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The RGD 627 Story - The Good Lopt, The Bad Lopt and the Ugly

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crustytv
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That title pretty much sums up this set! not the most attractive but nonetheless part of our TV history, therefore perhaps worthy of a fix. After all we see many Bush TV22's and Bush TV62's Pye LVxx's etc but how many of these do we see, so a little rarer.

I mentioned in another thread I took delivery of some bits, among them two televisions. A 1959 PYE V200 LowBoy and this RGD. It's a 1965 19" Dual standard RGD 627. This model is fitted with the S.T.C chassis and data is in the Kolster-Brandes section of the 1964-1965 Models Red book, page 431-442 (I'm in the process of scanning the data so it will be in the library later this morning)

EDIT: 11th March - found to be VC2 chassis so R&TS 1965-1966 page 441

Valve Line-up
v1 pcc189 VHF RF Amp
v2 pcf86 VHF frequency changer
v3 pc88 UHF RF Amp
v4 PC86 UHF frequency changer
v5 ef183 if amp
v6 ef184 if amp
v7 plc84 video amp (p) vision interference limiter (t)
v8 pcf80 sync searator (p) half frame multivibrator (t)
v9 plc85 half frame multivibrator (t) and output (p)
v10 6bw7 sound if amp
v11 6bw7 sound if amp
v12 plcl86 audio amp (p) and output (t)
v13 ecc81 line multivibrator
v14 py801 efficiency diode
v15 pl36/30p19 or pl302 line output
v16 R20 EHT rectifier
v17 a47-13w 19" CRT

Diodes
d1 gd12 vision detector
d2 oa81 frame sync pulse shaper
d3 dd268,by100 or s10ar2 ht rectifier
d4 & d5 oa79 fm sound ratio detector
d6 gex13 am sound detector
d7 gd9 am sound interference limiter
d8 & d9 oa81 flywheel sync discrimintor
d10 M1 agc clamp
d11 m1 vhf tuner agc delay

The a47-13w is a 19" CRT, electrostatic focusing, 110 magnetic deflection, Metal backed screen, bonded safety shield with CT8 final anode connector. 6.3V heater, a1=400v final anode=16kV, cut-off -40- -77 and B8H base.

This set also came with two lopt's in a box, I don't know the history other than to say the set does not have a lopt fitted and a number of valves are missing, a smashed focus pre-set and and exploded filter cap. Perhaps this set was laid to rest after suffering LOPT failure, consigned to the attic where it resided until finally disposed of.

I decided this evening to have a look at the lopt's. Both over-winds were in danger of breaking away as the pitch had all but fallen off one of them with the anode cap missing, the other one was also very loose but had more pitch attached.

With the lopt missing from the set, I guess it was reasonable to assume this component at some point had failed. I further had a suspicion that one of the spares lopt's might possibly be the failed one. Therefore I decided to keep it simple and try a ring trace to see if the scope would confirm any of this.

The scope was configured exactly the same for both tests

The one with the missing pitch went up first. The scope displayed a good ring trace so I would have reasonable confidence this should function.

The second one however was a different story, the ring was dampened. I think it is therefore reasonable to assume this was the failed component.

I shall in due course fit the first lopt.

Chris

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Posted : 22/02/2012 12:18 am
sideband
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There were quite a few of these around well into the 70's and I remember repairing a few of them. Good workers but a bit modern for you Chris? After all this has the 'new' 625 system although it does have a valve UHF tuner rather than a transistorised one.

Should be a good set once all the niggles have been sorted. You'll probably need to give the system switch a good clean but make sure it's dry before switching on. It was common to wire the switches for 625 only and remove the changover linkage so make sure this hasn't been done.

If there are tagstrips underneath the chassis particularly around the line stage, I've known these to become conductive and flash-over. Usually there is a sharp crack but the set carries on working. You think it's EHT flashover and spend ages looking for it.

Have fun! :=D

Rich.

 
Posted : 22/02/2012 9:39 am
crustytv
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There were quite a few of these around well into the 70's and I remember repairing a few of them. Good workers but a bit modern for you Chris?
Rich.

Hi Rich,

Yes it is rather modern for me, if we can call a 47 year old set modern :=D I do prefer the 1950's sets and some early 60's. Although KB did some wonderful mid to late 60's sets I wouldn't mind getting hold of the Kolster Brandes Imperial de Luxe SV30. Once we get into the 70's I have no interest. My Radio & Television Servicing stops a 1972, and as for colour Blurgghh! Just a personal choice and I admire those who have the advanced skills to tackle those beasts.

I have been trying to find a set from 1963 (the year I was born) I have a 1961 Ultra 1751 ( the motorised tuner jobby) and now this, so i'm getting closer. It's not pretty I agree, but it would be sad to see the old girl get binned so I was happy to take it and maybe get it going. It also makes a nice change from the 1949 hardwired chassis of LV20 I spent so much time on. I do find jumping around the years does provide some entertainment and observing the advancements made can be fun.

