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Ferguson '45' portable TV.

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sideband
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Firstly I would like to thank Graham (Parabola) for offering me the set in the first place and secondly to Jeff (ppppenguin) for getting the set to me via the Vintage Wireless Museum.

Having got the set home I'd already got a place on the bench for it so last night I had a quick look inside. It's in very good condition but looking a little tired....nothing that a good clean up won't put right! I noticed a couple of non-standard additions. Firstly a long mains lead (it should have a two pin connector at the back) and secondly a two pin 5A socket hanging out through the bottom vents on a short piece of twin flex. Having removed the top and bottom halves of the cabinet, this turned out to be an extension speaker connection which I had to remove in order to completely remove the bottom cover. I hope the speaker was not connected to chassis....!

Anyway having got the chassis on the bench, there is very little evidence of past work. One dropper section has been bridged and the permanent mains lead has been fitted because the original connector had been broken at some time. It's very neatly done so will stay for the moment. The only obvious visual fault is the EHT rectifier which is down to air. Can't see a crack so maybe it's under the metal cap.

At the moment, all I have done is taken a series of photos which are shown below. The gentle awakening and restoration will start shortly

Rich

 
Posted : 07/04/2014 3:01 pm
mark pirate
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It does look nice and clean internally, should be an easy restore, the EHT rectifier maybe the reason it was taken out of use all those years ago.

 
Posted : 07/04/2014 6:40 pm
sideband
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Possibly. I did notice that the brightness control was at max......

 
Posted : 07/04/2014 7:25 pm
sideband
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Had about an hour's play tonight. Snipped the mains filter cap and replaced a 0.1 heater decoupler (just after the rec heater). Disconnected the HT feed from the dropper and applied mains. All valves alight and lots of smoke from dust on the dropper which burnt off after about 10 minutes. Proves the heater chain and thermistor.

Next I will replace some critical capacitors (audio coupling, line drive coupling, sync coupling and perhaps some HT decouplers) and then bring up the set up on a variac so I can keep an eye on the HT and smoothing caps.

Rich

 
Posted : 07/04/2014 10:46 pm
sideband
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Had a good play with this tonight....nearly four hours in the workshop! Decided to see what the main smoothers were like. They gave a good kick on the meter which seemed promising so I disconnected them, isolated the HT feed to the rest of the set and wired a 10 K resistor from the HT rec cathode to the resrvoir cap and another to the smoothing cap. I then monitored the voltage as the rectifier warmed up. It settled nicely at just over 250V which is more than the caps would normally see so I reduced the mains input from the variac to give about 203 volts. I had to reduce the mains right down to 167 volts so I guessed that the caps were probably OK. They remained cold and after 20 minutes I decided to see how they held their voltage. Switching off, the caps were in no hurry to discharge so I left them and had a cuppa. On my return I was surprised to see that the voltage was still over 130V after nearly 15 minutes so I decided they were fine, discharged them with a 4.7k resistor and wired them back into circuit.

Next I replaced some critical capacitors...audio coupling, sync coupling, line coupling, and frame coupling along with two HT decouplers that were easy to get at so no more than 6 capacitors changed at present. Now the moment of truth let's see what happens! At present, no EHT rec as I can't find one but at least I should be able to see if the line stage is running.

Switch on, after a moment HT starts to rise and settles at about 205 volts once valves start to operate. Then.....a line whistle! Doesn't sound very loud but that might be me. I can draw a small spark off the line output top cap and a larger one from the EHT top-cap so things are looking very promising. At the moment I'm stuffed for the sake of an EY86. I've looked in my valve stash and I have EY51's, KY80's, DY86's and R19's. Can I find an EY86? Can I .....!!  I might have some EHT sticks in a box and if so, I'll try bodging one of those in to try and get something on the screen.

Rich

edit: As I have half-a-dozen EY51's I'm going to try making up a temporary substitute. It has the same heater voltage and current as the EY86 but is only rated at 350uA. I think it will be OK with a 14" tube.

Discovered I also have a TY86F. This was a special variant of the EY86 for Ferguson 306 TV's and it has a 7.2V heater. It may just be good enough to try as a temporary replacement.....more playtime tonight!

