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Old 14th Sep 2018, 12:10 pm   #41
FERNSEH
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Default Re: Stuck on a BRC 1400!

I do remember of one instance in a BRC 1400 in which the fuse blowing fault was caused by the mains dropper resistor itself. Replacing the part solved the problem and yet on cold tests no fault could be found with the original dropper resistor.

DFWB.
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Old 14th Sep 2018, 1:49 pm   #42
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Default Re: Stuck on a BRC 1400!

Quote:
Originally Posted by Nuvistor View Post
I think the Cathodeon CRT's were Mullard ones.
Wasn't Cathodeon a Pye brand?

Brian
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Old 14th Sep 2018, 1:56 pm   #43
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Default Re: Stuck on a BRC 1400!

Quote:
Originally Posted by FERNSEH View Post
I do remember of one instance in a BRC 1400 in which the fuse blowing fault was caused by the mains dropper resistor itself. Replacing the part solved the problem and yet on cold tests no fault could be found with the original dropper resistor.
Interesting. The original dropper had two o/c sections. I temporarily bridged the surge limiter before powering up with a lamp limiter. I cut the supply to the system switch solenoid at the same time.

The fuse no longer blew and a faint glow could be seen in the 30PL1.

I then replaced the whole dropper. Same result. HT present at the main smoothing can. Try on full mains the set came to life.

The set arrived with a blown mains fuse. The seller didn't know anything about the sets history. The system switch was found in the 625-line position.

Brian
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Old 14th Sep 2018, 6:29 pm   #44
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Default Re: Stuck on a BRC 1400!

"Wasn't Cathodeon a Pye brand?"

Hi Brian,
It was indeed.

DFWB.
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Old 14th Sep 2018, 10:14 pm   #45
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Default Re: Stuck on a BRC 1400!

Who at that time were partly or wholly owned by Philips who owned Mullard.

As the the saying goes “ what a tangled web we weave”
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Old 15th Sep 2018, 2:06 pm   #46
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Default Re: Stuck on a BRC 1400!

A nice pile of components and the ever essential Soldamop were waiting for me on getting home from work yesterday evening.

I look forward to getting back to the set on Monday evening.

Brian
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Old 16th Sep 2018, 2:16 pm   #47
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Default Re: Stuck on a BRC 1400!

Just wondering if this set has the scan coils with the built in thermistor in series with the frame scan coils, if so i seem to remember this causing frame linearity problems.

The easy way to find out is to short it out and see what effect this has on the picture

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Old 17th Sep 2018, 10:27 pm   #48
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Default Re: Stuck on a BRC 1400!

Bit more work tonight. The valve heater voltages read 6V on a digital multimeter. Not got around to trying a conventional meter where the voltage readings should be around 4V for a 6.3V heater. I guess the service instructions didn't cater for digital multimeters!

Unfortunately, replacing the capacitors as suggested by John hasn't improved matters. It might be the case of replacing everything in the frame timebases but will check the thermistor as suggested by Steve as well.

The switch off collapsing square occupies the top half of the screen rather than the central, probably due to the adjustments to enable the screen to be filled.

The width control. Knowing from experience it's never a good idea to attempt ex equipment spares. Despite clearing and enlarging the holes I couldn't get the damn control to fit and ended up ruining it.

Had no choice but to re-fit the original 1M control. As Dazzlevision predicted there was lack of width as I'd already changed the feed resistor to 680K. Not wishing to disturb it I fitted another temporarily on the print side in parallel. Well 680K 2 is about right: 340K!

On the plus side the CRT's beginning to look much better.

Cheers
Brian
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Old 18th Sep 2018, 10:15 am   #49
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Default Re: Stuck on a BRC 1400!

It was late last night. I think the cause could be the boost feed resistor to the height control as there's not much overscan. As John says these sets usually have plenty to spare.

The 960's height control can be set so only the centre circle of Test Card C is elongated to reach the top and bottom of the screen! See photo.

With the Ferguson, attempting to get the linearity right at a lower height setting can't be achieved either with the bottom cramping evident with slight fold over on Lin adjustments. A few more resistors to check.

The card placed over the contrast/hold controls has to be removed to get to the boost feed resistor.
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Old 19th Sep 2018, 11:09 pm   #50
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Default Re: Stuck on a BRC 1400!

Good evening,
I have had some success in getting the frame linearity correct. After changing all of the suspect capacitors and the PCL85 the frame linearity was still poor at the very top and bottom edges. The frame linearity main pot was still at its lowest resistance value end. I decided to try a lower resistance resistor in R117 position which is directly in series with the pot. On switch on I had frame roll though once adjusted this gave me more control of the main linearity pot and was able to get it right with the pot wiper nearly half way down its track. Once the height and picture shuffle rings were juggled I was able to get a cracking well displayed test card C.

If you are still needing a bit more height I found that changing C82, a 0.1uF blue/white cap on one end (heater decoupler near to the frame fault take off) helped a little and gave me a bit more height.

Christopher Capener
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Old 20th Sep 2018, 12:26 pm   #51
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Default Re: Stuck on a BRC 1400!

Excellent work Christopher. I'll be having another look at mine later. Would be nice to see a couple of pictures.

