I have an Oscilloquartz 8601 which is an 8600 with a different connector. It had drifted low so I traced out the schematic and removed a 91 pf capacitor to retune it back to 5 MHz. Attached is my schematic. Note the following: 1. The value of L1 is highly suspect. It's a single layer toroid which appears to be wound on a clear plastic core. It's too small and delicate to touch so I'm not going to try to measure it. 2. The varactor is actually a 1N5456A. I didn't have a model handy for that so I used the MV2201. 3. C6 is the 91 pf capacitor that I removed. 4. All of the important capacitors are AVX CY series glass capacitors. Since they have a temperature coefficient of +140 +-25 ppm/C, the oven temperature will have a significant effect on the frequency. 5. C1, C4, R9, and L4 represent the crystal parameters. 6. This is an LTSpice simulation, but it doesn't work very well. It has trouble starting. It's worth noting that the oscillator itself takes a few seconds to start up. Ed On 2017-12-08 10:32 AM, time-nuts-request@febo.com wrote: > Message: 13 > Date: Fri, 8 Dec 2017 13:05:14 +0000 (UTC) > From: Ulf Kylenfall<ulf_r_k@yahoo.com> > To: Discussion of Precise Time and Frequency Measurement > <time-nuts@febo.com> > Subject: [time-nuts] End-of-Range: Oscilloquartz OCXO 8600-3 > Message-ID:<1997737810.1024399.1512738314970@mail.yahoo.com> > Content-Type: text/plain; charset=UTF-8 > > > Gentlemen, > We have an Oscilloquartz OCXO 8600-3that cannot any longer be adjusted into 5,000,000 Hz.It is about 1 Hz out of 5 MHz and turning coarse/fineadjustment potentiometers cannot bring the frequencyinto its specification. > Oven temperature is about + 80C accordingto the thermistor and the operating voltageis at 24 VDC. > Have Googled but the only thing that turns upis datasheets w/o any details. > Before I take it apart and start lookingfor obviously broken components, isthere anyone that has a CLIP on this unit? > 73