe
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OK...got some advice on putting a small load on the PSU..tried it with a 3k load.and...still the same unfortunately...so I have another problem it seems
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Old 22nd April 2020, 02:31 PM   #56
tonewheelkev is offline tonewheelkev  Europe
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Smile PSU Boards....

Hi James
...please let me know what a couple of your PSU boards would set me back!?
I'm messing with an 1150 and an 1150-2...so not exactly a 'pair'.
Does your board also include any of the 'mods' that are mentioned in the 'modifying' thread that is also on the forum pages??
Might be a nice project in my continuing isolation.

Thanks
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Old 15th August 2020, 09:28 AM   #57
Clive Collins is offline Clive Collins
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Default Hart construction manual for JLH 80w Mosfet

I can provide Hart construction manual if anyone is still interested. Plus I have original articles. I kept everything. Have 1996 class A plus 1989 Mosfet. Great sounding amps. Have compared to expensive commercial amps but I still prefer the Mosfet.
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Old 17th May 2021, 09:10 PM   #58
didyman is offline didyman
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Hello Jamesfeline,

Do you have maybe a pair of PCB for sale? I have a bunch of K135/J50 selected pairs and would like to make use of them.
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