B&W TV 1963 Bush TV125CU - Skip Find

Chris, when you clean the tuner, release all of the buttons. You will then find that the band-switch actuator bar can easily be worked back and forth - from memory it is spring loaded and I used to use my thumb - see if I'm right!

You know what Terry I reckon the Ether forms a memory layer. I did exactly that and by accident my thumb activated the part you describe. Until now I was not sure if that was supposed to happen, glad it is normal operation. And yep you have total recall.

Lovely set Chris. That was the set that my parents had when I was just a baby. Ours didn't have the UHF tuner fitted though. Tas

I've been giving the knob wear issue some thought, considering all the options presented by Terry and seeing a thread where Audiomagpie drilled the shaft and knob, securing with a pin.

I remembered all my clock parts, I had a rummage and found a box of hand collets. There are many sizes, I might be able to cut the cross, although I've not figured quite how yet.

Chris, have you got a Abrafile? They seem to have vanished but were a very useful device - essentially a round file with teeth that suited a wide variety of materials. In particular, you could get one about 3mm in diameter with clips on the ends to fit a hacksaw frame. Similar blades exist for tile cutters, although much coarser, but I don't know if you can thread these through a hole - the Abrafile could be detached from the clips to allow this:  If you've still got an old fashioned hardware shop within reach that sells thing loose from drawers instead if plastic encapsulated cards, you never know what they might have! A model engineers supplies outlet might come up with something useful. Alternatively, a VRAT with a well equipped engineering workshop might volunteer to help you out ... (Hint, hint!) =================================================================================== Update: apparently the generic name is tension file but that doesn't seem to produce any useful results in a web search ... Update 2: You would have to remove the fixing from one end and contrive something to grip the blade after you've threaded it through the hole, but these could work: http://www.screwfix.com/p/forge-steel-t ... 2-pc/91629

I don't have a tool like that, I do have a Shapercraft 1000, which might work. Holding the collet without losing the ends of my fingers will be difficult.

I found another collet which is an exact fit for the end of the knob shaft, it's as though it were made for it. Even better is the square hole, I might be able to file this out with my old clock files, might be worth a go.

I should be able to use the corners of the square to pick up on the flanges on the tuner shaft. I offered the collet up to the tuner shaft, the hole is a little too small so it will need opening up before I try any filing.

... Holding the collet without losing the ends of my fingers will be difficult ...

Shouldn't be a problem - use a Mole Wrench with curved jaws to hold it.

You can get quite small ones for delicate work - I'm not suggesting that you use a massive plumbing wrench!

Whilst I was at it I decided to service the tuner mechanism, all the plungers were very stiff and slow to operate. I cleaned all the gunk/grease off and used clock oil to lubricate. Result being it operates very smoothly now and each one locks correctly.

I thought it may be stuck with dried up grease a while back.

Now I've cleaned the tuner they lock/unlock correctly and all the spindles are easy free turning, the knobs can perform the fine tuning function as long as you do it slowly.

As a result channel 1 feed from Aurora to the BBC1 channel on 405, a little fine tune and I have test card and a can hear tone albeit faint.

No cap's changed ( except snipped out C346) thus far but at least this little exercise has confirmed the tube is ok, the powesupply, the tuner and the time-bases, so now it's just a slow methodical process of replacing what needs replacing in those circuits.

I'm hoping the LOPT will hold up as I believe these were not the most robust. Although I have heard that there is a good one that Plessey produced for it. No idea about that except you can tell from the stamp/serial on the LOPT.

I'm hoping the LOPT will hold up as I believe these were not the most robust. Although I have heard that there is a good one that Plessey produced for it. No idea about that except you can tell from the stamp/serial on the LOPT.

