Emerson 662 restoration

[Eric H]

I'm going to rebuild this set for my next project.
It has a rejuvenated CRT but it's holding well into the good range so I think it'll be OK.

My first question is about the knobs.
It was missing most of them, I thought they were similar to the 637 knobs but the cover of the Sams shows large round knobs with the numbers on them.
The cabinet however has a number plate attached to it which wouldn't make sense if the numbers are on the knob.

Either someone added the plate later (looks factory) or Emerson used two different styles during production.

Here are some pictures, the knob shown is from a different model Emerson and matches up with the Sams picture pretty well, the wear pattern around the upper hole would be consistent with a larger knob but I'm not sure about the channel selector.

Does anyone have one of these with a set of knobs they could photograph?

[Eric H]

Here's a couple more pics just for fun.

The tube needs recoated badly, it fell off in sheets.

The Flyback looks great, the cabinet has a hairline crack towards the back top but I'm just going to reinforce it from inside.

The one picture is my 5U4 substitute device, just two diodes in an octal socket.
The benefit (besides saving 5u4's) is that they start to conduct at any voltage you apply with the Variac, the 5U4 doesn't even start to conduct until the line voltage gets up to 40 or 50 volts.
The bad thing is it will apply too much voltage to the Filters if you run it at full voltage since there is no drop.

They saved a 5U4 in this set because a filter shorted dead when I got above 100 volts, it tripped the 5 amp breaker in the variac and shorted one of the diodes. Prior to that I was getting a Raster of sorts.
The Filter can got so hot the paper sleeve came off with little effort, after that I kludged in those new filters underneath it.
Set has sound and a narrow raster now.

[bandersen]

Good luck! I have the older 10" model 648 with a similar cabinet.
I used Slip Plate recently and can testify that it works very well to re-coat a CRT.

[Eric H]

Did a little work the last two nights recapping, this set has a couple really tough spots, I had to snip and wrap rather than removing the leads completely.

I also had to make up a couple High Volt Capacitors, I needed an .018@1000 and an .022@1000, all I had was some .01@1600 so I made up two .020@1600v caps out of them, one is .004 over and one is .002 under but they were 10% caps to start with so I think they'll work.

They were also in a very tight spot under a mounting strip (actually over the strip with the chassis in the normal position) I moved them over (under) the strip and away from a large wirewound resistor also on that strip.

It ain't pretty but then it doesn't show.

I think I've done all the really tough ones so it should get easier from here.

I'm waiting on my Filters to arrive.

[Bill Cahill]

Eric, I've found that 5U4's start conducting at 35 volts ac input.
By 50 volts, you are getting fairly high surges, which go down as set starts warming up.

Diodes wil increase voltage too high without added resistance.
The tubes start warming up nicely for me.

On the escutcheon, if you look at the small white dot above that dial, I'd say that escutcheon was added. My guess is it uses the same knob as in schematic.
Bill Cahill

[Eric H]

They are such a time waster.

I was working on this Emerson, had good HV but no raster, it had a raster before I started so something happened.

Okay, the loss of raster was an easy fix, the .047 going to the CRT Cathode was bad, I cut and jumped it and got a raster but after soldering in a new cap I had no raster again, this time the HV was dead and the 6BG6 was red plating.

Found a Bumblebee in the Horiz Osc circuit that i missed, replaced it and soldered in the "two" wires that came out when I unsoldered the cap. (Emerson liked to just poke wires through without wrapping them apparently) still no HV.

Two days and several hours later I finally figured out that one of the two wires actually went somewhere else (-130 to pin 3 of the Horiz Osc 6SN7) it must have broken off when I changed the Bumblebee but it looked like it went in the same connection as the cap and that's where I put it. (confirmed the error by looking at the chassis photos I took before starting).

So two evenings wasted fixing my own stupid mistake.

[David Roper]

So been there, so done that. It's all good now, put down the hammer.

[bandersen]

Same here. As long as no vital component fried, be happy

[Eric H]

Originally Posted by bandersen

Same here. As long as no vital component fried, be happy

The 6BG6 took quite a pounding but it still works.

[Eric H]

I finally have a coherent picture on this set.
I've been beating my brains out the last couple days on a Horizontal frequency problem, I couldn't get less than three side by side images no matter how I adjusted it.

I checked and rechecked my work, rechecked resistors, rechecked the power supply wiring, still nothing.

I finally decided the problem must be in the Phase inverter section, a quick check of the voltages on the 12AU7 found 60 volts on pin one where there was supposed to be 27.
I checked the resistors around the tube, all OK.

I finally decided to switch the Phase inverter 12AU7 with one in the i.f. section and that's when I found the problem.

Someone had put a 12AX7 in place of the 12AU7, they look similar but are not the same at all and it wouldn't allow the Horiz Oscillator to run at the right frequency, on top of that when I switched the tubes around it caused a short in the 6CB6 i.f. tube that smoked the resistor.
The 12AX7 had the markings rubbed off and I took it on faith that it was the correct tube, if I had put it in the i.f. strip first I would have been chasing a different problem.

I found a 12AU7 and another 6CB6 and bingo, I was able to bring the picture into sync!

I love those Aha! moments when you finally solve a problem that's been driving you nuts.

The horiz is still a little drifty, possibly some resistors changing as they get hot or maybe the Micas going bad, but at least there's one less problem to solve.

[mstaton]

Lookin' good Eric! Glad you figured that out!

[Bill Cahill]

Eric, congrats! Looks like it's definately alive again.
Bill Cahill

[Glenz75]

Looking good now Great Stuff Cheers.