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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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DER 5649

Post by PYE625 » Mon Aug 01, 2016 8:28 pm

Hi all,

After nipping to Cambridge and collecting this nice little set, I could hardly wait to see inside.....
It has a BRC 981 chassis with plenty of dust thrown in too. The speaker cover had come off, but luckily was present.
Here are a few pics as received.
Sadly the telescopic aerial is missing, but it has a nice bayonet plug to connect to the nearest table lamp :bba
Attachments
rsz_img_2228.jpg
rsz_img_2227.jpg
rsz_img_2229.jpg
rsz_img_2230.jpg
rsz_img_2231.jpg

 
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Re: DER 5649

Post by Katie Bush » Mon Aug 01, 2016 10:38 pm

My knee caps have dropped off as I turn green with envy! :bba

Will that be eleven valves I counted in there? Or did I miss one? - Ah, I missed one at least..... Now I see twelve :bba

 
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Re: DER 5649

Post by Lloyd » Mon Aug 01, 2016 11:32 pm

Very nice! Looks mostly untouched as well. What state is the screen surround in?

Regards,
Lloyd.

 
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Re: DER 5649

Post by The_Teleman » Tue Aug 02, 2016 5:21 pm

Is this the set seen on gumtree ?, I was tempted but too far away from me
I'm pleased a collector got it look forward to the restoration
Well done for getting it

Chris

 
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Re: DER 5649

Post by PYE625 » Tue Aug 02, 2016 7:28 pm

Thanks everyone,
Yes it was on Gumtree.
The screen surround appears to be fine, no cracks, but a very minor scuff mark.
There are 12 valves and all Mazda types so probably original.

I have cleaned the chassis and it has come up nicely.
I have tested and replaced all 0.1 uf caps plus a dreadful Callins 1uf 350v as they were very leaky, plus a 0.25uf in series with the line scan coils.
One cap had split open.
There are one or two left, that seem ok, but will find out in due course :bba
Attachments
rsz_img_2233.jpg
rsz_11img_2238.jpg
rsz_1img_2234.jpg
rsz_img_2235.jpg
rsz_img_2236.jpg

 
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Re: DER 5649

Post by PYE625 » Tue Aug 02, 2016 8:36 pm

I tried to re-form the Callins 1uf pictured above, but it was hopeless.
It got warm rather quickly and basically resembles a resistor.

The large main smoothing can however, has re-formed and is ok.

Update.... Believe it or not, the Callins cap HAS reformed after letting it cool and re applying volts from my cap re-former.

 
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Re: DER 5649

Post by PYE625 » Tue Aug 02, 2016 10:08 pm

Well I guess it's first light time......

Here we go :aac

Switch-on via a lamp limiter and no smoke or bangs.... we have a dim raster eventually.... more power and all is still ok.
Full mains now and noise from the speaker plus brighter and fuller raster.
Feed in a signal from the converter with test card C.
Tune to CH1, adjust line and frame holds, alter fine tuning and we have sound and vision.
Good volume, contrast and brightness.

Clearly the frame stage needs some investigation (linearity pre-set at limit of travel.)
Also, there is too much width even with the pre-set at minimum.
Will have some further investigation tomorrow. dmm
Attachments
rsz_img_2243.jpg
rsz_1img_2241.jpg
rsz_img_2242.jpg

 
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Re: DER 5649

Post by marc » Tue Aug 02, 2016 10:13 pm

That's looking good Andrew :aad
I reckon a few resistors and you'll have it sussed :)

Marc.

 
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Re: DER 5649

Post by Red to black » Tue Aug 02, 2016 10:16 pm

I would ditch the Callins :qq1 , they were trouble back in the day :bba I cannot see them lasting any length of time even if they appear to reform.

Looking good though. :cca

 
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Re: DER 5649

Post by PYE625 » Tue Aug 02, 2016 10:19 pm

Thanks Marc.

There are a number of caps in the frame stage that could probably do with checking/replacing, plus some further voltage checks etc.

I found a date stamp in the cabinet of March 1969.

 
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Re: DER 5649

Post by PYE625 » Tue Aug 02, 2016 10:21 pm

Red to black wrote:I would ditch the Callins :qq1 , they were trouble back in the day :bba I cannot see them lasting any length of time even if they appear to reform.

Looking good though. :cca


I have re-fitted the Callins, but will likely replace it in time :qq1

 
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Re: DER 5649

Post by jayceebee » Tue Aug 02, 2016 10:45 pm

Excellent start, I thought that CME1602 would be pretty reasonable. :thumb

John.

 
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Re: DER 5649

Post by Cathovisor » Tue Aug 02, 2016 11:08 pm

The picture you have shows the classic signs of a dead cathode decoupler in the frame output stage...

