John Lindsley Hood 80 watt mono

[rocky raccoon]

Howdy -
I have a problem with my left channel of my JLH 80 watter. It's the last single PCB Wiliams Hart version - not the Hart version with separate boards for power supply & amplifier.
Does anyone have a copy of the kit instructions with circuit diagram & parts list for the Williams Hart incarnation of the JLH 80 watt amp (mono or stereo - it's the same board).

I would be so grateful if someone could help me out - There's a bottle of your favourite tipple in it -

I love these amps and while I ordered the kit, it took so long to arrive (parts out of stock) that they sent me a ready built set with no instructions.

my e mail is

iestyn.morris@quiksilver-europe.com

Any help much appreciated.

[AuroraB]

If this is the VMOS design presented in ETI many years ago, I still have the mag buried somewhere in my belongings...
If someone else doesn't chime in, I may be able to dig it out. Will take some time though....

[rocky raccoon]

It looks like this :
J picture by bloodyhell451 - Photobucket

Hope you can see it - I'm new to photobucket.

Any help greatly appreciated -

Best regards,

rr

[anthony.taylor1967]

Hi, just came across your post, I have reprints from ETI in my hand, but I'm not quite sure about the hart version. The one I have is with the cut out for the transformer. Not quite sure if I'm allowed to attach a file so I will send it to your email anyway. Ignore what i just said, i just looked and there is no schematic, but wait just found one lying around in a cupboardspin:

[anthony.taylor1967]

which version is it I did have 2 versions, 1 with the cutout for the transformer and the one with the power devices on the main board. but both do not look like yours. I wonder how many versions there are.

Regards - Anthony

[rocky raccoon]

As far as I know there are only two versions. The one with the cut-out on the power supply board and the one with all the gubbins on one board. We actually have 2 of the 35 watt versions, one stereo 80 watt version (single power supply) and two monoblock versions in our family. I'm the chump with the last Williams Hart one board version. By Bro has the twin board set of mono's and the other three amps are all back home with the folks. I also use the fully discreet phono pre amp & outboard power supply (as dos my Dad) and I have the full on pre-amp with outboard power supply as well. All were built by us axcept (guess what) my mono's.
When I get back to blighty I'm gonna scan everything a put it online for other disciples.

In the mean time I'd be very grateful for the one-board schéma & parts list. (number of resistor + value etc.)

There's a bottle in it !

[Fanuc]

Originally Posted by anthony.taylor1967

which version is it I did have 2 versions, 1 with the cutout for the transformer and the one with the power devices on the main board. but both do not look like yours. I wonder how many versions there are.

Regards - Anthony

The PCB was updated by Williams Hart electronics in the late 90's or early 2000's - third version. (Hart electronics was the original kit/PCB supplier that worked with JLH ) - Think one was '84 and then updated in '89 (PSU board wrapped around the toriodal etc and some updates. The very early ones I have seen photo's off. I have the later ones.

The reason for the new PCB (third) apparently, was that the performance was more built in - things like earthing etc, psu and amp on same PCB, and using newer plastic lateral mosfets (not T-O3). With the older PCBs there was alot you could do wrong constructing it if you where a novice.

It would be interesting to see some of the updates for the latest one. What values changed for DC offset, gain etc and PSU changes.

[rocky raccoon]

Originally Posted by Fanuc

The reason for the new PCB (third) apparently, was that the performance was more built in - things like earthing etc, psu and amp on same PCB, and using newer plastic lateral mosfets (not T-O3). With the older PCBs there was alot you could do wrong constructing it if you where a novice.

.

That's the boy ! Fanuc - do you (or does anyone) have the full blurb for this version ? Somebody please !

[rocky raccoon]

As a follow up - I had the Williams Hart mono fixed. It turns out that the output transistors had blown - taking out some zeners as well. The engineer had quite a time.

I can confirm that the circuit diagram and the parts list is the same for both versions - though the Hart version is closer to the original design - running a higher quiescent current than the Williams Hart. The heatsinking arrangements for the Hart are better - the L shaped plate in the Williams Hart version is not up to the same standard. This is going to be the subject of a futre project.

I can also confirm that APJ Audio
JLH 80W amplifier boards
is not only offering the boards for the Hart kit but is virtually able to supply complete Kits. I have ordered a power supply kit to turn a JLH Stereo Hart kit into a pair of Monoblocks. I don't think he has the transformer at the present time so that will have to be sourced elsewhere. I'll get back to you when I know more.

APJ Audio can also supply the construction manuals -

Thank god for this man ! Anyone interested in a pair of Monoblocks which can outperform commercial amplifiers up to £5000 (according to a friend who owns some very highly regarded examples of the breed) should give this man some custom !

Best regards

rr