Fleetwood model 4068... Advice?

[VintagePC]

...would be to reverse the connections to ONE of the coils and see if it oscillates.

D'oh! WE HAVE A WINNER!

Swapped the coil leads, and almost immediately found the sweet spot using the handheld. Followed it up and down the dial for a bit, then tried to find a station (plenty of squeaks and noise at this time...).

Found one, but it required cranking the volume about 1/2way and shoving the 'ANT' spade connector in to a 10 foot USB cable (which is currently masquerading as a radio antenna).

This was with the old tube, mind you; I did another check on the voltages while it's on a station, and it's now sitting at 106V... so as you suggest, the tube could indeed be weak. Will pop the other one in after it cools down to see if there's a noticeable difference. (Edit: Doesn't sound like a major difference to me... and the voltage on the new tube also reads 100 now)

I would have been willing to bet that I'd rewound the coil properly; I remember putting it on the end of a pen and pulling the broken wire off so that it unwound in an overhand fashion... and the current one is wired in the same way. (it will only go on the pen one way b/c of the lugs on one end.). Next step is to figure out if we match up with the dial; that'll have to wait until sundown when more AM starts coming in (and until I pop the chassis back in the case).

[electroking]

A night of BC band DX is in sight! Just have some fun, a poorly aligned radio is
much better than no radio at all...

Try for Radio-Canada in French from Toronto (860 kHz). Easy to identify
from the language, and should be a fairly solid signal. Bye for now.

[VintagePC]

Indeed. I played around with the set at about 10PM; there's a lot of AM DX coming in, especially in the higher frequencies.

I've run in to a spanish station, a station from NY, and ironically enough, one of the first I hit was an "oldies" station playing some '60s music... Felt like a time warp for a moment.

Wasn't able to find 860, but I'll try again tomorrow; I have 2x 50' pieces of unused CAT5 that will make for a nice antenna

I've set the dial indicator to run from the edge to edge of the dial, and some adjusting will probably be necessary; I found 1010 at ~90, but not entirely sure since some stations fade in and out.

[electroking]

The trick to get the stations in the right spots is to adjust the oscillator trimmer
(C2A) and the coil slug. This is described in the last two items of the alignment
instructions (numbers 5 and 6). They suggest using a signal generator tuned
at either end of the band, adjusting the coil at the bottom and the capacitor
at the top. As mentioned (item 7), these two steps will somewhat
interact and it is best to repeat them two or three times, until both ends
of the band are tuned with correct dial readings. You can identify two stations
that are near the edges of the band, and use them to do the adjustments.
You can finally perform item 8 (adjusting the trimmer on the other part of
the variable capacitor, C1) using a station that is near 1400 kHz. The last adjustment
does not affect the oscillator, and thus does not move the spot on the dial
where the station is received, but it peaks the resonance of the input circuit
to maximize the received signal strength.

I see you are getting about 110 kHz error near the middle of the dial, so you probably
did not goof in estimating the number of turns of the coil. Adjustment should
be possible.

Ideally, you would also have to do the IF alignment as described in items 1-3, but
that can be done without if you don't have the instruments. Good night.

P.S. You need plastic tools to adjust both the coil and the trimmer capacitor.
Usually, the coil slug needs a hex-shaped tool (Allen Key), you may be able to
carve a useable one from a soft plastic rod. The capacitor just needs a flat
screwdriver, again easily improvised.

[Reece]

Should be able to find WBZ Boston at 1030, they're a powerhouse. Other strong NY stations are WABC 770, WCBS 880. Of course, I don't know if their transmitting patterns shoot up your way. They are all pretty much news all the time and so identify quite frequently.

[VintagePC]

A stupid question perhaps, but where do I find the oscillator tuning slug? Is that in IF can #1? (if so, top or bottom?)

The alignment page refer to the "broadcast oscillator (L2) tuning slug, but there's nothing on L2 for adjustment.

I did run across WBZ, I think- FOX news?

