Bruce, I did that on the 'Output Board' but I haven't done the Oscillator Board yet. I need an LCR meter to make my work easier. It will be necessary to remove some components to get the correct resistor values but that should not be too big a problem.
I'll tackle that this weekend when (I hope) the replacement transistors arrive. Joe -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: Thursday, May 28, 2009 10:44 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Broken Ovenaire OSC 85-50 Joe Oven board solder joints are more likely suspects. Check all inductors for continuity and measure all resistors. Bruce J. L. Trantham wrote: > Bruce, > > I re-soldered all connections on the 'Output Board' tonight with no > improvement. I'll move on to other efforts this weekend. > > Joe > > -----Original Message----- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On > Behalf Of Bruce Griffiths > Sent: Thursday, May 28, 2009 7:13 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Broken Ovenaire OSC 85-50 > > Joe > > Whilst its easy enough to construct a miniature RF current probe using a > small ferrite core which is slipped over the wire in which the current > is to be measured, constructing one using a split ferrite toroid is more > difficult as such toroids are difficult to come by. > In principle one can construct ones own by cutting and grinding a pair > of toroids. > Unless one has access to diamond lapping equipment and diamond saws this > is probably impractical. > > Thus you will probably have to revert to measuring the RF voltage across > resistors in the circuit to get some idea of the RF current. > > Bruce > > > J. L. Trantham wrote: > >> Bruce, >> >> Simple enough suggestion. >> >> Replacement transistors should arrive before the weekend. I will try to >> replace the transistors and re-solder all the connections. >> >> I do not have a current probe but I do have an oscilloscope or two. Any >> suggestions of a current probe small enough to get into those small >> > spaces? > >> Joe >> >> >> >> -----Original Message----- >> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >> Behalf Of Bruce Griffiths >> Sent: Thursday, May 28, 2009 12:13 AM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Broken Ovenaire OSC 85-50 >> >> Joe >> >> In box is fine, 6MB is relatively small and not a problem. >> The brown caps look like they might be silver mica. >> It may be worth resoldering all the solder joints on these caps as they >> can sometimes go high impedance over time. >> >> The ceramic caps marked 103 are 10,000pF = 10nF = 0.01uF. >> >> If you have a current probe and oscilloscope it would be useful to look >> at the RF current flowing in the crystal, oscillator transistor etc. >> >> Bruce >> >> J. L. Trantham wrote: >> >> >>> Bruce, >>> >>> I sent you two pictures directly. I hope I did not choke your inbox. >>> >>> >> They >> >> >>> were a total of about 6 MB. >>> >>> If so, I can probably reduce the quality and get a smaller file. >>> >>> Joe >>> >>> -----Original Message----- >>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >>> Behalf Of Bruce Griffiths >>> Sent: Wednesday, May 27, 2009 11:03 PM >>> To: Discussion of precise time and frequency measurement >>> Subject: Re: [time-nuts] Broken Ovenaire OSC 85-50 >>> >>> Joe >>> >>> Low output can be caused by a high impedance path, an open circuit >>> component, an open solder joint, a low value cap, low gain transistor, >>> >>> >> etc. >> >> >>> The oscillator limits by either saturating or better cutting off the >>> oscillator transistor (would need to check to see which but its more >>> likely to be the latter). >>> If oscillator transistor cutoff is the limiting mechanism then too low >>> transistor collector current could be one cause. >>> >>> >>> Bruce >>> >>> J. L. Trantham wrote: >>> >>> >>> >>>> Bruce, >>>> >>>> Thanks for your analysis. Is this all in your head or do you use a >>>> >>>> >>>> >>> computer >>> >>> >>> >>>> program? >>>> >>>> >>>> >>>> >>>> >>> Both. >>> I used LTSpice to check. >>> >>> >>> >>> >>>> If I understand correctly, you are using the term 'buffer' to describe >>>> >>>> >>>> >>> what >>> >>> >>> >>>> I call the 'Output Board'. >>>> >>>> >>>> >>> Yes. >>> >>> >>> >>>> If so, then the Output Board seems to be doing >>>> what it is supposed to do and the problem is a low output from the >>>> Oscillator Board. Any thoughts as to the cause of the low output? >>>> Capacitors changing value, resistors changing value, inductors changing >>>> value (by the way, I need a refresher on how to read the color code of >>>> inductors), transistors loosing gain? I have not measured the >>>> >>>> >> temperature >> >> >>>> but the crystal has '79 C' written on it. The capacitors appear to be >>>> dipped silvered mica and the resistors appear to be carbon. >>>> >>>> I can send a picture of both boards if that would help. >>>> >>>> >>>> >>>> >>>> >>> Yes that may help. >>> >>> >>> >>> >>>> Joe >>>> >>>> -----Original Message----- >>>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >>>> Behalf Of