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

[vortalexfan]

Originally Posted by Electronic M

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.

I think I will just completely remove the old can capacitor completely out of the TV and just bolt a proper terminal strip down onto the chassis and just wire it up and go from there. Since the original filter cap was a 40/40/40 @ 450 VDC capacitor I don't think it will matter where I hook up the positive leads.

[vortalexfan]

OK So as luck would have it the tube socket for my Video Amp circuit on my TV is got a couple of damaged pins and I need a new tube socket, its an octal tube socket that mounts from below.

it looks like the one pictured in the link below.

https://www.tubesandmore.com/product...unting-centers

It also seems that I'll need a new 6AC7 tube as well for the Video Amp on my TV as one of the pins on the tube is broken.

[dieseljeep]

Originally Posted by vortalexfan

OK So as luck would have it the tube socket for my Video Amp circuit on my TV is got a couple of damaged pins and I need a new tube socket, its an octal tube socket that mounts from below.

it looks like the one pictured in the link below.

https://www.tubesandmore.com/product...unting-centers

It also seems that I'll need a new 6AC7 tube as well for the Video Amp on my TV as one of the pins on the tube is broken.

If the original socket is one of those molded bakelite jobs, try to find a scrap chassis with the same kind of socket and steal the contacts from it. It's easy enough to do. The only ones you cant repair is the flat phenolic wafer type.

[Electronic M]

Originally Posted by dieseljeep

If the original socket is one of those molded bakelite jobs, try to find a scrap chassis with the same kind of socket and steal the contacts from it. It's easy enough to do. The only ones you cant repair is the flat phenolic wafer type.

+1 Saves a lot of effort doing it that way. Takes a bit of skill to get the donor contact out intact especially if it was soldered, but still much easier than a socket swap.

[vortalexfan]

Well a bit of bad news I replaced the power supply caps and went to test my work and the 5U4G Rectifier tube is still arcing so it looks like it wasn't the power supply caps that was responsible for the arcing rectifier tube after all (actually I tested the original power supply caps after I removed them out of the circuit and they tested fine yet, they weren't shorted or anything.)

Any other ideas as to what could cause the Low Voltage rectifier tube to arc?

[kvflyer]

If you are sure that there is no extra load on the B+ (read, miss wire, leaky-shorted electrolytic capacitor) the 5U4 can be suspect too.

[vortalexfan]

Originally Posted by kvflyer

If you are sure that there is no extra load on the B+ (read, miss wire, leaky-shorted electrolytic capacitor) the 5U4 can be suspect too.

I've replaced all the electrolytics in the Power Supply chain, including the 20/10/10 @450 electrolytic can that's over by the high voltage cage area. And I've even tried 6 different 5U4 tubes and they all arc inside, and they all were new old stock 5U4 tubes or used ones that tested good yet.

Not sure what else to look for.

[Kevin Kuehn]

Double check that your replacement electrolytic caps are polarized correctly, if one is reversed it can fail and act like a dead short. Also look for any unusually low resistance reading from B+ to chassis ground. Check that both leads of the focus coil are not shorted to chassis ground. What value fuse is in the holder on the rear chassis? One would expect that fuse to go open if B+ is pulling excess current. You mentioned you don't have Sams 110, by any chance do you have Sams 101, folder 5?

[vortalexfan]

Originally Posted by Kevin Kuehn

Double check that your replacement electrolytic caps are polarized correctly, if one is reversed it can fail and act like a dead short. Also look for any unusually low resistance reading from B+ to chassis ground. Check that both leads of the focus coil are not shorted to chassis ground. What value fuse is in the holder on the rear chassis? One would expect that fuse to go open if B+ is pulling excess current. You mentioned you don't have Sams 110, by any chance do you have Sams 101, folder 5?

When I replaced the Power Supply caps I hooked the positive leads up to their own terminals and the negative leads up to the same terminal which I then bridged over to another empty terminal next to it so I had plenty of room for all of the wires, resistors and the electrolytic capacitor negative lead that all connected to the negative lead of the Power Supply cap.

As for the fuse size I checked the fuse that was in there and it was the correct size fuse.

As for the Sam's, I believe i do have 101 folder 5 in my stash, I'll double check when I get home, as I'm currently at my parent's house for the day.

I've worked on a couple of vintage B & W tv before and this is the first one I've had any major problems with before.

[vortalexfan]

Originally Posted by Kevin Kuehn

Double check that your replacement electrolytic caps are polarized correctly, if one is reversed it can fail and act like a dead short. Also look for any unusually low resistance reading from B+ to chassis ground. Check that both leads of the focus coil are not shorted to chassis ground. What value fuse is in the holder on the rear chassis? One would expect that fuse to go open if B+ is pulling excess current. You mentioned you don't have Sams 110, by any chance do you have Sams 101, folder 5?

