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Old 3rd December 2012, 01:14 PM   #381
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Thanks for the reply Hesener. I have the smds in place and the output stage is definitely not responsible for the oscillations.

It probably is the Hfe. Of course this useful advice could have come at a slightly earlier stage. Joachim recommended the highest Hfe devices to be used at the input...

At this stage i will probably do something more productive with my life and leave some other beta-testers to try their luck. This is a breadboarding exercise and not something meant to be done on a fully populated board, right?
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Old 3rd December 2012, 03:49 PM   #382
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Quote:
Originally Posted by hesener View Post
That's what we expect from you, and how the shunt actually behaves in reality ;-) I am still considering doing a separate PCB for it (if you don't mind of course) because it can be used in many different applications, due to its very good quality
Was going to keep that hush hush and do same but now I am looking forward to your board especialy as quality of paradise boards is stunning (I think I can say that with no danger of ridicule now that a few started to play with it.)

And yess PSU is prety good to (bit like Londoner tha is allright if you catch my drift)

If I may? can power devices be on the edge as then one has option to use outside case sinks?

Put my name down for 4 please
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Old 3rd December 2012, 07:20 PM   #383
RCruz is offline RCruz  Switzerland
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My experience seemed to indicate that high HFE will increase the tendency to oscillate. FWIW, I had transistors at around 400 for NPN and PNP, worked beautifully. My recommendation would be to put 400's in the input stage, and use the decoupling caps in both mirrors (100...1000nF X7R ceramic caps, size 1206 or 1210).
Hi Alfred

Maybe you could post a schematic with the correct placement for those ceramic caps.....
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Old 3rd December 2012, 07:22 PM   #384
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Originally Posted by analog_sa
Fixed the issue with the insufficient voltage across the output 2SK170. Indeed Joachim was correct - top FET needed replacement.

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I had similar issues...How did you choose the new top fet ? Different idss ?
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Old 3rd December 2012, 07:32 PM   #385
hesener is offline hesener  Germany
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Originally Posted by RCruz View Post
Hi Alfred

Maybe you could post a schematic with the correct placement for those ceramic caps.....
Hi,
from a schematic point of view its quite easy - they go from VPLUS (or VMINUS) to GND. The secret is in the placement - as close as possible to the emitter resistors of the current mirrors. Take a look at the bottom side of your PCBs and you 'll see what I mean
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Old 4th December 2012, 09:09 AM   #386
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I'm quite glad I had no Hfe matches, seems like a waiting strategy may pay dividends here... ;-)
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Old 4th December 2012, 09:13 AM   #387
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That is 1.9 + 3.4 = 5.3V the expected voltage here is V(L111) + V(L112) - Vbe(Q104) and that is 1.9 + 1.9 - 0.6 = 3.2V. It is actualy 2.1V to high, check the led voltages L111 and L112 and replace them if needed. Replace Q4 and posibly replace Q103.

There is one thing that I do not understand, V(L110) = 1.918V so V(R104) should be 1.9 - 0.6 = 1.3V and I(R104) should be 1.3 / 10 = 130mA and that should not depend on V(TP103), mmm... anyone else?
beetle, Any news on this?
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Old 4th December 2012, 09:37 AM   #388
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Quote:
Originally Posted by RCruz View Post
I had similar issues...How did you choose the new top fet ? Different idss ?


They don't work at IDSS. Probably a suitable Gm is needed. Did mine by trial and error.

Not sure but seems that varying the 220ohm resistor in the CCS may be another way of fixing this. In any case the CCS needs to output less than the K170 Idss.

It is becoming clear that the assembly guide can do with some added detail. While it's possible that the Paradise would work properly after just stuffing the board, it seems quite unlikely.

A warning that the circuit is prone to oscillations and some clear advice on how to avoid them per example seems absolutely essential.

The original advice on beta selection seems to also have been superseded now.

It is inconceivable that all builders will be reading through hundreds of posts from various threads in order to obtain such basic guidelines.
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Old 4th December 2012, 10:02 AM   #389
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Would Erno Borberly's jfet preamp article , which includes a cascaded jfet input be helpful in explaining the needs of the top jfet.

http://ken-gilbert.com/images/pdf/er...y_on_jfets.pdf

http://www.ltwiki.org/images/b/b1/Er..._articel_2.pdf

First article is the one that speaks to the cascode situation.
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Last edited by buzzforb; 4th December 2012 at 10:05 AM.
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Old 4th December 2012, 10:54 AM   #390
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Quote:
Originally Posted by analog_sa View Post

It is becoming clear that the assembly guide can do with some added detail. While it's possible that the Paradise would work properly after just stuffing the board, it seems quite unlikely.

A warning that the circuit is prone to oscillations and some clear advice on how to avoid them per example seems absolutely essential.

The original advice on beta selection seems to also have been superseded now.

It is inconceivable that all builders will be reading through hundreds of posts from various threads in order to obtain such basic guidelines.
Skip loot if you like butread bold part sorry for ranting a whole pageI agree with you about more detail and guidelines for oscillation on the guide
IMO this need to be updated with advice considering the need that a wide skill set is out there with 200 + builds taking place.

I don't agree on, as you point out, on the unlikely.

As a beta tester I built Paradise R2, I know of my personal correspondence with Joachim and Alfred, from this personal experience you can be assured that final (for now) R3 version would have never be relesed if any problem became evident in my build, build that was carried out in a rush without particular care in regards to matching, I never measured any of the J fets for example and purposely mixed up Hfe to the 10% tolerance as specified, I am also on R2 using very hi Hfe trough out the board as the % volt test circuit revealed once I started using it.

Only problem I had with this built was that I placed one of the electrolytic the wrong way around, this is easy to do so I suggest any one building paradise take a break before stuffing the boards, You been warned

As for the apparent problems arising from the component kits, I did purchase one by the way, I cannot comment, as I donít know what happened there,
Something is gone wrong certainly but I trust that steps are taken as we write to rectify the situation.

Would I have volunteered for such a task knowing of the 200 + builds?

NO WAY MATEY not for 200, maybe 20

500 transistors for 200 builds equal 100,000 pieces
Whit this large an order I would have gone directs to Manufacturer but is easy now to say.
Spread between Hfe in different goodies bag is normal, nothing that can be done about it, gett in touch with mate near you and swap. and make a few new friends in the process (I am doing that already) and no don't worry nothing wrong with me
The fact that BCXX-25 S Hfe are there is not acceptable
Where the blame need to fall need only to be established so we can take constructive actions to solve the problem.

This is DIY, problem solving is all part of the fun, if not for this and the satisfaction to have something one made that work beautifully as My R2 does, maybe one should order ready-made gear from the Shop whit all that it entails
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