Another forum member is kindly going to supply me with a suitable NOS 2M2 pot to replace the existing 1M control in the width position. I'll be able to remove the additional 680K feed resistor bodge too of course.

This is excellent as the usual plastic bodied types readily available don't seem to last long in old valved equipment they were never designed to be used in.

Uprating the feed resistor from 330K to 680K and the control from 1M to 2M2 is advised in both the 1400 and 1500 chassis. Later production models already have the new values in place.

It's surprising to note the same 330K/1M arrangement is used in the earlier 950 series but don't recall hearing stories of similar burn ups or recommendations to change them here.
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Old 20th Sep 2018, 6:14 pm   #52
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Smile Re: Stuck on a BRC 1400!

Good afternoon,
here are a couple of pictures of the HMV. One of the pincushion magnets were tweaked as the far left vertical white line had a slight kink and once adjusted straightened out nicely. I have finished putting the set back together but not before smacking my head on the top chassis brackets which rather hurt when I dropped a screw on the floor!! Luckily it was not the tube base

The pictures show the set switched to 405 line and playing one of the BVWS DVD's (the London record "handle with care" film). The picture when close up is extremely good and is a credit to the 405 line system for such clear images. The tube is very bright the camera does not give the set justice. I am awaiting the delivery of an UHF modulator to see how it looks on the 625 line standard.

Christopher Capener
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Old 20th Sep 2018, 7:51 pm   #53
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Default Re: Stuck on a BRC 1400!

Wow, that's a lovely set indeed. Clearly a 1968 model with its push through 23" CRT. I once had the Ferguson equivalent, the 3655 which also employed p/b UHF tuning. I obtained it in 1982 when 405-lines was still transmitting. The first programme I watched on it was a Schools programme on BBC1, channel 2 (North Hessary Tor).

Your HMV is looking good.

More work on the older Ferguson 16" 3645. Replacing the boost feed to the height control, C82, C100 and C104 improved matters immensely. I was pleased to note the valve heaters no longer looked like a string of 40W lightbulbs. Guess the original blue/yellow Dublier ones were leaky. The boost capacitor was also replaced with a 1000V rated replacement.

Cheers
Brian
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Old 20th Sep 2018, 11:32 pm   #54
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Default Re: Stuck on a BRC 1400!

Set running for a couple of hours.
Showing great potential.
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Old 21st Sep 2018, 12:37 pm   #55
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Default Re: Stuck on a BRC 1400!

That's coming along well Brian. They're good sets to work on.
I like my 17" BRC 1500 but would love to get hold of a 1400.

Regards
Symon.
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Old 21st Sep 2018, 5:53 pm   #56
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Default Re: Stuck on a BRC 1400!

Just remembered I might have discovered the cause of the initial fuse blowing.

I attempted to repair the deliberate break in the supply to the system switch yesterday, only for the tag to break off very easily at the microswitch through corrosion. I guess it must've arced.

The set was in the 625-line position with the set tuned to a VHF channel.

Later I'll be fitting the 2M2 pot kindly supplied by Malc (many thanks!) and will remove the VHF tuner for examination.
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Old 21st Sep 2018, 7:15 pm   #57
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Default Re: Stuck on a BRC 1400!

The microswitch on the tuner is broken at the centre contact, thus needs to be replaced. I have a couple of spare tuners but don't know if they have micro switches on them. I'll have a look later.

Replacing the width control with a 2M2 component has revealed a new problem- lack of width. The boost voltage is under 600V on 405, (should be a maximum of 670V), with the control set at maximum.

There's some high value resistors in the vicinity which have probably changed value.

Brian
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Old 22nd Sep 2018, 11:10 am   #58
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Default Re: Stuck on a BRC 1400!

I have a late 1400 which suffered from frame linearity problems. After replacing various capacitors I was rewarded with frame collapse. I had replaced the 1uF capacitor in the boost/height line with a new part and the set didn't like it. Only when I put the original back did it work. My manual shows this part as 0.1uF but was changed for late production. Any idea why a new capacitor won't work here? I tried two of different makes and no joy. Odd.
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Old 22nd Sep 2018, 11:58 am   #59
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Default Re: Stuck on a BRC 1400!

You could try putting a 0.1 across the new 1uf, perhaps the new electrolytic is more or less inductive in some way.
I think I read the reason for the 1uf was to hold the voltage on switch off to prevent a frame collapse for a short time, the 0.1 discharged too quickly.
Someone will know the correct reason.
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Old 22nd Sep 2018, 2:54 pm   #60
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Default Re: Stuck on a BRC 1400!

Hi to you both, I kept the 0.1uf capacitor as 0.1uf. Likewise I replaced C115 with a 1uf replacement.

In addition to near full width being available at the full setting of the width control the frame cramp, knowing it hasn't been completely eliminated, revealed itself too. Increasing the height shows it up further.
Clearly, something is playing up.

The low boost voltage at maximum width setting could be having an effect on the boost supply to the frame stage as well.

I'll look into the kind suggestions above and the high value resistors in the line output stage.

Funny to think, thinking I knew these sets inside out there's only one problem I've experienced before. That's when R45 failed to give lack of sync.

Experienced the width burn up too but replacing the feed with a 680K resistor and 2M2 control (which I've done here), had no further problems. Nor did I on another model I changed for preventative reasons.

Brian
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