new diytube st70 driver cap stuff

[Shannon Parks]

Hi folks,

I should be getting the shipment of boards in over the next few days, along with a Mouser order. I tried to make the board as 'cap friendly' as possible, even incorporating some holes to be used a tie wrap point for Auricaps. From Mouser alone there'll be four different coupling cap selections: Xicon metallized box, Wima metallized polyprop box, orange drop Sprague and polyprop Xicon. I ordered all four sets of these, but don't plan to do extensive testing immediately.

I also did a lot of testing on voltages seen by the coupling caps at startup with both a cold rectifier and a hot rectifier - in neither case was I able to get near the voltage ratings. So the huge 630V rated caps aren't necessary and 400V ones are OK.

Finally, I did tweak a couple values in the schematic I posted. I lowered the values of the LTP plate resistors to 43K and increased the LM334Z set resistor to 15ohms. This is a much more conservative setting which keeps the LM334Z stable at all times. I tested with pulses of 100Hz square waves at 2Vrms. The original setting just have a nominal drop of 5.5V across the device with almost 2V needed for operation. Now it has 11V across the device with closer to 1V needed for operation. I'll pay more attention to Mr Morgan Jones next time!! Yellow_Light_Colorz_PDT_06

Shannon

[TerrySmith]

Hey Shannon,

Do you have the part #'s for the Wima caps? I want to replace the .1 and .22 caps.

[Shannon Parks]

Hey Shannon,

Do you have the part #'s for the Wima caps? I want to replace the .1 and .22 caps.

Here it is, Terry. The trick is getting the right lead spacing, since they are so short - so you might double check them before ordering. Ultimately, I think the .1uF doesn't fit as well as I hoped, so I scratched it from the parts list in the end. Also, the FKM-series are in the catalog, though they will have one tolerance or the other in stock many times. Double check min qty needed for purchase and then choose the lowest tolerance (the last digit in the part number is % tolerance). Their values are not critical as the lower -3dB point is way down there.

Shannon

Code: Select all

   2   C1,C2         0.1uF,400V      505-FKP10.1/400/5   1.87
   2   C3,C4         470pF           505-FKM2470/100/5   0.21
   2   C5,C6         100pF           505-FKM2100/100/5   0.20
   4   C7,C8,C9,C10  .22uF,400V      505-M10.22/400/20   1.29