Old Muntz TV for sale Locally to me, Should I pick it up? - Page 3 - Videokarma.org TV - Video

Electronic M · #31 08-20-2019, 10:25 PM

Physical location of lytics usually is not critical. On cans that connect to chassis (and some that don't but run the can negative wire to convenient points) I often place the individual replacements at the point the wire to the can positive originates from even if that spot is on the far end of the chassis.

One thing to make sure of though if the can negative was insulated from the chassis and fed from one or more wires that are not directly connected to the chassis to keep that floating negative separate from the chassis...In my first year or two of restoring radios I messed up a Zenith Transoceanic replacing a floating negative lytic with individual parts that I tied the negatives of to chassis instead of the floating negative...Later I figured that mistake out and fixed it.

vortalexfan · #32 08-20-2019, 10:59 PM

Quote:

Originally Posted by Electronic M

Physical location of lytics usually is not critical. On cans that connect to chassis (and some that don't but run the can negative wire to convenient points) I often place the individual replacements at the point the wire to the can positive originates from even if that spot is on the far end of the chassis.

One thing to make sure of though if the can negative was insulated from the chassis and fed from one or more wires that are not directly connected to the chassis to keep that floating negative separate from the chassis...In my first year or two of restoring radios I messed up a Zenith Transoceanic replacing a floating negative lytic with individual parts that I tied the negatives of to chassis instead of the floating negative...Later I figured that mistake out and fixed it.

Its a capacitor can with a cardboard tube jacketand the capacitor didn't seem to have a ground that I could see on the jacket anywhere, it gave the different shapes for each section along with the values for each section but it didn't list anything about what the negative connection was for the can.
Could it of been that they used a non-polar capacitor can for the power supply filter caps??

Electronic M · #33 08-21-2019, 09:14 AM

No non-polarized lytics are not used for filter caps in these sets (sometimes single section non-polarized were used to couple the yoke and allow centering DC to be added).

If there is a metal can under the cardboard then there were negative terminals on it's bottom (they may have snapped off when it got busted off its wafer). If there is no metal can or terminals on the cap and just wires out the bottom then there has to be a negative lead if it is a multi section cap.

You need to get the schematic and trace things out if you can't make sense of the wiring that's there.

vortalexfan · #34 08-22-2019, 12:19 AM

Quote:

Originally Posted by Electronic M

No non-polarized lytics are not used for filter caps in these sets (sometimes single section non-polarized were used to couple the yoke and allow centering DC to be added).

If there is a metal can under the cardboard then there were negative terminals on it's bottom (they may have snapped off when it got busted off its wafer). If there is no metal can or terminals on the cap and just wires out the bottom then there has to be a negative lead if it is a multi section cap.

You need to get the schematic and trace things out if you can't make sense of the wiring that's there.

The reason I was asking about the ground connection with this capacitor is because on the bottom of the capacitor there's only 3 terminals for the "positive" leads and then theres the twist-loc tabs that held the capacitor to the phenolic wafer that snapped off the TV chassis and one of the twist-loc tabs has some wires attached to it but I'm unsure as to whether they are ground wires or if they are just using it as a convenient terminal strip.

Like I said the Capacitor is a cardboard cased multi-section capacitor with no apparent ground connection of any sort, at least not to the chassis anyways that I can see of.

vortalexfan · #35 08-22-2019, 12:29 AM

As you will see from the pictures that I took of this can cap, it has absolutely no mention on the case of having a ground of any sort, and you can even see the wiring on the capacitor that there is abolutely no ground connection on this capacitor, and that the one twist-loc tab is just being used as a terminal strip and that's it, nothing ground related.

Tom9589 · #36 08-22-2019, 07:47 AM

The one twist lock tab with wires on it is the common (negative) terminal of all three 40 mfd capacitors in the can. The design of this power supply calls for the this cap to be connected to a point other than ground. It might be a way for the power supply to generate a negative bias power supply. If you could get a schematic, it would be obvious.

