Hello time-nuts, Well, broke out a PRS10 that I had put away for a project some time ago and upon power up found that it had issues. Status indicated low lamp output and high lamp temperature. Duh! Upon removal of the lamp assembly it became abundantly clear that the magic smoke had gotten out. If I recall correctly, seems like there was another PRS10 with corrosion issues in the same area. My guess is that the heat does not help this situation. I suspect that I may have a full-on heater, which may have caused the tantalum cap (and possibly other) failures. Looks like this may be the weak spot in these oscillators. I'm very hopeful that a rebuild will bring it back to life. Thought you would enjoy the pictures though. Two are attached. Regards, Skip Withrow <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b> Virus-free <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b> <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

Skip, Good pictures and yes the smoke did get out. Can't tell on the bulb is it cracked pr blackened. Other then that looks pretty repairable. Its interesting that they put a resistor near the excitation coil. Is that a way of getting feedback for oscillation?? Regards Paul WB8TSL On Mon, Jun 13, 2016 at 6:32 PM, Skip Withrow <skip.withrow@gmail.com> wrote: > Hello time-nuts, > > Well, broke out a PRS10 that I had put away for a project some time ago and > upon power up found that it had issues. Status indicated low lamp output > and high lamp temperature. Duh! Upon removal of the lamp assembly it > became abundantly clear that the magic smoke had gotten out. > > If I recall correctly, seems like there was another PRS10 with corrosion > issues in the same area. My guess is that the heat does not help this > situation. I suspect that I may have a full-on heater, which may have > caused the tantalum cap (and possibly other) failures. > > Looks like this may be the weak spot in these oscillators. I'm very > hopeful that a rebuild will bring it back to life. > > Thought you would enjoy the pictures though. Two are attached. > > Regards, > Skip Withrow > > < > https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b > > > Virus-free > < > https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b > > > <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > > _______________________________________________ > 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. >

Hi In a run-away oven situation, the solder generally looks a lot worse and the board is a lot closer to black than chocolate brown. Best guess - that magic tantalum isn’t up to the job they are trying to make it do. Bob > On Jun 13, 2016, at 6:32 PM, Skip Withrow <skip.withrow@gmail.com> wrote: > > Hello time-nuts, > > Well, broke out a PRS10 that I had put away for a project some time ago and > upon power up found that it had issues. Status indicated low lamp output > and high lamp temperature. Duh! Upon removal of the lamp assembly it > became abundantly clear that the magic smoke had gotten out. > > If I recall correctly, seems like there was another PRS10 with corrosion > issues in the same area. My guess is that the heat does not help this > situation. I suspect that I may have a full-on heater, which may have > caused the tantalum cap (and possibly other) failures. > > Looks like this may be the weak spot in these oscillators. I'm very > hopeful that a rebuild will bring it back to life. > > Thought you would enjoy the pictures though. Two are attached. > > Regards, > Skip Withrow > > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b> > Virus-free > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b> > <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > <prs10-1.jpg><prs10-2.jpg>_______________________________________________ > 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.

Bob, I would guess the tantalum was up to the job. But only for the first 7 years of its life. We tend to keep using things way past the intended life. Maybe a case of just replacing the cap and cleaning up the stuff it sprayed out when they burn like that. I have fixed a lot of test equipment that is now on my bench thanks to those caps. Kind of a love hate affair. Regards Paul. WB8TSL On Mon, Jun 13, 2016 at 8:13 PM, Bob Camp <kb8tq@n1k.org> wrote: > Hi > > In a run-away oven situation, the solder generally looks a lot worse and > the board is a lot closer to black than > chocolate brown. Best guess - that magic tantalum isn’t up to the job > they are trying to make it do. > > Bob > > > On Jun 13, 2016, at 6:32 PM, Skip Withrow <skip.withrow@gmail.com> > wrote: > > > > Hello time-nuts, > > > > Well, broke out a PRS10 that I had put away for a project some time ago > and > > upon power up found that it had issues. Status indicated low lamp output > > and high lamp temperature. Duh! Upon removal of the lamp assembly it > > became abundantly clear that the magic smoke had gotten out. > > > > If I recall correctly, seems like there was another PRS10 with corrosion > > issues in the same area. My guess is that the heat does not help this > > situation. I suspect that I may have a full-on heater, which may have > > caused the tantalum cap (and possibly other) failures. > > > > Looks like this may be the weak spot in these oscillators. I'm very > > hopeful that a rebuild will bring it back to life. > > > > Thought you would enjoy the pictures though. Two are attached. > > > > Regards, > > Skip Withrow > > > > < > https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b > > > > Virus-free > > < > https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b > > > > <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > > <prs10-1.jpg><prs10-2.jpg>_______________________________________________ > > 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. >

My guess is the burned choke is in series with the Tantalum capacitor. This is a very common failure mode for these Tantalum capacitors. There are a number of things that will cause this failure. 1). power supply ripple too high (Tantalum capacitors do not like ripple). 2). Moisture absorbed by the Tantalum capacitor. 3). Voltage rating of the Tantalum capacitor too close to the supply voltage. ie a 6 Volt capacitor used on a 5 Volt supply. The solution is to replace the choke and the Tantalum capacitor. Replace the capacitor with a higher voltage capacitor. A lot of high end test equipment is prone to Tantalum failure because the design engineer used the same Voltage safety margin for the Tantalum capacitor as would have been used for an aluminum electrolytic. The Tantalum capacitor requires a higher safety margin because the Tantalum capacitor will short (as you experienced) by a spike above the allowed for safety margin. An aluminum electrolytic will absorb the spike, the Tantalum might short. You should be able to recover the PRS10. 73 Glenn WB4UIV On 6/13/2016 6:32 PM, Skip Withrow wrote: > Hello time-nuts, > > Well, broke out a PRS10 that I had put away for a project some time ago and > upon power up found that it had issues. Status indicated low lamp output > and high lamp temperature. Duh! Upon removal of the lamp assembly it > became abundantly clear that the magic smoke had gotten out. > > If I recall correctly, seems like there was another PRS10 with corrosion > issues in the same area. My guess is that the heat does not help this > situation. I suspect that I may have a full-on heater, which may have > caused the tantalum cap (and possibly other) failures. > > Looks like this may be the weak spot in these oscillators. I'm very > hopeful that a rebuild will bring it back to life. > > Thought you would enjoy the pictures though. Two are attached. > > Regards, > Skip Withrow > > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b> > Virus-free > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=oa-2322-b> > <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > > > > _______________________________________________ > 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. > -- ----------------------------------------------------------------------- Glenn Little ARRL Technical Specialist QCWA LM 28417 Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178 QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license" ---------------------------------------------------------------------------