[1000mp] TCXO-6 signal level

[Robert Watzlavick]

Hi, new to the group here.  I got a TCXO-6 for my FT-1000MP but when I 
installed it, any received stations disappear.  You can still hear some 
audio but it's just low level noise.  After some debugging, it appears 
to be a signal level problem of the TCXO-6 vs. the stock ref.  The 
output from the TCXO-6 is quite a bit lower than the stock ref and of 
all the places the ref clock goes, it appears that the level at Q4503 on 
the DDS-SUB unit is too low to drive the DDS.  I got the TCXO unit from 
eBay and I can't remember if he said it was for an original FT-1000 or 
the MP version (the auction is too old so the info is gone) but the box 
says TCXO-6.  With the TCXO-6 installed, the level at the DDS on the 
LOCAL unit (Q4503 pin 31) is less than 2.0 Vpp (vs. 2.6 Vpp with the 
stock ref) which I'm assuming is too low to drive the part.  The sub RX 
still works, probably because it has an additional buffer on the board 
(Q8066) before distributing the ref clock to the DDS/PLL/etc. However, 
the LOCAL board doesn't have that additional buffer so the signal level 
at the input to Q4601 on the DDS-SUB is only 0.1 Vpp.

I suppose the TCXO-6 could be bad but both the FET and BJT amps on the 
board appear to be configured for unity gain so if something is bad, it 
must be in the metal TCXO enclosure which I can't figure out how to 
open.  It appears to be soldered all around the edges on the bottom.  
The output is very clean and spot-on frequency wise.

If I unplug the connector for the ref between the LOCAL and DSP-D 
boards, it reduces the loading so the level from my TCXO-6 is enough to 
drive the DDS-SUB and audio is restored.  Therefore, I'm wondering if 
the unit I got is compatible with the MP.  The board I have exactly 
matches the TCXO-1 schematic from the FT1000 manual but the MP or MKV 
manuals don't have a schematic for the TCXO-6.  The sticker on the TCXO 
just says "TCXO" without any -6 or -1 indication.  Does anybody have any 
information regarding the differences between the TCXO-1 and TCXO-6?

If anybody has a TCXO-6 installed in an MP, I would sure appreciate it 
if you could measure the output level at the TCXO board so I can 
determine if it or something else in the radio is the problem.

Thanks in advance,
-Bob
K5RLW