Bush TV135LU

Mindful of confusing model numbers: whilst looking at something else I noticed two Bush manuals - one for the TV183S, the other for the TV183SS.

One uses the A774 chassis, and the other uses a peculiar "cut-down" version of the A640 chassis which, as far as I can tell, is an A640 with all the 405 bits missing! (IIRC that's an A791)

Posted By Nuvistor

I am on a nostalgia trip now, I have been looking at those other two manuals I mentioned earlier, realising how much I had forgotten.

I have no doubt if a Bush TV125/135 were placed in front of you, before too long it would all come flooding back as if it were yesterday. I'm reminded of a couple of events, the first when John (Jayceebee) initially came over to my workshop. John had not seen a Thorn 3000 in over 30 years but in went his hands, instinctively knowing where all the little pre-sets were located, pretty darn impressive and even John remarked how surprised he remembered.

The second event was a chap buying a GEC BT322 from me for his father. You see his father was an ex TV engineer who had alzheimers, had a devil of a job remembering things. However put a dead TV in front of him and he could fix them without hesitation.

It's amazing how the memory can store things and certain triggers can bring it all back again.

Now, what was I doing?....Oh yes, the LOPT and it seems to have a healthy ring.

Although the insulation between the tuning winding and the actual overwind measures open with a standard DVM, once 500vdc is applied between the two it is obvious that things are not good. It looks about 2 megohms according to my old insulation tester. So, it is perhaps not surprising that a few thousand volts will be effectively shorted to ground. 

Well it was sticky mess time by passing a small current through the overwind to heat it so the inner tuning winding could be removed along with the remaining tar. Then I removed the fabric tape from the former and replaced it with polythene tape for insulation. Re-fitted the inner winding ensuring a snug fit, and then re-assembled the LOPT. I sealed the open ends of the overwind doughnut with molten tar to secure it more with the inner winding. A horrible messy job, but I knew it had to be done.

So tomorrow, LOPT back into the set and we'll see if it works.

Just like playing mud pies as a kid !  ?

Except this stuff doesn't wash off so easily.  ?  

The only thing to shift it is white spirit or WD40. The worst is when small bits of tar get stuck to the soles and get trodden indoors. Yes, I have done it.  ? 

Posted by: Nuvistor

Presume you will be checking/changing the yellow TCC caps.

 

Nah....they'll be perfect Frank, even the mains bypass.... ? 

It's funny because at the back of my mind I still view any plastic cased film capacitor (other than the wax type and Hunts mouldseal) as being modern and therefore infallible. Stupid really, as it ain't necessarily so.

Those Supamolds were good in their day, they were fitted in lots of sets but seem now to have an unreliable reputation. On the UKVRRR forum there are many posts of them used in Hacker audio amps and most are found faulty.

Still modern yellow capacitors will not look out of place as replacements.

Well, I am sitting in the peace and quiet of the store, and have just heard the unmistakable sound of Merlin engines in the distance. 

On my knee I have Bush Technical Publication no. 1598, covering the TV 135L, TV 135LU, TV 135RL, TV 135RLU, TV 138RL and TV 138RLU. Appended to the manual in ink is a note which says "Intermediate Receiver - short production run between TV 125 and TV135." 

The pictured set is a TV 135LU... 

I don’t remember having that manual but we didn’t sell any L versions so I may have put it in the filing cabinet cabinet and never took it out.  

Most faults in the 125 chassis I didn’t use the manual, usually stock faults that got fixed and on to the next job. I did carry a number of manuals on the van but they were rarely required once you got to know your way around the different makes of chassis.

It's interesting then that this set was possibly of a short production run as an interim model. 

Weather too good to be in the workshop today, so re-fitting the LOPT can wait until tomorrow.  ? 

You have a rare TV there.

Yes warm today, few jobs outside this morning then I fell asleep in the conservatory for a while this afternoon, has  the song goes "Lazy Sunday Afternoon".  ? 

I should add that I have two copies of the service manual for the 135LU - would you like one? 

Posted by: PYE625

Weather too good to be in the workshop today, so re-fitting the LOPT can wait until tomorrow.  ? 

What do you mean ? Tomorrows even hotter ! Try throwing the doors and windows wide open and crank up the Quads along with some cooling alfresco refreshments ? ? ......that's what I intend to do. the LOPT can wait a little longer.  ? 

Into the workshop nice and early and re-installed the LOPT. Powered up via lamp-limiter and this time, no smoke and a healthy raster. It was clear that insulation in the overwind was defective as I first imagined and had been effectively dragging down the EHT. Not so now......

I took this pic immediately after the set warmed up, so really is first light.

As can be seen above, the set is essentially working but will of course need further adjustment/work. No capacitors or components have been replaced, only the over-wind treatment done. In fact, the chassis is still covered with dust and smells rather nice as it warms up.

Posted by: Cathovisor

I should add that I have two copies of the service manual for the 135LU - would you like one? 

That would be great Mike, and I'm sure Chris would like a scan for the library  ? 

The procedure Andrew researched, tested and devised for addressing the dreaded BUSH/Murphy LOPT fault,  was reported upon back in the Vrat 1 days, 2015 to be precise.

Its an invaluable piece of work and contribution to the community and as such it needs to be easily found. Therefore rather than having it buried away in a section thread, I have incorporated it into a service article for the B&W TV service section up top.

It can be found under Service| Black & White TV.

Andrew if there is anything you would like amended, added or removed, please PM me with your requirements.

Excellent start, you have the LOPTX repair really sorted out.