Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Jan Fri 24, 2020 7:07 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 34 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: First Tube TV Restoration - Emerson 612
PostPosted: Oct Mon 27, 2014 2:54 am 
Member

Joined: Oct Fri 03, 2014 9:05 pm
Posts: 118
Location: Marshall, Michigan
Earlier this week I got my first tube tv to work on, an Emerson 612. I have worked on older tv's before, but never one that uses tubes. The pictures I took are after I started taking it apart. The cabinet is in pretty good shape, with only some wear on the top. The chassis seems to have very few, if any repairs except for some really new repairs on two capacitors. I found two times were two resistors were used in series to substitute 1 resistor but whoever did that did a very good job so I'm not sure if maybe there was a shortage of those resistors at the time of assembly. Besides a recapping I need to by a new ballast tube to replace the one that is missing and the connectors for the antenna input are missing the plastic terminal and will probably need to be replaced. The 10bp4 tests good but just only, so I probably will have to look for a better one in the long run. Other than that this set seems to be fairly straightforward, the only annoying thing I've found so far is that there is no way to remove the high voltage cage without unsoldering the resistors on the back of the cage. One question I had was that the rubber on the anode cap has a crack which I assume should be replaced before using. Is there a way to just exchange the cap without replacing the entire high voltage cable, because the cable is in good condition. If anyone else has any tips or sees a concern please let me know. Thanks!

Image

Image

Image

Links to larger images:

http://i.imgur.com/gyvIUzb.jpg
http://i.imgur.com/XpMxcCB.jpg


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Oct Mon 27, 2014 1:44 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 2035
Location: Lafayette, CO
The high voltage wire solders on to the tip. Pull them apart and put a better cup there. Otherwise, you are looking at one of Emerson's PITA chassis. The set's tubes are heated by a couple of windings of the power transformer. The B+ starts out from a winding of that same transformer to gain about 15 volts A-C, referenced to chassis ground. This winding is also on the power line, so be careful. It's got a hot chassis, so be careful. You are probably familiar with rectifier bridges, so we won't go there. Those selenium jobs are the same thing, pre-solid state. The ballast that was there can be done away with....just figure some resistors between the bridge and the A-C transformer to roughly match the needed output to run the set. The rest is replacing capacitors, tubes, resistors, etc. Craig


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Oct Tue 28, 2014 12:24 am 
Member
User avatar

Joined: Mar Sun 01, 2009 10:27 pm
Posts: 5109
Location: Ann Arbor, MI
According to the Sams I got from the Early Television Museum, there was an earlier (I assume) circuit that used five 25Z6 tubes instead of the selenium rectifiers. The Sams seems to show that the extra boost winding on the transformer is not used when the selenium rectifiers are used.

The Sams gives the values for the resistors in the ballast tube. So just get a male octal plug and some resistors.

It sure is odd that they used a transformer for the filaments but did not also use it for the B+. They saved the cost of a winding on the transformer but added the cost of two rectifiers and five electrolytic caps! Strange.

_________________
Tom


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Oct Wed 29, 2014 1:36 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 2035
Location: Lafayette, CO
Notice how the chassis-mounted controls are insulated from the chassis. Craig


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Oct Thu 30, 2014 11:12 pm 
Member

Joined: Mar Thu 28, 2013 1:45 pm
Posts: 87
Location: Bracebridge Ontario, Canada
Wow, is that the way the chassis left the factory? That is pretty disgusting.


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Oct Fri 31, 2014 4:43 am 
Member
User avatar

Joined: Mar Sun 01, 2009 10:27 pm
Posts: 5109
Location: Ann Arbor, MI
All those extra holes are most likely for the alternate power supply circuit that used five 35Z6 rectifier tubes instead of the selenium rectifiers that are in this set. The chassis looks mostly untouched from the way it left the factory.

_________________
Tom


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Oct Fri 31, 2014 5:27 am 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 28211
Location: Detroit, MI USA
Emerson was not frequently praised for their build quality, although many of their sets worked OK. Some of their other sets may be a little neater but they don't usually compare to the way an RCA was built. This is a perfect example of designing a set that could be assembled and sold at a certain price point. It could have just as easily been built as a series string chassis and eliminate the transformer completely, but they may have wanted to include the transformer for advertising purposes. In those days, their cost on the transformer was likely only a few dollars at the most.

_________________
Dennis

Experience is what you gain when the results aren't what you were expecting.


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Nov Wed 05, 2014 5:10 am 
Member

Joined: Oct Fri 03, 2014 9:05 pm
Posts: 118
Location: Marshall, Michigan
Started working on recapping the chassis. I'm not the fastest but I made some progress. I think the hardest area to work on will be the bottom right because there is a lot of wires and it's a cramped space. I noticed a few interesting things while working. One is some of the larger mounted caps are wired to the chassis with some bare wire. I don't see any indication this is anything but factory but it seems somewhat cheap to me. Also it appears there was some sort of wax leaking from one of the transformers but based on the direction it melted it seems like it should have only occurred if the chassis was on it's side. As long as it's good it's not an issue, but interesting none the less.

