Suggest me a preamp for my F4!

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#123
When running Shuntky at 42-0-42V AC R21 and R22 are woefully under-rated and fused immediately.

C15, C16 and C2 are Low ESR 1000uF 100V caps by Rubycon.

R23 and R24 are OK at 4R7 0.5W but I had to go to 3R3 at 1W for R21 and R22.

Noactive devices are fitted yet, other than the diodes and zeners, so this is the current drawn simply by charging the caps and powering the zener chain.
 
#124
last page of Cook Book :

Also important notes :
- For Shunty : Resistors R21 ,R22 , R23, R24 , R23a , R24a need to be either plain
carbon 0,5W ones , or decrease them to 1E8 or 2E2 , if you insist to use metal films of
0,25W variety . Few clever Shunty builders pointed that these resistors are prone to
burning , if you use low ESR biggie electrolytics in input side of Shunty .
Click to expand...
 
#125
I must have misunderstood the cookbook. I assumed that 4R7 at 0.6W would be OK.

I'm now successfully using 3R3 at 1W. For safety I'm testing at each stage of the build just in case something expensive goes wrong.

R23 and R24 seem fine at 4R7 and 0.6W it was just the input resistors to the bridge rectifier.
 
#128
Zen Mod.

I've tried evey avenue that I can think of to identify a heatsink that will fit Q1 and Q1A on the Shuntky.

I have not even come close.

Do you have a part number and supplier for the heatsinks that you designed the PCBs for.

The only solutions that I have come with are to (1) remotely locate Q1 and Q1A or to build a heatsink out of alluminium parts (FUGLY).

The bigger heatsink for the SHUNTKY and the PUMPKIN are available from Farnell, who are a Worldwide supplier.

Andy
 
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#137
This is the 2 smaller ones right? Do they have a part number for the larger one? Or must it be sourced elsewhere? I think someone earlier in the thread said Farnell, still looking through the first mentioned, would like to order all from the same place, but oh well.

Russellc
 
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