MFOS VC Spring Reverb - D4

[popular with good friends]

Hello.
Is the value for D4 of this PCB a 5.1v zener?
Thank you!

[popular with good friends]

Also, is the power supply buffer on MFOS page necessary? If so, will 1 buffer work for 2 vc spring modules?
Thanks again!

[Paul Cooper]

Is the value for D4 of this PCB a 5.1v zener?

D4 is a 1N914 signal diode just like D1 to D3. The only zener and it is a 5V1 is Z1. This was the last module from Ray before his passing and there was a few discrepancies between the schematic and the PCB and mainly relate to the HP filter formed with R9, R39, R40 & C27.

R40 (100k) is solder on the rear of U1 between pins 3 & 4.





R9 (10k) is soldered to C27 (22nF) before soldering into the R9 position. It is important the resistor and capacitor are soldered exactly as per the photo below. R39 (1k) isoldered from the casing of the phono socket to the junction of R9 and C27.





Finally, D4 is shown as Z2 on the PCB silk screen and with an incorrect orientation. Photo below shows D4 in its correct position.







Two other differences which relate to C1 and C5.



C1 is a 1uF tantalum capacitor in the schematic and parts list but the PCB silk screen only shows a non-polarised capacitor. C5 on the PCB shows it being polarised but is actually a 100nF non-polarised ceramic capacitor.



When soldering in C1, make sure the +v side of the capacitor is facing towards U1.





The spacing for C5 is too narrow so simply form the leads to suit, it does not matter which way around it is soldered in.

Also, is the power supply buffer on MFOS page necessary? If so, will 1 buffer work for 2 vc spring modules?

You will have to help me with this one as I cannot spot any reference to a power supply buffer, plesae advise.

[popular with good friends]

Thanks for your reply.
I guess i was confused about the diodes, since the PCB shos D4 as a zener and the website showing correctly oriented D4 makes no mention of the discrepancy between PCB silkscreen and the parts list.
I guess i am referring to the power supply bypass caps, shown here.

[Paul Cooper]

The bypass caps are an integral part of the design and are positioned typically in pairs for bipolar supplies close to each chip as per the PCB layout. The schematic is electrically correct although in reality, they are not connected in parallel in one bunch but distributed around the PCB. If you are not using the same PCB layout but using say strip board then you should replicate this arrangement. The same applies to a second reverb module which will also need the same arrangement. The purpose of these decoupling (bypass) caps is explained on this site https://learn.sparkfun.com/tutorials/ca ... n-examples if you are not familiar with them.