Ooh, horrible black pitch overwind.. As long as it's not cracked, and hasn't started to bubble, it should be good. I have that to look forward to when Marc visits me next Friday, with my TV84.. Different LOPT, but same construction method.. I'm seriously thinking of taking the LOPT out and putting it in a warm dry place for a few days (or even weeks ) to dry out. Damp is the killer for these, and the dryer the LOPT, the better its chances.. It may pay, if you plan to work on it straight away, to limit the length of time it's allowed to run.. Arguably, running the set, and warming the LOPT by doing so, should also drive out the damp, but it's risky, and if it goes PHZZTTT.. That's an end to it. I would strongly advocate in favour of putting the LOPT in the airing cupboard for a week or two (provided that airing cuboard is actually kept warm, at this time of year?). Marion

The LOPT does look a bit bulbous on the over-wind ( back) compared to others I've seen. I've no frame of reference for a Bush TV125 lopt to compare, so that may be how they look. As this set will hold a special place in the collection due to its year and get used a fair bit, should the LOPT fail I will consider a rewind by Mike Barker or go down the tripler route.

Hi Chris,

That's not very different from the LOPT in the TV84 at all.. I'd say it looks OK at the moment, but it's that lumpy looking section at the back of the picture (the overwind) that's going to fail, if anything.

Luckily, we've had the hottest summer for years, and damp may not be such a major issue, but... I'd still opt for a cautious approach.

Judging from your screen-shot, you have good width, and plenty of brightness, so the LOPT is good.. It's certainly performing well.

I wonder if it's been replaced at some point, though it does look like an original to me.

Marion

As part of the usual precautionary inspection, etc, check to see if the thermistor mod has been carried out. As originally designed, the DC through it has a habit of snapping it in two!

After Terry's reminder and reading David's TV115 post today, it jogged my memory to double check my TV125 with regards the thermistor mod. It would seem someone has taken the trouble to follow part of the recommendation, in that they have moved the thermistor (TH32) and resistor (R358) from above the main dropper at the front, to behind the heat shield that's good. However they have left them in circuit in the unmodified configuration, not only that R358 is a series of two made up from 25R+50R=75R. I only gave it a cursory glance the other day so glad, I've been prompted to properly check, I have found a Radiospares 10R 10W so will perform the final part of the mod before I go any further. Quite odd that they only did half the mod 

Does anyone have data on the STC Current surge resistor CZ19?

Looking for info relating to its initial resistance, 0 degrees and resistance at 50 degrees.

One of my all time favourite sets! Worked on quite a few of these in the early 70s, but haven't seen one in the flesh since. That's a nice floor standing cabinet version too - and with a good line transformer by the look of it. It's probably due to the time of year and the very hot weather we've been having that's got it nice and dry so that you've been able to strike it up fairly quickly with no lopt issues

CZ19
resistance at 20 degrees 800 ohms
resistance at 0 degrees 1,700 ohms
resistance at 50 degrees 320 ohms

If it is any help I could provide a scan of the CZ range data from the Electroniques (STC) catalogue of 1967.

Peter

Hi Peter, that would be great for the library, I have a 1958 Brimistor data book in there but it only covers up to CZ12A

The original is sort of ok but the lead out wires are starting to come away from the ends and it has a couple of chips in the main body. I have six thermistors which look the right dimensions, pain is thermistors never seem to be marked and the trouble is measuring initial resistance, it varies. They all change due to handling and conditions (lighting to view, room etc). On the bench I took readings and noted, then checked again a little later and they had all decreased. I placed them on the window with it open to get a cool breeze over them, and took readings again ( see photo below). The first is the one extracted from the Bush, the 2nd is the closest in value to it, the last one is getting closer the more I cool it. If you take the data at face value how did they measure zero degrees, was it in a fridge? how did they drop the component temperature to take the measurements?  My workshop is an exact 20 degrees at present, I've no idea what the component is, I've no way to measure it but none not even the Bush measures the stated 800R for 20C I'm probably being well anal about this but it is intriguing to know. I will go with the 2nd as a replacement but thought I would share my, "hmmm I wonder how they figured the data" with you. Edit: left at room temp they are all dropping in value

• 1. Left 1 Bush 1149R
  2. Left 2 1061R
  3. Left 3 1588R
  4. Right 1 881R
  5. Right 2 826R
  6. Right 3 949R

A common practice for thermocouple calibration at zero deg C was to mix slushy ice and water.
I noticed the CZ4 in the 1958 edition has very similar characteristics to the CZ19, I wonder if they are related?

Eddie