Fleetwood Constellation Restoration Thread

[cbenham]

Originally Posted by VintagePC

Okay, here's where I'm going to need some info from the more experienced folks.

I had a look at the TV chassis and schematic to double check that it matches before I go ordering parts and find out there's a major discrepancy

There's one thing I found that is off - in the schematic, V8 is marked as a 6W6 and has the first audio stage coming in on pin 5. However, in the chassis, this is wired to pin 6 of the socket, and I found not a 6W6, but a 6V6 instead.

A quick search says they're pin-compatible but not exactly interchangeable, any thoughts on this?

There is no connection to pin 6 on either the 6V6 or the 6W6. Pin 5 is the control grid in both tubes. Sometimes pin 6 on the socket for these tubes is used as a tie point for a resistor or a cap to pin 5, just for the sake of convenience.
If the output transformer is original it may have a 2K to 4K primary impedance, great for a 6W6 but NOT for a 6V6. The 6V6 wants a transformer with a primary impedance of 5K to 6.5K.
Also a 6V6 used with a 2K to 4K transformer will make lots of nasty sounding distortion.

Hope this helps get pretty sound from this set.

[VintagePC]

Thanks for the extra info, it sounds like it could well be a problem in certain conditions.

Looks like only the VBO transformer is non-original, the others all look as though they are. I'll take a meter reading once I get a chance and post back here.

Edit: D'oh... impedance. I might have a meter that does that. have to look and see.

[electroking]

If you measure the primary impedance, be sure to have the speaker connected...

I trust the most likely reason for the 6V6 in the audio output socket is that whoever
installed it did not have a 6W6 on hand, and thought the 6V6 would work. Once again,
be sure that the cathode current on that tube is OK, otherwise much of the circuit
will be disturbed. Bye for now.

[VintagePC]

Originally Posted by electroking

If you measure the primary impedance, be sure to have the speaker connected...

I trust the most likely reason for the 6V6 in the audio output socket is that whoever
installed it did not have a 6W6 on hand, and thought the 6V6 would work. Once again,
be sure that the cathode current on that tube is OK, otherwise much of the circuit
will be disturbed. Bye for now.

Yes, I'll definitely keep a watch on that. I'm seeing that the line from that staged supply is going to the vertical section as well... I wonder if these things are all interrelated - someone goofed and put in a 6v6 for the audio, and then thought "huh, the vertical is off" and the tech replaced the VBO transformer because the staged supply wasn't immediately obvious?

I have to look around some as none of my general use stuff measures impedance but I found a vintage meter amongst my things and I'm hoping that at the very least it is a VTVM... Very possibly I'm mistaken but I thought I saw impedance functions on it as well. I didn't give it a second thought at the time when I found it but now I'll have to dig it up again and see whether it might aid me in my restore.

[VintagePC]

Got my caps in yesterday and have been working on the radio section.

Looks like it's been rewired for a 5Y4 when the schematic calls for a 5Y3.. Interesting given the 5Y3 seems to be more common.

Recap on radio part is complete, am going to try a careful powerup later today after double-checking I've got the 'lytics in the right way round... Power transformer is good, kicks out ~600VAC (center tapped 300V, this is leg to leg), 5VAC and 6.3VAC with the rectifier pulled, all tubes light up. Will need to source a replacement dial lamp at some point though...

If it cools down a bit I may start recapping the TV chassis... right now it's blistering hot and I don't fancy slaving over a soldering iron to boot.

[VintagePC]

First powerup results look promising. Nothing caught fire or exploded, so we're off to a good start

No AM reception by the looks of it. I get quite a bit of hum from the speaker at either end of the dial, and it quiets down in the middle. Hum disappears on other inputs (SW/Phono) so it's probably not a power supply filtering problem.

I can pick up some stuff in shortwave mode though, so it would seem that the amplifier region is working and we can narrow it down to the circuit region(s) involved in AM.

Will take a poke around inside and see what I can find.

[Edit: Nothing interesting. All the SW/BC switch does is switch out the coils and trim caps; those aren't shorted or open circuit (as appropriate) as far as I can tell. Logic tells me I'm now either facing a poorly performing tube or the AM alignment is way out of whack. Time to scrounge up a signal generator, I think...]

[VintagePC]

One question though - I noticed the flyback donut coating is cracked and rather brittle. What do you recommend to patch it up? I should have some friendly silicone (as in non-acetic acid producing type) floating around, but if I can't find it I'll be off to the hardware store...

Started my recap on the TV chassis, quite an adventure and it looks like the vertical section has had a major bodge job done on it way back when - wrong value control amongst other things. I'll keep that in mind if I see vertical problems after the recap, but I'm going to assume it was working as modified first. Parts look to be about as old as the set, so it's not recent.

