My next restoration victim, Silvertone

[Eric H]

Originally Posted by tom.j.fla

Hi Eric, Your Sams is 339-13 from 12/1956. With Sears look up for photo fact by chassis number and look under Sears not Silvertone.All the best,Tom

Thanks, I have one ordered.

[Eric H]

I've made quite a lot of progress on this one.

Got all the caps replaced, for the five section cardboard electrolytic I just removed it and installed the individual caps where the original leads connected so they are scattered all over the chassis, as luck would have it there was a ground point within reach of all of them.

The other cardboard tube contained two individual metal can caps, I just removed those and soldered the wires directly to the new caps and stuck them inside the tube in it's original location, I'll squirt some Silicone Rubber inside to hold them in place.

The rest were just common value tubular caps, I replaced them all with the usual yellow axials.

I ordered a supply of caps from Sals Capacitor Corner, they were cheap and got here fast, they look like very good quality and have long leads on them, this was the first time I ordered from him but I will be going back next time. http://www.tuberadios.com/capacitors/

The Electrolytics came from Mouser.

the set is making a great picture but the sound is nearly inaudible, seems like that's usually the case, tweaking the detector didn't seem to make any difference but I didn't really get into it tonight because I'm tired of working on it for now.

the Vertical Lin control is either damaged or dirty, the vertical is a flat line up to a point then it pops up to a full raster, I'm able to get decent linearity but I'll probably have to fix it to get it perfect.

[Eric H]

Found the problem with the sound, it was just a dirty socket on the ratio detector/af amp, now it plays nice and loud!

Found out this Sams isn't entirely correct for this chassis either, a couple of the tubes are different, including the ratio detector/af amp.

I had to use the tube chart in the cabinet to figure out what tubes were supposed to be in it.

[Eric H]

the next thing to do is replace the vertical hold and linearity controls, the linearity is shot, it's dead past a certain point and I can't get the vertical perfect.

It's a double pot in a single case, the Sams lists two different part numbers for replacing it. I suppose I could just use a couple pots of the correct value.

Question, Sams says the linearity is 6000 ohms with a 1000 ohm stop, the Height is eight meg with a one meg stop.
Where would you even find an 8 meg pot?

I think those holes punched in the back of the controls are probably the stops?

[Eric H]

One interesting thing happened, the vertical output tube died, I shut it off to do something and when I turned it back on no vertical, the amp meter I have in line with the Variac was showing almost an amp of current and one heater in the tube was glowing much brighter than normal.
I found another 6CM7 and was back in business.

I had been running the set with the Variac cranked up higher than normal trying to bring the B+ up a bit, (the Selenium rectifiers may be getting weak), possibly the extra voltage killed an already marginal (original Silvertone) tube.

[Kevin Kuehn]

For the linearity control, I wonder why you couldn't use a 5K pot with a 1k resistor is series? Seems like that would be a functional equivalent. 8 meg is going to be tough, other than another parts set. 10 meg are out there. http://www.allelectronics.com/make-a...ear-pot/1.html

edit - just found this. http://www.ebay.com/itm/1-Clarostat-...UAAOSwKPNTyrQw

If there's room to mount these type pots, I'd try it with a 1 meg resistor is series.

[Eric H]

Originally Posted by Kevin Kuehn

If there's room to mount these type pots, I'd try it with a 1 meg resistor is series.

That sounds like a good idea.
the chassis already has the mounting slots for individual pots so all I need to do is get a couple of the right, or close enough values.

I have a box full of Pots I bought off eBay so I'll go through those first, doubt there's an 8 meg in there but I might find something to replace the 6k.

[Eric H]

Okay, I've come up with an easy solution.

They only used one side of the pot, the side without the stop, circuit is hooked to the center tap, outer leg was hooked to ground through a 1k resistor.

I moved the resistor to the other outer leg and it worked but without enough range, then I realized that was the side with the 1k stop, so with the resistor it was 2k, took the resistor out and hooked the leg directly to the chassis and it works fine, the bad spot is outside the area needed to get the linearity right, the control works backwards of course but that's a minor issue.

The vertical controls have extenders on them so they stick out the back, accessible to the user, possibly there was a vertical issue at some point, or they were just obsessive about getting the picture perfect and they wore out the pot fiddling with it?

[Kevin Kuehn]

Sounds like a good workaround. So you can do the same with the 8 meg, or will the stop mess things up? Possibly you can eliminate the stop.

[Eric H]

The 8 meg pot is okay, I was only going to replace it because it's a combined control.

[Eric H]

I'm going to declare this one done!

I thought I was done a couple days ago but then I noticed a little vertical shrinkage and flagging at the top of the screen, increasing the AC voltage stopped all this.

I had noticed the B+ was about 20 volts low because the Selenium Rectifiers were getting tired, I was going to let it slide until these problems popped up.

With some help from the people over at the A.R.F. I ripped them out and replaced them with Diodes, after doing that I had to increase the size of the resistor feeding them because the B+ was 20 volts too high, then I had to install some snubber diodes across the caps to stop the hum bars caused by the diodes, it was a bit of work but after getting it all worked out the set looks great!

According the the 1956 Sears catalog, this was Sears Best portable, it's a cheap, series string set with a fairly low tube count but it works as well or better as some of the Deluxe RCA Portables I've worked on, and it's a heck of a lot easier to work on!

[decojoe67]

Looks good! I still love the soft B/W picture on these old sets better than the super-bright overly "crisp" HD flat-screens of today. Watching a classic movie like Double Indemnity or a Honeymooners episode is a totally different experience on these old sets.

[Kevin Kuehn]

That looks great. Horizontal and vertical linearity looks about perfect. And you sparked quite a technical discussion over on the ARF.