Old Muntz TV for sale Locally to me, Should I pick it up?

[vortalexfan]

Originally Posted by Tube TV

Would almost make me wonder if there was some issue years ago that was causing the fuse to blow and that's why they quit using it.
Mind you it could have been replaced more recently by someone plugging it in to see if it worked so that they could as more for it on ebay.....

Well actually now that you mention it, on the bottom side of the TV chassis by the High Voltage Cage there appears to be a huge char mark on the chassis like maybe something caught fire under there or something but I'm not sure.

[old_coot88]

Before investing further effort and $$ in that set, it'd be advisable to check the no-load current draw of the power xfmr, considering the xfmr has a history of being brutalized over and over.

Remove all the tubes (except HV rect), disconnect CRT from its socket, power up and measure AC current draw from the wall. This 'idle' current should be very low. If it's excessive, suspect some cooked windings in the xfmr.

[Tube TV]

Originally Posted by old_coot88

Before investing further effort and $$ in that set, it'd be advisable to check the no-load current draw of the power xfmr, considering the xfmr has a history of being brutalized over and over.

Remove all the tubes (except HV rect), disconnect CRT from its socket, power up and measure AC current draw from the wall. This 'idle' current should be very low. If it's excessive, suspect some cooked windings in the xfmr.

Yes agreed this would be a excellent plan.
Lets hope that the flyback isn't cooked.

[old_coot88]

Originally Posted by Tube TV

Lets hope that the flyback isn't cooked.

The fly shouldn't be affected since it was not in the current path of the B+ short.

[vortalexfan]

Originally Posted by old_coot88

Before investing further effort and $$ in that set, it'd be advisable to check the no-load current draw of the power xfmr, considering the xfmr has a history of being brutalized over and over.

Remove all the tubes (except HV rect), disconnect CRT from its socket, power up and measure AC current draw from the wall. This 'idle' current should be very low. If it's excessive, suspect some cooked windings in the xfmr.

OK, that's easy enough to do.

[vortalexfan]

Originally Posted by old_coot88

Before investing further effort and $$ in that set, it'd be advisable to check the no-load current draw of the power xfmr, considering the xfmr has a history of being brutalized over and over.

Remove all the tubes (except HV rect), disconnect CRT from its socket, power up and measure AC current draw from the wall. This 'idle' current should be very low. If it's excessive, suspect some cooked windings in the xfmr.

Well the only problem is, that as I pointed out in a previous post I have accidentally replaced two .05 MFD capacitors with 2 .0047 MFD capacitors because I misread the capacitor code on the outside of the capacitors, which I thought they said 473K on them but then after I installed them in the TV set I looked at the code marker again and saw that it actually said 472K not 473K like I thought it did.
So I have two capacitors in the TV that are outside of the tolerance rating of the original capacitors so I'm afraid to power it up until I get those capacitors replaced with the correct value capacitors which I currently don't have any .047 MFD 630 VDC capacitors in my capacitor stash.

I don't want to order anything yet unless I can make a full order and I can't do that until I know this thing is going to be worth my time ordering the rest of the capacitors I need to finish the job and I don't want to put an order in for just two capacitors because that's a waste.

Does anyone have a couple of .047 MFD 630 VDC film capacitors that they could spare?

[Electronic M]

Originally Posted by vortalexfan

Well the only problem is, that as I pointed out in a previous post I have accidentally replaced two .05 MFD capacitors with 2 .0047 MFD capacitors because I misread the capacitor code on the outside of the capacitors, which I thought they said 473K on them but then after I installed them in the TV set I looked at the code marker again and saw that it actually said 472K not 473K like I thought it did.
So I have two capacitors in the TV that are outside of the tolerance rating of the original capacitors so I'm afraid to power it up until I get those capacitors replaced with the correct value capacitors which I currently don't have any .047 MFD 630 VDC capacitors in my capacitor stash.

I don't want to order anything yet unless I can make a full order and I can't do that until I know this thing is going to be worth my time ordering the rest of the capacitors I need to finish the job and I don't want to put an order in for just two capacitors because that's a waste.

Does anyone have a couple of .047 MFD 630 VDC film capacitors that they could spare?

The test he suggests (pull every tube and power up for a current measurement) will work accurately no matter what capacitance you installed for paper caps...Basically, there will be no tubes to put signal into or take signal out of those caps, there won't even be B+ voltage anywhere...THe only part that should be energized is the power transformer...You could probably glue a pair of leads to a rock, solder that in place of the caps your scared of and not have it do harm or affect the results of the suggested test.

