Pete's dropped the CRT and chassis in to me. He's doing such a great job on the cabinet I thought it'd be about time to share my part of the project.

This Philips 90 degree chassis was an excellent performer in its day and should work well when finished.

First the CRT. From the label it appears to have been replaced in 1972. That means it probably only did 4 years work before colour arrived and this TV was relegated to storage.

I don't have a CRT tester – I believe the best way to test a CRT, like a valve, is in the chassis it's going to work in. But curiosity and another forum member got me to come up with a way of testing the tube's emission. The method and results I've detailed in another post.

The CRT's OK, so it's time to get stuck into the chassis then!

Part 1 follows.

Before I start I'll post a link to a most excellent synopsis of the process of getting an old TV running from the Early Television Foundation site in Hilliard, Ohio. If you ever do a road trip across the US of A this place is a must see.

http://www.earlytelevision.org/restoration_advice.html

There are only two issues in the article I'd take issue with and they are the use of detergent and water to clean the chassis (unwise with some of the transformers we encounter here) and the fact that I prefer to use the dim bulb technique rather than a variac to bring the chassis up for the first time.

The dim bulb technique has the big advantage of being suitable for unattended running. It brings up a chassis at its own rate. If something breaks down the bulb lights, effectively cutting the power and limiting the damage.

A 240v 100w tungsten lamp might be getting harder to find these days but not as hard as a variac and it's a lot cheaper!

Cleaning.

I use a dustpan broom and an air compressor for the initial clean, above and below the chassis.

Anything that doesn't clean up with this can usually be tacked with metho and paper towels. This includes the valves. Whatever you do, don't get them mixed up, especially those in the IF stages as there can be enough variation between the same type to affect the vision IF alignment slightly. You don't want to touch this if possible) You might clean the markings off some of them, don't worry about this too much.

Check the power plug and cable

You should probably replace the 50 year old power plug and cable. Bakelite plugs, 2 core power cables and rubber insulation on the inner conductors are all reasons to replace the power lead.

The Philips had a two core mains lead (no earth) and a broken bakelite plug - see picture below.

When fitting the 3 core cable I used a heavy soldering iron to create an earth point on the tuner/control bracket, as this is where the power lead was terminated. The original figure 8 PVC power cable passed under a U clamp along with all the other cables from the control head and was restrained with a knot. Totally unacceptable these days.

When fitting the new cable I used fibreglass cambric sleeving extensively, paying particular attention to where the power cable from the control head to the main chassis passed under the clamp. I separated the other control head cables from the mains and will cable-tie them down. The U clamp now holds the mains cables exclusively.

Time to bring up the chassis

A “Dim Bulb Tester” is simply a short extension cable into which has been wired a lamp socket in series with the Active. You plug the chassis's power plug into this cable. Fit a 100 watt tungsten filament lamp in the socket.

Here is how I go about it:

1. Remove the rectifier valve(s) – a pair of 6N3s in this case.

2. Switch on the power. The lamp will light brightly initially and fade to a dull glow after about half a minute. If so, the transformer and heater circuits are OK.

3. Switch off.

4. Remove the power stage valves from the chassis. Horizontal (6CM5), Vertical (6BM8), Audio (6BM8), Video (6CK6) and re-fit the rectifiers. I leave the small-signal-stage valves in place to slow down the ramping-up process – it treats the old electrolytics more gently, giving them time to re-form.

5. Connect a voltmeter to the main HT line. Pin 5 of the (empty) yoke socket is convenient on this set.

6. Switch on. The lamp will light brightly, then fade, then come back up again as the rectifier cathodes reach operating temperature.

Results

This chassis was fitted with UCC electrolytics that experience tells me will probably need replacing (one section has already been supplemented very early in the set's life with two 50μF Ducons in parallel) . Considering the rarity and cost of new replacement twist-lug cans (about $100 each!) I was motivated to try to resurrect them.

The HT voltage started at 46 volts. After 15 minutes running it was up to 97 volts. After an hour it had climbed to 181 volts and the lamp had faded to a dull glow. Another hour's running saw it stabilise at 188 volts. Electros all stone cold. Looking good!

So I took a chance and hit it with the full mains voltage.

HT came up after 15 seconds to 244 volts. That's about normal for a light load on the supply. After about 10 minutes it hadn't changed and the electros were all still cold.

So I left it running for about half an hour while I had dinner.

Came back to find HT at 200v, C33 hot, can bulging at the top and leaking electrolyte (see the picture). Oh well, if it hadn't happened now, it would have done so later.

So I decided to replace the two UCC cans after all. Looking at C34 (a Ducon can) I found some tell-tale white deposit around the lugs. Oh well, 3 new 50 + 50 500v electros please!

