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Old 22nd Sep 2018, 3:20 pm   #61
high_vacuum_house
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Smile Re: Stuck on a BRC 1400!

Your set is coming along nicely. the tube is coming up well

Here is my HMV working on the 625 line system now the UHF modulator has arrived. It is very difficult to get a decent picture with the camera due to the strobing effect. The picture and sound quality is excellent. The BVWS Gerald Wells DVD is being shown here.

I decided to try out my Thorn 1590 television at the same time to compare them.

I had a close shave with this one though. I had them running side by side but the 1590's contrast was horrible and the width and height were excessive. On going over the top to tweak the height and width controls I could see the set lit up inside rather well through the ventilation holes. The CRT heater was more of a lightbulb than a heater!!

On removing the back and pulling the CRT base off the 11 volt HT1 line was more like 15-18 volts! Going round the regulator showed the set HT volts pot (220 ohms) was O/C. replacement and adjusting cured the fault and it looks like the CRT got away with it. I ran the set for an hour with a DMM across the HT1 line and it was pretty stable. I wonder how long it would have lasted if I hadn't spotted the excessive picture size?

I could not get a good picture with them side to side due to strobing. Either one or the other would have a dark band across the screen.

Christopher Capener
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Old 22nd Sep 2018, 4:25 pm   #62
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Default Re: Stuck on a BRC 1400!

The HMV looks fantastic Christopher. Well done. I've ordered another modulator myself to further check 625. So far I've only tried it through a VCR playing a VHS tape.

As for the nasty 1591 fault I understand a power resistor can go o/c causing similar symptoms. The only obvious symptom to the viewer is some overscan. If lucky a major transistor might fail before the CRT is ruined.

Well done on finding the cause of your problem.

Cheers
Brian
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Old 23rd Sep 2018, 12:18 pm   #63
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Default Re: Stuck on a BRC 1400!

Well spotted on the 1591. The PNP regulator could leak with the voltage creeping as the set warmed up. The set HT controls did do this back in the day, but often intermittently. The 14" tube wouldn't tolerate this for more than a few minutes; your 12" one won't show any ill effects.
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Old 23rd Sep 2018, 10:16 pm   #64
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Default Re: Stuck on a BRC 1400!

Just a thought on the 1400 chassis. The local distance control works on 405-line VHF only.

However, if Tag 43 is moved to tag 44 allowing 625-line VHF reception, not only do the 405 and 625 contrast controls work but the Local Distance control becomes functional on 625 UHF!

Worth doing this if overloading is apparent which is a possibility with modulators.

405-line VHF works just as well. 625 VHF reception only works if the supply to the system switch solenoid is disconnected

Brian.
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Old 24th Sep 2018, 5:21 pm   #65
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Default Re: Stuck on a BRC 1400!

Thank you so much for the knobs Keith.

Found one of my spare VHF tuners which thankfully came complete with microswitch.

I'll try a transplant later.

Cheers
Brian
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Old 29th Sep 2018, 6:06 pm   #66
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Default Re: Stuck on a BRC 1400!

The microswitch was transplanted. An almost impossible job before I discovered it was attached to an additional rear plate on the VHF tuner. All worked as it should except for sometime later when the set wouldn't switch back to 405 from 625 with much smoke from R123. It's blackened but didn't fuse, probably due to switching off immediately. Back to mechanical means of system switching for now!

The knobs kindly supplied by Keith look good. Although not the original type it keeps to the black/silver appearance of the tuner knobs.

Replacing R140 (2M2) and R141 (6M8) improved matters in the width circuit. 625 boost volts are now about 610V with the control set mid way. I decided to leave well alone until the frame problems were dealt with.

Replacing some of the higher value resistors in the frame stage helped with the bottom cramping but has resulted in lack of height with the control set to maximum. The boost feed resistor to the height control has already been replaced. Next time I'll check voltages around the PCL805.

The set was tested on 625-lines VHF and UHF. All the 1400 horrors were present, flickering at times and pulling on whites. As with 405 the 625 alignment also appears to be slightly out. Surprisingly though there was no buzz on sound.

