I came across this wobbulator project found in the British publication Radio Bygones and would like to build it (scroll down to page 12 to see the wobbulator article):

[url]http://www.epemag3.com/index2.php?option=com_docman&task=doc_view&gid=79&Itemid=38
[/url]

It looks like a fairly easy build. I've always wanted to do 'scope alignment on my SW receivers and thought this would be a very economical way to achieve it.

The challenge is finding some of the key components here in the US. From what I can tell, the Toko coil numbers specified in the article are either obsolete or peculiar to the British/Euro market. Can any of you solid-state guys translate the parts I’ve listed below into something available from Digikey or similar supplier? I came up with a blank when searching for the Toko part numbers. Here they are:

L1 RWO6A7752EK (green core)
L2 154FN8A6438EK (violet/deep red core)
L3 154FN8A6439EK (yellow core)
L4 KXNK3767EK (pink core)

Also, the varactor, KV1235 or KV1236, isn’t something I see at Digikey or Allied.

Appreciate any help! Thanks,

Tom

Are you talking about the little transformers with the colored adjustible cores that are found in a lot of transistor radios?

If so I think the color of the adjustible core denotes what type it is so transformers from an older transistor radio may work provided the cores are the same colors as what you need.

I wondered about that. But since the four listed inductors are meant for four different frequency ranges (per the article), I wonder if that's true. I just don't know enough about post-tube era electronics to really know.

Tom

The transistor radio coils are colored to differentiate the osc from 1st IF, 2nd IF etc... They are generally at 455Kc, can't be same as coils in article...


Tom

Here is some info on currently available miniature IF cans.

http://www.mouser.com/catalog/specsheets/114211.pdf

There are also oscillator coils (no internal capacitor) available. By breaking the internal capacitor with a small screw driver, you can extend the tuning range higher than 455 KHz. The internal caps are brittle ceramic and break easily.

Rich

The given source, JAB Electronic Components, still carries them although they warn quantities may not be available because Toko has ceased production of that line. It might be they have a similar thing in a more 'modern', smaller, form factor, or one could wind your own, except Toko doesn't seem to believe in 'public' spec sheets.

While a similar form factor the ones spec'd are NOT the familiar 'transistor radio coils. You can find the frequency, Q, and package number in the JAB listing.

On a quick search I couldn't locate a US distributor for the Toko coils but Mouser says NTE618 is a cross for the KV1236.

Thanks Flipper. Time to experiment, I guess.

Tom

I found data for one of them, the KXNK3767EK

http://www.gqrp.com/toko.pdf

Given the center frequency and data for that coil one could estimate the varactor capacitance (as well as from the voltages) and estimate the other coils. And, presuming the tap ratio is the same or similar, reverse engineer your own.

You can get adjustable coil forms here... https://www.amidoncorp.com/items/81
and
http://www.cwsbytemark.com/index.php?ma ... th=206_225

Hmm. Might be a bit beyond my limited technical knowledge and expertise. I could certainly build the project if I had the parts on hand, but reverse engineering ... I'm not sure. But I'll do some investigating and thinking. Thanks for the info and advice!

Tom

I never had more trouble trying to find information on what are supposedly common parts from a 'big name' manufacturer.

There apparently IS a 'catalog' with data somewhere, because I can find individual pages, but I'll be darned if I can find the whole thing and either there's no rhyme or reason to the part numbering scheme or it takes a cryptologist to decipher. At any rate, the best information is still at JAB, since the part numbers at least show up. The first three coils are from the "10EZ" series and the last one is from the "10K" series. I did find the Toko catalog pages for those two 'series' but none of the part numbers are listed in the "STANDARD COILS SELECTION GUIDE" for either. They're probably in another "10EZ" section, like maybe IF transformers, or who knows what, but since I can't find a WHOLE catalog it's pretty much moot.

At the moment I can think of only three options, other than forget it. The first is to reverse engineer as previously mentioned. Two would be to contact JAB and see if they have datasheets, or more information than their page shows, on the specific coils in question. Three is to buy them from JAB.

Tom, here are the questions that I would ask myself (and some answers) were I to consider building this thing:

Q1) Does my scope have a sweep output terminal? Not all scopes do. If my scope has no sweep output then I have two possibilities:

A1) This design is useless to me so I will go find another circuit that doesn't need a sawtooth input from the scope (they do exist).

A2) Research sawtooth oscillators and possibly build one into the unit. This can use a simple 555 IC or a unijunction transistor circuit. The sawtooth oscillator would then feed the sweep oscillator / wobbulator (we generally call them sweep oscillators here in the US). In addition, a sawtooth output would feed the horizontal input of the oscilloscope. (It gets a little more complicated if I add a blanking circuit, but if the sawtooth wave is clean then the retrace will be faint enough to not mess up the display, and I won't need a blanking circuit)

Q2) Do I really want to attempt to build a design that uses several un-obtainable parts?

A1)No -- I will look for another design that uses commonly availabe parts.

A2)Yes -- Perusing BDSM porno sites has made me a glutton for punishment so I will do the research / math necessary to reverse-engineer the design and search through parts catalogues to find parts with the necessary ratings. The basic specifications for the varactor diode are given in the article and can also be googled. When you know the minimum and maximum capacitance of the varacter you will use, you can use basic handbook/textbook formulas for resonance to determine the inductance needed for each coil based on its upper and lower useful frequencies. Then back to Digikey-Mouser-Whoever catalogs to search and search and search.

Q3) Will I find coils with the proper inductance value that are compatable with the PC layout?

Q4) Do I want to redesign the PC board?

Q5) Shouldn't these ropes be a little tighter?

Actually Tom, it is doable -- it will just take some effort to figure it out. Otherwise, if you are mostly interested in antique radio with 455 IF's then take a look at Alan Yates simple little unit -- AND it includes its own sawtooth generator:
http://www.vk2zay.net/article/93
I put some stuff that might be of interest here but just for a while: ftp://ftp.sonic.net/pub/users/amckenna/temp/sweepgen/ . Another very simple unit here: http://vintageradio.me.uk/radconnav/misc.circuits/ (sixth entry down)

Good Luck, Al

Flipperbone is correct, all the coils are listed at Jab:


http://www.jabdog.com/toko-ez.htm

RWO6A7752EK
154FN8A6438EK
154FN8A6439EK


http://www.jabdog.com/toko-10k.htm

KXNK3767EK

I'd just order from them if they are in stock, because reading another site, someone made one of these units in 2009, and also had trouble finding them.