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Old 27th July 2005, 04:37 PM   #11
Geoff is offline Geoff  United Kingdom
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Quote:
Originally posted by EWorkshop1708
I don't see it being that hard to use the higher gain/ft transistors.

If they oscillate, just put a small cap over the B-C leads of the drivers with a low value base resistor.
It isn't, but see my previous post (#2) regarding the reduction in open-loop bandwidth.

The JLH does not use driver transistors so you cannot put a capacitor across them.
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Old 27th July 2005, 05:06 PM   #12
paulb is offline paulb  Canada
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Quote:
Originally posted by Geoff
On the subject of pcbs, I have a design for the higher power version (which could also be used with only single output transistors) and an associated power supply. The prototypes should have been built by now and the results pubished on my website but the person building them has had to defer expenditure until after his family holidays next month.

When the boards have been proven, I intended to see if there was any interest in having them made commercially. The boards will be standard eurocard size (160 x 100) to accommodate decent sized heatsinks for Q3 and Q8, terminal blocks for all connections to/from the boards etc. The power supply board will allow for on-board D-220 rectifier diodes, on- or off-board reservoir capacitors and either a 'follower' regulator (TL431 or Zener reference) or a capacitance multiplier.

The commercial boards will probably be double sided PTH since here in the UK these can be obtained in small quantities at a lower price than single sided, but I have arranged the layout so that anyone who wishes to etch thier own single sided boards can do so (there is only a single link on the upper side of each board).

Geoff
Hi Geoff,
I am interested and looking forward to seeing your layout (now I won't bother with my own). It may not be cost-effective for me to order UK boards, as the exchange rate is a killer, but I could perhaps etch a single-sided board. Alternatively, I could arrange a group buy here if the pricing looks favorable.
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Old 27th July 2005, 05:30 PM   #13
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wow
lots of replies....... thanks guys ...... it seems that I would stay with mj15003 after all...... I have determined that I would better be using mica pads under mj's instead of silicon and also a very good thermal greese. On other thread that I was asking in paralel with this one - it was about to hot mj15003's - they clearly noted that silicon is not beter than mica insulating pads..... So I might cool my output transistors after all. If not I still have this option to do
thanks for Your time and effort......


I meen MikeW version with MJW21194 and without zobel and anything..... and with one output pair .... and optimized Iq current and sch....
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Old 27th July 2005, 05:34 PM   #14
pooge is offline pooge  United States
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Perhaps some small value base stopper resistors in the output devices could help prevent oscillations.
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Old 27th July 2005, 06:48 PM   #15
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Quote:
Originally posted by pooge
Perhaps some small value base stopper resistors in the output devices could help prevent oscillations.
maybe - but if mjw21194 is o.k. of anything than this one will be my favorite....


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