[Electronic M]

I generally don't bother recoating a flyback unless there is arcing or corona coming off it after the HV starts working. Most flys are double hidden by a cage, and the back of a set so if they look crummy it is not like anybody will know. When it comes to electronics there is a very low correspondence between looks and ability to function properly...I've seen perfect looking parts be shot, and shot looking parts work perfectly...

[VintagePC]

Originally Posted by Electronic M

I generally don't bother recoating a flyback unless there is arcing or corona coming off it after the HV starts working. Most flys are double hidden by a cage, and the back of a set so if they look crummy it is not like anybody will know. When it comes to electronics there is a very low correspondence between looks and ability to function properly...I've seen perfect looking parts be shot, and shot looking parts work perfectly...

Ok. It was a preventative measure I was planning on, I figured once they start arcing the damage was already done and I was hoping to prevent it.

[Electronic M]

Arcing to external points takes a while to pose a threat, but don't let it go too long. Internal to internal arcing is usually harder to notice let alone cure and tends to mean the fly is on it's way out. If internal to internal arcing takes a path outside the fly (ie. you see a spark jump from one winding to another through the air) then that may be curable by recoating the fly, and should be done right after the condition is noticed to prevent damage.

[VintagePC]

Originally Posted by Electronic M

Arcing to external points takes a while to pose a threat, but don't let it go too long. Internal to internal arcing is usually harder to notice let alone cure and tends to mean the fly is on it's way out. If internal to internal arcing takes a path outside the fly (ie. you see a spark jump from one winding to another through the air) then that may be curable by recoating the fly, and should be done right after the condition is noticed to prevent damage.

Good point regarding internal vs external arcing. Though if the fly does end up being bad with no easily found replacement, I think I'd source some fine wire and try my hand at rewinding it just to say I tried. If it works, bonus Maybe overambitious but my 4068 track record of 1 for 1 at rewinding doesn't exactly deter me yet.

[VintagePC]

Finished my recap yesterday night. Was definitely a challenge getting at some of the caps, but it's all done and I've double-checked my electrolytic polarity already

Probably going to assemble a dim-bulb tester w/isolation transformer (have parts, just not assembled) at some point over the weekend and will try for a powerup after that. May give the chassis a good cleaning/polishing before I reinstall the CRT though since it is easy to get at now. Fingers crossed!

Any additional recommendations to beware of for a TV newbie besides the standard monitoring of B+/bad noises/smells/don't burn the CRT if no horizontal or vertical, and the staged supply mentioned earlier? (I've done a tube radio before and am familiar with basics, and have watched all of bob andersen's stuff, just not whether there's anything particular about this chassis design to beware of. I do know the risks/safety for HV, line voltage and hot chassis stuff.)

[VintagePC]

IT'S ALIVE!

First powerup today, nothing caught fire so I wired up the cable and switched her on. BOOM, picture and sound first try! (Will edit post and provide a picture in a little while, camera is on charge right now)

A couple of things need doing though... and I'm not sure where to begin on some of these... Any advice?

1. B+ seems a little high. Schematic calls for 260V, I'm getting around 310 with the variac at 95%.

2. Am hearing some soft ticking coming from the HV area. I think it may be a bad HV cap connection as I lost HV after nudging it while the set was off. Will investigate further.

3. On switch-off, vertical and horizontal collapse as is expected... but there is a REALLY bright spot left over gradually expands and fades away over about 30 seconds or so... this seems far brighter and more concentrated than seems healthy, and something I do want to resolve asap before I run the set too much more for testing.

4. Vertical height is about 75% of the screen space with the control at maximum. Probably something to do with the bodge job on that control. Again, something I need to investigate after #3 is done.

Good start though, I can smell the victory coming!

As promised, here we go:

[Electronic M]

Originally Posted by VintagePC

IT'S ALIVE!
A couple of things need doing though... and I'm not sure where to begin on some of these... Any advice?

1. B+ seems a little high. Schematic calls for 260V, I'm getting around 310 with the variac at 95%.

3. On switch-off, vertical and horizontal collapse as is expected... but there is a REALLY bright spot left over gradually expands and fades away over about 30 seconds or so... this seems far brighter and more concentrated than seems healthy, and something I do want to resolve asap before I run the set too much more for testing.

4. Vertical height is about 75% of the screen space with the control at maximum. Probably something to do with the bodge job on that control. Again, something I need to investigate after #3 is done.

Congrats! Looks like you did a good job.

