Batboard

Hello All. I have a TRN7408 in a VHF PURC5K. It has a 5 mhz OCXO, but I'd like to move it to 10Mhz to use a GPS disciplined reference we have available at our site. I only see JU12 which seems to switch the REF frequency from 5 to 20 mhz. If there another setting somewhere on the board that will allow for 10mhz?

Many thanks, Will

Will - see chart below:

Ref Input JU12 JU13 JU14 JU15 JU16 ACB HS Ref
1Mhz NC IN IN OUT A 100 khz
5Mhz B OUT IN OUT A 500 khz
10Mhz A OUT OUT IN A 100 khz
Note: A 5Mhz reference input is standard. JU13-JU15 are zero ohm chip resisters. The
reference loop is disconnected when JU16 is in position "B".

I referenced the above info in Motorola manual 68P81084E19 page 2 Table 3.

EDIT: Sorry but the above columns do not line up after I posted it. If need be
I may be able to fax it to you today or monday - just pm me with the info.
Aparently JU13-15 are on the solder side of the TRN7408 Synthesiser board.

Looks easy enough to decipher. I'll try it tonight and get back to you if I have no luck with it.

Many thanks, Will

Hey there. J12 is on the board marked in silkscreen, but the other 4 are not. I can see 1 0 ohm SMT resistor, and a couple other pads. If you can scan that in and send it. it would be greatly appreciated.

Will

Will - I do not have a scanner but can fax the pages on monday from the manual if you can pm me a fax number. Other than that I can usps them to you.

Got it. I was confused by the fact that my boards have J12 as an A/B jumper. Pulling it and moving the 0 ohm resistor to the pads halfway between u4 and u2 got me to 10mhz. Thanks again, and I hope you're feeling better.

Will