Regentone SRG18 cct oddity. - UK Vintage Radio Repair and Restoration Discussion Forum

Studio263 · 21st Jan 2008, 5:56 pm

Seek out the circuit for the Regentone SRG18 stereogram. It's in 1963 > 64 of R+TV S (red books) and in lots of other places I'm sure.
What makes it odd? Well, normally for accurate stereo reproduction you try and make the left and right amplifers as similar as possible, something that has most definitely not been acheived in the Regentone. One amplifer channel consists of the triode part of a UABC80 and a UL84, the other an ECL82! Aside from the crazy heater supply arrangements that this lot requires, the pentode parts of the two valves are completely different, necesitating different output transformers and different cathode resistors.
Looking at how the circuit is drawn it may be that the extra amplifer is a hasty add-on to update some unsold stock. The rectifier is a selinum type so I wonder if a UY85 was removed to make a hole for the ECL82 in the chassis?
I've had a go at posting up the circuit but failed miserably, could anyone oblige?

mickjjo · 21st Jan 2008, 6:52 pm

The SRG18 appears to use a similar circuit to the earlier SRG87 from 1960/61, but minus the tuning indicator! I guess it was cheaper to update an old mono design than to start again. Regentone was quite a low-end brand by that time and I doubt that anyone would have noticed any difference between the 2 channels, Negative feedback tends to even things out. The SRG87 circuit is available from Pauls service data site, so I wont post it here.

Regards, Mick.

Steve_P · 21st Jan 2008, 8:23 pm

Actually, in a way it's quite clever. They are using two triodes, one in the UABC80 and one in a ECL82. Problems will occur with component changes, either by servicing or by component drift, but with feedback, this should be minimised.

They could have used a UCL82 though, it must be said.

Cheers,

Steve P

Studio263 · 21st Jan 2008, 8:45 pm

Interesting that you should mention the SRG87 and negative feedback, I've just found that one in the 1960 > 61 volume. Look closely, the left channel does indeed have negative feedback (from the loudspeaker to the bottom of the volume control) but the right channel has none! A tuning indicator does not make up for a gaffe like that! Amends were made on the SRG18, so that must have been the "good" one.

It seems both models are derrived from a table set called the R10 (1959 > 60), which as I predicted has a UY85 as the rectifier.

Wading through the dog end of Plessey's output is really taking it out of me, I think I'll read the Beovision 3400 manual for a bit to recover my faith in the abilities of set designers.

Nickthedentist · 21st Jan 2008, 9:54 pm

Very interesting. Puts a stop to the "everything used to be better designed" attitude that a lot of people on this forum frequently uphold (including me sometimes, I hasten to add!).

Nick.

21st Jan 2008, 5:56 pm	#1
Studio263 Octode Join Date: Apr 2007 Location: Hampshire, UK. Posts: 1,578	Regentone SRG18 cct oddity. Seek out the circuit for the Regentone SRG18 stereogram. It's in 1963 > 64 of R+TV S (red books) and in lots of other places I'm sure. What makes it odd? Well, normally for accurate stereo reproduction you try and make the left and right amplifers as similar as possible, something that has most definitely not been acheived in the Regentone. One amplifer channel consists of the triode part of a UABC80 and a UL84, the other an ECL82! Aside from the crazy heater supply arrangements that this lot requires, the pentode parts of the two valves are completely different, necesitating different output transformers and different cathode resistors. Looking at how the circuit is drawn it may be that the extra amplifer is a hasty add-on to update some unsold stock. The rectifier is a selinum type so I wonder if a UY85 was removed to make a hole for the ECL82 in the chassis? I've had a go at posting up the circuit but failed miserably, could anyone oblige? Last edited by Darren-UK; 26th Jun 2008 at 11:59 pm. Reason: To accord with thread title change.

21st Jan 2008, 6:52 pm	#2
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: In need of a good laugh? The SRG18 appears to use a similar circuit to the earlier SRG87 from 1960/61, but minus the tuning indicator! I guess it was cheaper to update an old mono design than to start again. Regentone was quite a low-end brand by that time and I doubt that anyone would have noticed any difference between the 2 channels, Negative feedback tends to even things out. The SRG87 circuit is available from Pauls service data site, so I wont post it here. Regards, Mick.

21st Jan 2008, 8:23 pm	#3
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: In need of a good laugh? Actually, in a way it's quite clever. They are using two triodes, one in the UABC80 and one in a ECL82. Problems will occur with component changes, either by servicing or by component drift, but with feedback, this should be minimised. They could have used a UCL82 though, it must be said. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

21st Jan 2008, 8:45 pm	#4
Studio263 Octode Join Date: Apr 2007 Location: Hampshire, UK. Posts: 1,578	Re: In need of a good laugh? Interesting that you should mention the SRG87 and negative feedback, I've just found that one in the 1960 > 61 volume. Look closely, the left channel does indeed have negative feedback (from the loudspeaker to the bottom of the volume control) but the right channel has none! A tuning indicator does not make up for a gaffe like that! Amends were made on the SRG18, so that must have been the "good" one. It seems both models are derrived from a table set called the R10 (1959 > 60), which as I predicted has a UY85 as the rectifier. Wading through the dog end of Plessey's output is really taking it out of me, I think I'll read the Beovision 3400 manual for a bit to recover my faith in the abilities of set designers.

21st Jan 2008, 9:54 pm	#5
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,866	Re: In need of a good laugh? Very interesting. Puts a stop to the "everything used to be better designed" attitude that a lot of people on this forum frequently uphold (including me sometimes, I hasten to add!). Nick.