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Old 18th Nov 2019, 12:44 am   #1
19Seventy7
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Default Philips G8 G22K522

Hi,

I’ve managed to get my hands on an early 26” Philips G8. I opened the back to do a visual check before even thinking of applying power. I know that it’s best to cut, or replace, the mains smoother before firing up.

I also know that there are some big caps which need replacing (is it the red to a blue equivalent, or blue to red?) Tuner caps too.

There is also a black box connected to the LOPT and the anode cap on the CRT, there is a spare “plug” hanging off with a short wire (can be seen in 4th photo; round thing above green wire) but I cannot see what it’d connect to, if anything. Is this an after market mod?

There is an issue however.

The LOPT’s insulation has cracked, and is missing a chunk. The exposed coil looks in good condintion. (See attached)

Is there any way these can be re-insulated? Either myself or anyone else? If not does anyone know of a suitable replacement?

Thanks
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Old 18th Nov 2019, 2:33 am   #2
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Default Re: Philips G8 G22K522

Does this help at all?
https://www.***********/photos/12064036@N04/7990580955

The LOPTX is probably fine like that
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Old 18th Nov 2019, 2:57 am   #3
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Default Re: Philips G8 G22K522

Thank you for linking that.

I’ll definitely keep it for refrences. I notice it has a red capacitor, so are they the ones to stay? Blues get replaced? I remember reading on it a while back, but cannot remember where, nor the exact combination.

I’ll be doing some re-capping and re-resistoring before attempting turning it on, as there are some visibily stressed components on the power supply board.

The LOPT won’t cause any damage like that, would it?

It’ll of course be kept warm and dry, and has been so moisture shouldnt be an issue.

Thanks
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Old 18th Nov 2019, 8:42 am   #4
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Default Re: Philips G8 G22K522

Hi 1977.

The black box in the photo is the tripler. The connector dangling down should fit over a connector on the line output transformer. (Don't be concerned about the exposed insulated wire.) If the tripler has been disconnected and left dangling like that then it may mean that a previous engineer has decided that either it or the lopt has failed. Donberg in Ireland used to have some lopts but I'm not sure if this is still the case.

Re the red and blue smoothing caps in the power supply, that really only applied to Philips G11s and was because the terminals on the original caps had poor rivets and the connection would arc or become electrically detached. The ones in your G8 will probably be okay but you could re-form them for a few hours if you want to be sure.

And as for replacing tuner caps, I wouldn't touch anything in the tuner. It'll be absolutely fine.

One thing I definitely would change would be that little group of blue /green tuning caps on the timebase board. They go leaky, heat up and end up popping and going open circuit. This sends the EHT very high which can damage all sorts of things. I can't remember the value but I'm sure someone on here can fill you in. (You can see the caps at the top of your second picture above the right-hand smoother.)

Thanks 1977.

Kind regards.

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Old 18th Nov 2019, 11:29 am   #5
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Default Re: Philips G8 G22K522

Hi 1977,
Well you are a lucky chap turning up a G8! Although a 26" one is a bit of a heavy beast!

This was a fairly early all solid state chassis but was well liked by servicemen at the time as it was well designed for easy service. Due to the multiple plug in boards it was great for quick repairs in customer's houses- a board could be changed in minutes and the faulty one repaired back at the workshop.

This is in a different league to the late '70's Japanese sets you have attempted so far which tended to be totally reliable! The G8 was a frequent visitor to the workshop at the time and I seem to remember was a regular consumer of LOPT's!

As has been said, the black thing is the EHT tripler. It rectifies the high voltage output from the line o/p transformer and multiplies it up to about 26Kv. They were a common failure item in all sets from this era.

This will be a challenge to get working properly and iron out all the faults but well done for being willing to have a go.

I would advise not powering it up yet. Others with more experience with this chassis can hopefully decide what is the best way to proceed.

Good luck
Nick

Last edited by 1100 man; 18th Nov 2019 at 11:36 am. Reason: extra text added
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Old 18th Nov 2019, 12:40 pm   #6
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Default Re: Philips G8 G22K522

Hi,

Quote:
Originally Posted by Mikey405 View Post
The black box in the photo is the tripler. The connector dangling down should fit over a connector on the line output transformer. (Don't be concerned about the exposed insulated wire.) If the tripler has been disconnected and left dangling like that then it may mean that a previous engineer has decided that either it or the lopt has failed.
I did think it'd be connected to the LOPT as it's the only thing within reach. There is already a connection between the LOPT and the Tripler using one of these connections, connected onto the top left hand corner of the LOPT. I cannot see any other "pins" for a second connector.

