Help me get or clone a FM board for the Yaesu FT-920  - Page 1
Forum section: electronics / rf-microwave

author: DC1MC
author_rank: Super Contributor
timestamp: September 24, 2020, 05:46:45 pm
content: Hello everybody, I've recently got an Yaesu FT-920 that was not treated well and after repairing the jammed VFO encoders, I'm waiting for the LED replacement for the CCFL display backlight (a separate topic will be created) and the main power relay.The question is I've wanted to pimp it up, but the YF-116 A and C are nowhere to be found and the FM mode board (called very inovative FM-1) is also unobtanium at any price, I've actually seen people setting up fake e-commerce sites for it, so I assume that there is still a demand.So, being a bit adventurous, I was looking to see if I can reproduce it taking advantage of the JLCPCB offer, strangely enough most of the parts seem to still be available, except for the 8.215MHz crystal, this seem to be also unobtanium and I was not able to determine what connectors Yaesu uses for the board, they most certainly are Molex or Amphenol, but not I wasn't able to get anything equivalent.So now here's my set of questions form the blog ham community:- Does anyone have some of the FT-920 accessories collecting dust in a drawer, if so, please PM me ?- Does anybody have or know a source of crytsals with 8.215MHz and 7.760Mhz, best in HC-49U or similar package ?- Do you think is a good idea to spin something like 10-20 of these FM boards, is there a chance for some one to want them ?- If the current obsolete schematic is not easy doable, could someone recommend a more modern ham FM mode modulator/demodulator for an IF of 8.215MHz that can be fit on a small PCB ?- And finally, looking at the attached pictures and the P/N 5124-08BHPB (Yaesu P1090372) could anyone identify the connectors ?Any feedback and ideas are really appreciated.Many thanks,Mircea

author: geggi1
author_rank: Frequent Contributor
timestamp: September 24, 2020, 07:38:10 pm
content: The connectors looks lik the ones used on Yaesu crystal filters.

author: DC1MC
author_rank: Super Contributor
timestamp: September 24, 2020, 07:55:21 pm
content: Quote from: geggi1 on September 24, 2020, 07:38:10 pmTrue, but this does not help me identify them.

author: DC1MC
author_rank: Super Contributor
timestamp: September 24, 2020, 08:30:55 pm
content: Got the counterpart on the mainboard, is a Molex 3022-8A2.50mm (.098") Pitch Header, Single Row, 7.50mm (.295") Mating Pin Length, 8https://www.molex.com/molex/products/part-detail/pcb_headers/0022031081Of course long obsolete and unavailabeThat mates with:https://www.molex.com/molex/products/part-detail/pcb_receptacles/0022023054that look ALMOST similar wit the intended connector, also long gone and obsoletebut we have the modern replacementhttps://www.molex.com/molex/products/part-detail/pcb_receptacles/0022142084Also hard to find, but at least active.Now, the big deal is the crystals.

author: geggi1
author_rank: Frequent Contributor
timestamp: September 25, 2020, 09:09:48 am
content: There are several companies that can make custom crystals but its expensive.Another option is to check at several crystal manufacturers it they have these frequencies in their range of supply.If the crystals are used to mix down a signal you can always look into a DDS solution.

author: DC1MC
author_rank: Super Contributor
timestamp: September 25, 2020, 05:48:04 pm
content: Quote from: geggi1 on September 25, 2020, 09:09:48 amThe 7.760MHZ for the demodulator I've found already, the 8.215MHz is needed for the modulator, the original schematic is a Colpitts oscillator with a varicap that receives the audio. This frequency is really hard to come by and I wonder why, is not that isn't allover in the Yaesu and Kenwood device, most likely ICOM as well ?DC1MC

author: TheSteve
author_rank: Unknown
timestamp: September 25, 2020, 07:39:07 pm
content: I remember buying custom crystals years ago, they were 15 bucks each or so. Must be hard to find such manufacturers now.If Icom or Yaesu have used them in anything semi recent then you may be able to buy them direct. I know Icom parts support is pretty good overall.Edit - Contact Elecraft and see if they have a crystal that they can sell you. It looks like they use 8.214 or 8.215 in one of the crystal filters for the K3.