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Old 15th January 2013, 12:10 PM   #1101
PMA is offline PMA  Europe
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Have you connected the metal case with analog ground of the PCB?? Directly, or at least through a capacitor like 10nF - 100nF. If you do not do this, then you have a perfect RF antenna.
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Old 15th January 2013, 12:27 PM   #1102
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Of course i have connected it. Now i realise the 2MHz has been at the Paradise output all along only it wasn't so clearly visible because of 50Hz and other noises and the scope had trouble syncing.

So, in a way - back to square one, only this time the regulators are rock solid and not adding to the rf chorus.

Caps somewhere? Base stoppers on input transistors? The base stoppers are my least desirable option, first for the lack of particularly nice 16 x 10ohm resistors and second because of the amount of desoldering.

Still curious: are the other 200 builders not experiencing any oscillations? Especially with the inputs shorted? Are my boards cursed?
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Old 15th January 2013, 01:05 PM   #1103
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DIYers usually do not measure much and do not measure into deep. DMM is like nothing.

Base stoppers, most likely.
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Old 15th January 2013, 01:52 PM   #1104
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@analog-sa

hi, did you check on different places on the board how the rf-oscillations are distributed? there are two main possibilities: they are generated in the power-supply part or in part of the signal processing chain.

you surely have the 1uf smd decoupling caps mounted (i did not read back through all your posts)?
is the 2mhz signal present on the power rails?

i am shure that a systematic analysis of your board will teach as all a lot
hesener seems to be a great guy, did you consider his offer to send him your board for analysis? i really would be nice to find out where this problem is originating.


a bit off topic: it i funny to see how this resembles my field of work, treating cancer patients.
there every year people rush to congress with wonderful treatment results gained from observations on a small group of patients. then everybody gets interested and things get studied properly on a big number proper way. and - things turn out much less wonderful that anticipated and all those with unrealisticaly high hopes get disapointed.
same pattern i see here, deploying this design to a large community we do find that there are rougher edges than expected. but there is a large amount of expertise gathered here, so i am confident that we end up with a product that may exceed quite a few commercial products in the end.

Last edited by hugenh; 15th January 2013 at 01:56 PM.
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Old 15th January 2013, 04:22 PM   #1105
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Quote:
Originally Posted by hugenh View Post

you surely have the 1uf smd decoupling caps mounted (i did not read back through all your posts)?


A quick recap for your benefit then. It's excruciating to read through long threads.

Yes, i do have the smd caps, which is probably irrelevant. The mishaps began with the CCS parts of the regulators oscillating @7MHz. It was measured, simulated, cure found and applied and all is now well with the regulators. So, PS is definitely out of this picture.

Hesener was extremely kind to offer his help with the board. At the end it was me who declined his offer. Moreover in less than a month US based forum members will be visiting and i have already promised a phono-stage shootout

I also have little doubt that someone in Hesener's immediate vicinity will experience the same symptoms before long. After all there is nothing at all exotic about my build. It uses almost entirely, with the exception of the fets, the components from the group buy which appear to be first rate.

Per example in this post there is an oscillogram, which most probably shows exactly the same problems as the ones i had/have. Scope cannot sync as the power supply is also oscillating.

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Old 15th January 2013, 04:57 PM   #1106
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Analog Sa, any chance of a quick picture to see how you have fitted the caps to cure the CCS? I'm trying to get my head around best placement.
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Old 15th January 2013, 05:07 PM   #1107
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Mine are still polystyrene, soldered at the back directly on the transistor solder pads with the leads cut as short as possible. SMDs will fit perfectly as the pads are adjacent.
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Old 15th January 2013, 05:29 PM   #1108
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Quote:
Originally Posted by analog_sa View Post
Mine are still polystyrene, soldered at the back directly on the transistor solder pads with the leads cut as short as possible. SMDs will fit perfectly as the pads are adjacent.
Me being thick...I'd appreciate a picture though..

Sent from my GT-I9100 using Tapatalk 2
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Old 15th January 2013, 05:37 PM   #1109
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Likewise.
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Old 15th January 2013, 06:23 PM   #1110
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Battery died after first pic...
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File Type: jpg reg caps.jpg (251.9 KB, 286 views)
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