Thanks for all the tips, Its chaps like you, Trev, Malc, Robt & Terry etc that can offer this great catalogue of known stock faults that helps us who try to follow in your footsteps. :thumbl:

I've not had the chassis out yet but I have a feeling it may have been pulled about a bit, lets hope there are not too many nasties lurking. At least I will have the valves for this as my stock is 98% TV valves.

Cheers
Chris

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Posted : 22/02/2012 10:29 am
malcscott
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Hi Chris, these were very reliable sets. I serviced loads of them when i first started in the trade. Nice to see you have saved one. i have plenty of nos valves for it if you need any. Malc :thumbl:

 
Posted : 22/02/2012 11:19 am
crustytv
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Hi Malc,

Thanks, I've been slowly building up my Valve stock so hopefully I will be fine but its always nice to know "Malc's Speedy Spares" or MSS as I call it, are still in business ;)

Regards
Chris

p.s.

I hope to drop the DAC90A over to you on Friday if that's ok. Most likely after 11am as I have an eye test at 10am

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Posted : 22/02/2012 11:44 am
crustytv
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I put the A47-13W on the CRT tester looks like this set lived a hard life.

There appears to be a little heater to cathode leakage see pic 1 also the emission is way down. It may recover once it has some juices running through it, they often do, it remains to be seen but this does not bode well.

I can always give it a tickle but I may be on the look out for a spare A47-13W :'(

I shall endeavour to get the new lopt fitted soon, then see what the set coughs up and if the screen lights up at all.

Chris

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Posted : 22/02/2012 2:52 pm
neil1974
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Hi chris. i used to have a 627 myself, so ill be interested to see the results. cheers neil.

 
Posted : 22/02/2012 5:03 pm
Anonymous
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Loverly sets to work on (bar the system switch). Resistors in the width circuit used to drift in value and the slider width control is suspect. The uhf tuner would go low gain, new valves will sort this .Some suffered from inter carrier sound buzz. Try the discriminator. Field fold-over, the pcl85 cathode bias cap.
To me the pictures on these sets always looked a bit soft.

rob t

 
Posted : 23/02/2012 12:26 am
crustytv
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Well a break from the Mullard Tester and back to televisions 8)

This chassis was used on a number of dual standards, the Kolster-Brandes WV05,WV60, Regentone 197,198,298 and of course the RGD 626,627 ( this one) 628 and 726. 19" rimband on the KB WV05,Regentone 197,198 and finally RGD 626,627and 628. The 23" rimband on the KB WV60, Regentone 298 and RGD 726.

If you recall this set had suffered LOPT failure, and 5 valves were missing these are identified as the following :-

v9 plc85 half frame multivibrator (t) and output (p)
v12 plcl86 audio amp (p) and output (t)
v14 py801 efficiency diode
v15 PL36 Line output
v16 R20 EHT rectifier (U26 will sub)

Someone has broken the 405 contrast pre-set (see pic 3) so I will have to find a spare.

I had two LOPT's so the faulty LOPT was identified by ring trace so I know which one to use. I just have to fit some TC connections for the EHT rectifier and one for the eff diode or line out to the LOPT.

Next comes the tricky bit I will need to identify each wire and figure out where each connects back to the LOPT getting it back in circuit correctly. I find this uncomfortable picking up where someone else left off as I like to be the one who removes, documents then refits. Still Its all part of the fun and games 8))

The system switch looks remarkably clean and has not been fixed so I'm hopeful 405-625 will work. I was quite surprised also to find a hard wired chassis, I expected to find a PCB, considering many sets earlier than this (PAM in 1958, GEC 1960 and many others) had started to introduce PCB.

Once figured out a familiarised then I would normally snip the filter cap but as you can see it has already decided to puke it guts so need to worry about that ( see pic 7). The main smoother seems to have a minor bulge but I will see how it fairs when it gets introduced to power. I have a horrible feeling the CRT is going to be poor on this after the tester showed it to be very low emission, so first light sooner the better to see.

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Posted : 06/03/2012 11:11 pm
sideband
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Those blue and yellow Plessey caps should be changed....nasty things!

Rich.

 
Posted : 06/03/2012 11:52 pm
Terrykc
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... I was quite surprised also to find a hard wired chassis, I expected to find a PCB, considering many sets earlier than this (PAM 1958, GEC 1960 and many others) had started to introduce PCB ...

"Hand wired chassis" featured strongly in the advertising for these sets.

The same basic chassis survived for many years with subsequent versions given a 'VC' number.

IIRC VC1, VC2, VC3 & VC4 - then a jump, for no apparent reason that I could fathom, to VC51 & VC52. Finally, minus the system switch, etc., it appeared as the VC100* single standard chassis which was eventually superseded by the PCB based VC200.

Quite a long run for, essentially, the same design!

