Yaesu FT-900 service manual (technical suppliment) plea for help

[WastelandTek]

On the bench I have an FT-900 that is missing some 40dB of RX sensitivity.  I want to poke around the first mixer and see what is going on but every instance of the "Technical Supplement" I can find online is the same illegible scan.  The text circuit description and component lists are good enough and helpful, but the schematic is pretty much useless.

Does anyone here possess a better scan or a physical copy of this document? 

This is an example of the scan I can find http://www.iw2nmx.it/Yaesu/FT-900/FT-900%20Service%20Manual.pdf available at several sites, pages 69 and 70 being of particular interest.

Thanks.

[CapLeaker]

Been in the same boat as you before fixing these FT-900.  Its a nice looking rig for sure. Luckily I do have a better schematic for it, but you need to install a .djvu reader, something like WinDjView. This isn't perfect, but at least much better what you got. 

73!

[WastelandTek]

Much, much better.  Thank you so much!

Being able to actually read the interconnection diagram was particularly helpful and got me going on this again.  The fault ended up being an open 0.33uF inductor in the RX path on the LPF board, L5016, it appears to be, with C5058 and C5059, a low pass filter situated between the T/R relay RL5014 and the RX jumper to the RF unit J5004.

I include all this detail because, interestingly, these components are not present in the schematic revision you posted and my fear is that some future searcher might be confused.  I rolled up a coil out of magnet wire somewhat close to the 330nF called out and was able to hear a test carrier weaker than 140dBm, so success there, but the omission of these components on the other schematic revision suggests that Yaesu determined at some point that this filter was not needed and similar success might be had by simply deleting the capacitors and replacing L5016 with a jumper.  All this is quite conveniently accessible under the bottom cover so if anyone would like to take a look I suspect later revisions of the radio might have shipped in that configuration.

The DjVu format can be conveniently converted to PDF at https://djvu2pdf.com/ I would have uploaded the conversion, but the resulting file is too large even zipped.

Thanks again for the upload.  I believe this is the highest resolution Yaesu FT-900 schematic available on the internet at this time.  Once again, the EEVBlog forum delivers.