Janus Alpha Revisions
This page contains a list of revisions needed to the Alpha level Janus boards
JanusPower1 - C40 needs to be tied to pin 3 (input) U5 (-12 v regulator) instead of pin 3
JanusPower2 - U8 (+5v supply) needs to be a larger regulator -- getting quite warm delivering approx 200 ma
Janus220UF - Pads on 220 uF caps (C22,23,24,25) need to be larger - currently a bit of a challenge to get them soldered.
JanusU12Rail - Negative supply for U12 (NE5532) needs to be returned to -5v supply instead of ground.
Add LED's to the Power rails - the board is very dark without! An LED connected to a CPLD pin would also be very useful for showing clocks/signals etc. (VK6APH)
Add a note not to fit J2 unless you actually have a balanced input to use. The pins are after the input attenuator so can pick up noise if cables etc are run near them. (VK6APH)
C72 and C66 need increasing to 4700pf since the corner frequency is too high and the 3MHz PWM clock is visible on the output. We need to add a 3.3mH inductor in series with R35/36 which are now 1k. The attenuation at 3MHz is now > 70dB. Note: These changes are to enable us to increase I and Q to 11kHz from baseband in the future. (VK6APH)
Soldering the 100k resistors on the DIN connector is a pain. Is there room to add resistor packs to the board - perhaps on the back? (VK6APH)
Move silk screen near input jacks so can read what each is once socket has been fitted to the board. (VK6APH )
Add 'scope 0V test point. (VK6APH)
Update circuit. R21 = 100, R25 = 866, R34 = 120, R27 = 3k3, R36 & R35 = 1k, R13 & R14 = 39k (1%), C72 & C66 = 4700pf.(VK6APH)
Increase pad size on 24MHz crystal X01. (VK6APH) Possibly make pads for small and larger version crystal XO1. (DL6KBF)
PowerInputConnector - can we find space for a 4-6 pin 0.100 header to inject +/- 12v, +5v supplies for applications not using an Atlas bus (Ozy+Atlas 2 card stack)
ClockSync - Change clock oscillator to 12.288 MHz VCXO. Add RC LPF from CPLD to control input on VCXO. This will allow slaving the ADC and DAC clocks to Gibraltar's 10 MHz reference. Footprint for VCXO is compatible with present oscillator so VCXO becomes a built-time option. (KK7P)