Here is the TI document on "Case Marking." It may not be a 74S30.
http://www.ti.com/lit/an/snoa039c/snoa039c.pdf --- Graham == On Fri, Oct 28, 2016 at 11:27 AM, Adrian Godwin <artgod...@gmail.com> wrote: > That's one sweet soldering iron. Is it an American Beauty ? > > > On Fri, Oct 28, 2016 at 4:31 PM, Peter Reilley <preilley_...@comcast.net> > wrote: > > > 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?dl=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:time-nuts-boun...@febo.com] On Behalf Of Peter > >> Reilley > >> Sent: Tuesday, October 18, 2016 8:11 AM > >> To: time-nuts@febo.com > >> 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. > >> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > >> > >> > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to https://www.febo.com/cgi-bin/m > > ailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.