Defiant 7109

That looks nice fresh and untouched, just the way we like them.  ?  So what's next, spider fest !

Removal of the chassis from the cabinet was next and it was not as difficult to successfully remove the control knobs as I first imagined. These need to come off before the chassis, complete with the CRT, can be withdrawn. More hoovering out the dust and a previous repair is spotted....a "new" capacitor in the last picture. Well, probably new in 1965 or whatever  ? 

There are of course a fair number of wax capacitors that most likely will be defective, plus one or two brown Wima types thrown in for good measure.

All in all, I can say the chassis is in very good condition and next step will be to test the CRT emission.

The bad news is I do not have a base for the B&K crt analyser, but the good news is that I have tested the crt with heaters powered for resistance via a DVM and there would appear to be emission. The LOPT overwind also would appear good, so I am quite hopeful of things so far.

It has been too hot this afternoon, so I will take a small break until later. But I have removed the crt to enable safe and easy access to the under chassis where I will begin to test the capacitors and look for any obvious faults.

Posted by: PYE625

The bad news is I do not have a base for the B&K crt analyser, 

Hi Andrew, once we get home (weekend at a steam fair) I'll send you the pinout/colour code for the correct adaptor to piggy back off another one

Cheers Marc, that'll be great  ? 

I have been cleaning the LOPT compartment this evening. The output valves look rather tired, their getters being somewhat depleted, especially the boost diode. What was left of the outer tar ring covering the overwind of the LOPT just fell away as it was lightly brushed. It would serve no useful purpose in this condition, so any remainder was removed.

A look over the chassis underside revealed nothing untoward, so a light brush and vacuum here too. The brown capacitors have the name "Plesseal" on them, but are surely made by Wima. The main electrolytic can has been removed and tested for the correct value's of capacitance. All were slightly high, but certainly well within sensible limits. It is reforming nicely. The date of April 1959 on the capacitor can clearly be seen.

I can hear the Church clock chiming eleven, so enough for tonight and time for bed.

Is it a Plessey chassis, they did make many Co-op sets. The Plesseal does look like a Wima.

Posted by: Nuvistor

Is it a Plessey chassis, they did make many Co-op sets.

Sometimes I feel invisible  ? 

https://www.radios-tv.co.uk/community/black-white-tvs/what-is-this-defiant-tv/#post-17457

Honest I did look back but missed that link.  ☹️  

I have replaced a few capacitors that were directly in the higher voltage stages, namely the Wima type as these were very leaky indeed. The mains RF bypass capacitor was the first one to get replaced.

It really is time for first power up to see what things are like. I used a lamp limiter and applied power. Dead. Mains fuse 1.5 amp open. Replaced it and things improve. Valves light, noise from speaker, line whistle and EHT. A dim raster is visible. Operate tuner and it is alive. Feed in channel 11 from the aurora and we have sound and vision. Some adjusting of height, linearity width etc and a picture is visible. The crt emission is not great to be quite honest though.....

Not a lot else wrong with it at the moment, the CRT may improve with use.

Well now...  Just because a CRT type is not listed in the B&K manual, does not mean I have no base. I do. It is number 10. I happened to go through them and found it fitted. I set the heater voltage to suit, fitted the base and tested the CRT. Almost zero. Ok, time to try a clean and balance. No improvement. Right then....rejuvenate !  This time, the results were better. The reading was now into the end of the "bad" area.

Trying the set again proved better too. But alas, this was only for a short time. As I watched, the picture slowly faded to the level as before over a time of about 10 minutes. Back onto the B&K and results are zero again. This time, no improvement could be made with rejuvenate. So, the CRT is low, but at least the set is operational. The CRT wants to remain asleep.  ? 

I am assuming the CRT is a Mazda CRM173 as stated in the service data, but there is no label on the CRT. Is the CME 1702 the type fitted? Hmmm.. not sure.

Hi Andrew,

should be fairly easy to tell which type is fitted.

The CRM173 did not have a straight gun so required an ION trap magnet, whereas the the CME1702 was straight and therefore did not require a magnet.  The pictures you uploaded I can clearly see the ION trap so Its a CRM173. Looking at my Mazda wall chart I don't believe there is a Mullard or Brimar equivalent. 

Oh dear, that's a shame. CRT can't be a CRM as I don't see any focus magnets, must be a CME? If so a Mullard AW43-80 I suspect with be a suitable replacement, the neck diameter is slightly different but the Mullard is a couple of mm less so it shouldn't be a problem fitting the scan coils.

John.

Edit. Post crossed with Chris but just checked my 1968 Mullard book and for the CME1702 it suggests fitting the AW43-80Z as a replacement also to "Remove the ion trap magnet" and to join pin 7 to 11.

Edit 2. Is that wire ring just forward of the base connector an Ion trap? The magnet marked seems too far forward to be an Ion trap, a centering magnet surely but I'm no expert here.

I was always led to believe that the neck diameters were different but the Mazda data book suggests that they are the same at 38mm

Posted by: Jayceebee

 The magnet marked seems too far forward to be an Ion trap, a centering magnet surely but I'm no expert here.

Hi John,

Its been a number of years since I've played with Black and White sets but I'm fairly certain that the tube in Andrews set is possibly a CRM173 and that is an ION trap that I've highlighted in the photo on the previous page of this thread. I also have a number of traps in stock which seem to tally along with data, happy to stand corrected though.  ? 

I stand corrected, certainly looks the same as in that datasheet. I also expected to see two huge magnets for focus as in my 1756U. Looking closer at the Madza data the CRM171,2 are indeed 35mm necks, the CRM173 and CME1702 are the same as Mullard at 38mm.

Hi guys the crt in this set is definitely not the bent gun type as the magnet you refer to is the picture shift control 

if you look closely at the crt neck you can see all the parts of the gun are in line eliminating the need for a ion trap also as you noted no focus magnets so this could only mean the type number must be a CME 1702/3. I only ever came across a mullard AW43-80Z in one set & that was a bush obviously a replacement as I'm sure these crt were only supplied as replacements 

These sets usually performe very well as mine did but it like so many others had to go to make way for the pye collection 

Chris 

Hi, I can confirm that the gun elements are in line and the magnet assembly causes picture shift with no variation in overall brightness. The metal ring causes very slight shift and a small variation in brightness when moved. The focus control is electrostatic with three taps on the base.