Matthias I am afraid I am not much help here. I did look at the a19/20 interpolators. A lot going on in that small space. I guess i would check the 200 MHz feeding into it. The VCO is fairly simple in using a gate and a delay line. I will guess the delay line is coax. But there are all kinds of gates to control the system and Flip Flop used as a mixer. Not easy to deal with. Regards Paul.
On Sat, Jul 4, 2015 at 1:44 PM, Matthias Jelen <matthias.je...@gmx.de> wrote: > Dear Time-Nuts, > > I´m still struggling to get my 5370A to work reliable again. It keeps > showing error 04. > > Sometimes it is working without any problems for hours, sometimes it´s a > matter of minutes until the error is displayed, and sometimes I doesn´t > come up without the error at all. I don´t think it´s related to > temperarure, the usual procedures with a hairdryer and cooling spray didn´t > show any effects. > > I dug into this a bit. It seems like the startable VCO on one of the > interpolator boards isn´t working reliable anymore. The error stays with > the board, no matter if I put it into the slot for the start channel or the > stop channel. If the unit is in the non-working-state, there is no RF at > the output of the VCO. As soon the VCO oscilates, the PLL locks and > everything works fine, only the tuning voltage is a bit outside the range > given in the service manual. If the VCO stops oscillating, the tuning > voltage runs to it´s lower rail, just as expected. I opened the PLL loop > and tuned the VCO with a external power supply, this works as expected - no > regions in the tuning range in which the oscillator stops working or > similiar. > > I checked the signals going to the board, and they all look OK. > > I fooled the logic that detects a tuning voltage outside the allowed area, > and as expected, the error 04 isn´t displayed anymore, but also as expected > the unit still stops working. > > I pulled the board, removed some components and supplied power to the VCO > from an external power supply - same behaviour here. > > So I came to the conclusion that the VCO itself is defective, although I > have no idea what could cause a VCO to behave that way. > > Now for the strange part: A noble member of this list sent me a spare > interpolator board which was pulled from a working unit. This shows exactly > the same behaviour! Also at this board the tuning voltage is outside the > given window, and the oscillator doesn´t start from time to time. > > If a dead VCO module is a common problem, I´d expect that someone on this > list also experienced this problem before. Otherwise, I think it´s unlikely > that I found two defective interpolator boards in a row. I stil have the > feeling that I´m overlooking something simple. So `d be happy to receive > any comments on this. Also, if someone wants to get rid of a 5370 that > needs repair I might be interested. > > I guess this is what you can expect if your´re using test equipment which > was introduced before you were born, but it´s part of the fun... > > Thanks, > > Matthias > > > _______________________________________________ > 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.