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Old 5th January 2007, 12:43 PM   #1501
paulb is offline paulb  Canada
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Hi Geoff, your post arrived as I was composing mine. Thanks for the enlightenment.
I should note that I had no problems whatsoever with oscillation or bias stability (following Geoff's bias adjustment recommendations). The power supply for this amp was much more difficult, actually, as I chose to parallel two power transformer outputs with their primaries wired in series (to use transformers I had on hand).
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Old 5th January 2007, 01:13 PM   #1502
united is offline united  England
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Thanks Geoff and Paul for your clear and concise replies. It seems that the high power version would be a better option as it seems to be less stressful on the output transistors. The 3055s on the 1996 jlh I built gave up the ghost too often.

The pcbs I have are from Williams Hart and are of poor quality, does anyone know of a supplier of pcbs of the layout you recommend? Also for the cap mult circuit. I have no way of making pcbs.

Jeremy
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Old 5th January 2007, 01:44 PM   #1503
paulb is offline paulb  Canada
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I ordered mine from Olimex and am quite pleased with the results. If you need help to submit the Gerber files to them you can email me directly.
http://www.olimex.com/pcb/protos.html
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Old 5th January 2007, 05:25 PM   #1504
MikeW is offline MikeW  United States
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Quote:
Originally posted by paulb
Congratulations! Enjoy!

I've placed all the new information I received from Geoff (schematics, layouts, gerbers, etc.) on my personal webspace at
http://members.shaw.ca/paul.r.brown/...%20Moss%20JLH/

This is the same stuff I posted individually here a few pages ago. Geoff is still planning to update his site but hasn't got to it yet.

Are the output transistors mounted off the board. If they are mounted to the board the pin outs are wrong. It should be B C E.
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Old 5th January 2007, 06:29 PM   #1505
Geoff is offline Geoff  United Kingdom
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Quote:
Originally posted by MikeW

Are the output transistors mounted off the board. If they are mounted to the board the pin outs are wrong. It should be B C E.
Mike

The layout was done for output transistors that are not mounted on the board. The pads and holes are sized to suit 5mm pcb terminal blocks so that (short) flying leads can be taken to both TO-3 and flatpack transistors. This gives greater flexibility for alternative heatsink types and keeps the pcb, and board mounted components, a little further away from the hot heatsink surface. It also meant that a virtually identical layout could be used for both single and double sided boards, with the need for only one jumper on the single sided pcb.

Geoff
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Old 5th January 2007, 06:53 PM   #1506
MikeW is offline MikeW  United States
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Thanks. Hope you are doing well. My JLH is still sounding goood.
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Old 6th January 2007, 11:32 AM   #1507
united is offline united  England
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Quote:
Originally posted by paulb
I ordered mine from Olimex and am quite pleased with the results. If you need help to submit the Gerber files to them you can email me directly.
http://www.olimex.com/pcb/protos.html

Thanks for the link Paul.

Does anyone know of something similar over here in the uk?

Also, where can I obtain tantalum film resistors or vishay? How about the exotic paper in oil caps?

Sorry to seem such an ignoramus but it's been years since my last diy fling. It was the days of Farnell having an actual catalogue which they sent me!

J
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Old 6th January 2007, 11:44 AM   #1508
mikelm is offline mikelm  England
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Quote:
Originally posted by united



Thanks for the link Paul.

Does anyone know of something similar over here in the uk?

Also, where can I obtain tantalum film resistors or vishay? How about the exotic paper in oil caps?

Sorry to seem such an ignoramus but it's been years since my last diy fling. It was the days of Farnell having an actual catalogue which they sent me!

J
They still have a catalogue - but their CD catalogue is very well done and easy to use and most times i prefered* to use this. ( as opposed to their website which is not that great )

*past tense because I now live in the US.
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Old 6th January 2007, 11:49 AM   #1509
paulb is offline paulb  Canada
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Quote:
Originally posted by united
Thanks for the link Paul.
Does anyone know of something similar over here in the uk?
Olimex is closer to you than me, they're in Bulgaria.
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Old 6th January 2007, 12:23 PM   #1510
united is offline united  England
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Oops, I saw the pricing in $ and jumped to the wrong conclusion. I'll send you an email so you can give me a few pointers on how to place an order. Thanks yet again.

J
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