I found some new-production clamp-mount replacements at Tube Depot for a reasonable price so I ordered some. The asking price for NOS twist-lug cans was out of the question and anyway, when I replaced the UCC cans in my AWA with these ($$ ouch!) I had to re-form them anyway. There is room to pop-rivet the brackets in if I am careful. They won't look quite authentic but then neither do shiny new twist-lugs and these ones should last longer.

So while I'm waiting for my bits to arrive, I'll replace the few remaining paper caps, including the B+boost cap, which is showing signs of heating – not good!

Next instalment soon! In the meantime, have a look at the pictures.

Looking good Ian!
Have you enjoyed working on it though?
I"ve had some major delays with the 60 year old glue on the veneers. The old glue is not holding out and its breaking down and their lifting everywhere. But its getting there just a slow repair.
Pete
Im determine to save the original veneers. Normally I would replace the complete veneers on a cabinet where their lifting from every seam. .

Good stuff Ian, especially emphasising the process of reforming the electros gently over a length of time.
Makes you shudder about the danger of old equipment being turned on from dead cold after 50 years or more.
Having been that stupid myself I can vouch for Ian's approach and confirm that old electros explode if jerked to life but can be re-used when ramped up gently.
I'm a variac man mainly but do have the dim bulb handy if as Ian points out you want to leave something to simmer unattended.
Will hang out for the next part as i'm still learning about this TV stuff and a practical example is the best teacher.
Fred.

OK, the electros have arrived.

First step is to get the 3 twist-lug cans out of the chassis. Make a drawing first, or take clear pictures.

Cut the wires and components off the lugs and make room for what will come next.

Using a large pair of sidecutters, grip the soldered-in twist lugs and break them away by twisting them. This may take some force. Don't waste your time trying to desolder them.

Once you have the lugs broken off you can generally tear the can off the chassis.

Take the mounting clamps for the new caps and drill clearance holes for the pop rivets you'll use to mount them. Make sure you orient them so you can get at the clamp screws. Rivet them in place.

Install the caps in the clamps, spacing them up a bit from the chassis so the lugs on the caps don't short to the chassis.

Reinstated the wiring. Took the opportunity to change some out-of-tolerance resistors.

Bring the chassis up without the yoke plugged in, firstly using the dim bulb. After a couple of minutes you should have about 120 volts at pin 5 of the yoke socket.

Assuming this goes OK, plug in the yoke (no CRT yet) and a speaker. Put the EHT connector in a glass jar for safety!

With this set, EHT (as observed by the 1S2 filament) came up normally, but no sound - there should be noise in the sound on no signal.

Time to connect the CRT and see what we have. Use care to support the CRT and the chassis carefully.

A thin bright line across the screen. No video, no audio, no vertical deflection. Let's get the vertical running first.

Voltages around the output stage check out. 6BM8 triode anode (pin 9) measures 600v - should be about 200. Shorting it to ground causes the line to flick up and down so everything after the oscillator is working.

Triode grid and cathode are both sitting on about +8 volts, so 600v on the plate makes no sense. Replace the 6BM8 - we have vertical!

Excessive height, bad linearity. Check around height pot - circuit doesn't match. Someone has rebuilt it using the circuit from the earlier 17" chassis. No, some of the parts are original so this looks like it's a factory variation. It's a cross between the 17" and the 21".

Now the vertical is becoming intermittent. Strange, almost all parts have been changed. Might be a breakdown in the output transformer feedback winding - a known issue with this circuit. My scope is at the office - I'll have to bring it home tomorrow night.

DC voltages around the tuner and IF stages check out. My scope has the bandwidth to track this down - tomorrow night it is!

CRT raster is bright and well focused. It looks like this tube is a regun job by one of those small tube rebuild companies that were around in the 60s and early 70s. Getter looks good too. They did a good job on this one!

Boy complicated Ian !
Hey I dont know if this is any help ,but I have a 21 inch Pye chassis ??
Somethings may be usable, I dont know enough about electronics, but its here if you need it Ian.
Thanks again Ian and I hope its not being a cow of a thing.
Pete
1958 w102 chassis

OK, hooked up CH2 modulator and a DVD player.

Looking promising, what I thought was a fault in the IFs turns out to be just low gain - 3 stages of 60 year old 6BX6s. (We can probably live with this since it will run from a modulator). Plus the usual noisy pots and almost no H sync. Vertical locking but intermittently jumping around.

Finally it collapses to a 6 cm high image.

Scope shows it's the oscillator. Checked and found vertical blocking osc transformer primary is O/C. Deja vu all over again!!! Just like the HMV E1 I did last year. Pete, it's possible I could use the transformer from the Pye W201 but it's likely to suffer the same fate after 60 years! Besides, have you given up all hope of restoring it?

I disconnected the transformer and did a quick lash-up to configure the circuit as a multivibrator with feedback from the 6BM8 output anode. It works and locks solidly but at half the frame frequency and a few other issues.

