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DER 5649

Pre War 240/405, Post War 405 Line, B&W Dual Standard, Colour Dual Standard, B&W S/S 625, Colour S/S 625 line, Hybrids. Standards converters & modulators, video recorders.
 
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Re: DER 5649

Post by PYE625 » Thu Aug 04, 2016 6:38 pm

Thanks Sideband, an interesting post and yes, very similar faults.

I also had soft focus (hard to see in the previous photo's) and it turned out to be a 1meg (R99) supplying boost HT to the focus taps that was open circuit.
I also found the width kept on increasing as the set warmed up and this turned out to be R106 and R107 that had gone quite high in value, a couple of 2m2 from the wiper of the width control.
Its now stable after replacing them.
Attachments
rsz_img_2248_2.jpg

 
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Re: DER 5649

Post by PYE625 » Thu Aug 04, 2016 8:31 pm

The picture is more or less sorted now, but I have an unusual problem regarding the sound.

The primary winding of the sound output transformer is intermittently open circuit.
Placing a few volts DC across the primary, with the set switched off of course, there is crackling from the speaker.

The primary is meant to be 600 ohms, but a cold resistance check reads open circuit.
Bother !!

 
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Re: DER 5649

Post by Focus 2 » Thu Aug 04, 2016 9:41 pm

Check the leads from the tags on the transformer incase they're dry jointed. I had similar problems with a frame output transformer once, finding it cured an intermittent frame collapse problem.

Excellent result, well done.
Brian

 
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Re: DER 5649

Post by PYE625 » Thu Aug 04, 2016 9:44 pm

Thanks Brian,

I did take the speaker out with the transformer, but it is certainly a dud primary :aai
(You can see it in situ in my third and fourth pics at the beginning of the post).

Will have a rummage round and see if I can find something to replace it.

Unfortunately, I don't have anything suitable, so rather stuck at the mo. :ccb

 
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Re: DER 5649

Post by nuvistor » Thu Aug 04, 2016 11:28 pm

I have a scrap radio chassis that uses a UL84 output valve, I don't know the sound output valve in the TV but if the TX I have is a possibility I can check the windings to see if they are intact. If its good and any use I can post it.
Frank
Edit, if you are going to run the set any length of time with the o/c TX I would remove voltage from the output valves screen grid or you will need a new valve as well.

 
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Re: DER 5649

Post by Focus 2 » Fri Aug 05, 2016 6:19 am

These transformers seldom if ever fail but there is a first time, especially through age! If the problem is intermittent it could be close to the tags. It would do no harm in going over them with a hot iron. As I mentioned earlier a stubborn case of intermittent frame collapse I experienced was cured on doing this to the frame tx.

I have a BRC 1400 sound output transformer I could send you if you need it.

Cheers
Brian

 
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Re: DER 5649

Post by The_Teleman » Fri Aug 05, 2016 8:53 am

Do you have a close photo of the transformer?
I'll have a look to see if I have something that will do the job

Chris

 
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Re: DER 5649

Post by PYE625 » Fri Aug 05, 2016 8:54 am

Thanks chaps....

I will post a photo of it later when at home this evening :aad

 
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Re: DER 5649

Post by slidertogrid » Fri Aug 05, 2016 1:54 pm

Transformer failure as far as o/c primary is unlucky and not that common, as suggested no harm in checking the lead-out wires from the bobbin to the tags.
However I have found quite a few speaker transformers faulty in radio and record player amplifiers. Not o/c but causing low level rustling noises when the amp is running at low volume. I have had this at least three times over the years, once in a DAC90a which was very intermittent.
I would say any transformer that uses the same output valve would do providing you can mount it on the speaker.
Rich.

 
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Re: DER 5649

Post by PYE625 » Fri Aug 05, 2016 5:55 pm

Thanks for all the kind offers everyone.
Focus 2 (Brian) is kindly sending me a tx from a 1400 chassis, so i'm hoping it will fit :qq1
The hole to hole gap is approx. 5.5cm
Here is a picture of the duff tx....
Attachments
rsz_img_2260.jpg
rsz_img_2262.jpg

 
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Re: DER 5649

Post by PYE625 » Fri Aug 05, 2016 6:01 pm

slidertogrid wrote:I would say any transformer that uses the same output valve would do providing you can mount it on the speaker.
Rich.


That could be rather tricky as the sound output valve is a PCF80 believe it or not.
Why on earth they didn't use say a PCL83, I cannot imagine.

 
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Re: DER 5649

Post by Katie Bush » Fri Aug 05, 2016 10:55 pm

PYE625 wrote:
slidertogrid wrote:I would say any transformer that uses the same output valve would do providing you can mount it on the speaker.
Rich.