Quote:
Re the red and blue smoothing caps in the power supply, that really only applied to Philips G11s; The ones in your G8 will probably be okay but you could re-form them for a few hours if you want to be sure.
Ah okay, I did read it some time ago (When i was looking for my first TV, so over a year ago now!) so I've obviously confused it over time.

Quote:
And as for replacing tuner caps, I wouldn't touch anything in the tuner. It'll be absolutely fine.
Could this be a G11 again, or a variation of a G8? I'm sure I remember reading about somewhere that they're something to look out for, but of course can easily be wrong.

Quote:
One thing I definitely would change would be that little group of blue /green tuning caps on the timebase board. They go leaky, heat up and end up popping and going open circuit.
Will do! I'll put them on my list of components that need changing, thank you for that heads up!

Quote:
Originally Posted by 1100 man View Post
Well you are a lucky chap turning up a G8! Although a 26" one is a bit of a heavy beast!
I was very lucky to get it, it was hit and miss whether I'd be able to get it. I.e. convincing someone for the 3+ hour round trip! It was actually lighter, slightly, than I expected it to be, although I did have help bringing it up two flights of stairs!

Quote:
This was a fairly early all solid state chassis but was well liked by servicemen at the time as it was well designed for easy service.
I can see why, I like the swing out chassis, in the U shape, I noticed straight away how accessible it looked to service. Looking at it too looks less confusing, as every panel is labelled, which definitely helps a beginner.

Quote:
This is in a different league to the late '70's Japanese sets you have attempted so far which tended to be totally reliable! The G8 was a frequent visitor to the workshop at the time and I seem to remember was a regular consumer of LOPT's!
The Hitachi is still going strong, with somewhat regular use, at least once a week for a couple of hours.

I did wonder if my LOPT was the one it left the factory with, as it doesn't quite match the one that Rambo linked (No yellow band on top coil)

I did wonder if this could be why there's a spare plug from the Tripler?

Quote:
This will be a challenge to get working properly and iron out all the faults but well done for being willing to have a go.
I'm quite excited to work on this, and hopefully get it working. I've never seen a DG tube either, so I'm curious how well the convergence is compared to PIL, even after setting up.

I wont power it up yet then, I wasn't going to after seeing the LOPT, without checking anyway, and also as I said, some of the resistors and the tropical fish capacitors, which have cracks in them.

Thanks for your replies! Much appreciated
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Old 18th Nov 2019, 1:14 pm   #7
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Default Re: Philips G8 G22K522

Hi.
Right - you've got a challenge there! Don’t get me wrong – it’s a great set but will need some waking up and as Nick says they are a very different beast to the reliable Japanese sets you might be used to.
Anyway, let's get going.
Remove the tripler for the moment as it’s in the way and it’ll be a while before you’ll need it! Now look at the big capacitors on the power supply (left hand side). Are they leaking or do they look OK? Check the fuses on this board – two down the side and one sneakily under the mains connector. Hopefully they are OK. Now over to the line output panel opposite. About a third of the way up is a fuse. Is it still there, and if so, has it blown? Even if not, remove it. See the red plug going from the line output to the timebase panel? Remove it and leave it off for the moment
Now take a deep breath and give the set some mains. Are the CRT heaters alight?, If so, good. Now check for around 200v at the fuseholder I mentioned. The power supply does buzz quite a bit, so don’t worry.
Now you’ll need to replace those green capacitors Mikey’s going on about before we go any further. Can we have a few shots of the interior? I suspect you’ll have a decoder board and a separate IF board, but sometimes the later combined board was fitted, though the heatsink I can see suggests the former. Some very early sets had an extra board on the decoder instead of an IC, but hopefully not.
This will be quite a learning curve, but I suspect many of us TV engineers on here cut our teeth on the G8 so there will be a lot of help available. G8s were always welcome - and frequent - visitors to the workshop.
Let us know how you get on!
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Old 18th Nov 2019, 3:19 pm   #8
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Default Re: Philips G8 G22K522

This thread, https://www.vintage-radio.net/forum/...d.php?t=133925 about a previous G8 restoration is worth a read and there is also a link to a TV magazine article which shows the power supply circuit.

Oh what fun: it's got an SCR in it! Do be aware though that the chassis is connected to one side of the mains. Ensure that the mains plug is wired correctly and that the chassis metalwork is connected to mains neutral.

Sit tight, this is going to be a nice long thread!

