Hermes lite 2.0 (build8) replacement parts

[Janez S58J]

Hi

I am new to this group. My purpose is to build HL2 starting from an empty PCB (I have HL2 build8 PCBs from 2019).

It is hard to get some parts (mostly out of stock or out of production). I found some replacements, but not sure if they are right. So I kindly ask for confirmation:

1. X2 (ASTXR-12-38.400MHz-514054-T) to be replaced by 520L15IA38M4000 (from CTS). Difference (slightly smaller - 2.5x2.0mm, 1.5 PPM and 10pF load capacitance).
2. X1 (N3225SA-25.000M-STD-CSR-3) to be replaced by NX3225SA-25.000MHZ-STD-CSR-1 (difference: higher min temp, should be OK since my HL2 will operate at room temp).
3. U4 (KSZ9031RNXCC) to be replaced by KSZ9031MNXCC (difference: lower max supply current: 221mA (RNXCC) vs 66.6mA (MNXCC)).
4. U6 (5P49V5923B000NLGI) to be replaced  by 5P49V5923B532NLGI (difference: different "dash code" - I have no idea what that is!!!).
5. Q6 (MCP9700T-E/TT) to be replaced by MCP9700AT-E/TT (difference: the replacement part has even better temp. accuracy).

I am looking forward to your comments/confirmations or possible other replacement ideas.

Kind regards

Janez, S58J

[Steve Haynal]

Hi Janez,

The only concerns I have with your substitution list are:

1. I'm not familiar with the replacement part, but you want to ensure low phase noise for this oscillator as it drives the ADC.

4. The dash code represents a preprogrammed startup frequency. It should work but I have not verified that. Makerfabs had difficulty sourcing U6 for one run so we substituted 5P49V5925B000NLGI8. This has more outputs which are left unused, but we can confirm this part works. Search for 5P49V5923 on this list and you will find more details.

73,

Steve

kf7o

[Janez S58J]

Hi Steve

Thank you very much for your answer. I placed an order for U6 (5P49V5925B000) as well as for X1 and Q6. For the X2, as you stated, I need a deeper insight into it's datasheet. After additional check I also noticed that the  replacement for U4 (KSZ9031MNXCC) does not differ only in terms of lower max supply current. 

Kind regards

Janez, S58J

P.S.

I had already build one HL2, but while inspecting for why there is no response from FPGA (checking for different voltages) I accidentally bridged the input voltage to the 3V3 path .... One can imagine the outcome... I wish I have seen earlier the F4HTXs comment about the importance of soldering the bottom of the FPGA to the ground.

ponedeljek, 12. april 2021 ob 06:06:47 UTC+2 je oseba softerh...@gmail.com napisala: