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Old 2nd Oct 2022, 6:09 pm   #1
bionicmerlin
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Default Ultra BRC 1500

This sad looking set has had a bad life . Must of had 40 Or more a day during its working life then in retirement itís been stored in a wet or damp place. On top of that it was used as a parts set. I thought it should give it a second chance.
I replaced the missing dropper,frame output transformer and the main smoothing cap and a few other bits.
W8 the H.T. rectifier diode was shorted . I put in a 1N4007 to get it working. Can someone please advise if there is a better choice.
It powers up but takes ages for the raster to appear then it comes on instant to a full screen ish. I get a picture thatís fussy round the edges and a few black lines across the top of the screen.
CRT looks ok contrast and brightness wise.
Sound has bad hum when tuned to a signal.
Hopefully I can get some help to speed my progress up .
And I had the famous words said to . Oh last time it was used it worked.
I did laugh to myself Andy
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Old 3rd Oct 2022, 8:55 am   #2
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Default Re: Ultra BRC 1500

It is looking very promising. We would use the BY127 diode for the HT rectifier. It looks like its a 24" screen which always did loOk a bit fuzzy around the edge corners even with new tubes fitted. This might improve after running the set for a while.
As for the hum I would have to listen to it before making any suggestions. But I would check all the voltages around the PCL82 making sure there is nothing amiss here but with what you say its coming from before the volume control so could be a problem on the intercarrier sound and FM demodulator stages. Check any electrolytic capacitors.

At Radio Rentals we were doing all the mods and putting these 1500's out as reconditioned sets on new Rentals into the early 1980's and can still remember all the parts we would change out to avoid future problems.
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Old 3rd Oct 2022, 9:00 am   #3
Welsh Anorak
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Default Re: Ultra BRC 1500

Firstly the 1N4007 is fine - was a BY127/133.

With a TV that's been stored for years, especially with a Mazda tube, it's worth letting it work for a good while. The tube will sharpen up, but it probably won't be as good as you'd like. You'll find the focus control does very little - that's normal unfortunately, though replacing resistors in the area may improve matters slightly.

There will be capacitors that need changing - the one across the mains for a start needs changing for a Class X (remove it for the moment if you don't like loud bangs!). Also the frame cathode decoupler and the audio HT decoupler will be past their best, and any two-tones will need changing.

Also change the sync separator's feed 47K (R44?) resistor for a good quality 1W replacement. Hopefully the main smoothing block will reform and your hum will drop.

Then give it a good soak test and see how it does.

They always workied before they went wrong, didn't they? I think customers thought some gremlin crept in during the night.
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Old 3rd Oct 2022, 10:07 am   #4
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Default Re: Ultra BRC 1500

Thank you both for your advice. Itís not as big as a 24 inch . The main smoothing cap was missing so I lashed 3 separate ones together. Not very neat I know. I will keep the diode I put in for now but will upgrade to BY127 in the future.
I will do the things suggested over the next few days. Thanks again Andy
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Old 3rd Oct 2022, 4:03 pm   #5
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Default Re: Ultra BRC 1500

Sounds like the sort of set that was sold untested off the pile from disposal places in the late '70s! It is looking good and as others have said the tube may improve with use.
I have the same model in my collection, mine also was a right rebuild needing lots of capacitors and resistors. Much more work than my 950 and 1400 had needed! My tube looked a little grim at first, but it woke up eventually.
This photo is of the set after being on only a few minutes after not being switched on for a couple of months so once the tube wakes up it does seem to remain OK. Apologies for the poor photo!
Good luck with the set I will follow with interest!

Rich.
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Old 3rd Oct 2022, 8:27 pm   #6
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Default Re: Ultra BRC 1500

That looks like a 20" Ultra 6807.

A little concerning is the raster appearing suddenly. It sounds like the line oscillator is slow to start up, a situation which should cause the fusible resistor R127 to spring open if it doesn't get going before the PL504 has fully warmed up. If the resistor doesn't spring open you run the risk of damaging the line output valve and line output transformer. When my 1500's line oscillator was reluctant to start, it was caused by the 180pF capacitor, C53, but I expect any of the components around the blocking oscillator or the 30FL2 could be capable of causing the same trouble.

For the focus issue, check R120, which can go high in value.

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Old 4th Oct 2022, 8:20 am   #7
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Default Re: Ultra BRC 1500

It is just possible that the CRT has an intermittent O/C cathode connection that makes contact when the heater expands the break.
If you have EHT with the blank screen observe the screen in a darkened room. If there is a faint focused raster with very slight signs of a picture, this may be the cause of the delayed warm up. The brilliance control will have little or no effect under the fault condition.

