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-   -   Bush Dual standard chassis. (https://www.vintage-radio.net/forum/showthread.php?t=179625)

Nuvistor 3rd May 2021 9:40 am

Re: Bush Dual standard chassis.
 
I found the hybrid TV135U a decent set and gave very little trouble often the first repair after 4 or 5 years. The TV135R however was a different matter.
I didnít have many LOPTX failures in those models but the TV141 and later models had a bad reputation, I kept transformers on the van, at least they were easy to replace.

dazzlevision 3rd May 2021 9:53 am

Re: Bush Dual standard chassis.
 
Quote:

Originally Posted by Welsh Anorak (Post 1370365)
I'm very surprised that transistors were used on the cheaper models' tuner and IF strips - this would be one of the earliest examples of them being used on a large screen TV, wouldn't it?

There was an era of some UK manufacturers offering either a traditional all-valve (apart maybe, from the UHF tuner) d/std mono TV concurrently with a Germanium hybrid model:

RBM with the TV135 hybrid and the TV135L (restyled cabinet version of the TV125).

GEC Sobell with the 2012 and 1012 hybrid and the 2010 and 1010 all-valve.

Thorn had a version of the 950 all-valve chassis with a transistor integrated UHF/VHF pushbutton tuner - the 970 chassis.

Pye/Ekco were the bravest, with their 31F/40F hybrid chassis (following on from their all-valve 11U chassis), which was let down by the "rocket propelled, flying pushbuttons" of the integrated UHF/VHF pushbutton tuner!

Decca stayed with valves throughout the d/std era (IIRC) and ITT/STC/KB did the same.

Philips were a bit later in the hybrid market with their 210 hybrid d/std chassis sets.

slidertogrid 3rd May 2021 3:16 pm

Re: Bush Dual standard chassis.
 
Just to add to my confusion with these chassis' I decided to look at a Murphy version I have. This has the same chassis as the Bush but this set has a Fenbridge guard which I would expect to predate the direct vision tube in the Bush This set however has a Transistorised UHF tuner so presumably a later model to the Bush...
This set needs a few broken controls replacing it has no EHT and when switched to 625 promptly burnt out its Brightness control! Happy days!
Bad news is that it has a Mazda " Gold star" Tube- Good news it seems to have a replacement LOPT..
I will come back to this one!
I had lots of the earlier sets with the plate glass screen back when I was I lad but I didn't see many of these later PCB ones, I went on to the A640 which I really liked, they seemed to go on for ever if the LOPT held on!
Rich

slidertogrid 3rd May 2021 3:20 pm

Re: Bush Dual standard chassis.
 
4 Attachment(s)
Pictures of the Murphy.

dazzlevision 3rd May 2021 5:23 pm

Re: Bush Dual standard chassis.
 
Quote:

Originally Posted by slidertogrid (Post 1370509)
Pictures of the Murphy.

Your set is the Murphy version of the TV135R. Murphy sets seemed to use the Fenridge guard rather than a direct vision CRT for a few years after Bush sets went direct view. The last ones were used in the Murphy V153 and V159 (which used the same chassis as the Bush TV141 & TV148. The transistor UHF tuner in your Murphy may have been added after it was bought....

Out of interest, what is the model number of your Murphy, which looks like the earlier model V849, which was designed for rental (and had a simpler/cheaper cabinet).

Techman 3rd May 2021 11:41 pm

Re: Bush Dual standard chassis.
 
I worked on loads of those TV125s and their variants back in the mid 70s. I really liked them, but I remember that the line transformers didn't like damp old houses, other than that, I seem to remember that most of the faults were a thermistor or various valves.

dazzlevision 4th May 2021 10:46 am

Re: Bush Dual standard chassis.
 
1 Attachment(s)
The attached photo of an RBM fitting instructions sheet might be of interest. It reinforces my view that the Bush TV125 and TV135 models (and the Murphy V800 & V900 series) all used the same LOPT.

Heatercathodeshort 4th May 2021 11:29 am

Re: Bush Dual standard chassis.
 
That is a very useful sheet especially as the connections were changed with modified transformers. The Mazda Gold Star tubes held up well on emission compared with the earlier CME1901 etc but they did suffer from O/C cathode connections. You will probably find it is OK as most of the problems were encountered within the first three years. J.

slidertogrid 4th May 2021 5:57 pm

Re: Bush Dual standard chassis.
 
Yes very useful ! Many thanks.:thumbsup:
I am going to get the Bush back on the bench first and put some power through the overwind. Then I will see if I can find out what is wrong with the Murphy .
What is the best method to warm up the overwind?
I have got a mains transformer that I think is around 20/24 Volts secondary will that do ? Should I use AC or rectify it or doesn't it matter?
Rich.

dazzlevision 4th May 2021 6:50 pm

Re: Bush Dual standard chassis.
 
I should add that the colour of the LOPT connecting wires can vary (according to the relevant Bush service manuals).

PYE 405 4th May 2021 8:46 pm

Re: Bush Dual standard chassis.
 
Quote:

Originally Posted by slidertogrid (Post 1371062)
What is the best method to warm up the overwind?
I have got a mains transformer that I think is around 20/24 Volts secondary will that do ? Should I use AC or rectify it or doesn't it matter?
Rich.

AC or DC it won't matter, but I found about 35v was needed to get it hot enough to aid seperation of the overwind in my case. Obviously you want it to slide off without undue force, but not so hot that you can't hold it.
Oh, and it will be messy. Be prepared to peel off all the soft tar to reveal just the overwind doughnut. You won't harm the windings as they will be covered in a fabric tape.

PYE 405 4th May 2021 9:11 pm

Re: Bush Dual standard chassis.
 
Seperating the overwind from the bobbin and the inner 625 tuning winding may seem quite drastic and would never have been done back in the day when replacement LOPT's were readily available. Different story now of course.

A supply of 2inch Kapton tape could be used to re-insulate the tuning winding. It may withstand the heat better than polythene tape, although my effort is still working well almost six years after doing it.

One thing to watch is that you maintain correct position and connection of the tuning winding upon re-assembly otherwise there will be no 625 line EHT.


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