* I first encountered the VC100 in 1969 before BBC1 and ITV were duplicated on 625 lines and the chassis appeared in the retail market. (It was used in sets on a 625 line only cable system.)

Whether we had the first examples of the single standard version of if there had been an export version, I don't know.

When all else fails, read the instructions

 
Posted : 07/03/2012 12:03 pm
Anonymous
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Irish TV started 31st December 1961.
Only places that already had a lot of 405 sets for BBC had 405 lines. The other TX sites VHF and 625 line only. There were 625 only sets from 1962. A VC100 with BandI/Band III tuner quite likely in Ireland. UHF I think only began with RTE1 in 1977 or 1978 and then RTE2 in 1979. Some places still Band III only RTE1 & RTE2, but UHF TV3 and TG4 (Analogue). All VHF TV & Analogue TV closes simultaneously 24th October 2012 all of Ireland and N.I. (UK still!)

I get this 2nd hand as I moved to Ireland about Feb 1983, a few months after C4 started. Still only 1 & 1/2 channels RTE1 BandI and RTE 2 Band III 625 line. The band I turned off in 1999 after a long period of simulcast on Band III (yes, RTE1 625 line on Band I and Band III from same transmitter!). The closure of Eastern Band III 405 in 1984 or 1985 allowed RTE 1 625 on Band III in the Mid West.

 
Posted : 07/03/2012 12:30 pm
crustytv
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Just been reading through the circuit description and came across an add-on for the set, a "baby alarm unit" just goes to show nothing is new and this was back in 65.

I wonder what the chances are of coming across one of those devices, it would be good to find one.

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Posted : 07/03/2012 12:55 pm
crustytv
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quick update, I've identified the wire placements for reinstating the LOPT, I've attached little labels as I don't trust myself. :roll:

R70 the 405 contrast as I mentioned previously had been broken, its a 500K pre-set, I checked my spares and had the exact value and type required.

So hopefully tonight or maybe tomorrow I can give it some mains to see what gives, now do I just give the full beans or shall I wimp and go for variac. The last few sets I just went full mains but this one bothers me for some reason.

Chris

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Posted : 08/03/2012 1:30 pm
sideband
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For what it's worth, sets that have a solid state reccy I tend to wind up on a variac whilst monitoring the HT rise and then just slowly advance the mains until it's more or less correct but aiming for the lower limit. I like to be gentle with old electrolytics! With valve reccy's it's easier to use nearer full mains because obviously the heater has to get up to temperature before it does anything. If the set it adjusted for 240V, I'd run it at 220ish just to see what happens then give it full mains when you're happy.

I'm always in favour of a gentle awakening rather than just going for broke.....but then that's me!

Rich.

 
Posted : 08/03/2012 3:39 pm
neil1974
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With my sets i just switch on and hope for the best. i do check for obvious faults first. and for the most part the set has either worked or not,apart from the odd cap that complains 8)) . cheers neil.

 
Posted : 08/03/2012 3:46 pm
Jamie
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With most sets I give it the full go. If this were my set however I would use a variac. It has been fiddled with previously and it has a spare LOPT. If you apply full mains and the same fault that caused the other LOPT to go wrong is still there.. You've lost another LOPT ;)

 
Posted : 08/03/2012 5:22 pm
crustytv
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I think your right Jamie that's probably what's been nagging at me it's been fiddled with, so I will lean towards caution this time and bring it up gently.

Well R70 500K replacement is now in place, the pre-set is a perfect match. After dinner I shall set about the LOPT installation and report back. Nothing else has been touched or replaced for those that might be thinking "Oh just give it some power!" well to those I say, not much point without a lopt and the pre-set needed doing as it is the 405 contrast. I think the tube might be stuffed so I want all the picture control I can get to get a good chance of first light being spotted.

I've had a good read of the circuit, the dropper sections are intact but a tad rusty, I won't be surprised to see one or two of those go ping. I shall dig out the valves that are missing too & do some quick cold checks.

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Posted : 08/03/2012 6:05 pm
Norman-Raeburn
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Hi Chris, I have the KB version of this on the bench at the moment. I was going to contact you regarding the lopt connections but yo seem to have worked it out. We used to have hundreds of these on rental and the lopt's were fairly robust. My one which I was working on today has started to smell and fizzle, guess what, the lopt has gone up in smoke. I hope it's just the overwind that has gone. Regards, Norman

 
Posted : 08/03/2012 6:35 pm
Jamie
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On another note, Is it normal for LOPT's to fizz somewhat? My KT3 LOPT has always done it ever since I can remember. The LOPT phyiscally looks OK and i'm sure Roger would have spotted it if it wasn't. The CRT also produces a rather faint high pitched tone for the first few minutes of warm up, Though I am the only one that seems to be able to hear it.

P.S Chris, Good call! That set looks 'fun'

 
Posted : 08/03/2012 6:44 pm
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