So work is far from complete. The CRT is certainly looking a lot better than it did when I first got the set working.

Cheers
Brian
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Old 1st Oct 2018, 12:21 pm   #67
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Default Re: Stuck on a BRC 1400!

R133 had doubled in value. Happily a replacement put a final end to the height problems. Adjusting the linearity sleeve on the CRT neck improved stretching on the left.

Here's a locked picture taken with the 405-line boost voltage set to 620V. I didn't dare set it higher as it exceeded the correct 670V on a blank channel or when the hold control was mis-set. I know they'll be some variation but shooting up some 50V seems rather excessive.

Replacing the 30PL14 sorted out some line hold drift. This was excessive before replacing the 30FL1 but this valve obviously needed changing too.

Certainly seems to be working well on 405-lines now.
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Old 2nd Oct 2018, 3:44 pm   #68
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Default Re: Stuck on a BRC 1400!

Getting better and better Brian. I really must get my Marconiphone 4661 out and give it a bit of a run. It's one of the last 1400s and it fitted with a 17" squarer CRT
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Old 2nd Oct 2018, 7:54 pm   #69
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Default Re: Stuck on a BRC 1400!

A couple more pictures taken yesterday.
The CRT is certainly looking much better.

The image with the gap on the right was taken on 625 lines. Otherwise 405. The former is something else to look at!

Would be nice to hear more about the Marconiphone 17".

Cheers
Brian
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Old 2nd Oct 2018, 10:48 pm   #70
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Default Re: Stuck on a BRC 1400!

I did a thread on it absolutely ages ago. In fact having looked it up, it's almost ten years ago Time really does fly. Anyway, here's a link to the thread. https://www.vintage-radio.net/forum/...ad.php?t=33642
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Old 3rd Oct 2018, 12:40 pm   #71
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Default Re: Stuck on a BRC 1400!

Great threads Tas. Funny to note my Ferguson and the HMV I used to have were Schedule B models. Both don't suffer from the UHF sound buzz problem. The schedule C set I had was a buzzing nightmare on the other hand.

I note the easily accessible VHF tuner on the Ultra you had. A far cry from being buried under the chassis frame as with the 3645 but a price for portability I suppose.
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Old 3rd Oct 2018, 8:10 pm   #72
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Default Re: Stuck on a BRC 1400!

Looking at your thread Tas revealed an interesting UHF cramping fault I've seen before on the Ferguson 3655 I used to have.

It appeared to develop suddenly. Replacing the scan correction capacitor then PL504 and PY801 valves failed to make any difference. The two valves were replacements fitted over 20 years before and were still going strong.

I didn't get to cure the fault as a move meant I had to give up some of my sets. Another forum member took it.

I wasn't aware of the R62 and R70 mods. This would no doubt cure the problem on the 3655. I guess the originals must be sound with any variations in value enough to cause the fault.

Seeing the 3645 under discussion here has a right hand side black bar not present on 405 could be down to the same resistors. They'll be changed when I get back to the set tomorrow.

It's brilliant seeing tips like this and to help each other.

I'll have another look at the solenoid too.
I'd prefer to fit a lamp-like mains switch to the solenoid to allow 405 or 625 line VHF working. I was surprised at how good Band 1 625 VHF looked using the VHF-UHF modulator.

It's of course what I used to do in my DXTV days.

Cheers,
Brian
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Old 4th Oct 2018, 10:23 am   #73
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Default Re: Stuck on a BRC 1400!

Looking at Tas' thread on the Ultra I might have to propose an alternative mechanical system switch arrangement. I succeeded on doing that before on a set where the system switch contacts had arced away. I was able to rectify the fault by replacing the full system switch. The chances of being able to do that today is unlikely.

On the 3645 the fusible resistor smoked, hissed and flashed badly when it wouldn't change back to 405. The resistor, although badly burned has survived, probably through rapidly switching off. I don't have another to try.

It should be possible to fit a mechanical push/pull device using stiff insulated wire. Have to see if this can be done without drastingly altering the sets appearance.
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Old 4th Oct 2018, 10:49 am   #74
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Default Re: Stuck on a BRC 1400!

