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Forum 141

RGD Deep 17.

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Till Eulenspiegel
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Hi Frank,

when the frame hold is adjusted the best interlace is realisable just before the picture begins to slip.  However, the sync pulse amplitude at the anode of V7P  was measured and found to be only 50 P - P.  I'd say that is too low so it's possible the ECL80 sync valve is suspect.  When it's replaced I'll report back my findings.

This simple differentiator frame sync coupling was used in many other late 1950s TVs, the Stella ST1007 for example.  Even the series resistor R83 has the same value -  680Kohms and it's same for many Thorn group sets, the Marconi VT161 for example.      

StellaST1007 FrameTB

Till Eulenspiegel.

 

 
Posted : 11/11/2019 9:07 pm
PYE625
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Hi Till, I had a similar problem on the Murphy V280C, but in this case it was a tired 6/30L2 double triode valve in the frame stage. I never did get round to examining the voltages and waveforms, I perhaps should have done before simply exchanging the valve.

No proper fault-finding there I'm afraid...... "Guilty, your honour".

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 11/11/2019 10:13 pm
Till Eulenspiegel
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Hi Andrew,

been swotting up about the Murphy V280 series, well, as much as one glean from the Radio and Television servicing books.  Really need the Murphy service manual to find out how some of the circuits work.

Like the Deep 17 the V280 employs a differentiator to extract the frame sync pulses but the processing of frame sync is done in much more thorough manner compared with the RGD and Stella. The latter two have got away with doing it on the cheap, not so Murphy. The picture interlace should be perfect in the Murphy. As simple as it is interlace is OK in the RGD though.

Till Eulenspiegel.

 

 
Posted : 12/11/2019 9:57 pm
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Till Eulenspiegel
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The ECL80 sync separator valve was replaced and now 200volts of negative going sync is present at the anode of the pentode sync separator.   The sync pulse tips are almost down to ground potential.

Now the line and frame holds are really effective, picture lock is maintained over a wide range of control adjustment. An extra bonus is good interlace which is important and a large screen TV set.

Till Eulenspiegel.

 

 

 
Posted : 16/11/2019 11:20 am
Nuvistor
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Shows that the design was a good one, excellent news, are there more things to fix or is it finished?

 

Frank

 
Posted : 16/11/2019 11:29 am
Till Eulenspiegel
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Hi Frank,

                  I reckon it's safe to say we can sign this job off.  The poor contrast range turned out to be the three position white spot limiter adjustment was set up for maximum peak white clipping.   Need a channel selector knob. Found something that will do until the correct part is found, if ever that is. 

Circuit of the Deep17A and Regentone TR177A was carried forward into the models TEN4 and 110degree CRT models TEN17.

Till Eulenspiegel.

 

 

 
Posted : 16/11/2019 11:48 am
Till Eulenspiegel
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Just before the Covid-19 crisis the owner of the set reported that the Deep 17 had developed a fault but because of the lockdown was unable to return the set to the shop. Today the set is now on the workbench. The set had a considerable amount work done to it nine months ago so the expectation was the it'll be something easy to fix. Not so, the AW43-80 has an open circuit heater, something I didn't expect. In sixty years of TV servicing I never experienced an O.C. heater in one of these tubes. The only suggestion is that the tube had developed the well known partial short circuit of the "M" type heater and as a result of that the heater burned out with 0.3amps flowing through it.

It's a very good set so it's well worth looking out for a replacement tube for it. 

Till Eulenspiegel.

 
Posted : 15/08/2020 4:03 pm
Nuvistor
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@till

Perhaps bad soldered joints in the CRT base, but you have probably ruled that out. Replacement CRT’s are a problem I think that has been discussed before, hopefully a suitable one will turn up.

 

Frank

 
Posted : 16/08/2020 10:06 am
Till Eulenspiegel
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Hi Frank,  I re-soldered the tube base pins but with no results.  How about that old trick of flashing the tube with EHT? There's nothing to loose. 

Actually we're on the lookout for two AW43-80 tubes. The Stella ST1007 needs one, although that one is just low emission and still displays a picture.