Another point worth looking into is the blue plastic spark trap [usually blue] on the CRT base. These tend to break up resulting in the spark ring shorting out the crt pins.
This can be puzzling if you have never encountered it. Just remove it if it is damaged. Old tubes don't flash over. John.
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Old 4th Oct 2022, 9:17 am   #8
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Default Re: Ultra BRC 1500

Which knobs are original? Rich's look smarter than the ubiquitous smaller diameter ones, but which is correct? I see yours only has one, Andy, but they aren't hard to source.
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Old 4th Oct 2022, 1:08 pm   #9
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Default Re: Ultra BRC 1500

Before you go any further, check the bottom end of the dropper isn't o/c. This supplies the LT to the transistor IF/video stages and if it's o/c the voltage will be way too high and can cause odd symptoms from no picture to hum bars or even popped transistors.
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Old 4th Oct 2022, 1:50 pm   #10
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Default Re: Ultra BRC 1500

Thanks everyone for your help . Itís coming in faster than I can do things. Much appreciated.
Andy . Itís a new dropper. ,tested as well as the original was missing.. Good point about the knobs on Richís set . I might have some better knobs itís just finding them. I just put 2 odd ones just to try things for now. Mine has the smaller 19 inch tube. I also have changed R44 and some doggy caps and the blue and white. Glyn thanks.
John I did check the spark trap is Infact black and ok . It only dawned on me itís a Polish tube Unitra. Itís also got a extra earth bodge lead on the tube . Not used but still there.
I will try the set later when itís a bit darker and maybe take a screenshot if my camera is up to it. Thanks everyone not just who I have mentioned.
Progress so far . Andy
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Old 4th Oct 2022, 3:18 pm   #11
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Default Re: Ultra BRC 1500

That is a late production example. Both the 20" (yours) and the 24" had Polish Unitra tubes towards the end of the production run of the 1500 chassis. I guess mazda had stopped making monochrome CRTs by then...
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Old 4th Oct 2022, 5:50 pm   #12
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Default Re: Ultra BRC 1500

Quote:
Originally Posted by bionicmerlin View Post
Itís also got a extra earth bodge lead on the tube . Not used but still there.
Andy
The lead you mention goes to the 'dag earth spring is there another lead connecting the spring to chassis? if not the outer coating will be floating meaning the EHT reservoir capacitor is open circuit which in itself can cause odd effects on the picture...

Mine is also 20" I can't remember what make the tube is or if it is a replacement. It's not a Unitra, I would have remembered that! As far as I know the knobs are the originals, but various styles were used over the years, and they were often replaced due to the nylon splitting and or the knob being lost.

I used to keep a set on the van salvaged from a scrap 950 or 1400 and would replace them as a set.
I wouldn't be too fussy so long as the knobs you have on the set are all the same style
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Old 5th Oct 2022, 12:50 am   #13
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Default Re: Ultra BRC 1500

Rich . There is a earth linking the 2 springs already connect to earth on the board on the CRT socket.

I got a bit of a setback. Half expect. The tuner has decided to give up .i will do the normal mods and hopefully that will get it going . Andy
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Old 5th Oct 2022, 8:23 am   #14
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Default Re: Ultra BRC 1500

The UNITRA tubes tend to have a softer picture compared with the Mazda/Mullard. Focus is not so sharp and the screen phosphor has a 'blotting paper' appearance. J.
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Old 5th Oct 2022, 5:19 pm   #15
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Default Re: Ultra BRC 1500

Yes, we were using Unitra tubes for replacements in the early 80s as the re-gunning firm we used were only doing colour tubes and the Unitras were cheap (nasty) and cheerful which suited our service manager! I was fitting them to Pye 169 and ITT VC200s I thought it spoilt a good set but I suppose they were getting old.

I remember seeing some new old stock Thorn 1500s that turned up from somewhere, they were fitted with the Mullard tubes with the purple label. They were below par compared to the earlier Mullard tubes. I think they were imports relabelled.
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Old 6th Oct 2022, 10:59 am   #16
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Default Re: Ultra BRC 1500

Yes, the purple label ones wre disappointing - possibly Unitras relabelled? The 'real' Mullard red labels lasted well. Mind you, when they were around mono viewers werent too discerning.

In the early Eighties we were offered (for peanuts) over 100 20" Ferguson late 1500s which we'd been looking after for a holiday park that had to be replaced by colour sets. However there was little demand for resale, and where would we put 100 TVs? They apparently were eventually loaded into a lorry and dumped...
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Old 6th Oct 2022, 9:24 pm   #17
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Default Re: Ultra BRC 1500

It seems by the early 1980s even people renting wanted colour sets.

The holdouts of B&W viewing like the elderly & the partially sighted could probably buy a new set on credit by this time.
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Old 6th Oct 2022, 9:56 pm   #18
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Default Re: Ultra BRC 1500

That's very true, Decontrolled colour sets, that is secondhand ones that didn't require a large advance rental were flying out. There was a slight reprieve in the early '80s for black and white especially for older people on a pension caused I think by a fairly large jump in the price of a colour licence.
I had not long become self employed working from home and advertised used sets in the local paper, the phone didn't stop ringing for a couple of weeks for cheap Black and whites... Luckily I got on very well with my ex-employer so I had a plentiful supply of ex rental 'bangers'.
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Old 7th Oct 2022, 9:17 am   #19
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Default Re: Ultra BRC 1500

Another reason elderly people stuck to black and white was the (erroneous) information that colour sets were damaging to the eyes of people with failing cataracts.

We sold and rented a few black and whites to otherwise quite well off customers. When this myth was disproved - it did come from the medical profession - there was a welcome rush to buy colour sets!
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Old 7th Oct 2022, 10:44 am   #20
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Default Re: Ultra BRC 1500

Quote:
Originally Posted by Welsh Anorak View Post
Another reason elderly people stuck to black and white was the (erroneous) information that colour sets were damaging to the eyes of people with failing cataracts.
I didn't know the myth was so spacific, bit I regularly heard elderly people say, "I don't want one of those coloured sets, they hurt me eyes".
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