Odd Electrolytic
 

In making a list of capacitors to replace in a 1949 Sylvania I came across an electrolytic in the AGC section that is rated 10Mfd -12V, 150V. Looking at the circuit I believe it actually can experience both polarities. Other than non-polarized electrolytics I've never heard of such a thing and those have equal voltage ratings.

Have any of you come across these in the past?

I think I'll replace it with a metalized polypropylene if there's room.

John Y.

Not being able to see the component, nor the schematic to the set, I'd say you're on the right track to go with an NPO replacement.

Thanks.

BTW, here's that part of the schematic. Notice the biasing of the AGC amp. The cap in question is C126.

John

That's an interesting setup for AGC.... Could you offer up more of the schematic so I can see things in a clearer context...?

Other than that if you can scare up the capacitance in a non-polar you should be OK, IMHO.

In normal operation that AGC line will never go positive. You can use a 25-50 volt positive grounded electrolytic without fear.

I'm sure I can deal with it. I've just never seen an electrolytic rated this way and wondered if anyone else had.

I've included the schematics for both the chassis and tuner.

John Y.

What numbers or values are printed on the old part? The voltages on the schematic look like to be kind of squished together testpoint voltages or typo error . I would go with 10uf @ 150v based on the schematic.

Wow, I thought Motorola was weird - what year did Sylvania drop the split horizontal and HV power supplies? That's a neat but weird feature...

I don't have the set yet. I'm just getting parts ready for when it arrives. I actually hope the old electrolytic is in it to look at.

If you look at the parts list I posted you'll see that it has the same ratings for it. This is true for the sevice bulletin and the following two supplements.

In normal operation perhaps it should be negative but if it were to never go positive there wouldn't be a need for the AGC line clamper diode.

John Y.

Thats a pretty oddball capacitor . I've never seen a dual voltage rating like that.. But then ..Were talking sylvania 1949..

OK dude..I just talked to a very old TV repairmen that remembers running across these type of caps on those particular chassis's ie. My father

He said that they were a special order type cap. He also suggests trying to find a non-polar 10 uf @ 150v..

Good luck trying to find a electrolytic...At 150v..
polyfilm..
http://search.digikey.com/scripts/Dk...name=EF2106-ND

I agree.

John

I imagine the same year they realized how much it was costing them. :eek:

The Motorola HV supply is similar isn't it?

The September 1949 Sylvania News describes three types of HV supplies.
1. The Fly Back
2. The RF HV Supply
3. The Pulse Type HV Supply. (A blocking oscillator triggered by the horiz. sync)

Do you know of any sets that used the pulse type?

John Y.

Only the 7 inch electrostatic Motorollers are RF supplied, the bigger ones use a conventional flyback type (that in my case, isn't working right, yet :( )

Wasn't the pulse type used in early European color sets?

For weird cap values, I've seen some in ohms @ frequency. Go figure.

Talk about a bonkers TV though, I think your Sylvania takes the cake!

But I loved it as a kid back when my folks had one. I always remember it working well.

I'm working on restoring a 9T1. It has an 8" CRT but I guess that doesn't count as bigger since it has the same chassis as the 7" units. There are some rather large caps in the HV section to replace. 6KV and 10KV.

Which Motorola do you have?

I think the biggest problem with the RF HV is that if the sweep stops the HV doesn't and you risk burning the CRT.

John Y.