Fleetwood model 4068... Advice? - Page 2 - Videokarma.org TV - Video

VintagePC · #16 05-15-2010, 03:10 PM

I think we have a winner- that layout is a perfect match for what is stapled to the inside of the cabinet... (though I think my set uses something other than 12AX7s... I _think_ 6AUsomethings... is that possible?
Does the AM-only offer any indication as to year, or no?

VintagePC

electroking · #17 05-15-2010, 03:23 PM

The year would be also 1962 (RCC supplement No. 58), in fact the two schematics
I posted may have been on the market at the same time. Many areas in Canada
at the time had no FM at all, so a cheaper AM-only chassis was a good selling
argument.

If I may add a few comments, I would say that this is a fairly good introductory
project to tube radio restoration: the radio part of this unit is as simple as it
gets while remaining useable for listening, and the amplifier should be reasonably
good (with negative feedback as it is), although you should not expect tremendous
bass from such small output transformers. The negative feedback is effected
by resistors R40 and R41.

If you have a working AM radio (a car radio would be best for this), do some
listening after sunset (or before sunrise), you should get a number of stations.

You may be right in assuming that the audio stages before the outputs are
somewhat different from the schematic, this will have to be confirmed. Note
that in the schematic, each 12AX7 is part of both channels, so if one
of these tubes is shot, no sound will come out.

I look forward to the under chassis pictures. Bye for now.

VintagePC · #18 05-15-2010, 03:35 PM

interesting... very interesting indeed- the only reason the set has stereo then, is for the phono. (though since the pickup is ceramic, I'll probably look in to getting a magnetic one with a pre-amp... don't want to damage those vynils....

A quick google shows that the 6AU6 seems to be half of a 12AX7...

Also, any chance you've got a dial stringing guide or just a "common" stringing method to try? I know it's usually 2 turns around the tuning cap and 3 around the tuning knob... unless there's a piece of dial string missing that should just about do it.

Thanks!

electroking · #19 05-15-2010, 03:43 PM

You got it wrong here: a 6AU6 is a pentode, while a 12AX7 is a dual triode.
One half of a 12AX7 would be a 6AV6, which also includes a pair of diodes.

Also, a 12AX7 has a 9-pin socket, while a 6AV6 would have a 7-pin socket.
So just pull those two tubes in front of the 6AQ5s and count the holes...

Sorry I can't help you with the stringing, there are just two many different
ways it is done. Unfortunately, the diagram is not shown for this model in
my service manual, but when you can post a clear front view of the front
of the chassis, showing the tuning shaft, the pulley on the variable
capacitor, and the pointer on the dial, maybe someone else could provide help.

Regards.

P.S.: I looked at your picture again, and those two tubes do indeed look
like 6AU6s! It is indeed possible to design a single pentode audio stage to drive
a beam power tube, but that would be somewhat different from the schematic.

electroking · #20 05-15-2010, 04:15 PM

Hello again,

I did a thorough search of the Fleetwood data in my collection of RCC
manuals, and I believe this will be the closest we will get to what you
actually have on hand. Somewhat simpler amplifiers, but still an
interesting project. This is from vol. 53, 1961.

VintagePC · #21 05-15-2010, 06:24 PM

right you are- I mis-read the post; that user was also misinformed and asked whether a 12AX7 could be replaced with two 6AU6s. (Later corrected as 6AV6s)

's what I get for not reading the whole thread.

I'm almost certain the tube layout diagram is the same now- I'll get out the tripod and get you guys some less hasty (and well lit) pictures tomorrow, including the record player. I hope to log the restoration and add it to my web site for everyone to view.

I'll be keeping this thread alive as I go through various stages of restoration, asking for advice and posting pics- I'll start by giving the tubes a thorough inspection (and check the filaments with a DMM) before I go any further. They all look to be original Fleetwoods- fingers crossed!

I plan on restuffing all of the caps, just for the hell of it; I love old hardware and authenticity- . One of my Commodore 64 still has the "Warranty sealed" sticker on it and is in near pristine shape.

We have exactly one AM radio station left near enough that I should be able to receive... classic and modern country; at least it's not talk.

What are the chances that the chassis is cadmium coated? It's not oxidized at all (and you can see rust around the power cord)- my bet is steel.

I'll also have to replace the line cord- the prongs on the existing one are more crooked than a 419 scam

Many thanks for all the help so far and in the future - "May your tubes always light!"

VintagePC (and radio!)

VintagePC · #22 05-16-2010, 10:47 AM

OK, just finished cleaning out the bottom of the chassis and got a good look at everything:

- It is an AM setup. Oddly, the dial has three settings: Phono, Radio, and Stereo.

- There was a sticker on the chassis that said "2053" so we have the right schematic. 4068 is probably the cabinet/overall design.

- All tube filaments check good with a DMM.

- I'll get some decent pics as soon as my camera batteries finish charging.

- Components look almost new! The caps say "Plasti-seal" and don't appear to be covered in wax... rather a heat-sealed plastic. Thoughts?

- Speaker cones are in pristine shape... surprised the mice didn't get to them!

- Phono cartridge is invertible... for slow/fast records.