It could be that the solenoid's coils have overheated if energised for more than a second or two and this may have distorted the plastic former, causing the solenoids plunger to be unable to move freely inside it - worth checking.
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Old 4th Oct 2018, 1:44 pm   #75
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Default Re: Stuck on a BRC 1400!

Will look at that DV. I do have a spare solenoid coil as well.

Then, I have to be extremely careful as the 100W fusible wouldn't survive another overload. It's already badly blackened. Have to find a source as if the resistor burns out the set will stop working of course.

Cheers
Brian
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Old 4th Oct 2018, 9:03 pm   #76
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Default Re: Stuck on a BRC 1400!

Ran up the set again this evening. Uncertain why maximum setting of the width control continued to give lack of width with 405 boost volts at 620V with the control set at maximum.

I don't suspect the valves as the set warms up at the normal time with no width/boost voltage variation after the set's been running for sometime.

Most of the capacitors have been changed except C117 which is a mustard type thus unlikely to be defective.

I noticed I'd overlooked R 139 (3M9). It had risen to over 5M so was confidently replaced.

This made a big difference, despite checking the new resistor prior to fitting the result was 610V boost volts with the width control at maximum! What on earth is going on?!

I ended up reverting to a 330K feed resistor to the 2M2 height control. The 680K replacement I fitted measured perfectly out of circuit.

This did improve matters, boost now 630V on 405. Under normal conditions the correct boost volts should be just above mid setting.

I prefer keeping it below the specified figures in the interests of preserving vintage components if the correct width can be obtained.

Run out of things to check.

Apart from this and of course the system switching the set is otherwise working very well.

Cheers,
Brian.

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Old 5th Oct 2018, 7:33 pm   #77
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Default Re: Stuck on a BRC 1400!

Frank over on VRAT suggested the stabilising thermistor Z4. He was right. As with the height variation problem in the 960 it was down to this component (height stabiliser in that model).

I reverted the width control feed resistor to 680K before testing.

I got the boost voltage upto 630V before the sticks in the EHT tray started to tick. I don't think they could have coped with anymore. I do have the means to repair an EHT tray which I'll do in due course.

Improvement but not perfect. I can't get over how much better the CRT is looking compared to the awful results on first getting the set working.

I don't know if I've already mentioned this, but the cause of the valve heaters glowing too brightly turned out to be C82, the heater supply decoupler. I wonder what was going on for it to behave in that manner?

Cheers
Brian
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Old 9th Oct 2018, 4:31 pm   #78
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Default Re: Stuck on a BRC 1400!

You will need to check for any Callins capacitors (tall black ones) If you find any then replace them on sight. They are a known problem. There is almost certainly one in the sound section. I still have to replace the one in my 1400. I had a breathing problem on my set which was down to a faulty HT decoupling capacitor in the line stage. The only real problem I had with my set was the white plastic pop in plastic cover around one of the controls broke off at the 'pips' that hold it in the PCB. Here is a pic of my Fergie before I fixed the frame linearity. Good luck with yours.
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Old 9th Oct 2018, 8:27 pm   #79
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Default Re: Stuck on a BRC 1400!

Hi Andy,
All the Callins capacitors have been replaced. They were four in my set:
C81, C52, C83 and C115. The first two were replaced with 10uf 450V types.

I'd be interested to hear which component you replaced that sorted out the breathing.

Although no such problems with this 3645 my older Thorn 960 has this problem after warm up.

Cheers and many thanks for your contribution Andy. Your 3645 looks great.

Brian
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Old 1st Nov 2018, 8:06 pm   #80
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Default Re: Stuck on a BRC 1400!

As an update the three EHT rectifier sticks were replaced by diodes and a new height control fitted.

The height still only filled the screen at maximum setting of the control. Replacing the height stabilising VDR X2 sorted that out.

Unfortunately it's still not possible to adjust the width to give the correct test card display. It shows up more on 625-lines. With just about everything checked in the line output stage that can cause the problem attention will be focused on the line oscillator stage.

In spite of this, the set is otherwise working very well now.

Images show results on 405 and 625.
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