Edit: Also, two questions:
1. Do the resistors have a major effect on tuning/alignment? I want to order replacements for all of them so I can do a decent job of the point to point wiring instead of the hack-job it currently is with clipped and soldered leads.
2. The set can run at wall voltage, versus the 117 it was designed for... However, will this unduly stress the tubes? If so, what sort of dropping resistor would I need? (so I can add it to this parts order)

[electroking]

Wall voltage should be fine. Tube heaters do increase in resistance when the
voltage goes up, so the added dissipation is less than could be deduced from
a simple calculation.

The coil tuning slug should be inside the cardboard form. Did you reuse the
original form or did you make one yourself? It may be lost due to the damage
you observed on the coil. Maybe you could find something compatible in your
junk box. You might also find a useable slug inside a discarded IF transformer.
The slugs in your IF transformers should not be disturbed.

I don't thinkg replacing good resistors is a great idea if the soldering is half-decent,
even though it may not look that good. Some of the parts in there (coil, IF
transformers, etc.) are too easy to break.

Pending the fix on the coil, you may start adjusting the oscillator trimmer capacitor
just a bit at a time, and seing how you have to readjust the tuning knob to get
back on the station. That will tell you which way to turn to move the oscillator
in the desired direction. Good luck!

[VintagePC]

Ok, I'll leave the resistors alone (but for $6, I'm still ordering a spare set just in case...)

There was nothing in the original cardboard form (which I re-used). You can see it in 1040.jpg ( http://vintagepc.co.nr/radio/IMG_1040.JPG - not posted in the build log b/c of fuzziness). That picture was taken as soon as the chassis came out of the set and the mouse fluff removed.

You can also see the inside of the coil is shiny; I would assume the slug was threaded for positioning; it looks like there may never have been one... (also note the schematic doesn't show the "adjustable" symbol on L2 like it does for the IF cans)

I should have something in the parts box; I know for sure that I have the core from an old antenna (that can be cut to size), but that's too long. Roughly what size am I looking for?

[Reece]

If there is no slug, then the oscillator would be adjusted with the trimmer capacitor screw on the small section of the tuning capacitor. Find a station at the high end of the dial that you know the frequency of. If you tighten the screw 1/8 of a turn, this will move the station up the dial. Turn the dial higher and find it. If you turn the screw out 1/8 of a turn, the station will move down the dial. Continue "walking" the station either up or down the dial, whichever applies in your case, 1/8 turn at a time, until the dial pointer is at the correct frequency.

Each little trimmer cap is in parallel electrically with its tuning capacitor plate section. Together they act as one capacitor. When you tighten a trimmer, its capacity goes up so to keep the same frequency the large cap plates have to open up more, and vice versa.

After you get the stations at the high end of the dial where you want them WRT to the dial markings using the trimmer, then on a weak station around 1400 or so (can be WAY down in the mud weak) peak it for max volume using the trimmer on the other, larger section of the tuning cap, which is the antenna section.

Holy mackerel, it just dawned on me that you rewound an oscillator coil, and made a pretty one per the picture at that. Ain't a whole lot of newbies to tube radios that have done (or would even try) that! That's the fun of this stuff to me: making something out of nothing!

[VintagePC]

Emmm.... you sure that's right? In my case, the smaller one is the one ID'ed as C1A, which is in the antenna circuit.

The larger one (more plates) is C2A, which is in parallel with the oscillator.

The alignment instructions also contradict you; they say to adjust C2A first (bigger) and C1A last (smaller) (then again, they also say to adjust L2, for which there is no evidence of adjustments ever having been possible).

Holy mackerel, it just dawned on me that you rewound an oscillator coil, and made a pretty one per the picture at that. Ain't a whole lot of newbies to tube radios that have done (or would even try) that! That's the fun of this stuff to me: making something out of nothing!

Awesome feeling, isn't it? Excuse me while I laugh maniacally while I power up the set, the lights dim, and lightning flashes in the background.... "IT'S ALLLLIIIIIIIIIVEEEEEEEEEEE!"