VintagePC

Reece · #23 05-16-2010, 11:54 AM

Hi, looks like an interesting project. Just a couple of notes: the function switch probably connects the cartridge left/right outputs together in "phono" position: there were still plenty of monaural records around in 1962, as stereophonic records only came out in 1958, and for a number of years both stereo and mono records of the same issue were sold, the mono being a little cheaper. A stereo record played with a mono cartridge would be damaged.

As to your dial cord, if you need new cord, look in your fishing tackle box, or that of a buddy, for some of that woven line. It's strong and should work fine. Not the monofilament line.

VintagePC · #24 05-17-2010, 05:55 AM

More pictures posted at the above link. (#s 39-46)

A couple of things to note:

- Sorry the second chassis shot is fuzzy- It looked sharp on the camera screen. The camera must have focused on a shiny bit.

- The cabinet appears to be solid oak (!!) and some crappy paint-on plastic veneer. They didn't prime it, so the veneer is peeling off everywhere. (and beyond recovery). I plan to strip it with a cabinet scraper and use some varathane 1000 on it.

- I've started cleaning and oiling the turntable (oil for motor-driven parts, lithium grease for mechanical linkages etc.). You can see this in some of the shots. The guy that painted the cabinet couldn't even be bothered to take care- there's brown paint everywhere (including on the knobs!)

- Can someone refer me to some info on the cartridge on the turntables? It is a BSR turntable. More specifically, which of the two stylii to use for what.

- Some of the detail paint is in poor shape- the gold lettering on the turntable controls, and also the "fleetwood" logo on the tubes (but not the other markings) wipes off at the slightest touch. Not a biggie, but I think at least something should be done about the control lettering.

Thanks for the dial stringing info- I was aware of using fishing line; has anyone had success with waxed dental floss as a temporary fix?

electroking · #25 05-17-2010, 09:50 AM

Microgroove or LP stylus is for 45s, 33 LPs.

Standard or 78 stylus is for 78 RPM shellac discs (manufactured until the late
fifties in Canada, early fifties most everywhere else).

Will have a look at your pictures, I am quite busy this week. Bye for now!

VintagePC · #26 05-17-2010, 11:02 AM

Thanks for the info- I'll have to look in to it some more, since the little flip-switch cover is missing; there's no indication which tip is what.

(Time to take out the microscope and look at the tips... which would also show how worn they are!)

It seems the turntable is a BSR UA-14. Some googling reveals that:
a) these typically had TC8M cartridges, and
b) if that is the case, we have a crystal cartridge on our hands.

As such, it is very likely that the crystal is dead; I might well look in to replacing the cartridge with a magnetic one to save wear on the discs. (I know I'd need a preamp, re-balance the tone arm, yada yada yada...) Ugh, not something I want to think about now.

What's more, the TC8M appears to be MONO! This would make sense, since there are 4 leads running through the tone arm, but one of them is not connected to anything... seems the "stereo" in this set was nothing more than snake oil, unless the audio outputs share a common ground. Probably sold as "stereo capable" or some such, requiring an after-market upgrade.

Edit: Yup, crystal:
http://www.hupse.eu/radio/reproducers/TC8S.htm

AUdubon5425 · #27 05-17-2010, 02:30 PM

You could sub a ceramic cart of the same output voltage and not worry about building a preamp circuit, although that's not particularly hard to do. Personally, on a unit like this where I would be playing old records (especially 78's) I'd stick with ceramic because of the many different record equalizations in use until the late 1950's.

Reece · #28 05-17-2010, 02:36 PM

If you need needles or a new cartridge, the folks at Canadian Astatic (I have no connection, just have bought from them) are very helpful. You can send the model number of your set and all the numbers off the cartridge and they can match it from their vast store of information and parts. Upgrading to a magnetic (with preamp) might be possible, but depending on the capabilities of the changer, tracking at as low a force that you'd like might not work. Changers generally take more tracking force than manual turntables because they are dragging around all of that mechanical baggage to operate the changing mechanism.

http://www.canadianastatic.com/

VintagePC · #29 05-17-2010, 03:43 PM

Errr... wha?

I thought the tracking force was the amount of pressure the tone arm has on the LP.

What has that to do with the force of the motor driving the mechanics? (We have a nice Dual w/ Shure mag pickup in the main setup, and it has a changer spindle too).

Let me go get some detailed snaps and post them...

Edit: Styli are TC8G and TC8RS... Apart from some dust, they still look to be in good shape (pics coming...)

Reece · #30 05-17-2010, 05:09 PM

Sorry if I confused with motor power: what I was getting at has nothing to do with that. The tone arm in a changer does not have the complete freedom of lateral movement like a fully manual turntable. There are mechanical connections under the changer base from the arm to various parts of the mechanism to trigger the various change functions. The result is the arm has more work to do than just track and play the groove and there's more resistance to lateral movement of the arm. The only force that moves the arm to the center of the record is provided by the needle being held in the groove. The resistance to lateral movement has to be overcome by more tracking force to hold the needle in the groove. Too little a force and the needle jumps out and won't track. The better changers (like your Dual) have more refined mechanisms and can go lower in tracking force. Do you know the tracking force of your Dual? I would suspect the changer in your Fleetwood would require a couple or three grams more to track successfully. Hope this didn't go on too long!!