OK so a little update, I was able to get the broken terminals in the video amp tube socket replaced with some terminals from a parts tube socket from a junk single tube suitcase record player, and I powered it up and the 5U4G tube is still arcing even with all of the power supply caps replaced.

Although I did think of something that could be causing my issues still,
there is an oddball dry electrolyitic capacitor in the power supply that I didn't bother replacing because it was a Dry Electrolytic and usually with my experience those Dry Electrolytics rarely fail.

Plus its an oddball value that I've never seen before, not even in modern TV sets, its a 500 MFD 5 VDC Dry Electrolytic Capacitor that is tied into the power supply chain, and maybe in this case that Dry Electrolytic did short out and that's whats causing my Rectifier tube to arc inside.

Does that sound like it could be a possibility?

[Electronic M]

Possible but highly unlikely.

To troubleshoot this (and I have had to troubleshoot similar issues before) disconnect the B+ rail and filter cap connection to your the 5U4 (remove all load from it). If it stops arcing you have confirmed the B+ rail has a short or severe overload. If it continues to arc with no load then the socket may have a short or the transformer may be supplying too high an AC voltage.

Assuming the arcing stopped reconnect the first filter cap then reconnect small parts of the B+ 1 at a time (not all at once) the first one to cause arcing is your short, and you'll have to pick it over with a fine tooth comb to find the root cause.

I've fought a few B+ shorts. Sometimes they are obvious if you look everywhere, sometimes they are hidden... Case in point: a 40s zenith chassis with only a couple rubber wires in seemingly good shape...the single rubber wire feeding the eye tube had one dry patch of insulation that had disintegrated right at the eyelet where it passed through the chassis, and was invisibly shorting to chassis there... just because you can't see a problem, and have replaced the likely suspects doesn't mean the problem isn't there.

[Kevin Kuehn]

All the electrolytic caps should be replaced, dry or not. Over time the dielectric breaks down just like the paper caps do. That 500 mfd cap can be replaced with a 470 mfd. Voltage rating can be higher, say a modern 25v shouldn't be much bigger than the original.

[vortalexfan]

Originally Posted by Electronic M

Possible but highly unlikely.

To troubleshoot this (and I have had to troubleshoot similar issues before) disconnect the B+ rail and filter cap connection to your the 5U4 (remove all load from it). If it stops arcing you have confirmed the B+ rail has a short or severe overload. If it continues to arc with no load then the socket may have a short or the transformer may be supplying too high an AC voltage.

Assuming the arcing stopped reconnect the first filter cap then reconnect small parts of the B+ 1 at a time (not all at once) the first one to cause arcing is your short, and you'll have to pick it over with a fine tooth comb to find the root cause.

I've fought a few B+ shorts. Sometimes they are obvious if you look everywhere, sometimes they are hidden... Case in point: a 40s zenith chassis with only a couple rubber wires in seemingly good shape...the single rubber wire feeding the eye tube had one dry patch of insulation that had disintegrated right at the eyelet where it passed through the chassis, and was invisibly shorting to chassis there... just because you can't see a problem, and have replaced the likely suspects doesn't mean the problem isn't there.

Well I'm actually wondering if that 500MFD 5 VDC capacitor is the problem because I looked at the Sam's and it says that the 500 MFD 5 VDC capacitor is the Bias Filter Capacitor, which if that's working right it may very well cause my rectifier tube arcing issue.

As for the B+ Voltage Rail and where it connects to the rectifier tube and how to test it where is that point on the Rectifier tube socket?

[vortalexfan]

Originally Posted by Kevin Kuehn

All the electrolytic caps should be replaced, dry or not. Over time the dielectric breaks down just like the paper caps do. That 500 mfd cap can be replaced with a 470 mfd. Voltage rating can be higher, say a modern 25v shouldn't be much bigger than the original.

I checked the Sam's for this TV and I Figured out that the 500 MFD 5 VDC Capacitor is the Bias Filter Capacitor, so it seems that if that capacitor has indeed failed like I am suspecting that it did, then it could very well be the source of my 5U4G's Arcing problems.

Would a 470 MFD 6.3 VDC electrolytic cap work as a replacement for this capacitor?

Also there's a 100 MFD 150 VDC capacitor that was a replacement at some point for C7 which was a 100 MFD 25 VDC electrolytic capacitor that must of failed at some point in time.
The strange thing is that when they hooked up the negative lead on that capacitor instead of using using the floating ground rail on one of the tube sockets or something they hooked the negative lead of that electrolytic to the chassis, which might also be causing some of my issues, C7 by the way according to the Sam's is the Vertical Output Tube Cathode Bypass Capacitor.

[Electronic M]

a 6.3V cap is a fine sub for the 5V.

The B+ connection point will be one of the 5U4 heater pins...Without the schematic in front of me, I can't tell you which, but it shouldn't be hard to figure out.