Image

Image

Image


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Nov Wed 05, 2014 3:02 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 2035
Location: Lafayette, CO
That wax from the transformer was probably there from day one. They have to let the shellac dry. Also, with that weird power supply there's bound to be at least one of the original electrolytics grounded in some way. What I did long ago was to put in a discrete bridge. You've got an input.....an output----and there you go. A pair of power resistors at either end will keep current and voltage in specs. Emerson did the same thing with a ballast but as you see it is rather messy. Craig


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Nov Thu 06, 2014 5:57 am 
Member
User avatar

Joined: Mar Sun 01, 2009 10:27 pm
Posts: 5109
Location: Ann Arbor, MI
There are at least 4 electrolytic caps where the positive terminal is grounded and the negative terminal is a source of negative voltage. Well, if you use bare wire then you do not have to strip any insulation. A big cost savings I am sure. :)

_________________
Tom


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Nov Thu 06, 2014 7:04 am 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 28211
Location: Detroit, MI USA
To a company which built things at as low a cost as possible like Emerson often tried to, using any insulated wire where it wasn't need might not have got past the bean counters. I don't have my old Radio Master parts catalog in front of me at the moment, but I'd bet the difference in cost on a 1000' spool of wire was significant between bare and insulated even in 1950.

_________________
Dennis

Experience is what you gain when the results aren't what you were expecting.


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Nov Thu 06, 2014 9:17 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10602
Location: Redlands CA
These are not the easiest sets to rebuild, look at all those Twist-Lok cans!!

I have the one with the 5 25Z6 rectifiers, it's an even bigger nightmare! I managed to wire a cap in backwards and blew out 4 NOS tubes.


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Nov Thu 06, 2014 10:40 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 2035
Location: Lafayette, CO
Eric...and others...try using a 6.3 volt a-c source to test the bridge. This assumes solid-state diodes are being used. If you get 15 volts DC, things are wired correctly. I really don't trust that circuit only for its complexity. Craig


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Nov Mon 17, 2014 3:27 am 
Member

Joined: Oct Fri 03, 2014 9:05 pm
Posts: 118
Location: Marshall, Michigan
Update post. I've been slowly recapping the chassis over the past week or so. At this point all the paper caps have been replaced and some out of spec resistors. I still need to replace the selenium rectifiers. I don't have the tools to restuff the large caps and since I'm in an apartment I can't really do that right now anyway with the tar smells, so for now I'm thinking I will mount the caps under the chassis. Luckily even though there are a lot of cans they are all single cell except for two. One small annoyance is the large resistors mounted on the high voltage cage seem to be bad so I will have to replace those, though I think I will be able to buy some terminal strips and mount them in the lower right corner. For replacing the selenium rectifiers I remember you need to add a 5 or 10 ohm resistor first, does that sound about right?

Image

Image


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Nov Mon 17, 2014 3:40 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 2035
Location: Lafayette, CO
10 or so ohms sounds fine. You will probably increase that later to put the B+ on specs. PLEASE try the bridge with low voltage AC first. Craig


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Dec Mon 15, 2014 4:28 am 
Member

Joined: Oct Fri 03, 2014 9:05 pm
Posts: 118
Location: Marshall, Michigan
Sorry for not updating in a while, I have been busy and the slow progress I had been making wasn't worth making a post about. I finally finished recapping the chassis. I also make a ballast using new resistors and a base off of ebay. The hardest part for me was replacing the large resistors that were mounted on the high voltage cage. Most of them were either open or very high in the thousands of ohms instead of a few hundred. I wired them underneath the chassis. I am ready to power the set up but first I want to get an isolation transformer and a variac to slowly power the set up. Does anyone have a suggestion of what kind to get? Are there any two in one isolation transformers and variac systems? Also once I do have a variac how slowly should I power up the set. Has anyone written a guide or made a video? Thanks for the help

Image

Image


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Dec Mon 15, 2014 7:20 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10602
Location: Redlands CA
I don't know the specs on the ballast but are those resistor high enough wattage to handle the load?


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Dec Mon 15, 2014 2:43 pm 
Member

Joined: Oct Fri 03, 2014 9:05 pm
Posts: 118
Location: Marshall, Michigan
Eric H wrote:
I don't know the specs on the ballast but are those resistor high enough wattage to handle the load?


The sams only gives the ohms, but I used 3 watt wire wound resistors. Let me know if the sounds like to low a wattage and I can build a new one.


Last edited by pendulum on Dec Mon 15, 2014 6:59 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Dec Mon 15, 2014 6:34 pm 
Member
User avatar

Joined: May Fri 29, 2009 4:35 am
Posts: 2159
Location: Chicago, IL USA
According to Riders Vol 2, the ballast is:

10 ohm - 3W (pins 1, 2)
10 ohm - 3W (pins 1, 2)
75 ohm - 5W (pins 4, 5)
75 ohm - 5W (pins 5, 6)
75 ohm - 3W (pins 7, 8 )


I would increase those 75 ohm resistors on pins 4,5,6 to at least 5 watts.


Top
 Profile  
 
 Post subject: Re: First Tube TV Restoration - Emerson 612
PostPosted: Dec Mon 15, 2014 7:01 pm 
Member

Joined: Oct Fri 03, 2014 9:05 pm
Posts: 118
Location: Marshall, Michigan
bandersen wrote:
According to Riders Vol 2, the ballast is:

10 ohm - 3W (pins 1, 2)
10 ohm - 3W (pins 1, 2)
75 ohm - 5W (pins 4, 5)
75 ohm - 5W (pins 5, 6)
75 ohm - 3W (pins 7, 8 )


I would increase those 75 ohm resistors on pins 4,5,6 to at least 5 watts.


Thanks bandersen, I'll make sure to rebuild it correctly before I try to power the set up. Also while looking around for variacs and an isolation transformer I found the sencore pr57 which seems like a nice all in one unit. I think some people here use them, do you guys think that is a good unit?


Top
 Profile  
 
Post New Topic Post Reply  [ 34 posts ]  Moderators: 7jp4-guy, Mr. Detrola Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 10 guests



Search for:
Jump to:  


























-->


Privacy Policy :: Powered by phpBB