Decca Dual Standard DR303

Very much like my recently acquired Bush TV75 - similarly described as working, but soon developed a problem as we assessed its condition.

Up to a point, can't blame a seller for trying out a set before selling it, but unfortunately, not all of them have our insight. I guess it's the lucky ones who get away with it, and if a set appears to work there is just a hope in the seller's mind that it will fetch a better price.

That's a very grandiose-looking set there, Andrew

Look forward to its rebirth - as and when... 

First job I presume is removing the 3amp fuses for 1amp ones. CRT looks nice and bright though, keep you out if trouble for a while sorting it out and it's a chassis type no PCB's so should be in nice condition.

It is rather in a "posh frock" and I did spot the 3 amp fuses

Some more pic's.....spot the sweaty looking mains bypass wax capacitor.....eeeeek !!

Spotted that on e-bay and wondered if someone on here would nab it, well done. Another large set to accommodate though

As you rightly say shame folk cannot resist plugging it in, lets hope they've not run it too long if there's more caps like that leaking and causing all sorts of untold stress. I might be wrong but I believe the DRxxx series LOPTS are the Achilles heel. Having said that after 50 odd years that rings true for pretty much all sets now. well except perhaps Thorn Jelly pots.

Should be an interesting thread to follow, look forward to reading more when you find time.

Hi Andrew,

I was following that set on eBay and wondered if it would land somewhere on our forum and by gum it did ! 

Looking forward to seeing more of it on here and as Catho alluded to it does look a very 'stately' set indeed, nice ! 

Marc. 

Is that a Philips VHF Tuner, there is a label on the back of the tuner? If the UHF tuner is also a Philips they were the best PC86/PC88 valve tuners for sensitivity I came  across. The Pye and the Bush UHF valve tuners were pretty deaf.

Chris said
 Another large set to accommodate though
 

I know I know I know......I must be raving mad 

But it is a 19 inch, so will not be too  big  

Now, anyone sensible would have the workshop ready first. As for me, well I get another set long before the workshop is anywhere near ready. I guess set's like this don't appear every day, so you have to strike while the iron is hot. (That's my excuse)   

For those that like to play along at home, the service data covering the Decca DR101, DR202, DR303, DR404, DR505 & DR606 now resides in the data library

Always interesting looking at the circuit designs.

There are 3 EB91 double diode valves in the set, one I can see a good use for but other set makers were using solid state diodes for the ratio detector and vision detectors. We will never find out but would be interesting to know why valves were chosen for those tasks. The third EB91 is used for DC restoration of the video signal, not many other sets in 1963 were using that system, the other half has a peak white limiter for 405.

The input to the VHF tuner as another interesting aspect, there is a high pass filter, then a balun before the first tuned circuit. Some cheaper tuners that used a single triode as RF amp had a choke to reject MW transmissions but this tuner goes quite a bit further in rejecting out of band LF transmissions. The balun, now was that there due to this tuner being capable of being used in areas were balanced feeder was more commonly used for the aerial?

Any suggestions from the forum members welcome.

Thanks Frank, some interesting observations.

We can only guess as to the reasons for the EB91's... More valves = less heater dropper requirements?  Easier to use existing designs or components, or the designers felt valves were more reliable than the germanium diodes?  Would it have been cheaper to use valves at the time?  An EB91 looks nicer than a solid state diode?  

Perhaps if the VHF tuner is a Philips unit, it may have also been used in continental sets where differing requirements in feeding the aerial may have been needed.

What caught my attention was the PSU arrangement....why go the extreme of using TWO smoothing chokes (CH4 and CH5)    

You will be able to recognise if it's a Philips tuner, they used printed circuit 'biscuits' edge on with the contacts wrapped around the edge of he PCB. 

If it is one of those be careful of the fine tuning 'wand' a small white Nylon Rod about 25-30mm long with an aluminium boss on one end. The nylon fractures, common fault in  the 60's, easy to replace if available. Various techniques to removing the old one, looks a bit daunting a first.

The smoothing chokes are also a solenoid, used to move the 405/625 switch, notice the switch contacts on the HT output of the chokes.

Cleared some space to get into my manufacturers filing cabinet, found that I have the Decca manual for this series chassis. I'll get it scanned, includes some useful waveforms which are not included in the trader sheet.

Edit: Now in the library, I couldn't be asked to clean up the cover or some rust stains/foxing in Photoshop, sometimes life is too short. Its perfectly readable, the huge schematic was a challenge to do on an A4 scanner.

Chris said
[...] the huge schematic was a challenge to do on an A4 scanner.  

I have spent a few days - when I should have been decorating - modifying and fixing an Armstrong 526 tuner amplifier for a friend at work, for his 'man cave'. There's still faults with it, but it is at least now working, not killing its PSU, and I am pleased to say the silicon mod has worked well: the upgraded PSU has worked well and it is *loud* and clean. I was working with a p*ss-poor scan spread across multiple pages and angled amongst other things. I *eventually* got it pieced together in Paint Shop Pro 9 into one readable diagram.

It is, as you well know, NOT a trivial matter to create good scans, especially of circuit diagrams. Must confess that's why I love my big old A3 Epson 🙂

Cathovisor said

I have spent a few days - when I should have been decorating - modifying and fixing an Armstrong 526 tuner amplifier for a friend at work, for his 'man cave'.

At least you have your priorities right! 

Hi,

After a nice ride down to near Sevenoaks in Kent, the set is now at home with me here in Chatteris. 

Wow, didn't expect the red doors, very smart.

Hi Andrew,

Well, I thoughtful it looked good on the eBay advert but it looks way better now you have it back home. 

I'm looking forward to seeing this beauty come back to life.

Marc.