Found a Sylvania SS/Tube hybrid - Page 2 - Videokarma.org TV - Video

Jon A. · #16 09-28-2015, 02:14 PM

A D12 Sylvania with a solid wood cabinet, very nice. I recall Ron, a.k.a. sampson159 saying that the D12 was introduced at the time Sylvania gave notice to the industry that they would make the best color TV.

I love my '79 with the E48-2 chassis. My only gripe about it is that the cabinet seems cheap.

MRX37 · #17 09-28-2015, 03:26 PM

Well I think I have a clue as to why the TV won't power up. I pulled the chassis to get a better look and...

This ceramic cup wasn't attached to what I assume is the rectifier tube.

The cup is a very loose fit, so I examined it closely to try and find out why:

It's hard to tell from the pic, but the metal connector inside the cup is discolored, my guess is from electricity arcing. The metal tip of the rectifier tube is very dark.

So I wonder if that tube is still good? perhaps bending the contacts on the connector for a tighter fit might do the trick?

Edit: Nope. Same deal. Works for a second before the breaker trips.

Where are those diodes located? Perhaps I can pull them out and test.

sampson159 · #18 09-28-2015, 06:07 PM

this was the set that started sylvanias drive to the top.very,very good sets and a preamble of things to come.the next was the famous d16 series.same tuner as yours with a really fine crt.then came the best of them all,the d16 slide control.absolutely the best hybrid set right beside the zeniths of the era.excellent crt,simple designed chassis and nice cabinetry.they were also priced about 100.00 less than the zeniths and rca sets.sadly,they are gone now.in the shop days,the margin was 5 sylvanias to every 1 other set.in the southend of colunbus,we had the largest sylvania dealer in the country.

roundscreen · #19 09-28-2015, 10:22 PM

Nice set. I have one with the same chassis but the cabinet is trashed. The tube in your pictures is not the hv rectifier, It is a 6bk4 shunt regulator. The plate socket in your set will have to be replaced. The wire and cap are cooked and it will arc over if you use it. Also you will have to plan a play date with a soldering iron. re solder all the tube sockets and bad connections on the boards. Replace the power filters and breaker if replacing the diodes does not work.

zeno · #20 09-28-2015, 10:30 PM

I will pull the manual tomorrow & see where diodes are.
The plate cap you can pull off any set with a 6BK4.
There are many of them.

73 Zeno

MRX37 · #21 09-29-2015, 02:48 PM

Quote:

Originally Posted by zeno

I will pull the manual tomorrow & see where diodes are.
The plate cap you can pull off any set with a 6BK4.
There are many of them.

73 Zeno

Cool.

And there may be many plate caps where you are. Me? Not so much. So for now I've cleaned it up with sandpaper best I can and bent the contacts to make a tighter fit. Hoping that will do for now.

zeno · #22 09-29-2015, 04:15 PM

Quote:

Originally Posted by MRX37

Cool.

And there may be many plate caps where you are. Me? Not so much. So for now I've cleaned it up with sandpaper best I can and bent the contacts to make a tighter fit. Hoping that will do for now.

That should be OK for now. What I meant was it was used in a lot of TV's
& you can get one off a junker.

4 diodes are under chassis under the power transformer. Test them first.
If any read shorted clip off one end & test again to be sure.

73 Zeno

MRX37 · #23 09-29-2015, 04:35 PM

Right under the transformer? Okay. Maybe after dinner I'll see about pulling the chassis out.

MRX37 · #24 09-29-2015, 05:06 PM

Okay here's a shot of under the transformer. (linked for big)
http://i.imgur.com/TYAlSkF.jpg

I found 3 diodes, and something that looks like it popped, possibly the 4th diode? (look for the question mark near the bottom center of the image)

If it's the 4th diode, far as I know diodes don't just pop like that, so could something upstream pop it?

Findm-Keepm · #25 09-29-2015, 06:54 PM

Quote:

Originally Posted by MRX37

Okay here's a shot of under the transformer. (linked for big)
http://i.imgur.com/TYAlSkF.jpg

I found 3 diodes, and something that looks like it popped, possibly the 4th diode? (look for the question mark near the bottom center of the image)

If it's the 4th diode, far as I know diodes don't just pop like that, so could something upstream pop it?

4th isn't a diode, but your degaussing thermistor lost it's nickle. Dust out things and take another photo if possible - there should be a 4th diode if they are in a bridge.