 
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Re: DER 5649

Post by PYE625 » Wed Aug 03, 2016 7:34 am

Cathovisor wrote:The picture you have shows the classic signs of a dead cathode decoupler in the frame output stage...


I know, but there isn't one. The cathode goes straight to ground on the frame output :qq1

 
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Re: DER 5649

Post by The_Teleman » Wed Aug 03, 2016 9:04 am

Isn't this the chassis that the frame stage derives its bias fron the heater chain?
I seem to remember a similar chassis that did
If so check the heater circuit this could have a fault not evident from the glow of the valves

Chris

 
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Re: DER 5649

Post by Focus 2 » Wed Aug 03, 2016 9:15 am

Looking good so far. As for the Callings cap it looks to be surprisingly in good condition. Many I've seen have split leaking its interior everywhere. Nevertheless I consider it essential it's changed asap.

I take it the CME 1602 is a rim band version of the 1601? One could presumably be used in the 16" 960 portable.

March 1969 would appear to be a late model.

Brian

 
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Re: DER 5649

Post by Cathovisor » Wed Aug 03, 2016 11:58 am

PYE625 wrote:
Cathovisor wrote:The picture you have shows the classic signs of a dead cathode decoupler in the frame output stage...


I know, but there isn't one. The cathode goes straight to ground on the frame output :qq1

Huh?! Oh, hang on, I remember this one.

IIRC the idea is that the heaters are fed via a diode acting as a wattless dropper, and by deriving the bias from the heater chain it would show up as a massive hum bar if the diode went short, thus alerting the user to a fault condition.

 
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Re: DER 5649

Post by PYE625 » Wed Aug 03, 2016 12:02 pm

Thats true...the frame stage derives bias from the heater chain as Chris The Teleman also says above.
An interesting arrangement.

 
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Re: DER 5649

Post by PYE625 » Wed Aug 03, 2016 7:14 pm

So, this evening out came the Callins and I fitted a 1uf 400v modern "Suntan" polyester cap as it was pretty much the same physical pitch.
(Modern 1uf electrolytics are so small lol)

Excess width was due to R109 330k being completely open circuit which feeds boost HT to the top of the width control.
C62 0.02uf which provides feedback from the frame output to the linearity control was very leaky, replacement has brought about a big improvement.
Again, I have used the "Suntan" range of capacitors as they are the same reddish brown as the "Erie" types and have the same pitch size.
Whilst I was at it, I replaced a few others in the frame stage too.
(The manual is available in the library) :qq1
Attachments
rsz_img_2244.jpg
rsz_img_2245 (1).jpg
rsz_img_2246.jpg
rsz_img_2247.jpg

 
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Re: DER 5649

Post by Focus 2 » Wed Aug 03, 2016 7:23 pm

Wow, that's looking very good! Well done.

Brian

 
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Re: DER 5649

Post by jayceebee » Wed Aug 03, 2016 7:29 pm

Cathovisor wrote:
PYE625 wrote:
Cathovisor wrote:The picture you have shows the classic signs of a dead cathode decoupler in the frame output stage...


I know, but there isn't one. The cathode goes straight to ground on the frame output :qq1

Huh?! Oh, hang on, I remember this one.

IIRC the idea is that the heaters are fed via a diode acting as a wattless dropper, and by deriving the bias from the heater chain it would show up as a massive hum bar if the diode went short, thus alerting the user to a fault condition.


This arrangement was also seen in the 1400 chassis, a good idea in principal but if the heater rectifier went s/c most people would ignore the rolling mess on the screen and continue to listen to the sound resulting in severely overrun heaters. The later 1500 went one better where the LT supply for the tuner and IF strip was obtained from the bottom end of the heater chain. If the rectifier went s/c you lost the LT supply which removed both picture and sound leaving a blank raster.

John.

 
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Re: DER 5649

Post by The_Teleman » Wed Aug 03, 2016 8:09 pm

Excellent results, well worth saving this set
Don't come across many DER sets
Well done !


Chris

 
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Re: DER 5649

Post by PYE625 » Wed Aug 03, 2016 9:06 pm

The_Teleman wrote:Excellent results, well worth saving this set
Don't come across many DER sets


Chris


Furthermore, I can't imagine there were many 405 line only sets still being produced by 1969.....this must surely be one of the last?

 
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Re: DER 5649

Post by Lloyd » Wed Aug 03, 2016 11:33 pm

Great result! I'm sure I was told that these were one of the last 405 only sets. They are really good picture wise, and stay stable for hours on end, in fact I had one running all day at a vintage show in York a few years back, it worked faultlessly all day!

Regards,
Lloyd.

 
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Re: DER 5649

Post by sideband » Thu Aug 04, 2016 8:11 am

There is an account of the one I restored here.

Much the same sort of problems. Mine is still working well but I think I may need a new boost diode.....

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