 
Posted : 09/04/2014 12:45 am
sideband
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Not so long to play tonight but we have .....First Light! :thumb

Yesterday I couldn't find an EY86 and thought about making up a temporary sub with an EY51 and a bit of bodgery. Then I found a TY86F wich is a special version of an EY86 with a 7.2 volt heater. I decided to see if it worked in place of an EY86 even if the EHT was a bit low. As long as there was enough, it would be better than nothing. My reasoning was that as the heater current was a bit lower, there might be just sufficient extra voltage available to allow the valve to work. Well in went the TY and on went the set. It takes a while for the line to wake up so possibly a lazy PL81 or PY81. Anyway after a few moments, up came a blank raster...only half the screen and not very linear but at least we had plenty of brightness. It also sounded like the line was running slow. Next connected the Aurora and switched to Ch9 and some sort of testcard was resolved...well three images side by side running across the screen. Twiddling the line hold control had no effect.....back to this in a moment.

I decided to investigate why the line hold didn't work. Couldn't find anything obvious. The control itself looked a bit odd...then the penny dropped. You have to press the knob in first to adjust the control...well I didn't know!! It's got a switch contact on the back and when the button is pressed, it disables the flywheel sync. Set the hold for a floating picture, then release. So switched on again and when the running picture appeared, pressed the knob and adjusted the control...not enough range so checked the pre-set line hold. It was at one end so while holding the line hold button in with the control at approx mid-way, set the pre-set line hold for a floating picture. This worked OK and when the main line-hold was released I had a reasonably stable line lock.

The frame linearity was way out and there is some hum on the picture. The linearity was virtually corrected by replacing the frame cathode bypass capacitor (50uF) and I also changed a couple of the feedback caps. The frame is still unstable with a tendency to collapse if you adjust the hold control. There is no sound apart from a faint hum from the speaker and there is also some line tearing and what looks like some EHT arcing or brushing coming from somewhere.

So that's where we are at the moment. I am always amazed at how these old 405 sets come back from the dead. Hopefully there is nothing nasty about to happen with the LOPT. The tube is excellent and it should be a good set when finished.

 
Posted : 09/04/2014 10:55 pm
sideband
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Had another quick session on this last night. The cause of no sound was a completely O/C anode load to the triode of the ECL80. Now can tune in sound and vision....but not together! Also replaced two more caps in the frame stage. Now have too much height and the height control doesn't work (it didn't do much before either).

I then found that the PY81 valve base is physically loose in the chassis. It looks like some kind of self-locking valve holder. Next job is to remove the CRT as it is almost impossible to replace any more components (properly) without doing so. Not the easiest of sets to work on. Once the chassis and tube have been separated, the rest of the 'orrible 'unts in the sync and line stages can be replaced. This is one of those sets where one-by-one replacement doesn't really work. Fortunately I know the set is basically good and the LOPT and CRT are good so a block change of capacitors should see things greatly improved. I can also check the high-value resistors in the frame stage.

The restore continues!

Rich.

 
Posted : 11/04/2014 9:46 am
mark pirate
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I think you are being very sensible in blanket replacement of the caps, I did the same with my GEC set, as replacement was impossible with the CRT in situ. Don't forget to check all the resistors at the same time, I had to remove the tube for a second time to replace out of spec resistors. I always include the boost cap in the initial cap replacement.

 
Posted : 11/04/2014 9:59 am
sideband
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I always include the boost cap in the initial cap replacement.

Interestingly, the boost reservoir cap in this set is a 24uF electrolytic rated at 500V. It gave a good kick on the meter when I checked it but I must admit I was a bit worried about applying full boost (450V) to it after x number of years out of use. However it seems to be OK but there's still an element of doubt....! There is plenty of boost anyway (think I measured 420) and it wasn't running warm. If I have to replace it, I'll probably use a couple of 47uF 400V in series which will give 23.5uF 800V.

Rich

 
Posted : 11/04/2014 1:57 pm
Marc
 Marc
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Hi Rich,

I'm not sure but I think it was Till who had a good example of a failed boost cap in his '45', that must have gone with a hell of a bang ! :ccf
I used a couple of 47uf 400v in mine.

Marc.

Marc
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RSGB call sign 2E0VTN

 
Posted : 11/04/2014 2:27 pm
sideband
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Hi Rich,

I'm not sure but I think it was Till who had a good example of a failed boost cap in his '45', that must have gone with a hell of a bang ! 

That's the element of doubt I was referring to..... 

Rich

 
Posted : 11/04/2014 2:38 pm
AidanLunn
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I always include the boost cap in the initial cap replacement.

Interestingly, the boost reservoir cap in this set is a 24uF electrolytic rated at 500V. It gave a good kick on the meter when I checked it but I must admit I was a bit worried about applying full boost (450V) to it after x number of years out of use. However it seems to be OK but there's still an element of doubt....! There is plenty of boost anyway (think I measured 420) and it wasn't running warm. If I have to replace it, I'll probably use a couple of 47uF 400V in series which will give 23.5uF 800V.