Cheers
Nick
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Old 18th Nov 2019, 9:05 pm   #9
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Default Re: Philips G8 G22K522

Hi,
Quote:
Originally Posted by Welsh Anorak View Post
Now look at the big capacitors on the power supply; Are they leaking or do they look OK?
Yep, those look fine to me, no signs of stress or damage. Will the cracked resistors and caps will be okay, just to test as you said, with the Tripler disconnected? (see attached)

Quote:
Check the fuses on this board – two down the side and one sneakily under the mains connector.
Haven't yet got around to doing it as I've been busy with other stuff but I'll have some time and space in a little bit.
I know the two fuses down the side are okay, but haven't yet checked the one under the connector, same as the fuse on the LOP panel.

Quote:
Now you’ll need to replace those green capacitors Mikey’s going on about before we go any further.
Will do, what should the value be, does anyone know? I haven't been able to find a service manual as of yet.

Quote:
Some very early sets had an extra board on the decoder instead of an IC
I've seen an IC inside, I think it was on the board that's on the bottom of the chassis, on the very left, if that's of any help?

Quote:
Originally Posted by 1100 man View Post
This thread about a previous G8 restoration is worth a read
I've actually read that thread, some time ago, which got me interested in the TV more so, originally I was just attracted to them by the cabinet design, but finding out more got me even more interested in them. I'll have a re-read to remind myself of it, the TV magazine too.

Quote:
Oh what fun: it's got an SCR in it!
Something to keep an eye on for faults?

I just thought I'd double check about those resistors and caps before applying power, I don't want to cause any more damage.

Edit: Apologies for the poor quality of the second image, best my phone camera could do

Thank you for your help! I really appreciate it!
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Old 18th Nov 2019, 9:34 pm   #10
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Default Re: Philips G8 G22K522

Hi,

All three PSU fuses are good, as are both on the LOP panel, the one 2/3s up has been removed.

The LOP panel and timebase board have been disconnected, too.

Thanks
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Old 18th Nov 2019, 9:36 pm   #11
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Default Re: Philips G8 G22K522

Oops, forgot to add photos of interior:
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Old 18th Nov 2019, 10:07 pm   #12
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Default Re: Philips G8 G22K522

Have you discovered where the convergence controls are yet?
Clue.
Remove the trim below the speaker grill and loosen the screw that holds the grill in place.

The customers, and particularly their children were always intrigued with what is hidden behind there.
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Old 18th Nov 2019, 10:12 pm   #13
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Default Re: Philips G8 G22K522

Okay so i’ve tested it for a few seconds,

The heaters glow!

I’ll get to replacing the caps Mikey mentioned, and we’ll go from there. So far so good. Fingers crossed the rest of it goes as well.

Edit post crossed with Rambo. Thanks for telling me that! It was puzzling me!

Thanks again
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Old 18th Nov 2019, 10:37 pm   #14
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Default Re: Philips G8 G22K522

He plugged it in!

Good job the HT fuse is missing (I think).

Don't be so hasty 1977.
Start by mounting that tripler where it belongs, you might need to improvise

Check the BT106 isn't shorted, that's the big thing on a threaded stud on a heatsink on the little power board. check with your multimeter on ohms, between the long pin and the heatsink
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Old 18th Nov 2019, 10:59 pm   #15
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Default Re: Philips G8 G22K522

Was I not meant to plug it in, or have I missed something? I didn't think it'd be too bad as it was last used, working, 2 years ago, which I thought is a relatively short time compared to it's almost 50 year life.

I was going off what Glyn said, following all steps he said to do, removing the fuse, too.

It was on for seconds, just enough for me to see the heaters glow, then it went off again, and unplugged.

Where does the tripler mount? I cannot find where it should go.

I'll have to check it tomorrow now, as it's sat in the living room for the time being, being almost 10 PM, don't think it'd be appreciated if I were to work on it now

Thanks for your reply
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Old 19th Nov 2019, 1:09 am   #16
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Default Re: Philips G8 G22K522

Refer to the hi res picture in the link in post #2. Your tripler is a later and better replacement. I can't remember if the mounting holes are in the same place.

This is one of the first all transistor chassis. They had to use a pair of transistors for the line output, a single one of the type available at the time was not man enough, the two transistors are in series and need a balancing adjustment if they are replaced. There are a number of faults that will blow them instantly at switch on.

I haven't worked on a G8 for 40 years, and there will be age related gotyas that I don't know about.

