Emerson 668 b

[stromberg67]

Found an Emerson 668B at our museum, and for a donation got it. The original 14BP4 has very good emission, and the overall condition is very good. Of course it will be re-capped and cleaned, and aligned if needed. Nice little table model that fits in with the rest of the collection. Info in SAMS 125-6.

[Username1]

Very cool ! !

I like Emerson !

Keep posting as you go ...

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[stromberg67]

Thanks username1. It's going to be interesting. After removing the mouse house, I found that the mouse didn't do too much damage beyond some insulation on one wire, and a peaking coil, 21 ohm, 663 uH. Can't seem to find those, and am wondering if someone could suggest a source. I've already tried Mouser, Digikey, and MCM. Must be a source as the folks doing early color use them.
Anyway, the chassis is in very good condition. Hope to have it up in a couple of months because the summer is looking busy otherwise.
Thanks for any suggestions about the coils.
Kevin

[Username1]

Well I don't know where you might get a coil if you have already looked at
the usual sources..... Don't forget ebay..... You may just have to re-wind
and repair what you have..... But anyway good luck and keep us posted !

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[Electronic M]

Depending on the circuit it may not matter what the resistance is, and even if it does if you buy a lower resistance part you could probably add a series resistor to get the same effect as the original.

[Kevin Kuehn]

I got one of these same sets two winters ago. Started on it, but then got distracted with cleaning out my folks house. So I'll enjoy watching you bring your set back to life. It's a nice looking set.

[wa2ise]

Originally Posted by stromberg67

... and a peaking coil, 21 ohm, 663 uH.

Usually, peaking coils are a resistor and a coil wired in parallel, they usually wrapped the coil around the resistor. But you don't need to, just use a 22 ohm resistor and a 680uH coil connected in parallel to create a new peaking coil.

[stromberg67]

Well, the re-cap is almost done. and I've found something a "technician" did years ago: installed a 3 amp slo-blo fuse where a .25 amp fast blow belongs, in the horizontal output circuit. No apparent physical damage, and the 6BG6 tests as new. Shorted input cap in power supply, as expected, and all three cans have been re-stuffed. Going to mine a CTC-7 parts chassis for a peaking coil to use until a correct value can be obtained, 620uH to replace a 663uH, with the correct resistor in parallel for now.
Kevin

[stromberg67]

Fired up the chassis today and obtained great audio and no smoke. Still need to
replace three caps in the horiz output section that are most likely the cause of the .25 amp fuse blowing. Taking it slow and careful, as some of the components are difficult to get to.
Kevin

[stromberg67]

Having scoped the video and sweep circuits, I've confirmed that most all waveforms are just about right-on. Also found that a mouse had chewed on the horizontal oscillator coil, opening the windings. Going to post a WTB in the classifieds for an Emerson # 716052 osc. coil, JW Miller # 6212, and a # 738037 horiz. phasing coil, JW Miller # 6314. Also need a 630uH 21 ohm peaking coil, # 708115. Found a part at Allied, but don't need 500 pieces.
Darn mice!
Kevin

Update: Found the needed parts at VETCO Electronics, which has a number of NOS JW Miller parts. Hope this can help others looking for such items.
vetco.com
Kevin

[stromberg67]

Update: all the sweep caps and the synch peaking coil are replaced, and as many know that can be a hassle in a "layered" chassis. Now will install the replacement synchro-guide tapped coil. One question about that: the schematic and the replacement coil spec sheet do not indicate which side of the center tapped coil go where. After consulting an RCA schematic for the CTC-11, it looks like the higher resistance winding goes to the plate of the oscillator, and the lower side, after the center tap, goes to the grid. Can someone offer guidance on this please?
EDIT 7/10: it actually is the other way, low to plate, high to grid.

I've been fortunate to find on ebay a Wallace's Telaide with the waveforms, etc., but don't know if it would have the resistances of each winding noted.

Anyway, I'll go ahead and connect it up according to what I've found, and just proceed carefully. Not the easiest chassis to work on, but if all goes well I think I'll have a decent TV on which to watch B/W programming.

[stromberg67]

Installed the new horiz osc coil, and applied power slowly for low B+. The oscillator came up with a good waveform, but still no HV at full PS voltage. Going to check the output stage and associated components, but at least the new coil functions.
Also, a good use for cheap/free meters from Harbor Fright.

[stromberg6]

After much hair pulling, and a welcome assist from a fellow TV nut, I've been able to get some OK pics from this TV. There are still issues with horizontal drive, and AFC, but it isn't blowing fuses, and the 6BG6GA is only slightly red-plating. Drive makes no difference in the red-plating, so I just let it stay on.
Horizontal fold-over is evident at the left, and i suspect the power supply needs more investigation. At least it makes a picture.
Kevin

[Marco-nix]

Nice find Stromberg...they are very rare in Canada.. we can find some plastic Emerson ( end of 80's ) but not like yours..

[stromberg6]

Thanks for the nice comments all.
Saturday night I poured myself a nice big cold drink, and connected three meters to the main power supply points, turned the TV on, and sat back and watched for a while. As expected, the pic started to bend at the left top after about a half hour. The meter readings were strange. I started to adjust the various user controls, and found a "sweet spot" with the contrast control where all voltages became "normal", and a decent pic was obtained. Suspecting the 6AC7 video output is gassy, or maybe some other defect. All caps replaced, and out of spec resistors also. Many resistors were well within spec, which I found strange but gratifying. I'll pull out another 6AC7 from stock and see what happens. Maybe I should stick to RCA's .
Kevin