Extended FP III resistance issue [resolved]

Neuronal · 7375

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Offline Neuronal

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Reply #30 on: November 24, 2020, 04:31:53 PM
what is the target I am shooting for for KReg?

Bob D
Rega P2, Cosecant DAC, Reduction, EFP III, Paramount V1.0 + soft start, Omega CAMs + DeepHemp 8s


Offline Paul Birkeland

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Reply #31 on: November 24, 2020, 04:43:20 PM
I can't remember exactly and the manual isn't specific, but I would imagine a reasonable range would be 4-12V.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Neuronal

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Reply #32 on: November 25, 2020, 05:00:07 PM
I rewarmed all the joints in the shunt reg board, and the KReg popped up to 4.1 V on both sides - plugged it in and tried it out. First record was the Whatnauts 12" of Help Is On The Way, and it sounded AMAZING (to my ears, more lower noise and more bass extension for sure).

Thanks again for everything, and a happy thanksgiving to all!

Bob D
Rega P2, Cosecant DAC, Reduction, EFP III, Paramount V1.0 + soft start, Omega CAMs + DeepHemp 8s


Offline Neuronal

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Reply #33 on: January 18, 2021, 06:50:10 AM
PB - thanks again for your help with this fix. I definitely learned a lot! Two quick questions - the C4S boards got pretty banged up with all the soldering/desoldering I did, and now that I have a much better understanding of what is going on I was thinking of building some clean C4S boards that will hopefully last forever. The ones used for the EFPIII upgrade are no longer made, but there are these little mini boards for the Sex 3.0 upgrade that should mount on the stand-offs alright (I think). Could these be used for the outer C4S boards in a EFPIII? Would these be basically drop-ins? Related to this - is the MJE5731A a drop-in replacement for the MJE340?

thanks again for all the advice -
Bob

Bob D
Rega P2, Cosecant DAC, Reduction, EFP III, Paramount V1.0 + soft start, Omega CAMs + DeepHemp 8s


Offline Paul Birkeland

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Reply #34 on: January 18, 2021, 07:02:19 AM
The small C4S boards we sell can be substituted for the outer boards without a ton of difficulty.  An MJE5731A and an MJE340 are not at all compatible.  The 340 is an NPN and the 5731A is a PNP. 

The MJE350 can be substituted with an MJE5731A for better thermal capabilities.  A tip50 can be substituted for the MJE340, though that's severely overkill in a Foreplay.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Doc B.

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Reply #35 on: January 18, 2021, 07:16:54 AM
Also bear in mind that the orientation of the different transistors can be reversed (e.g. MJE350 and MJE5731A are reversed), so you want to check the pinout before you install a different type.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline Neuronal

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Reply #36 on: January 23, 2021, 04:19:16 PM
thanks PB and Doc!

Bob D
Rega P2, Cosecant DAC, Reduction, EFP III, Paramount V1.0 + soft start, Omega CAMs + DeepHemp 8s


Offline Neuronal

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Reply #37 on: February 21, 2021, 05:06:11 PM
OK, I got the Sex 3.0 C4S boards - just to verify, the underlying circuit on the board is the same as on the boards that came with the EFPIII, right? So if I just take the components/values that are supposed to go on the EFPIII boards and stuff them into the correctly marked spots on the SEX3.0 board (i.e., position R1 on one board is wired up the same as position R1 on the other board) I should be good to go?

Quick related question - I was reading on another thread that people like tantalum resistors for R1, but these come in limited values. How far off can I be and feel ok about it (as these control the current, right?) I'm building the paramount soft start boards now, for example - cool to sub a 220 for the specified 215? in the EFPIII circuit, can a 250 be subbed for the 237?

thanks as always!
« Last Edit: February 21, 2021, 05:10:44 PM by Neuronal »

Bob D
Rega P2, Cosecant DAC, Reduction, EFP III, Paramount V1.0 + soft start, Omega CAMs + DeepHemp 8s


Offline Paul Birkeland

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Reply #38 on: February 22, 2021, 05:37:26 AM
I wouldn't go for the tantalum resistors, they don't really fit the boards all that well. 

What I would suggest is putting the parts into the boards but not soldering them, then posting photos. 

You will not need the black jumper.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Neuronal

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Reply #39 on: February 22, 2021, 06:26:17 AM
will do!

Bob D
Rega P2, Cosecant DAC, Reduction, EFP III, Paramount V1.0 + soft start, Omega CAMs + DeepHemp 8s