I need a 1-403-290-11 detector transformer which after 35 or 40 years is no longer available from Sony. It was used in the tuner section of many models. Unfortunately, the wiring is badly corroded so the transformer is not repairable. Among them (there may well be others):
You might want to post a query on the FM-tuners group on Yahoo (affiliated with the
formatting link
site). Lots of tuner collectors and tuner-repairers hang out there, and they may be your best chance to locate a parts unit.
From the look of the schematic of one of the models you cited, it looks as if the Sony transformer is essentially a standard one for a ratio detector, with a center-tapped primary and with a cap across the full primary winding (presumably to resonate it at 10.7 MHz, adding some amount of IF filtering). You might be able to adapt a more common ratio-detector transformer (if you can still find one, and if it has a center-tapped primary winding) by adding such a cap.
Unfortunately it looks as if ratio-detector transformers are pretty much unobtanium these days, at least on the new-parts market. Opening up and rewinding a 10.7 MHz IF transformer to add the extra winding and the resonating cap(s) might turn out to be your only solution, if you can't find one in a junked Sony.
Or, has had its internal series resistance increase to unacceptable levels; this would lower the Q of the resonant circuit, increase losses, and make it less effective as a narrow-bandwidth filter.
Can you blueprint it ? I mean make a drawing showing the connections and di mensions like a mechanical drawing ? If so I can look in my boneyard. I don 't have any Sonys lkike that but Marantz, Sansui, Pioneer, a few others. tr ansformers are usually made by transformer companies. Also, the chip that d rives it has an equivalent likely, finding tuners that use the equivalent m ight turn up the right part in a totally different unit.
It has two in the FM IF strip. But the OP probably has already confirmed on a scope that the IF signal is getting through. That's probably what led hi m to the problem.
There was an era when every one of those things was the same almost. Everyt hing but the Revox and you do not want to see the print of one. I can't fig ure out how the damn thing works ! Well actualy I can but it would take tim e, the Revox is an extremely sophisticated unit.
Anyway, Sony might have been the first one to use ceramic filters, because
Clevite had ceramic filters in the early sixties. I've seen articles that came out in 1964, and probably earlier.
I'm not sure how long they took to appear in products, and certainly the early ones I read about were for 455KHz, which of course was pretty useful so maybe that's all that got mentioned in hobby circles. Later in the decade they did appear in Japanese products, low end shortwave receivers and CB sets. There were mechanical filters made in Japan in that era (the ones that now need refoaming), and they did appear in some products, but the catalogs put them in more products than I'd expect (or rather, the products were cheap enough to be suspect), making me wonder if someone was mixing up mechanical filters with ceramic filters.
I have no idea of when 10.7MHz ceramic filters became common. Since FM was wideband, their selectivity wasn't needed like they were at 455KHz, so those might have arrived later, once the value of replacing a bunch of IF transformers (and the need to align them flat over a wide bandwidth) was seen as useful.
Even 1 volt DC on a ceramic resonator is enough to induce metalisation creep over the edge of the thinest element inside , given some time. Being 40 years old and/or dampness/condensation can induce it also, whether powered up or not, dissimilar metals and moisture providing the "DC". Easy job to remove them , well 3 pin ones anyway, and of course should show no DVM-R reading
This receiver was stored in humid conditions, and the glue (contact cement) that was used to hold wires in place inside the transformer attacked the wire coating and wire.
On this particular transformer it looks like there was a 'knot' of wires soldered and glued, possibly a factory repair when the transformer was made.
Regards, Tim Schwartz Bristol Electronics snipped-for-privacy@bristolnj.com
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.