Electronic M · #37 08-22-2019, 08:48 AM

95%of the time that a can is covered in cardboard and mounted to phenolic it's can negative terminals are NOT connected to ground but instead tie to a floating negative line at a different potential than the chassis. The can is not a tie point but the negative of the caps and the wires connected to the can are a negative rail.

One other use for the wafer and separate negative from chassis: in some series string sets the chassis is not used as a ground/B- and serves only as a shield with it's only connection to the rest of the circuit being a parallel cap and resistor to couple it to signal ground, but limit chassis shock current.

vortalexfan · #38 08-22-2019, 09:46 AM

Quote:

Originally Posted by Tom9589

The one twist lock tab with wires on it is the common (negative) terminal of all three 40 mfd capacitors in the can. The design of this power supply calls for the this cap to be connected to a point other than ground. It might be a way for the power supply to generate a negative bias power supply. If you could get a schematic, it would be obvious.

I do have a schematic but it's hard to make heads or tails of it as far as finding the Power Supply or what not.

Tom9589 · #39 08-22-2019, 02:30 PM

You know, SAMS Standard Notation might be one of the best things that ever happened for the television service industry.

Electronic M · #40 08-22-2019, 02:56 PM

Quote:

Originally Posted by vortalexfan

I do have a schematic but it's hard to make heads or tails of it as far as finding the Power Supply or what not.

If there is a power transformer, look for it. If there is a power rectifier look for it. Even the wackiest non- standard schematics and circuit designs can be followed if you find the recognizable stuff and trace from it to what you need. If parts values are only listed in a separate table print the table and have it next to the schematic. If the schematic is on multiple pages print it out and stick the sections together into a single page.

jr_tech · #41 08-22-2019, 04:32 PM

Photofact set 110, folder 9 covers 14 Meck models from 1950...I suspect that the power supply in question is very similar to the one shown in that folder:

The common (connections to the can) of C1 (40,40,40) is floated from chassis ground so that a minus 3 volt supply can be created to provid bias to the video detector stage.

jr

vortalexfan · #42 08-24-2019, 01:58 AM

Quote:

Originally Posted by jr_tech

Photofact set 110, folder 9 covers 14 Meck models from 1950...I suspect that the power supply in question is very similar to the one shown in that folder:

The common (connections to the can) of C1 (40,40,40) is floated from chassis ground so that a minus 3 volt supply can be created to provid bias to the video detector stage.

jr

Yes I found the power supply stage after looking over the schematic from Beitman's that I have (unfortunately I do not have access to the Sam's folder for this TV, I have every Sam's Folder from this time period except 110, and I don't wish to pay the $30 that Sam's is asking at their website for this Photofact folder copy.)

It does seem that it does have a floating ground which I'm not sure how it would work to do that with a terminal strip and 3 47 MFD 450 VDC electrolytic caps when the only terminal strips I have have the mounting tabs that mount it to the chassis also doubling as chassis ground terminals, which I don't need in this case.

Notimetolooz · #43 08-24-2019, 08:40 AM

Quote:

Originally Posted by vortalexfan

It does seem that it does have a floating ground which I'm not sure how it would work to do that with a terminal strip and 3 47 MFD 450 VDC electrolytic caps when the only terminal strips I have have the mounting tabs that mount it to the chassis also doubling as chassis ground terminals, which I don't need in this case.

Don't let the lack of a proper terminal strip prevent you from doing the job right.
http://www.radiodaze.com/terminal-strips/

vortalexfan · #44 08-25-2019, 10:33 PM

Quote:

Originally Posted by Notimetolooz

Don't let the lack of a proper terminal strip prevent you from doing the job right.
http://www.radiodaze.com/terminal-strips/

Thanks for the link, I think I found a terminal strip there that will work for what I need.

Electronic M · #45 08-26-2019, 08:52 AM

If the can wafer wasn't busted, and you had a 75W soldering iron I'd have suggested using the terminal strip you have and soldering the mount tab of the strip to the negative terminal lug of the can(instead of bolting it to chassis)....I do this sometimes and as long as you have a big iron and make a solid solder joint it works pretty nice. Some might complain it is not original workmanship but as long as it isn't a high buck set stuff like this doesn't make much difference.