Featured
Latest
The RGD 627 Story -...
 
Share:
Notifications
Clear all

Forum 141

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

258 Posts
17 Users
0 Reactions
39.6 K Views
Anonymous
(@anonymous)
Posts: 16868
Group Deactivated Account
 

The lopt in these sets were good i only ever replaced one, mind you the last one i repaired must of been 20+ years ago. The main problems were high value resistors and the pre sets, mainly in the width circuit.
rob t

 
Posted : 08/03/2012 8:31 pm
sideband
(@sideband)
Posts: 4222
Famed Member Moderator
 

On another note, Is it normal for LOPT's to fizz somewhat? My KT3 LOPT has always done it ever since I can remember.

It might not be the LOPT. Chokes tend to 'sing' at line frequency and it's sometimes difficult to pin-point the area.

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.

The clue is in the comment above. Remember that the heaters of the tube are fed from a winding on the LOPT so they are running at line frequency. There are also some chokes on the CRT base that feed the heaters. The chokes are probably 'singing' at line frequency which lessens as they heat up. Sometimes the CRT heater will also 'sing'...less likely though.

Rich.

 
Posted : 08/03/2012 8:56 pm
Jamie
(@jskinner97)
Posts: 1755
Prominent Member Registered
 

Hi, Thanks Rich that's ok then. Nothing bad at all.
The KT3 has proved reliable yet.

Jamie

 
Posted : 08/03/2012 9:07 pm
crustytv
(@crustytv)
Posts: 11904
Vrat Founder Admin
Topic starter
 

OK I'm doubting myself now.

The green circled connections I've made, I was confident were correct. The yellow circled one I thought went here but it's too short and looks like the spare lug was not used or its been cleaned or the wire was cut, but maybe not, so maybe there are more wrong or maybe not :wft?: this is why I hate picking up where someone left off.

That last connection wire (yellow circled) if followed back connects up to the line scan coils

Norman!if you have a diagram or a photo of yours would help

Chris

CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek

 
Posted : 08/03/2012 9:08 pm
Norman-Raeburn
(@norman-raeburn)
Posts: 174
Reputable Member Registered
 

Hi Chris, In the last photo you have, the coloured wires are fitted the same as mine so it looks like you have sussed them ok. I have the lopt out of my set at the moment and hope to refit it tomorrow with a tripler. If you need further information as to where the leads go to, please ask. Norman

 
Posted : 08/03/2012 9:44 pm
crustytv
(@crustytv)
Posts: 11904
Vrat Founder Admin
Topic starter
 

Hi Norman,

Phew at least i'm not going crazeeeee I hate that moment when doubt takes a hold. The line scan wire is short because it pulled through the chassis :=D

Ok Power coming up if you hear the explosion you know it was me 8))

Edit: 23:00

Wound variac up to 200v probed various parts of the circuit DC voltages present throughout, C136, C138, C66, C122 @274V, pin 9 py801 274v, pin 1&4 pl36 270V, various parts of the system switch read the same most of the valves on pin 6 or 7 read various voltages from 64v - 270v, cathode of crt 83v. Just bugger all heaters which are intact. R164, R157, L77 all reading fine with voltage.....Brain tired, need sleep, will pick it up tomorrow.

CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek

 
Posted : 08/03/2012 9:48 pm
Terrykc
(@terrykc)
Posts: 4005
Member Rest in Peace
 

On another note, Is it normal for LOPT's to fizz somewhat? My KT3 LOPT has always done it ever since I can remember.

It might not be the LOPT. Chokes tend to 'sing' at line frequency and it's sometimes difficult to pin-point the area.

The simplest way to pinpoint where the noise is coming from is to use a tube - e.g.: rolled up sheet of paper - which keeps the ear well out of harm's way whilst the other end is moved over the suspect area of the set.

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.

The clue is in the comment above. Remember that the heaters of the tube are fed from a winding on the LOPT so they are running at line frequency ...

No! The EHT rectifier heater is fed from the LOPT! The CRT is fed from the heater chain, usually at at the earthy end ...

When all else fails, read the instructions

 
Posted : 09/03/2012 12:50 pm
Anonymous
(@anonymous)
Posts: 16868
Group Deactivated Account
 

I think somewhere along the line that you've missed that the above quoted text was referring to a Philips KT3 and not the RGD of the thread's title. Therefore, the original comments re LOPT fed CRT heater are valid.

 
Posted : 09/03/2012 1:14 pm
crustytv
(@crustytv)
Posts: 11904
Vrat Founder Admin
Topic starter
 

Got to then bench and did a check, yep tired head and eyes last night! I had missed that the PCC189 was missing :roll: tucked up out of the way but no excuse. Fitted one and up the heater chain came all glowing nicely.

The on/off volume control is stuffed no doubt when the filter cap expired.

A few fireworks inside the PCL82 a few pops in the speaker that stopped. Line output and eff diode lit but no light in the U26 (EHT rect). Some investigations required now.

V12 is interesting it was missing from the set, the trader sheet dated 64 states PCL82 the R&TS data states PCL86. I installed the 82. Looking at my Mullard Equivalents book they are not listed as interchangeable. Norman what do you have in yours?

Chris

CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek

 
Posted : 09/03/2012 1:18 pm
Terrykc
(@terrykc)
Posts: 4005
Member Rest in Peace
 

I think somewhere along the line that you've missed that the above quoted text was referring to a Philips KT3 and not the RGD of the thread's title. Therefore, the original comments re LOPT fed CRT heater are valid.

Ah yes! Grovelling apologies for missing that - I must admit I was puzzled by the reference to chokes in the CRT heater circuit!

The tube of paper trick will work with any set though ...

