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Old 5th December 2012, 02:01 PM   #421
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And if you use more than 26 V in they are going to get hot so Kerafol 86/83 is prety good
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Old 5th December 2012, 02:20 PM   #422
vrun is offline vrun  Germany
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Thanks RCruz, Frans, Bksabath ... now I know I should have deferred that Reichelt order ;-/

Next Question:
Right after lunch (never do something on a full stomach ) I "tested" my diode strings.
(almost everything OK but) On one board L201-209 would not lite...
So I checked the 1st 4 only... with the PS still on 20V...
...even the lowest current setting on the PS did not rescue me ...
Now I need 4 additional green LEDs ... and I don't want them to look different (no, no, no).

What brand and type are the green LEDs from the GB ?
Thanks

Last edited by vrun; 5th December 2012 at 02:22 PM. Reason: edit
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Old 5th December 2012, 03:10 PM   #423
miepa is offline miepa  Austria
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Default resistors

hey guys, did anyone of you use
PRP PR9372 0,25W resistors
to built the paradise R3, or some other kind of 0,25W resistor?
or has everybody used the CMF55?

thanks!
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Old 5th December 2012, 03:28 PM   #424
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None of the simple advice relating to my oscillation problem worked. So far i have been trying to not completely ruin the boards and have avoided haphazardly replacing components.

But is seems some more decisive action is now required. Judging by the number of successful builds it simply has to be related to a component, either out of spec, or in some way mismatched to the circuit.

So, in order to narrow this down a bit i've been thinking: there are a whole lot of transistors, not even sure why so many, which only seem to deal with dc op points of the input devices and the servo signal. Would it be possible to remove Q11 and Q5 and supply the input devices emitter resistors via resistors from the related PS lines?

This should eliminate 16 semiconductors from the "suspicious" list, right?

Or is this just silly - it's a dc signal after all.

If there are no objections to this, as a next step i am thinking of removing the parallel devices and leaving just one input pair.
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Old 5th December 2012, 03:33 PM   #425
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What you can try is to measure the DC over the emitter resistors of the input stage.
You then can calculate the idle in each transistor by Ohm´s law.
U = R x I so I = U/R.
That gives you a clue if they all conduct and if there is any greater difference.
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Old 5th December 2012, 03:44 PM   #426
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Not sure why you mention this Joachim. There are no dc issues on the board at all. All input devices work at a very similar 3.4mA...

My idea was to remove the "unnecessary" part of the circuit in order to simplify it for troubleshooting the oscillation issue. Any suggestions about that? Alternatively i could build it afresh on a proto-board, get parts which work and then move them to the PCBs. Just seems like extra work and potentially different layout.
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Old 5th December 2012, 03:55 PM   #427
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Quote:
Originally Posted by Joachim Gerhard View Post
Put a cap of ca. 1nF parallel to the input.
Had no effect.
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Old 5th December 2012, 03:57 PM   #428
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Base stoppers before each input transistor, say 4.7 to 10 Ohm.
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Old 5th December 2012, 03:58 PM   #429
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Quote:
Originally Posted by hesener View Post
With your oscilloscope, can you see oscillation in the 40-50MHz range? (just checking....) Please also check the supply rails (AC coupling, of course)
Not really. It's a 60MHz scope with sync issues. DC rails are entirely noise free.
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Old 5th December 2012, 03:58 PM   #430
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Yes, i ment the isle in the input transistors but that is fine in your case.
You can try to take out the helper transistors in the mirrors.
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