Someone with more recent experience will hopefully give you a methodical pathway to bring it to life which will include checking things cold with a meter first, like those line transistors.
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Old 19th Nov 2019, 11:13 am   #17
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Default Re: Philips G8 G22K522

Does anyone have a link to a circuit diagram- I think that would be really useful at this stage.

Like Graham, I haven't looked at a G8 for nearly 40 years so would be handy to refresh my memory!

They were all long gone when I caught the tail end of the TV trade in the early '90's- it was all grey plastic single board sets by then

In fact, The only one I had was given to me at school by the caretaker. Every inch of it was soaked in Nicotine as it lived in his tiny office. It worked, but the tube was so poor you could hardly see the picture. I transplanted the chassis into a Pye CT205 cabinet which had a good tube and it became my bedroom set for some while. There wasn't many kids who had a 22" colour TV in their bedroom at that time!

1977
Don't worry too much about the flaking surface of the resistors in your picture. They tended to do that but you would have to measure the value to be sure. The fact it worked a couple of years ago is a good sign, but as the tripler is dangling and the HT fuse was missing, I suspect it does have faults!

The appearance of components can be misleading. Those that look to be burnt or crumbly are often perfectly fine and those that look perfect are often the faulty ones! That's where a logical approach to faultfinding comes in coupled with experience.

Those green caps mentioned by Glyn may well have rather strange values when you remove them. They would have been specially made in those values at the time and you will need to make them up using two caps in parallel to get the exact value. I seem to recall they can cause havoc if they are faulty. The value of capacitors is not usually very critical but those in the line stages of TV's often are.

All the best
Nick
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Old 19th Nov 2019, 12:50 pm   #18
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Default Re: Philips G8 G22K522

Hi,
Quote:
Originally Posted by rambo1152 View Post
Refer to the hi res picture; I can't remember if the mounting holes are in the same place.
I don't think they are but I've got some better lighting now so it'll be easier to have a look round and look for it's mounting spot.

Quote:
two transistors are in series and need a balancing adjustment if they are replaced. There are a number of faults that will blow them instantly at switch on.
I think I know the ones you mean, and if it is those that I think of, there's chance they've been replaced. The board (if it is those) that they're on has had work done on it, and I think relatively recently. There are, what looks to be, new(ish?) caps, purple in colour if that helps, on that board, which don't match any other caps in the set.

Quote:
Originally Posted by 1100 man View Post
Does anyone have a link to a circuit diagram
It's typical really, ive noticed someone had manuals and diagrams for sale online, and for quite a while, then I get the G8 and they've gone off sale!

Quote:
but as the tripler is dangling and the HT fuse was missing, I suspect it does have faults!
Is that the fuse I removed? All fuses I saw were intact and in place, but I removed one, which glyn mentioned, before I powered it up. It's back in now for safe keeping.

I'm also starting to wonder if it was under restoration and was suddenly stopped, reasons unknown

Quote:
you will need to make them up using two caps in parallel to get the exact value; The value of capacitors is not usually very critical but those in the line stages of TV's often are.
What would the recommended +/- tolerance be for the values in the LOP stage? Once I can find out the value of the caps in place already, i'll get to ordering the parts

Thank you again for your help
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Old 19th Nov 2019, 1:16 pm   #19
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Default Re: Philips G8 G22K522

Sorry if this is a silly question,

But is this BT09?

If so, ive been getting an odd reading, with my DMM on the 200 Ohms setting,

Testing it, ive had a flash of numbers on the DMM, 113.0 being one of them, then it goes back to 1, retrying it gives me different numbers, but a return to 1.

Thanks
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Old 19th Nov 2019, 2:13 pm   #20
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Default Re: Philips G8 G22K522

It is the BT106 thyristor. It's not shorted ot else you'd know. They are difficult to test with an ordinary meter, so don't worry.
Hang your meter on the 205v rail, switch on and see what you get. It might be a tad over that as the PSU is unloaded but if you have voltage there the PSU uis in order (probably) and you can move to the right panel where things will need some work. Start by getting that tripler where it belongs - or else remove it for the time being. As Grahjam says, you might need to improvise a bracket - and did you say there was a lead off? That shouldn't be the case - one input, one focus, an earth and the EHT is all there should be.
Also, a little easing oil in the balancing coil won't go amiss as the core will definitely be seized so it'll be ready for when you need to adjust it. There's a good descrpition of how to do this in a TV magazine. For now it's time to source those capacitors.
Meanwhile i've dusted off my big G8 folder ready for action!
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