1.) Adjust the voltage from the variac to what the schematic specifies as the line voltage present when the authors of it took their chassis voltage measurements if the B+ is within approximately + or - 20%(I probably would not worry if it were within 30%) of the listed B+ you should be fine. The grid in many rural parts of the USA(and I'd guess Canada too) were not designed for loads such as many large kitchen and home appliances, and at different times a day the grid(and thus the B+ which varies in direct relation with the power grid) could be below 100V or well above the 117 that was the common standard then....TV makers were aware of this and made sets which could tolerate a fairly wide range of power grid voltage. If your set's B+ runs more than 30% high when plugged directly into a wall outlet then I'd do something to lower the voltage coming in. A few things you can do to lower the power grid voltage reaching it(that don't involve tying up your variac constantly) are to use a 100'+ long extension cord(it's resistance will lower the voltage some) or get a 120V to 2-20V stepdown transformer and wire it up as a line bucking transformer(there are threads on this if you search).

3.) This could be normal for this model... You may be able to dim of suppress the spot by adjusting brightness or contrast after shutoff. I have sets that do this which are fine, but there is one where there is a small black dot in the center of the screen where this effect burned the phosphor clean off at some date prior to my ownership of it. There are threads and IIRC even vintage electronic magazine articles on how to modify sets to not produce the spot.

4.) Look for out of tolerance resistors, wiring mistakes, and test the tubes. Some sets(Muntz was infamous for the degree to which this applied to them) will sort of work with tubes that test in the lower end of good, but only work well with a VERY strong example of a given tube type. You may need a tester and a source of several samples of the given vertical tubes, from which to choose the strongest, in order to get enough oomph to get the vertical to fill. Running the set with high B+ should also help with shrunken vertical.

EDIT: BTW the program you have on looks to be a letter boxed program(google that if you don't know that term in this context) letter boxed programs naturally don't fill the screen vertically so when adjusting the screen use a native 4:3 aspect ratio test pattern or program. Despite the program being letter boxed I can still tell the vertical is too small because the two horizontal Closed Captioning dashes well above the rest of the image, which should be JUST above the the top of the viewable area of the CRT, can be seen on screen.

Good luck!

[VintagePC]

Thanks for the reply. Last I checked having the variac around 90% gave me the recommened 117V, but that was a different location. Will re-check and decide what to do. It's not so much the operating B+ I'm concerned about as the initial jump up which goes to 400ish volts when the caps are rated for 450. Probably still okay but I like large safety margins
I am familiar with the transformer trick to drop line voltage, IIRC you anti-phase the primary with the secondary and drop the total voltage by the amount the secondary is rated for.

I'll also see about some circuitry to kill that dot; perhaps it is normal but I'm pretty sure it's way too intense to be good for the phosphor... and that's with brightness and contrast at minimum when I shut off the set.

Edit: What kind of keywords should I be using to locate a circuit to fix this? I tried a few things that immediately came to mind but I'd imagine there's a specific term I don't know that would help immensely... and I did try "afterglow" without much luck) Could it be cured with an appropriate resistor to bleed off the HV quickly at poweroff?

Edit2: seems like the magic words are "spot killer". Mostly patents and unhelpful passing references, but this gem did turn up:

Originally Posted by wa2ise

I think all you really needed to do to build a spot killer was to bypass to B+ the brightness line feeding the CRT grid 1. This in sets that fed the video into the CRT cathode. SO when the set was turned off, the B+ would collapse, and the bypassed grid would be pushed very negative, cutting off the cathode. and the cathode cools off by the time the time constant of the cap and resistances around it bleeds off charge.

Looking at my schematic I think I do have a cathode-driven set... so what type and size of capacitor would I be looking at?

Edit 3: More looking at the schematic... looks like G2 is AC coupled to B+ already... which would presumably achieve the same effect vs G1. The spot doesn't immediately appear when power is killed... the raster collapses and fades but then the spot comes back. Perhaps upping the value of this capacitor (C70, .03µF) would do the job?

Will venture into vertical height land shortly. I don't _think_ there's a miswire as it all made sense when I was verifying the schematic against the chassis and hunting caps to replace... but you never know. I very much suspect it's related to the replaced VBO and height control bodge job though; the control is definitely the wrong value called for in the schematic and some other resistors in that chain were replaced too because I noticed they didn't have a full 360° wrap around the lugs like the factory ones do.

On that note... is it a good idea to run these sets tilted on their sides for access to the underside while working? I recall reading that it's generally not good since it means any sag in your filaments will result in a heater->cathode short.

Last thing for now... I pulled 3 bumblebee caps from this set... are audiophiles still going nuts over those? If so... where's the best non-fleabay place to sell them?