That could be rather tricky as the sound output valve is a PCF80 believe it or not.
Why on earth they didn't use say a PCL83, I cannot imagine.


If you think that weird, my HMV 1824 (TV set) uses an EF80 as its audio amp/output valve! So that's an RF/IF amplifier valve doing the job of both, AF amplifier, and AF output in one.... :ccb

At least a PCF80 looks a bit like an audio amplifier valve!

 
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Re: DER 5649

Post by PYE625 » Fri Aug 05, 2016 11:08 pm

I guess you can get away with it for low power audio use.
In a small set, the need for a massive volume and floor shaking bass is simply not there lol.

 
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Re: DER 5649

Post by Focus 2 » Sun Aug 07, 2016 8:32 pm

Here's the sound output transformer from the 1400. Hopefully it'll be ok. The speaker connection tags are at the far right and left tags.
I'll get it in the post tomorrow.

Cheers
Brian
Attachments
Edited_ImageEasyImageEditor_20160807_135.jpg
Edited_ImageEasyImageEditor_20160807_136.jpg

 
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Re: DER 5649

Post by PYE625 » Sun Aug 07, 2016 9:13 pm

Thanks Brian :aad

Today, I removed the tube and cleaned all cosmetic parts, re-fitted and it looks rather smart in the dark green rexine.
Got Mrs Mills to tinkle the ivories for me :bba
Shame I can't hear her lol.

(By the way, I have put a temporary resistor across the primary to save the pcf80 from damage :qq1 )
Attachments
rsz_img_2265.jpg
rsz_img_2266.jpg
rsz_img_2273.jpg
rsz_img_2277.jpg
Can't be easy to relax in the presence of Bernard Manning.

 
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Re: DER 5649

Post by marc » Sun Aug 07, 2016 10:34 pm

Nice to see it with a bit of spit and polish on it.....err the telly that is, not Mrs Mills :bba

Marc.

 
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Re: DER 5649

Post by PYE625 » Tue Aug 09, 2016 8:28 pm

Well, I have to say the picture is pretty darn near a 625 line set and with normal viewing of a program, you'd be hard pushed to tell the difference I reckon.

 
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Re: DER 5649

Post by Focus 2 » Tue Aug 09, 2016 10:18 pm

Very true as these images show from another 16" BRC set, the d/s 2633 with the 960 chassis also shows.
Taken on 405-lines.

Incidentally the set is fitted with the 1400 LOPT from the same scrap chassis as your sound output TX. A modified 980/1580 EHT tray provides the EHT.
Cheers
Brian
Attachments
Edited_ImageEasyImageEditor_20160809_147.jpg
Edited_ImageEasyImageEditor_20160809_146.jpg
Edited_ImageEasyImageEditor_20160704_118.jpg
Last edited by Focus 2 on Tue Aug 09, 2016 10:25 pm, edited 2 times in total.

 
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Re: DER 5649

Post by PYE625 » Tue Aug 09, 2016 10:21 pm

Cracking little sets these BRC's :bba

 
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Re: DER 5649

Post by Focus 2 » Wed Aug 10, 2016 8:05 pm

Had a nice PM from Andrew to say the 1400 sound transformer is working in his DER 980 set.

Nice to think parts from the scrap 1400 chassis I was given over 20 years ago have allowed two 16" portables to function properly.

cheers,
Brian

 
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Re: DER 5649

Post by PYE625 » Wed Aug 10, 2016 8:15 pm

It goes to show the generosity and kindness of people on here, without which, many sets would be inoperable.

Also, never to throw anything away, as its so easy to do during a clear-out and then regret it later. (Me the guilty party :cch )

 
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Re: DER 5649

Post by PYE625 » Wed Aug 10, 2016 9:31 pm

I can now listen to Mrs Mills ........ :aaj

 
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Re: DER 5649

Post by Focus 2 » Thu Aug 11, 2016 2:04 pm

Nowt wrong with a bit of Mrs. Mills! She often guested on Cilla's show from where I remember her from (I'm nearly 51).

Great to hear the set's working well with full sound. Your efforts in cleaning the interior are especially impressive. Thought I was looking inside a new set!

Cheers
Brian

 
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Re: DER 5649

Post by davidh1041 » Thu Aug 11, 2016 8:34 pm

Hi Andrew, i have a chassis from one of these, complete except for the LOPT which i fitted into the GEC. Let me know if you need anything. Regards David

 
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Re: DER 5649

Post by Tazman1966 » Thu Aug 11, 2016 8:42 pm

Same here Andrew. I have a spare chassis from one that was dropped. The board was smashed but I painstakingly rebuilt the tracks as I couldn't resist seeing if it worked - and it did!

Tas

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