[time-nuts] OXCO Issues -- Latest

[Frederick Bray]

Interestingly, there is a hole in the foam to adjust the pot.  There is 
no corresponding hole in the can, only one for the piston capacitor 
adjustment.   It appears that the pot is part of the oven control 
circuit.  Maybe Ovenaire had a test fixture to make the adjustment 
before putting everything in the can?

I am about to the point where I will probably just reassemble it and 
drill a hole for the pot.  (That won't be hard to do after looking at 
the distance between the two existing holes in the foam and figuring out 
where the hole in the can should go.)

I have looked at the board under a lighted magnifier and can't see any 
cold solder joints or similar flaws.  I suppose I could heat each one up 
with a soldering iron to make sure.  I have tested all the resistors 
while in circuit and all values read less than or equal to the marked 
values.  I realize that it is still possible that one has increased but 
that due to other circuit components the reading is still less than the 
value of the resistor.  Perhaps I should just shotgun the ones in the 
oven control portion of the circuit?  I have found no open diodes.  I 
also have turned the pot 1/2 turn in each direction and returned it to 
its original position in the hope that this will have cleaned it.

I will have to go back into the power supply anyway.  There are a couple 
of strange things, such as the previously mentioned fluctuations on the 
12 volt line.  Then, there is the fact that the -7 volt supply is still 
a volt too low.  It came up after I replaced some electrolytic 
capacitors and some out of value resistors but there's still more to 
do.  This doesn't impact the OCXO as it only uses 12 volts.

Thanks again for all the suggestions.

Fred





On 5/12/2013 3:16 PM, Don Latham wrote:
> If there's a pot set that's inside the case, indeed inside the "foam"
> then there has to be a procedure for setting it before final assembly,
> no?
> can't believe an engineering setup that requires tiny tweaks with
> assembly and disassembly. . .
> Don
>
>