Old Muntz TV for sale Locally to me, Should I pick it up? - Page 19 - Videokarma.org TV - Video

vortalexfan · #**271** 11-06-2019, 11:48 AM

Quote:

Originally Posted by Kevin Kuehn

What did pin 4 measure? If you have dc voltage on pin 4(screen) and nothing on 3(plate)I'd suspect the primary of your output transformer could be shorting to ground. You could also try measuring those two pins in respect to chassis ground. Any voltage readings on those two pins will indicate if there's a short in that transformer primary.

Actually the output tranny is attached to the speaker and the speaker unplugs from the chassis, and it's currently not connected to the TV, would not having the speaker in circuit mess things up?

Kevin Kuehn · #**272** 11-06-2019, 11:51 AM

Another thought... pull the 6V6 and see if the voltage on pin 3 changes, either referenced from pin 8 or ground.

Kevin Kuehn · #**273** 11-06-2019, 11:54 AM

Quote:

Originally Posted by vortalexfan

Actually the output tranny is attached to the speaker and the speaker unplugs from the chassis, and it's currently not connected to the TV, would not having the speaker in circuit mess things up?

Well of course if the output transform is unplugged.

You see on the schematic that the b+ goes from one side of the transformers primary to the other side connected to pin 3(plate) of the output tube. But still it does not explain why R62 would be over heating while that speaker is unplugged, if in fact that's what's going on.

Kevin Kuehn · #**274** 11-06-2019, 12:12 PM

Here's a picture of the upper portion of this TV's Schematic for anyone following along. R62 is being feed b+ from the focus control.

https://live.staticflickr.com/65535/...25cda511_b.jpg

Hopefully not to confuse more, but here's most of the Riders schematic on this TV. They show the 6V6 screen supply coming from before the 390 ohm feeding the plate. Not that it maters much, just interesting that it's not the same.

https://live.staticflickr.com/65535/...4b26de80_b.jpg

Electronic M · #**275** 11-06-2019, 12:57 PM

Quote:

Originally Posted by vortalexfan

Actually the output tranny is attached to the speaker and the speaker unplugs from the chassis, and it's currently not connected to the TV, would not having the speaker in circuit mess things up?

It will mess quite a lot up. This set uses a stacked B+ scheme. The audio output stage acts as a series dropping resistance. The video output, IF and possibly the tuner depend on the audio output to supply them with B+.

From here on out make sure the speaker transformer is connected on every power up of the chassis.

vortalexfan · #**276** 11-06-2019, 01:09 PM

Quote:

Originally Posted by Kevin Kuehn

What did pin 4 measure? If you have dc voltage on pin 4(screen) and nothing on 3(plate)I'd suspect the primary of your output transformer could be shorting to ground. You could also try measuring those two pins in respect to chassis ground. Any voltage readings on those two pins will indicate if there's a short in that transformer primary.

Pin 4 is spot on voltage wise on the 6V6 tube, and pin 3 once I connected the speaker was giving me a +25 vdc and dropping. So not sure what's going on with that.

vortalexfan · #**277** 11-06-2019, 01:14 PM

Quote:

Originally Posted by Kevin Kuehn

Another thought... pull the 6V6 and see if the voltage on pin 3 changes, either referenced from pin 8 or ground.

6v6 tube pulled I get over 300 volts DC on pin 3 of the 6V6 tube socket, and it drops as the rest of the tubes warm up. Perhaps I have bad 6V6 tubes?!

Edit: I installed a known good (a brand new never used Sovtek 6V6 tube) into the TV and measured Pin 3 in reference to ground and got over 300 VDC on pin 3 and got some audio out of ther speaker as well, but when pin 3 is measured against pin 8 of the 6V6 tube as per the manual I only get 25-30 VDC on pin 3.

vortalexfan · #**278** 11-06-2019, 01:31 PM

Quote:

Originally Posted by Electronic M

It will mess quite a lot up. This set uses a stacked B+ scheme. The audio output stage acts as a series dropping resistance. The video output, IF and possibly the tuner depend on the audio output to supply them with B+.

From here on out make sure the speaker transformer is connected on every power up of the chassis.

The speaker is connected now, and my higher voltage readings should reflect that fact.

vortalexfan · #**279** 11-06-2019, 02:08 PM

Ok so I measured all the voltages for the 6V6 and the readings I got are stumping me and don't make any sense to me:

Measurements made in reference to pin 8 of 6V6 tube

Pin 1: 0 V
Pin 2: 6.7 VAC
Pin 3: 25 VDC Should be 205 VDC
Pin 4: 21 VDC Should be 225 VDC
Pin 5: -177 VDC should be -8 VDC
Pin 6: -0.219 VDC Should be 0 V
Pin 7: 0 V
Pin 8: 0 V

Disregard what I said earlier about pin 4, I made the mistake of measuring that in reference to ground rather than to pin 8.

