Bush TV12B Restoration

[mark pirate]

If after testing the EF50`s you still cannot get a signal , make sure the pins are clean and give them a wiggle.

Hi Lee, already done that, I will test the valves tomorrow.

I'm looking forward to seeing a picture on it Mark.

Hi Mike, So am I!
I was a bit disappointed to be honest, but I don't like a restoration to be too easy!

Mark

[Jac]

Sutton Coldfield was ch. 4.

Jac

[mark pirate]

Thanks Jac, I have made a note of it.

Mark

[beery]

Hi Mark,

These sets use reaction on the sound RF stage to increase the gain. If the sound sensitivity (reaction control) is turned too far the stage will oscillate, knocking out both sound and vision. Try it with the sound sensitivty set to minimum.

Cheers
Andy

[mark pirate]

You know how it is, when you cant leave a project alone....
I dragged out the valve tester and went through the EF50's, all tested a bit low.
But one had zero emission, and I do mean none whatsoever!

A quick trip to the workshop turned up a dozen used specimens, most of which tested good to very good. I picked the best and headed indoors, I soon had the valve in place and the set fired up.

With the Aurora tuned to channel four I now had test card C and sound
The results and the culprit can be seen below.

Mark

[MonochromeMarc]

Hi Mark,

What a darn good picture, that's what I call a result
Hope all goes well on soak test.

Well done that man !

Marc.

[McMurdo]

looking good! First impressions of the pic compared to the TV22??

[beery]

Fantastic!

[mark pirate]

Hi Kevin, The TV22 had a superior picture before the LOPT died, but to be fair the CRT is as good as new with no ion burn at all.

The TV12 still needs a bit more tweaking and I will be swapping some of the low EF50's. I also may get an improvement when I fit a new EY51.

The LOPT for the TV22 is being rewound at the moment, so it will be interesting to have the sets side by side for comparison once it is up and running again.

Hope all goes well on soak test.

Hi Marc, so far so good, It has been running for the last hour and seems fine.
Even the ion burn is less noticeable than it was.

I will give it a good run tomorrow while I make a start on the cabinet.

Mark

[brianc]

Excellent work, Mark.

[mark pirate]

Thanks Brian, I wish I had tested all the valves in the RF deck before spending time trying to work out why I could not get a signal through it!

I have never come across a valve that showed absolutely no emission whatsoever, the Needle on the Taylor did not move at all

I had it running over two hours last night with no problems, but there are a few niggles to attend to.
There is some sound on vision, the speaker is rubbing slightly and turning up either brightness or contrast increases the picture size.

A couple of the pots also need a clean, but other than that it has come up very well for a set that was in such a poor state.

Hopefully I will get it finished off over the next few days.

Mark

[ukcol]

Originally Posted by mark pirate

.......... it has come up very well for a set that was in such a poor state.

And in just 10 days! Well done Mark.

[BassoonBloke]

Hello All,

I've come across an EF50 that looked perfect, but had a crack in the glass at a pin junction. So just a total loss of vacuum. Because you cannot see the getter you would never know there was a problem. Surprisingly it didn't work.
If you peel off the aluminium outer jacket I bet the same has happened to your EF50.

Cheers,
Alan.

[mark pirate]

If you peel off the aluminium outer jacket I bet the same has happened to your EF50.

Actually I have never thought of undressing one, I will give it a go.
I don't think it has lost it's vacuum, it felt the same temperature as the others when in the set, there is no bent pins or any obvious damage that I can see.

And in just 10 days! Well done Mark.

It is not finished yet though, but hopefully will be by tomorrow

I must admit that there has been a fair few hours put into this restoration, I estimate that half of it was getting it cleaned up!
I think it was easier to restore than the TV22 in some ways.
I have one more Bush Bakelite set (TV32) to restore, but the next set on the list is going to be A Pye set from 1948.

Mark

[HamishBoxer]

Great job and enjoyed following the posts.

[ukcol]

I'm looking forward to the Pye write up.

[mark pirate]

I have now run the set for a good few hours, I found the sound on vision fault was down to yet another faulty EF50.
I initially thought it was down to poor contacts on the valveholder, but substituting a known good one cured the problem.

I removed the speaker to see if I could repair the slight rubbing on the voicecoil.
It is one of those strange back to front Celestion speakers also used in the DAC10 radio, it was a bit mucky so I fired up my air compressor and the amount of muck that came out was truly amazing!

It had definitely helped, but it was still rubbing. I loosened off the screws on the magnet and a bit of sideways pressure on the magnet with a large screwdriver improved it to the point where the distortion had all but gone.

I carried out a good washing both inside and out on the cabinet, and once dry gave it a good polishing with T-cut followed by neutral shoe wax.
It has come up a treat and has a lovely deep shine

I refitted the safety glass and the chassis to the cabinet along with the knobs, which also polished up well.

It has certainly been an interesting restoration, especially just after completing a TV22, The receiver is a better quality unit in the TV12, and just needed five capacitors replacing, unlike the 25 that had to be done on the later TV22. I also prefer the layout on the TV12, I never really liked the idea of the screening can containing the LOPT, PL38 and PZ30. All that heat round the LOPT can't help with it's reliability.

The set has been running for over five hours with no problems, all that is left is to put the back on and start on the next set...

Mark

[MonochromeMarc]

Hi Mark,

Altogether an excellent restoration and very well written up too
Looking forward to the next....slice of Pye perhaps

Marc.

[McMurdo]

Sound on vision you say! I get a bit of that creeping on mine when it's been on half an hour or so. I've masked it for now by turning the audio down on the aurora, I wonder if its also an EF50 maybe drifting when it gets hot.

[mark pirate]

I am not sure if the EF50 had a loose internal connection, but it got worse 10 minutes after warm up, I also found tweaking the tops of the coils improved both sound and vision considerably. I noted the original position of each before adjusting, less than half a turn was needed.

I am sure it could perform even better with a new set of EF50's and realignment.
But I am quite happy with it overall, the set is very stable from switch on.
Both timebases are rock solid when the picture comes up, which takes around one and a half minutes to appear.

I will give the set a good run over the next week to see if any problems arise now the back has been refitted.

I'm looking forward to the Pye write up.

Looking forward to the next....slice of Pye perhaps

I will be making a start on the Pye tomorrow, so will start a new thread for it.

Mark