The point here is to verify the expensive/rare power transformer does not have an internal short/current leakage (read that verify the trans ain't ruined). If it don't draw too much current order all the caps when you have the dough, if it draws too much current shelve the set for a few months till you can track down a good transformer or kick it down the road to its next owner.

[vortalexfan]

Originally Posted by Electronic M

The test he suggests (pull every tube and power up for a current measurement) will work accurately no matter what capacitance you installed for paper caps...Basically, there will be no tubes to put signal into or take signal out of those caps, there won't even be B+ voltage anywhere...THe only part that should be energized is the power transformer...You could probably glue a pair of leads to a rock, solder that in place of the caps your scared of and not have it do harm or affect the results of the suggested test.

The point here is to verify the expensive/rare power transformer does not have an internal short/current leakage (read that verify the trans ain't ruined). If it don't draw too much current order all the caps when you have the dough, if it draws too much current shelve the set for a few months till you can track down a good transformer or kick it down the road to its next owner.

OK thanks that's what I wanted to know. I'll proceed with the test then, since I don't actually have to fear ruining the set with the wrong value capacitors in it with this test, that was my main concern.

[Kevin Kuehn]

Originally Posted by vortalexfan

OK thanks that's what I wanted to know. I'll proceed with the test then, since I don't actually have to fear ruining the set with the wrong value capacitors in it with this test, that was my main concern.

To put things into perspective for you, powering the set with all those original leaky paper and electrolytic caps has been much more risky than if you powered it with the two off-value new caps installed.

[vortalexfan]

OK so a little update, I powered on the set with all but the H. V. Rectifier tube removed from the TV and the TV's current draw leveled out at about .39 Amps or 7.3 watts according to my Kill-A-Watt Meter, which is fairly low.

So I'm guessing that the transformer is actually fine yet and my problem is just a bunch of paper caps that have shorted to ground somewhere in the TV (more than likely the two .01 MFD caps on the AC line for noise supression are the ones to blame because they are soldered to ground on one side and if they've shorted, they've more than likely shorted to ground.)

[Kevin Kuehn]

Originally Posted by vortalexfan

OK so a little update, I powered on the set with all but the H. V. Rectifier tube removed from the TV and the TV's current draw leveled out at about .39 Amps or 7.3 watts according to my Kill-A-Watt Meter, which is fairly low.

So I'm guessing that the transformer is actually fine yet and my problem is just a bunch of paper caps that have shorted to ground somewhere in the TV (more than likely the two .01 MFD caps on the AC line for noise supression are the ones to blame because they are soldered to ground on one side and if they've shorted, they've more than likely shorted to ground.)

I doubt the AC line caps are drawing all that current. They'd of exploded by now with unlimited AC current flowing. You can simply snip one lead of those so they are out of circuit. They are not needed for the set to be operational.

[jr_tech]

Scratches head... how does 122 Volts @ .39 Amps equal only 7.3 Watts?

jr

[jr_tech]

Originally Posted by jr_tech

Scratches head... how does 122 Volts @ .39 Amps equal only 7.3 Watts?

jr

Answer: power factor for this unloaded power transformer must be quite small, about 0.15 !

Just measured an unloaded tv power transformer of similar size on a kill-a-watt meter, readings were:
122 Volts, 0.26Amps, 9 Watts, 34 VA, 60Hz, 0.28 PF (power factor), so I believe that the PF could be as low as 0.15.
Did you happen to get a power factor reading?

jr

[vortalexfan]

Originally Posted by jr_tech

Answer: power factor for this unloaded power transformer must be quite small, about 0.15 !

Just measured an unloaded tv power transformer of similar size on a kill-a-watt meter, readings were:
122 Volts, 0.26Amps, 9 Watts, 34 VA, 60Hz, 0.28 PF (power factor), so I believe that the PF could be as low as 0.15.
Did you happen to get a power factor reading?

jr

Here are my Kill-A-Watt Meter readings for my TV's Unloaded Transformer:

123.4 Volts AC
0.40 Amperes
8.2 Watts
50.6 VA
60.0 Hz
PF (Power Factor) 0.16

Hope this helps.

P. S. depending on the time of the day my voltage readings coming out of my outlets can range between 119.8 VAC and 124.5 VAC, when I took my Kill-A-Watt Readings just now my Voltage reading was 123.4 VAC when I took it this morning it was 122.5 VAC.

[jr_tech]

So, because of the low power factor of the unloaded transformer, the .40 Amp current draw does not appear to be excessive at all. Your transformer is behaving much the same as the known good transformer that I measured and is probably good.

jr