[electroking]

The instructions we have (see the second figure in post number 20) do call for
adjusting the oscillator at two points with both the trimmer cap and the coil.
The manufacturer may have dropped the adjustable coil in production, in which
case the oscillator would be aligned only at the high end of the band, and
some error would have to be tolerated at the low end.

Typically, you will find a hole in the chassis above the coil so the tuning tool
can be inserted from the top. Do you see the hole?

Note regarding the alignment instructions: I don't see any contradictions.
Items 1 to 3 refer to the IF alignment (which can be left out). Items 4, 5 and 6
are the steps for aligning the oscillator to get the stations on the right
spots, with 7 telling you to repeat 5 and 6. Finally item 8 is the peaking of
the input circuit resonator, using the trimmer on the RF section of the variable
capacitor, that is the section that is NOT part of the oscillator circuit. Regards.

P.P.S.: the variable capacitor section for the oscillator may be bigger or smaller
than the RF section, depending on the coil used. Tracing the leads to the proper
circuit (and also checking the labels C1/C2 on the alignment drawing) is the
best way to determine which section is which.

[Reece]

I've never seen a two-gang tuning cap where the oscillator section was larger than the antenna section. Doesn't mean it couldn't be. On some very older sets they were the same size.

You can easily find out: tune in a station at the high end and tweak the screw on the smaller gang of plates. The station should move either up or down the dial.

The schematic may not exactly match your set. Does this set have FM? Those would be the really small gangs with just a few plates. For AM I'm talking about the plates that look about like this: scroll down to the picture of the dual gang air variable, with trimmer screws on the side. I couldn't quickly find a picture of a typical cap with the oscillator section smaller than the antenna section, but they used to be the "standard" in most radios.

http://www.midnightscience.com/catalog5.html

[VintagePC]

Apart from # of plates, that's exactly what I have. Take a look at http://vintagepc.site50.net/site/ima...e/IMG_1025.JPG

You can see it there; it turns out you're right and there's an error on the tube layout diagram; the tuning caps are mislabeled there, which is what threw me off.

I now see this is not true; the yellow wire runs to the lug of the coil (thus smaller section) and the green wire is bridged by the antenna (2-wire flat cable you see)

Thus, BIG=antenna, SMALL=coil, and therefore REECE=correct.

There is indeed NO hole in the chassis above the coil; the only one is a fold-out pin to which the ground lug of the coil is soldered. (and it does not extend over the center of the coil).

[electroking]

Did you look for a tuning slug accessible from below? It may be hard to reach,
but alignment is a bench job rather than an 'in-cabinet' job. If you find no tuning slug,
you will have to do with a single adjustment point as discussed above.

You're right of course regarding the mislabeling on the instructions. The antenna
lead (flat cable) is connected to the rear section (C1 on the schematic but marked
C2 on the figure). Good luck!

[VintagePC]

Did you look for a tuning slug accessible from below? It may be hard to reach,
but alignment is a bench job rather than an 'in-cabinet' job. If you find no tuning slug,
you will have to do with a single adjustment point as discussed above.

Nada. I don't see any possible way to adjust the coil.

This may well be intentional because the alignment on the set has to be in-cabinet; the dial face is mounted to that as opposed to the actual chassis itself - if it's out on the bench, you can't see where you're supposed to be!

In addition, we've already found a few differences on the schematic and the actual set, such as the line (filter) caps/resistor values and loudness taps/caps on the volume control.

Taking a pot-shot, I'd say the 4068 model is based off the 2053 and is either a later run or intentional design change, resulting from component supply issues or so (but it was either short-lived or so similar they did not want the added cost of making new schematics/layout diagrams). I'd be interested to see whether the tuning caps are also mislabeled on a "true" 2053. (note they're also mislabeled on the sheet stapled to the inside of the cabinet).

I will re-draw the schematics with the additions and upload them to the build log when I make the next update. There's really not much new going on that's picture-worthy at this point, hence the long delay in updates.

Also noticed that there's some rust on the magnets at the back of the speakers... worth worrying about, or no? It just looks like a small surface coat, not like the whole magnet is disintegrating.