And actually, I just figured my problem, I had C3 and C4 wired in backwards because C3 just now vented with a loud popping noise, which I'm surprised it took this long to vent.

Kevin Kuehn · #**280** 11-06-2019, 02:37 PM

Quote:

Originally Posted by vortalexfan

And actually, I just figured my problem, I had C3 and C4 wired in backwards because C3 just now vented with a loud popping noise, which I'm surprised it took this long to vent.

Bingo! Congratulations on finding that error. I was just about to ask you what voltage you measure on pin 8 referenced to ground, but it probably doesn't matter now. It does kind of irk me that Sams didn't provide a voltage reference for pin 8 relative to ground. I have no idea why they thought it was smart to put 0 volts relative to the same pin they have you measuring from.

vortalexfan · #**281** 11-06-2019, 03:06 PM

Quote:

Originally Posted by Kevin Kuehn

Bingo! Congratulations on finding that error. I was just about to ask you what voltage you measure on pin 8 referenced to ground, but it probably doesn't matter now. It does kind of irk me that Sams didn't provide a voltage reference for pin 8 relative to ground. I have no idea why they thought it was smart to put 0 volts relative to the same pin they have you measuring from.

OK now that that's fixed and the TV is running as it should, (its running at 167 watts which is well within tolerance considering today's higher line voltages, and this TV was rated at 105-120V AC) now I just need to get a raster which its not producing inspite of having HV, Vertical and Horizontal running.

Its amazing though that one misinstalled electrolytic cap would cause that many issues.

Kevin Kuehn · #**282** 11-06-2019, 03:26 PM

Quote:

Originally Posted by vortalexfan

OK now that that's fixed and the TV is running as it should, (its running at 167 watts which is well within tolerance considering today's higher line voltages, and this TV was rated at 105-120V AC) now I just need to get a raster which its not producing inspite of having HV, Vertical and Horizontal running.

Its amazing though that one misinstalled electrolytic cap would cause that many issues.

Amazing? Are you serious? You basically had installed a short circuit to ground across a significant portion of the power supply.

So now you are sure your vertical, horizontal, and high voltage circuits are all working properly? Or was that an assumption on your part?

Electronic M · #**283** 11-06-2019, 03:32 PM

Quote:

Originally Posted by vortalexfan

OK now that that's fixed and the TV is running as it should, (its running at 167 watts which is well within tolerance considering today's higher line voltages, and this TV was rated at 105-120V AC) now I just need to get a raster which its not producing inspite of having HV, Vertical and Horizontal running.

Its amazing though that one misinstalled electrolytic cap would cause that many issues.

The sounds you described are not a guarantee (and may not even be an indication) of working horizontal. To check....
If you have a working or non-working CFL that the glass is not busted on take that and place the glass against the H output top plate lead as well as next to flyback doughnut and see if it lights from the RF energy a working HV system produces... If it lights hold a well insulated screwdriver next to the HV connection metal contact with the set on and see if you can draw an arc. If it has over 1/4" arc your HV is present.

Once you confirm HV is present we can talk about making the screen light...

vortalexfan · #**284** 11-06-2019, 03:37 PM

Quote:

Originally Posted by Kevin Kuehn

Amazing? Are you serious? You basically had installed a short circuit to ground across a significant portion of the power supply.

So now you are sure your vertical, horizontal, and high voltage circuits are all working properly? Or was that an assumption on your part?

I saw the horizontal and vertical oscillators kick in on at the Kill-A-Watt meter when the TV was warming up, also I heard the horizontal and vertical oscillators running, which is a really high pitched whistling noise.

vortalexfan · #**285** 11-06-2019, 03:43 PM

Quote:

Originally Posted by Electronic M

The sounds you described are not a guarantee (and may not even be an indication) of working horizontal. To check....
If you have a working or non-working CFL that the glass is not busted on take that and place the glass against the H output top plate lead as well as next to flyback doughnut and see if it lights from the RF energy a working HV system produces... If it lights hold a well insulated screwdriver next to the HV connection metal contact with the set on and see if you can draw an arc. If it has over 1/4" arc your HV is present.

Once you confirm HV is present we can talk about making the screen light...

I was able to confirm High Voltage, I was able to draw a 1/4" arc off the 1B3 tube's anode, however there is no high voltage at the picture tube's anode button.