Degaussing nickel should be an FR191 or a FR291 - and don't buy from the ripoff on ebay. Check Moyers or Talon

MRX37 · #26 09-29-2015, 07:51 PM

Okay, thermistor shouldn't be a big deal, I probably still have one or two from a junked TV chassis that'll work.

Cleaned out some of the dust and got a better pic. I think I found the 4 diodes:
http://i.imgur.com/evv5Qbq.jpg

Now... best way to test these I figure is to clip a lead and put my multimeter on them and see if I get continuity only one way. Best way to do that is to completely pull out the chassis. There's one wire stopping me from doing this, and indeed stops me from completely removing any TV chassis I intend to fix:

The flyback wire.

Before you suggest the screwdriver method of making sure it's discharged, let me give a big NOPE to that! There's got to be a better way to remove it, right?

Findm-Keepm · #27 09-29-2015, 09:34 PM

Quote:

Originally Posted by MRX37

Okay, thermistor shouldn't be a big deal, I probably still have one or two from a junked TV chassis that'll work.

Cleaned out some of the dust and got a better pic. I think I found the 4 diodes:
http://i.imgur.com/evv5Qbq.jpg

Now... best way to test these I figure is to clip a lead and put my multimeter on them and see if I get continuity only one way. Best way to do that is to completely pull out the chassis. There's one wire stopping me from doing this, and indeed stops me from completely removing any TV chassis I intend to fix:

The flyback wire.

Before you suggest the screwdriver method of making sure it's discharged, let me give a big NOPE to that! There's got to be a better way to remove it, right?

Two things - the rectifier diodes will check as a regular diode, with front to back resistance one way and open the other, or use a diode test function on your DMM, or just replace them outright with heftier ones - we used 1N5407s because they were cheap and good insurance that you wouldn't have a call back or have to pull the chassis again.

Second - to discharge the anode lead on the CRT - I use a grounded (chassis connected) clip lead attached to a long bladed screwdriver to discharge the CRT, then let it set for a few minutes and repeat. Then I grasp the 2nd anode rubber cup where the wire enters the cup and twist slightly, with some force to one side to dislodge the legs of the anode connector.

Remember -the CRT is what is charged (its a big capacitor with plates of aquadag and a dielectric of glass), and will obtain a "surface charge" just sitting, so always discharge the anode button to the aquadag before doing anything around the CRT.

MRX37 · #28 09-29-2015, 09:46 PM

Quote:

Originally Posted by Findm-Keepm

Second - to discharge the anode lead on the CRT - I use a grounded (chassis connected) clip lead attached to a long bladed screwdriver to discharge the CRT, then let it set for a few minutes and repeat. Then I grasp the 2nd anode rubber cup where the wire enters the cup and twist slightly, with some force to one side to dislodge the legs of the anode connector.

Remember -the CRT is what is charged (its a big capacitor with plates of aquadag and a dielectric of glass), and will obtain a "surface charge" just sitting, so always discharge the anode button to the aquadag before doing anything around the CRT.

Hoooo... nope nope nope nope nope! If I have to I'll leave the wire connected and work around it instead.

Findm-Keepm · #29 09-29-2015, 10:02 PM

Quote:

Originally Posted by MRX37

Hoooo... nope nope nope nope nope! If I have to I'll leave the wire connected and work around it instead.

I take it you've been shocked before, or have a pacemaker?

Do what you are comfortable with - Safety first.

The discharge procedure is pretty much standard - RCA wanted a 56K resistor in series with the ground, but later made a discharge tool - basically a HV probe with a pushbutton discharge button.

As long as the 2nd anode lead is connected, the cathode of the HV rectifier has juice on it, and still poses a danger if you are working near it.

I've been bit a dozen times and never had any ill effects - just an adrenaline kick and a few choice words.

MRX37 · #30 09-29-2015, 10:15 PM

Actually no I've never been shocked before. Been repairing CRT TV's for 10+ years, never been shocked once.

Because I knew early on that CRT's pack a nasty punch, so I just leave the wire connected and work with the chassis inside the set... or desolder the flyback from the board. Since that's not an option I'll work around it. Pain in the ass, but it won't leave me lying on the floor twitching...

Okay very first diode I clipped reads as a dead short in both directions. I think I've found the problem. I'll have to put this on hold until I can spare the cash to order some diodes. Unless I can substitute some from a junked TV chassis. Problem is while I know how to read resistors and capacitors, or can look them up easily enough, I have no idea how diodes are rated and what ratings matter...

Like I know you can replace a capacitor with one rated for a higher voltage so long as the capacitance is the same. You can replace resistors with higher wattage ones so long as the resistance is the same. What about diodes?