There was a time when the AW43-80 was considered the best black and white CRT ever made for domestic TVs.

Till Eulenspiegel.

 
Posted : 16/08/2020 11:26 am
Katie Bush
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@till

Definitely, try the EHT flash. As you say, nothing to lose, and all to gain, though I have heard it said that the results can turn out to be short lived. Conversely though, I've also heard of CRTs being flashed as far back as the mid '60s, and still going at the end of the 405 line service.

 
Posted : 16/08/2020 7:37 pm
Cathovisor
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Somebody needs to find a Grunther Heatamec - which was made especially for this job.

 
Posted : 17/08/2020 10:13 am
Till Eulenspiegel
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Googled "Grunther Heatamec" and found this interesting Swedish website. Couldn't find the Grunther instrument but there's lots of interesting stuff including an advert for Pye TV sets. Scroll down to page 83. Also a Toshiba TV set.

https://www.aef.se/Amatortidningar/Radio_och_Television/radio_television_1960_03-ocr.pdf

Till Eulenspiegel.

 
Posted : 17/08/2020 11:25 am
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Till Eulenspiegel
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News Flash!  The CRT heater has been repaired using the flash method. Waste of time using the EHT to weld the broken heater. use the high energy pulse present at the anode of the line output valve.  After several attempts, success!  The set will be given a long soak test before the job is signed off. Standby for more reports.

Till Eulenspiegel.

Deep17 CRT

   

 
Posted : 03/09/2020 7:41 pm
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PYE625
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That is good news !

Yes, I can imagine a little more current would be required than the EHT could produce.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 03/09/2020 8:35 pm
Till Eulenspiegel
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Returned to the workshop at 22:30hrs and switched the RGD on again. Except for a slow warm-up frame output valve the set is displaying a nice bright test card C.

Will just keep testing the set until we're completely sure the set can be returned to it's owner.

I do remember one these sets being still in use right up to end of the seventies. By then it would have been over twenty years old.

The cabinet style of the Deep17 was used in the high specification RGD THE17. This set used the 70* MW43-69 CRT so the cabinet might have been slightly deeper. PCF80 triode-pentodes were employed in the vision IF amplifiers. The model THE17 was released late 1956. The Deep17 was late 1958 at the same time Tyne-Tee-Television were doing their test transmissions to get the station ready on January 15th 1959. RGD advertising promoted the set as tested in the Tyne-Tees-TV region.

Till Eulenspiegel. 

 
Posted : 03/09/2020 9:56 pm
Nuvistor
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Hope it stays ok, most items in these TV’s are either readily available, can be repaired or found in a scrap chassis except the CRT. 
I didn’t stock CRT’s in my workshop in the 60’s and 70’s, no need, a replacement or regun could be had the same day even Saturday mornings, unfortunately only second hand or occasionally NOS now.

Fingers crossed it survives.

 

Frank

 
Posted : 04/09/2020 7:41 am
Till Eulenspiegel
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The tube is holding up well. The set has been switched on for than five hours today and the picture remains bright and sharp.  Heater volts correct at 6.3V so there is no problem with a partially short circuit heater.

Till Eulenspiegel.

 
Posted : 04/09/2020 3:47 pm
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Katie Bush
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I guess the real acid test will be in how many switch on cycles it can withstand. Probably a million reasons why not, but, would it be possible to snub the surge with addition of, say, a PTC device of some kind, across the heater?

 
Posted : 06/09/2020 3:35 pm
sideband
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Looks like it might have failed already. Over on Paul's forum https://www.vintage-radio.net/forum/showpost.php?p=1286594&postcount=9

 
Posted : 06/09/2020 6:55 pm
Till Eulenspiegel
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The set was taken away from the workshop yesterday and I received the bad news this morning, no continuity between pins 1 and 12 on the CRT base.  So we're on the lookout for a replacement tube.

And it was such a good picture. 

Till Eulenspiegel.

 
Posted : 06/09/2020 7:49 pm
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