Hi There often are series resistors / inductors ahead of the power bricks in all these designs. I have found several of them fried. After replacement, everything seems to work ok. I have no idea why they cook out, but they do…
Bob On Nov 16, 2012, at 2:50 AM, Charles P. Steinmetz <[email protected]> wrote: > Bob wrote: > >> I've heard much talk in this group about the power supplies on the Z3805. >> * * * my Z3805 * * * started producing a real bad smell after a >> few hours, the classic burnt transformer type. * * * I opened the >> unit and found the 25W 5V, +/-15V (made by AT&T) was real, real hot. >> >> Is this the supply driving the heater inside the 10811? > > There appear to be quite a number of different boxes available labeled > "Z3805" these days, so information you get may or may not apply to the > particular unit you have. My Korean-made Z3805A takes nominally 24-27 V DC > power and has a dual-oven 10811 OCXO. I presume -- but do not know for sure > -- that the ovens run from the raw DC supply, not from a DC-DC converter. > > If the smell did come from the DC-DC converter block, it suggests a failure > either in the converter itself or in the circuitry that is powered by the 15 > V supplies. I think the former would be more likely -- the converter should > have internal protection that would step in before it got hot enough to > smell, in case of a load fault. > > A failed oven controller in the 10811 could also produce a burnt smell. > > Whatever it was, it will very likely give a repeat performance at some > inopportune time, unless you chase down the trouble first. Not easy with an > intermittent fault, but particularly if it was one of the 10811 ovens acting > up, it would be nice to catch it before it happens again. > > Hints: (1) use your nose, up close. Does one part have a residual smoky > smell? (2) Look very carefully, using a magnifier. Does one part have ID > markings that look faded or scorched, or small cracks? Is anything leaking > out of the DC-DC converter? Also look carefully at resistors and polar > capacitors. > > Best regards, > > Charles > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