When all else fails, read the instructions

 
Posted : 09/03/2012 1:47 pm
crustytv
(@crustytv)
Posts: 11904
Vrat Founder Admin
Topic starter
 

Just put the PCL82 on the Mullard Tester and it shows as having insulation failure on the control grid, that will explain some of the fireworks then.

Just found a NOS and that tests 100% so have put that in. Now to see why there is no EHT, timebase?

Chris
p.s

Re: Terry's & Parabola's comments, this is the only issue with allowing members to drift the topic, off-topic. I guess it's one of the drawbacks to the freedom allowed here, meaning members have to follow more intently. Other forums would have removed the non RGD related posts to negate that confusion happening in the first place.

CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek

 
Posted : 09/03/2012 1:49 pm
Norman-Raeburn
(@norman-raeburn)
Posts: 174
Reputable Member Registered
 

Hi Chris, I am sorry I can't help identify the sound output valve type, the legend on mine is worn off. The lopt is shot in mine so it is back on the pile. I shall put a wanted post on later. regards, Norman

 
Posted : 09/03/2012 2:46 pm
Terrykc
(@terrykc)
Posts: 4005
Member Rest in Peace
 

Hi Chris, I am sorry I can't help identify the sound output valve type, the legend on mine is worn off. The lopt is shot in mine so it is back on the pile. I shall put a wanted post on later. regards, Norman

If it is a Philips valve, there is an indelible mark that helps - it's actually etched into the glass so that it can't rub off!

Just above the base you will find two rows of characters.

One is the date code and will look something like B5C3 representing Factory, Year, Month and Week thus: B= Mullard's Blackburn factory; 5 = 1965; C = March (A= Jan and so on); 3 = 3rd week of the month. The only thing it doesn't tell you is the name of the girl who assembled it! ;)

The week number was added in the 60s, so you can easily spot a valve manufactured in the 50s! I haven't a clue if any changes were made in the 70s though ...

The other row is the important one here as it is an internal Philip's reference to the valve type - if two valves have the same code, they are both the same type. I believe that some valves can have more than one code but I've never encountered one. (Or should that be two ...?)

This trick used to be very useful: customer comes in with anonymous valve - usually running an errand for someone else, so has no idea what it might be ...!

Examine valve visually. Looks like a 'something' CL82 - but is the 'something' an E, P or U? Simples! Check an ECL82, PCL82 and UCL82, looking for a match. If that doesn't work (but it usually did!) try the 'CL86 variety.

Of course, if it was a Mazda valve, all bets were off - unless it was a re-branded Philips valve, of course!

Re: Terry's & Parabola's comments, this is the only issue with allowing members to drift the topic, off-topic. I guess it's one of the drawbacks to the freedom allowed here, meaning members have to follow more intently. Other forums would have removed the non RGD related posts to negate that confusion happening in the first place.

Of course, I wouldn't have the faintest idea to which forum you might be referring, would I ...? :roll:

When all else fails, read the instructions

 
Posted : 09/03/2012 3:56 pm
sideband
(@sideband)
Posts: 4222
Famed Member Moderator
 

If it's of any help, the triode anode of the PCL82 is the same length as the pentode anode. With the PCL86, it's about half the size so a physically smaller triode.

Rich.

 
Posted : 09/03/2012 4:13 pm
Norman-Raeburn
(@norman-raeburn)
Posts: 174
Reputable Member Registered
 

Hi Terry, My valve is a Mullard, the markings are W12 with 80C4 underneath that. I hope somebody can elaborate. Norman

 
Posted : 09/03/2012 4:27 pm
crustytv
(@crustytv)
Posts: 11904
Vrat Founder Admin
Topic starter
 

Update:

I had heaters and everything else looked ok but no EHT so I started with the HT side nothing it had all gone, hmmmm checked the HT rectifier DD268, it had expired, a deceased diode, dead! fitted a 1N4007, powered on and could hear the 405-Line start to whistle which was music to my ears. First light! & frame collapse (see pic 3) excellent :=D

The system switch cleaned up nicely, all grot removed and it looks in excellent condition. (see pic 4)

Now to the frame TB and work from there.

Chris

CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek

 
Posted : 09/03/2012 6:53 pm
malcscott
(@malcscott)
Posts: 1566
Prominent Member Registered
 

Great work so far Chris, i bet you have a picture on it tonight, Malc.

 
Posted : 09/03/2012 7:05 pm
Terrykc
(@terrykc)
Posts: 4005
Member Rest in Peace
 

Norman, 80C4 will be the date code. However, as 8 is the factory code for Philips, Eindhoven. Radio valve lab. glass group which looks a bit experimental to me, I would suggest that it is actually a B, which is the code for Mullard, Blackburn

Your valve has a week code, which wasn't introduced until 1961, so the 0 must be 1970 and C4 is the 4th week of March.

W12 is the all important type code, but now I have a problem because all the lists I've tracked down have very few 3 digit codes - and don't reach anywhere near the end of the alphabet.

However, W1 = PCL86, which is either a coincidence or Philips added extra digits to the 2 digit codes which aren't in the documentation I've found.

This list only contains two digit codes.

There are 3 digit codes in this one.

Anyway, Rich's pointer to the triode anode length will sort out the difference, either way!

When all else fails, read the instructions

 
Posted : 09/03/2012 7:28 pm
neil1974
(@neil1974)
Posts: 624
Honorable Member Registered
 

The results look good so far Chris. hopefully as said we will see a picture on it soon. cheers neil.

 
Posted : 09/03/2012 8:07 pm
Jamie
(@jskinner97)
Posts: 1755
Prominent Member Registered
 

Very Good Chris, Can't wait to see good ol' Test Card C on it!

 
Posted : 09/03/2012 8:20 pm
Page 2 / 13
Share: