I recently got this neat old Sears TV (OEM tosihba). I got this TV form my graet grandma. The TV does need repair to make it work but not unexpected for TV that was made sometime in 1968. The tv has bad vertical linearity ( the virtical doesn't fill the screen completely), a hum bar ( bad PSU cap), sound has distortion and is not very loud, and contrast control doesn't change way the picture looks. I do have CRT tester that could test this CRT in this TV but it don't think it works and I don't want to ruin the CRT testing the tube. The CRT has very good brightness and will make a good picture I think. The first thing it needs is those 50+ years old Japanese electrolytic capacitors replaced. It will be a while before I can get to working on it. I have to try an fix a Montgomery ward TV form 1987 and webcor console record player form the late 50s and then I can get to work on this Sears TV

Shango just started on a similar one.

https://www.youtube.com/watch?v=hqH8dZuUuoQ

If yours is solid state it will need every small electrolytic in the
hoz & vert & every control cleaned. They were that way even at 5 yrs
old. They will work good then.

73 Zeno:smoke:
LFOD !

It looks to be all tubes and no transistors.

I recently got around to working on this old sears tv and have made some good progress. I have recaped the tv. The tv now makes a pretty watchable picture but the sound is still not working right. The sound is very staticy like it's tuneing in a very weak signal.

I need to test the following tubes 6gh8 detector amp-vert mult and 6hz6 audio detector. My tube tester is a knight 600B and I do have the books(manuals). I couldn't find these tubes listed in the books I have. So I'm stuck at the moment and if any one knows how I can tests these tubes in my tube tester it would be much appreciated.

For the tester get a tube substitution guide & see if any listed subs
are there & test it that way. May not be perfect but it should show
up a really bad tube.

https://www.ebay.com/itm/255079450151?hash=item3b63eb8627:g:l9QAAOSw-Xdg90sh

Audio tips
A HISS like a weak FM station is the audio IF stage.
A BUZZ or ticking is the audio detector stage.
The buzz can be effected by the ACG, fine tuning & your source.

73 Zeno:smoke:
LFOD !

For the tester get a tube substitution guide & see if any listed subs
are there & test it that way. May not be perfect but it should show
up a really bad tube.

https://www.ebay.com/itm/255079450151?hash=item3b63eb8627:g:l9QAAOSw-Xdg90sh

Audio tips
A HISS like a weak FM station is the audio IF stage.
A BUZZ or ticking is the audio detector stage.
The buzz can be effected by the ACG, fine tuning & your source.

73 Zeno:smoke:
LFOD !
I bought the book and I will have it by the end of the month. I think the 6gh8(sound if amp-vert mult) because the vertical was shrunk but I was able to adjust it to fill the screen. Thaks for the help.

6GH8's & their cousins #GH8 were probably the worst tube
ever built. Some RCA color sets used 5 of them & after a few
yrs they would be weak or leaky. Always suspect them !

Another tube checker tip. The first number of a tube is the filament
voltage. A 6GH8 is the same as a 5GH8 or a 4GH8. Just the filament
needs to be set to the proper voltage to test. You can also smoke out
a bad tube by turning up the filament one notch ( say from 6-7volts) this
can find leaky tubes that act up after the set runs a while & gets REAL hot
inside.

BTW You may be tempted to adjust the transformers in the audio. DOO NOT do
it unless you take precautions ! AND dont change disc caps. They almost
never go bad !

73 Zeno:smoke:
LFOD !

6GH8's & their cousins #GH8 were probably the worst tube
ever built. Some RCA color sets used 5 of them & after a few
yrs they would be weak or leaky. Always suspect them !

Another tube checker tip. The first number of a tube is the filament
voltage. A 6GH8 is the same as a 5GH8 or a 4GH8. Just the filament
needs to be set to the proper voltage to test. You can also smoke out
a bad tube by turning up the filament one notch ( say from 6-7volts) this
can find leaky tubes that act up after the set runs a while & gets REAL hot
inside.