Bruce Griffiths >>>> Sent: Tuesday, May 26, 2009 10:43 PM >>>> To: Discussion of precise time and frequency measurement >>>> Subject: Re: [time-nuts] Broken Ovenaire OSC 85-50 >>>> >>>> Joe >>>> >>>> A quick analysis if the buffer indicates that the gain with a 50 ohm >>>> load is about 1x. >>>> The gain into a 1M load should be about 4x. >>>> Simulating the output stage indicates that the maximum output achievable >>>> is about 1.6V pp into 1M or 0.4Vpp into 50 ohms. >>>> However distortion is a bit high. This requires about 0.4Vpp at the >>>> input to the buffer. >>>> >>>> The dc level on the red wire is reasonably consistent with quick >>>> simulation of the level without oscillation at an oven temperature of >>>> 90-100C. >>>> When oscillating the current drawn by the oscillator may increase >>>> slightly, bringing the value closer to that observed. >>>> >>>> Bruce >>>> >>>> J. L. Trantham wrote: >>>> >>>> >>>> >>>> >>>>> Well, a little work with a scalpel and a small flat bladed screw driver >>>>> >>>>> >>>>> >>>>> >>>> and >>>> >>>> >>>> >>>> >>>>> I was able to open the package. Inside is what I call an 'Output >>>>> > Board' > >>>>> that contains the output circuit and the 'FINE' frequency adjust along >>>>> >>>>> >>>>> >>>>> >>>> with >>>> >>>> >>>> >>>> >>>>> the 'Oven' which has the 'COARSE' frequency adjust. Attached to the >>>>> >>>>> >>>>> >>>>> >>>> 'Oven' >>>> >>>> >>>> >>>> >>>>> is what I call the 'Oven Controller Board'. With the removal of 3 >>>>> >>>>> >> screws >> >> >>>>> and the 'nut' on the 'COARSE' frequency adjust, the 'Oscillator Board' >>>>> >>>>> >>>>> >>> can >>> >>> >>> >>>>> be removed. >>>>> >>>>> I have 'derived' the schematic from inspections of the 'Output Board' >>>>> >>>>> >> and >> >> >>>>> the 'Oscillator Board'. I made no attempt at the 'Oven Controller >>>>> >>>>> >> Board' >> >> >>>>> since it seems to be operating ok. More on this below. >>>>> >>>>> I have attached the schematics of the output board and oscillator >>>>> >>>>> >> boards. >> >> >>>>> >>>>> >>>>> >>>>> >>>> I >>>> >>>> >>>> >>>> >>>>> made some measurements of DC and RF voltages on the output board. I >>>>> >>>>> >> have >> >> >>>>> multiple pictures that are too large to attach. If anyone would like >>>>> > to > >>>>> >>>>> >>>>> >>>>> >>>> see >>>> >>>> >>>> >>>> >>>>> these, I can send them. >>>>> >>>>> At start up, the 85-50 draws about 0.5A then falls to about 0.25A as >>>>> > the > >>>>> 'oven' heats up suggesting the temperature regulator circuit is >>>>> >>>>> >>>>> >>>>> >>>> functional. >>>> >>>> >>>> >>>> >>>>> The 'COARSE' and 'FINE' frequency adjusts work and the frequency can be >>>>> brought spot on as compared to my GPSDO. >>>>> >>>>> I have ordered new transistors in the hope that these are the problem. >>>>> >>>>> >> I >> >> >>>>> >>>>> >>>>> >>>>> >>>> am >>>> >>>> >>>> >>>> >>>>> a little puzzled by the drop in voltage at the 'Red' wire to the oven. >>>>> >>>>> >>>>> >>> It >>> >>> >>> >>>>> serves both the 'Oscillator Board' and the 'Oven Controller Board'. >>>>> > 2.5 > >>>>> >>>>> >>>>> >>>>> >>>> VDC >>>> >>>> >>>> >>>> >>>>> seems a little low for the oscillator. >>>>> >>>>> Also, the gain of the output stage of the output board seems a little >>>>> >>>>> >>>>> >>> low. >>> >>> >>> >>>>> 0.1 V P-P goes to 0.36 V P-P. >>>>> >>>>> I have a second, good, 85-50 but would like to avoid opening it if >>>>> >>>>> >>>>> >>>>> >>>> possible. >>>> >>>> >>>> >>>> >>>>> Any help would be appreciated. I hope I made no mistakes on the >>>>> >>>>> >>>>> >>>>> >>>> schematics. >>>> >>>> >>>> >>>> >>>>> Joe >>>>> >>>>> >>>>> >>>>> >>>>> -----Original Message----- >>>>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >>>>> Behalf Of Gordon Batey >>>>> Sent: Sunday, May 24, 2009 6:50 PM >>>>> To: time-nuts@febo.com >>>>> Subject: Re: [time-nuts] Broken Ovenaire OSC 85-50 >>>>> >>>>> I had an earlier model 20 mhx ovenaire osc that had very low output. I >>>>> opened it up with a scalpel and found the TTL chip had failed and was >>>>> >>>>> >>>>> >>> only >>> >>> >>> >>>>> letting a small amount of the osc signal thru. I was able to use an >>>>> external TTl (74LS20 I think) to restore it. As I recall I was unable >>>>> >>>>> >> to >> >> >>>>> readily get to the chip so I replaced it with an external one. >>>>> >>>>> Good luck. >>>>> >>>>> Gordon >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> 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. >>>>> >>>>> >>>>> >>>>> >>>> _______________________________________________ >>>> 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. >>>> >>>> >>>> >>>> >>>> >>> _______________________________________________ >>> 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. >>> >>> >>> >>> >> _______________________________________________ >> 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. >> >> >> > > > _______________________________________________ > 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. > > _______________________________________________ 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.