Tonight I'll have a look at what I did with the HMV E1 and what Philips did in the last hybrid models they made, which were MVs in the vertical.
Plus find out what's happened to the H Sync, and strip some pots down to clean them.

G day Ian,
The Pye 21 inch 1958 w102 is just a spare chassis .
Yoke and crt are stuffed from condensation on the yoke. But the chassis looks good.
Plus I have more w101 and w102"s
This output transformer that you mentioned, is it a part that I can buy and replace it?
Please excuse my lack of knowledge on electronics , its not my trade.
Let me know about this w102 chassis I can drop it around if you feel it will help you.

Pete, it's the little transformer in the vertical oscillator circuit. They were a very common source of trouble in early sets. Back when I was servicing these things for my job in the 60s and 70s it wouldn't be unusual to need to replace several of them in a week. Particularly Rola TV207s in early Krieslers! Job sheet would read "Brand: Kriesler. Fault: Picture rolling"

Not too many years after this set was made, designers discovered they could do without this pesky transformer and many (including Philips) did. So that's the approach I'll be taking.

Pete, your chassis is finished!

I adapted the oscillator circuit that Philips used in the last valve chassis. It worked first go, all I had to do was adjust R89 to get good range on the hold control. There was still too much height at minimum setting of the pot. After I corrected a mistake made by a previous repairman it was all good.

I corrected the vertical blanking to match the circuit.

I tried the original 6BM8 back in the vertical and it's still dead. So there was more than one fault in the vertical.

The horizontal sync fault was R111 in the cathode of the hor sync amp O/C. I replaced a handful of resistors that had gone high in an attempt to get the set to lock properly on 16:9 copy protected letterboxed content. I spent some scope time with it and determined that the circuit is working as intended, it just doesn't like having the blanking interval full of digital stuff.

I changed R82 from 330k to 120k to clean up the vertical sync. It now locks solidly with good interlace on the type of signal it was designed to handle!

Sound and vision IF gain is a bit down but short of replacing all 5 original 6BX6s at $8 a pop it'll be OK.

Thanks Ian!
Its great to see it working again.
You did a great great job on that chassis ,
All we need now is for me to finish the cabinet off.
Pete

Hi Ian, just a thought with the 6BX6, I have used 6EJ7/6EH7 ( one is a sharp cut off, the other a remote) instead of 6BX6 in all sorts of circuits with success as they are a pin to pin replacement. I found that 6BX6's have a "name" like a 6V6 does and attract a price accordingly even though millions of them were produced and both are as common as rat droppings.
The 6EH7/6EJ7 has no "name" so I bought a box of 50 or so new AWV make for a few bucks from an ebay guy, no one else bid..
They are a higher slope tube, that may cause a problem in a straight IF strip but I have just stuck them in and away they go.
Fred.

Yes Fred the 6EH7 as 1st IF and the 6EJ7 for the rest was on my mind too. They would give a performance boost as well. Would probably be OK in this design as all the traps are at the front of the strip and the interstages are bifilar wound, hence broad as a barn door.

But then I thought, it's being driven from a modulator and doesn't really need to have sub 1 mV sensitivity. It worked pretty well as is, just no snow on no signal.

I must say that even 6BX6s were cheaper than I thought they'd be when I checked. There would be thousands of them in NOS. My $8 a pop was based on exchange rate and shipping added.

It has occurred to me after Pete picked it up that the vertical sync issues I was having on letterboxed content might have been made worse by a low-emission 3rd IF 6BX6 clipping the signal - I didn't try it. Pete, one to try after you get it all back together......

Ian,
Hey mate if you think it needs them, no problem I can buy them.
TVs are my passion , I dont drink , no wine women and song, so I dont mind buying valves,hahaha
Where is suppliers?
Pete

Here's one source, Pete.

https://www.tubedepot.com/products?utf8=%E2%9C%93&keywords=6BX6
https://www.tubedepot.com/products?utf8=%E2%9C%93&keywords=6EH7
https://www.tubedepot.com/products?utf8=%E2%9C%93&keywords=6EJ7

Fred is right, the 6EH7 is cheaper and the newer frame-grid pentodes work much better. But the 6EH7 is only for the 1st vision IF position, far left-hand front of the chassis, looking from the back. All the rest can use 6EJ7s (or 6BX6s)

In terms you'll understand, it's a bit like putting a red motor in a Holden in place of a grey motor that's done 80,000 miles. The newer technology gives a performance improvement, especially when the old tech is getting a bit tired. But if you never use more than a quarter throttle and there are no hills (i.e. running from a modulator), you won't notice the difference.

But see how it goes on your modulator and source, I would have ordered them if I thought it really needed them.

Thanks Ian,
I will pick up more about electronics as time goes by!
Look at that guy that lived to 109.
I've still got time left.😆