BTW You may be tempted to adjust the transformers in the audio. DOO NOT do
it unless you take precautions ! AND dont change disc caps. They almost
never go bad !

73 Zeno:smoke:
LFOD !
The only tube that looks like it was replaced was the damper tube. The rest look to be original to the set.

Let me guess, it was filled with those lousy grey oil filled caps that look like electrolytics?

Heres the subtitution numbers for 6GH8A. You might find something that matches up with your Knight.

https://i.postimg.cc/3x33wt2M/Screenshot-2021-08-23-12-02-32-1.png (https://postimages.org/)

There's a assortment of substitution books on World radio history in PDF format free for download.

Enter this in google to search them.

tube substitution site:worldradiohistory.com

I like how that old tube substitution book has the repeated typo of typing B instead of 8...6EAB is going to get a heck of a lot fewer search hits than 6EA8.



https://i.postimg.cc/3x33wt2M/Screenshot-2021-08-23-12-02-32-1.png (https://postimages.org/)

There's a assortment of substitution books on World radio history in PDF format free for download.

Enter this in google to search them.

tube substitution site:worldradiohistory.com

I like how that old tube substitution book has the repeated typo of typing B instead of 8...6EAB is going to get a heck of a lot fewer search hits than 6EA8.


I wonder if it happened in the PDF searchable text conversion. I've seen errors like this before with certain styles of fonts.
I can't imagine Sams making such a error.

I can't imagine Sams making such a error.
You are kidding, right?:D

You are kidding, right?:D

I can't imagine Sam's doing that exact error either....Sam's usually likes to print diodes backwards and get tubes and transformers backwards on layouts or adding extra zeros to capacitor values so capacitance on the parts list and schematic of the same folder won't match for some specific part. They even mirror imaged a roundy so that it's folder had the controls on the left (opposite of reality). :D

The tube tested shorted but with very good emission

It a tube tests shorted it isn't usually a good idea to go any further.
A short might damage the tester or at least throw off the emission test.

Try smacking it on a wooden table and see if that clears the shorts.

Its know time to get back to this project. I need to get a 6gh8 as the tube is bad and it also fell on the floor and got smashed into thousand little pieces whoops. I have never had to buy any tubes in the past online as have few good tubes that i have got out of junk equipment. I do Know I can go to eBay and get tube but I would like to know if any one here knows a better places to get tubes or has 6gh8 they would be willing to sell.

I buy a lot of the tubes I don't already have from this guy when he's at the local swapmeets. I don't have experience ordering from him from his site, but I'd assume he handles that well too. http://hamtubes.com/

The 6GH8 has many subs. Check your stash for 6EA8 or 6U8.

The 6GH8 has many subs. Check your stash for 6EA8 or 6U8.

+1
Those tubes tend to be better than the original 6GH8 in many applications.
My Sam's sub book also lists 6AX8, CQ8,GJ8,LM8,HL8 and 6KE8 as potential subs.

I have bought from the Tubestore, see if they have what you need.

https://www.thetubestore.com/

Thanks for information I will go look threw my tube stash and see if I have substitute.

Shango just started on a similar one.

https://www.youtube.com/watch?v=hqH8dZuUuoQ

If yours is solid state it will need every small electrolytic in the
hoz & vert & every control cleaned. They were that way even at 5 yrs
old. They will work good then.

73 Zeno:smoke:
LFOD !

We saw alot of "little" Sears stuff come in the shops I worked in here in eastern PA over 40 years ago. Still, we knew they were as simple as a GE S-2 LOFL, and people wanted them fixed. Also, I knew they were Japanese unless 528/529 prefix, with tubes not stocked for any set over 10 years old.

If the elder-boss wasn't in to turn them away for that reason, I would write them up and quietly source that 4DK6 (or whatever) at home, then say "hey look what I found?":D and if the boss was in that day, he'd say it's a "bastard" number he did not remember ordering.
The bad caps responded to freeze spray back then, dirty pots responded to Lube a trol.