There is no regulator in the unit. The power pin is connected directly
to the S30 chip.
Pete.
On 10/28/2016 1:31 PM, J. L. Trantham wrote:
Have you measured the voltage on the 'power' pin for the chip with 12 V applied
to the OCXO (or 5 V applied)?
Is there a 5 V regulator on the board?
Joe
-----Original Message-----
From: Peter Reilley [mailto:[email protected]]
Sent: Friday, October 28, 2016 9:11 AM
To: J. L. Trantham
Subject: Re: [time-nuts] Opening an Isotemp OCXO
Thanks for the link. I did not find any S30 chips that would run off
12 volts.
Could the whole OCXO be a 5 volt unit?
Pete.
On 10/28/2016 9:53 AM, J. L. Trantham wrote:
Peter,
Thanks for the update.
No time to spend right now but I found this by googling 'TI S30 SOIC chip'
http://www.ti.com/packaging/docs/partlookup.tsp#divline
Hope it helps.
Joe
-----Original Message-----
From: Peter Reilley [mailto:[email protected]]
Sent: Friday, October 28, 2016 8:24 AM
To: J. L. Trantham
Subject: Re: [time-nuts] Opening an Isotemp OCXO
I did finally get it open. I used a very large old style soldering
iron and .003 inch steel
shim stock. I would melt the solder on the straight seams and insert
small pieces of
the shim. Solder does not stick well to steel so the shim kept the
soldered seam open.
I used a soldering iron rather than a torch because I can control the
temperature.
I could not use the shim at the corners. After all the straight seams
were separated
I could pull each corner using a screw in the mounting hole and melt the solder
at
the corner. Slowly working my way around, corner by corner, I got it
opened. I did
not damage anything so I should be able to close it up after I fix it.
Looking around with my scope it seems that the output driver chip is bad as I
expected.
It is a TI 14 pin surface mount DIP. It says S30 on it which if it is
a 74S30 it is an
8 input positive NAND gate. The board layout confirms this as the 10
MHz signal is
connected to pin 2 and all other inputs are tied high. Pin 8 is
connected to the output.
The chip is run off 12 volts so it must be CMOS. But I cannot find any
chip like that
that will run off 12 volts. Any suggestions for a replacement?
Also, using an 8 input NAND chip for a driver seems an odd choice.
When I put 12 volts on the unit the S30 chip gets really hot. After I removed
the chip
the unit seems to work OK. The current jumps between about .1 amp to
.9 amps. It seems
like the temperature regulator is an on/off type controller.
The device on eBay, item 261920574725, looks exactly like what I have.
I have placed a bunch of pictures in my dropbox.
https://www.dropbox.com/sh/52e9d1rva9kpb3w/AABmbIj1aK7Zk2J9SNMmu-JAa?d
l=0
Pete.
On 10/18/2016 10:57 AM, J. L. Trantham wrote:
Pete,
I'm not familiar with your OCXO but I found one shown on 'theBay' (item
261920574725) and it appeared to have an option for 'mounting screws', four of
them, on the bottom. Interestingly, the 'link' to the datasheet for that unit
did not show threads for mounting screws.
If your unit has that option, I would suggest placing four long screws,
mounting the item in a vise, use a small torch (I've used a hand held propane
torch turned down very low to open a number of units from 5061A's) around the
bottom of the case while gripping the top with an appropriate sized Channel
Lock plier and lifting off the top.
If you can repair the OCXO, it should be easy to reassemble the unit with
solder.
TheBay unit looks like it has a screw cover (which likely has a rubber gasket)
for mechanical adjustment of the frequency. I'd remove that before applying
the torch. :^).
If you get it open, I'd love to see some pictures of the insides.
Good luck and hope this helps.
Joe
-----Original Message-----
From: time-nuts [mailto:[email protected]] On Behalf Of
Peter Reilley
Sent: Tuesday, October 18, 2016 8:11 AM
To: [email protected]
Subject: [time-nuts] Opening an Isotemp OCXO
I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at the MIT
flea market.
As expected it was dead. It heats up as expected but looking at the
output with a scope there
is nothing. However looking at the output with a spectrum analyzer I
can see a faint 10 MHz
signal. It seems that the oscillator is running but the output
circuitry is dead. Reasonable
assumption?
Anyway, has anyone had any luck unsoldering the tin case without destroying it?
Pete.
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