Notifications
Clear all

Radio Sobell 516

Page 2 / 2
 
PYE625
(@pye625)
Famed V-Ratter Registered
Posts: 4934

You can't beat a straight forward well designed set such as this.

Good old fashioned engineering built to last a lifetime. Several lifetimes too, no doubt.

ReplyQuote
Posted : 23/01/2022 9:58 pm
sideband
(@sideband)
Famed V-Ratter Moderator
Posts: 4045

I should add that I carried out some basic checks around the output valve since the original coupling capacitor was so leaky and the cathode resistor was burnt. The 6V6 doesn't seem to have suffered and appears very healthy so the valve tester wasn't lying! The voltage across the 270 ohm was 12V which equates to 44mA...slightly less than given in the service information. Actually that works out to 0.528 watts so is slightly in excess of the 1/2 watt rated resistor recommended for the 270 ohm......hmmm I fitted a Philips type half watt in there so I might change it for a 1 watt instead.

I shall look at this more closely next time....

ReplyQuote
Topic starter Posted : 24/01/2022 11:38 am
turretslug
(@turretslug)
Honorable V-Ratter Registered
Posts: 522

Good old 6V6, they just seem to go on and on.

Curious that someone fitted a VR56, later becoming CV1056- that's based on the "straight" characteristic EF36, when a VR53/CV1053, based on the vari-mu EF39, would have been a more orthodox substitute for a 6K7. Maybe someone in the past fitted the VR56 'cos they had it to hand and left it there on the basis that "it worked".....

ReplyQuote
Posted : 24/01/2022 11:34 pm
sideband liked
sideband
(@sideband)
Famed V-Ratter Moderator
Posts: 4045

@turretslug 

Thanks for that information! I shall sub that for an EF39 since I have several of those otherwise it means pinching a genuine 6K7 out of my Barker 88. 

I must admit that I didn't think things were quite right in the AGC department during my tune around the SW bands so having an EF39 in there might improve things.

I hadn't actually got round to checking if the VR56 was a good sub. It looks as if it's been in there a very long time and I suppose it's worked well enough for normal listening.

ReplyQuote
Topic starter Posted : 25/01/2022 10:15 am
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered
Posts: 5789

@turretslug Long time ago now but I remember when Tudor Rees was offloading large quantities of CV1053s in his newssheets. I bought a few - straight-sided envelope and light grey metallising. 

ReplyQuote
Posted : 25/01/2022 11:35 am
sideband
(@sideband)
Famed V-Ratter Moderator
Posts: 4045
Posted by: @sideband

@turretslug 

I hadn't actually got round to checking if the VR56 was a good sub. It looks as if it's been in there a very long time and I suppose it's worked well enough for normal listening.

Looking on the valve museum website it seems the VR56/EF36 was more an audio valve so the gain must be pretty low at RF plus of course it isn't vari-mu. That might account for why the radio was so loud on strong signals and very quiet on the weaker ones. Even R4 wasn't as good as it should have been. OK when I next get into the workshop I shall sub it with an EF39.

ReplyQuote
Topic starter Posted : 25/01/2022 1:50 pm
turretslug
(@turretslug)
Honorable V-Ratter Registered
Posts: 522
Posted by: @cathovisor

@turretslug Long time ago now but I remember when Tudor Rees was offloading large quantities of CV1053s in his newssheets. I bought a few - straight-sided envelope and light grey metallising. 

I've a couple of these in the stash, too- there seem to have been a lot of these, and the CV1347 (ECH35-alike), with tubular envelopes and "British sky grey" metallising and date-codes as late as the mid-'70s, some three decades after grid-cap IOs started looking old-hat. Maybe there's an urban myth to be concocted around secret stashes of EMP-resistant latter-day WCRs kept in bunkers around the country during the Cold War.... There are also a lot of late, tubular-bottle, low-loss base CV1099, CV1100 etc. around which might have been made for such as the large numbers of R1155s still in service post-war in applications such as training and even the likes of the early Shackletons- the military of the era loved to have lots and lots of spares and someone else (thee and me) was honouring the cheque. Maybe someone in stores saw that there were still Pye PCRs nominally on the inventory and periodically re-ordered the CV1053s and CV1347s just in case- I know that in the relatively minor example of our own stores that every now and then one of the stores staff would notice that there were only 3 of such-and-such in the Linbin and so they'd better order some more.... I'd point out that not only were they very expensive, but it was part of something of which the last examples had been scrapped quarter of a century previously.

I do recall that in the case of the big 1983 MOD Donington stores fire, the initial loss estimate of something like £1.5 billion was later revised to nearer £200 million when it was realised that much of what had gone up in smoke was spares for equipment that hadn't been used since 1945! A great deal of the sundries that came across from North America in the last 18 months or so of the war were never used by the miltary and Sideband's VR56 is possibly representative. Supposedly, vast amounts of aluminium (aloo-min-um?) stock from Alcoa and Alcan was delivered in late 1944 and early 1945 for putative aircraft production- every now and then, someone on a US forum asks, how come so many Brit radios have aluminum (sic) chassis....?

ReplyQuote
Posted : 25/01/2022 6:08 pm
sideband
(@sideband)
Famed V-Ratter Moderator
Posts: 4045

Well I was a little surprised.....I tried an EF39 and a 6K7 last night in place of the fitted VR56 (EF36) and there wasn't much difference in the way the radio operated except the AGC was obviously working. Gain-wise though it was about the same. Short of working in a Faraday cage and using an external aerial well away from the house, there isn't much I can do about the horrendous interference I get on AM now. Only part of the SW band is reasonably interference free which restricts me to the Voice of China, an Indian music program or a religious program with a heavy American preacher.......! R4 on MW is about the only station I can listen to without interference and further up (or down depending on whether you use frequency or metres), Sunrise Radio has no interest for me at all.

I think I'm going to have to build a loop aerial with an ATU (aerial tuning unit) to get through all the noise.

ReplyQuote
Topic starter Posted : 28/01/2022 1:15 pm
Page 2 / 2