Rich

If in doubt, take it out.

 
Posted : 11/04/2014 5:19 pm
sideband
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Only an hour or so to play today. Have removed the CRT with no problems and it was a lot easier than I first thought (Thanks Till). Lay set face down. Remove CRT base and ion trap. Remove three screws from top CRT support then remove three screws from bottom CRT support. There is one more just behind the scancoils holding the I.F screening bracket to the chassis. Remove EHT cap (you may have to slacken the CRT fixing band around the mask to get the EHT lead through the gap between the mask and the fixing. Then grip chassis firmly each side and lift. The whole chassis should lift away with the scancoils.

It's now much easier to get to everything. The cause of the EHT brushing that I observed has been found...the CRT EHT cap has broken grips...two fell out when I unclipped it so I need to find another. The clean-up and complete restoration can now begin properly starting with replacement of the the rest of black Hunts caps. Every one removed so far has been faulty so the others will all be the same. Besides I do not intend to keep removing the chassis so a blanket change will be best.

Still can't decide how these push-in valveholders are supposed to fit. If necessary, I'll fit normal ones.

Rich

 
Posted : 11/04/2014 10:52 pm
mark pirate
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Those black Hunts are even worse than the wax ones, no doubt there are some of those nasty little brown mouldseals lurking in there too 

 
Posted : 11/04/2014 11:46 pm
sideband
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Yep...quite a few of those. Fortunately all the heater decouplers seem to be ceramic so should be OK.

Is anyone familiar with the type of valveholder fitted to this set? Looks like they just push through but I dont see how they are fixed. The boost diode and line output holders are loose and just being held by components and wiring. I've seen this type (around 40 years ago) but don't recall the method of fitting.

I'll post some pics tomorrow.

Rich

 
Posted : 12/04/2014 12:13 am
sideband
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As the wife was working most of today, I managed a good few hours in the workshop :qq1 .

I replaced the remainder of the moldseals and checked as many of the high-value resistors as I could find. None of those needed changing. Without exception, every single moldseal measured poorly on the bridge. What I noticed was that capacitors subjected to higher voltages seemed to test better than others that had only seen low voltage.... :aab . The AGC decouplers were very bad and wouldn't balance on the bridge at all.

I also checked the 8uF decoupler in the I.F stage and the 24uF boost reservoir. Both passed testing with flying colours.

There is one small moldseal left in the line output stage to change, then it's on to the mechanical work and a good clean-up. I should be receiving a new EHT cap in the post soon so hopefully the EHT brushing that I observed will also be cleared. I'll probably remove the cage around the LOPT next and see if I can work out how these push-in valveholders are secured.... :aab

Rich

 
Posted : 12/04/2014 9:31 pm
sideband
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I found another Moldseal hiding just behind the I.F sub-chassis so I changed it as otherwise it would have been almost impossible to reach when reassembled. Next I had a think about the loose valveholders. I have decided to replace them with conventional holders. It will mean drilling some 6BA size holes but there is plenty of room and no danger that the screws will foul anything. I have removed the LOPT and screening cage otherwise I could not get a drill in there. That's as far as I've gone tonight. I'm reasonably certain that the loose valveholders are press-fitted during manufacture. It remains a mystery why only the line output and boost diode holders are loose....!

Rich

 
Posted : 13/04/2014 10:57 pm
Refugee
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They would go back in with a very small amount of epoxy perhaps not even enough that it could be seen once they have been pushed down to set.

 
Posted : 14/04/2014 2:54 am
sideband
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Yes but they won't push down flush like the others (sorry should have said that previously) otherwise epoxy would have been my preferred method....it would save a lot of work! It looks like they are tapered underneath which would suggest a tight interference fit but they'll need considerable pressure to push them down.

I suspect these valveholders are press-fitted when the chassis is made before any components are fitted. Why these are loose I have no idea.

Anyway I've made the decision to change them now.

Rich

 
Posted : 14/04/2014 9:24 am
sideband
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Only about an hour today, enough time to remove one of the old valveholders (PL81) and prepare for the replacement. I was able to unsolder wiring and components from the old valveholder without too much trouble.

Once the old valveholder was removed I was even more convinced that these are pressed in using a power press as there is no visible means of fixing them. Basically a tight interference fit. The hole left in the chassis has a flat on one side and this seems to serve as just a location guide for the press-fit holder. The flat has to be carefully filed away to make the hole round so the standard holder can be fitted. That's as far as I got tonight apart from marking the centres of the two 6BA holes to be drilled.

Rich

 
Posted : 15/04/2014 10:53 pm
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