CTV [Sticky] 1974 20" Ferguson 3C03; Thorn 4000 ; Super Rare
I did have a go at etching the test board from the other day, [........] the results were poor.
Oh well, thanks for trying. 👍
In which case, as a backup, I might as well start implementing my “fall-back” plan, and start building the Main vertical PCB on my matrix board.
It should be much easier to build than the tiny TF's I built recently. Two reasons; one, for this board I will have something to copy using the one vertical board I do have. Second, with a much larger board, I have a lot more space to play with.
I've already replicated all the component positions, so once soldered in, all I need to do is point to point wire them using the Thorn board as a guide, I can even sort f replicate the trace pattern with wires. As long as I'm diligent, it should prove reasonably straight forward. If nothing else, it'll give me something to do leading up to, and over, the Christmas holidays.
Everything has been removed from the dry fit matrix, filed and logged in storage trays. I've mapped on paper, photos, circuit plan view and the board to follow. Let the fun commence.
That is true dedication Chris! It should look and work like an original when completed. I remember doing something like this only once before many years ago with a valve timebase board that had a large hole burnt in it around the PL504. I cleaned up the hole and Alraldited the matrix board over it and then rebuilt the PL504 stage with a stand-off valveholder replicating the original layout as closely as possible. I remember it all worked afterwards so thought it was worthwhile. I'd never have got away with it at Philips but this was a private job. As far as I know, the set worked for a good many years afterwards since the customer upgraded to a colour TV some years later.
First things first, establish the ground plane for the PCB to the heat-sink/PCB frame. Tested, I have continuity from the board chassis ground.
Fitted L401, the 2-pin socket, 10-pin PL16, C408, C409, C410, C411 & R412
PL16 took a while as only 3 of the holes lined up with the existing matrix holes. Careful measuring and it's a nice snug fit.
Just a quickie to show how I'm tackling the component hook-up on the rear. I'm using a mixture of joining pads and hook-up wire, where possible, replicating the 4k trace. No idea how long the sticky annotation labels will survive once in the set, but it will help me when diagnosing faults, which I'm likely to introduce.
I don't know if you've read the section at the bottom right corner of the circuit diagram (part 2) it shows some of the mods that were done. If you were to do the mods it would save quite a few components if that helps at all.
Hi Jim, do you know if these are performance enhancing? The changes to the pots and resistors look to centralise them under normal operation. The mods to the blanking circuit look possibly like the work of the bean counters.
Just to say, at this stage I won't be implementing any of the modifications.
Rightly or wrongly, I've chosen at this stage to pursue the Matrix path, that choice has the most potential for me to screw up, opposed to a nice easy etched board to just drop components into. My concentration has to be focused on the task in hand, that being to replicate what I have before me. Getting all those components manually hooked up, without introducing man made errors, is enough for my befuddled brain to cope with.
If I have to start cross-referencing changes Thorn introduced, I can see me getting in a right pickle. Rest assured, once (if) I get the replica V-Def board working, I will then go back and modify, but only where appropriate, (see John's comment above) both boards. I'm not bothered about wasting components.
Today I've installed the thick films, TF401 & TF402, R411 and R417, more hooking up to do now.
@jayceebee I've been thinking (and that's a rare thing) and I guess it's probaly best to copy like for like and get the board working first and only do mods as needed. Also I can't find any more info about them mods apart from what's on page 12 of part 7 of the manual. That cotradicts the removal of C415 and suggests changing the value to sharpen up field blanking pulse. I will have a look at some old notes and see if they shed any light on the things.
Slow progress today, due to Christmas decorations duties, so will be putting in some extra time this evening to make up for it. Most all the components are in across the bottom, and TF402 partially connected up to that area of the circuit. Glad I added labels as without them, it would be a little harder to follow.
I Just keep thinking........"Hand-wired", and this is the way ITT did the CVC1 !!!!!! I'm so lucky just to be doing one board, and not an entire set.
Well, you could hit me in the face with a wet kipper..... I'm totally Gobsmacked. 😲
Looks like I built the missing thick films for nothing. I've been tipped off to a mother load of mostly NOS Thorn thick films for the Thorn 4000 & 9000 series. Bought them and just hope they don't go missing in the post! Who would have thought Thorn 4K spares are out there.
Many thanks to the chap who contacted me via the website, I'm so very grateful to be able to obtain these from you.
Unbelievable, bit like winning the lottery there. What do you reckon for seeing the Queens speech on at least one of them next week? 🙂
That's it for now, only a few more done and TF401 annotated. I've got to stop now, my ocular migraine started from all this close work under a bench mag lamp.
Unbelievable, bit like winning the lottery there
If it were like winning the lottery, there would have been a vertical board along with triplers, spare CRT's & deflection coils. This was more like a nice healthy scratch-it 😉
Knowing my luck, I'll get to the end of building this Vertical Deflection base board and then someone will pop up say, “Oh, I've one of those you can have”.
What do you reckon for seeing the Queens speech on at least one of them next week?
No hope and Bob Hope on that score.
All the components have now been soldered in, and the idents applied to the rear. All that remains now is to do the final hook-ups. I reckon another solid day or two, if I take it easy. Although I've been checking and double-checking as I go, I will then spend a couple of more days going over all the hook-ups again to be certain I've not missed something.
Two things; one, I've not installed the two 470R 5W resistors. These were to simulate mid-point of the vertical shift. I'll await the arrival of the thick films, which contains a vertical shift. Two, I'd missed a capacitor, it was across pins 18 and 19 of VT403. It's a small ceramic, 5000pF -20/+80% at 500V, this is C414. I pondered over why it was ceramic and if it was important. The only ceramic I have is huge by comparison, RS flat 5000pF 1% at 500V. I decided to stick in a 502K @630V and hope it will be OK.
All that remains then will be to install the TIP41C & TIP42C, output pair.
On the home stretch now, working my way into the top right corner. This hard-wiring is doing my head in, no matter how careful I am even double-checking, I'm still introducing errors. I just went back over the work this morning and found I'd wired the anode of W401 to C407..... totally wrong. I'm even doing this in my sleep, my OCD has something to really occupy itself with now. 😉 🤣
It's a real dilemma, I find if I break away from it, I lose the groove and concentration. However, If I stick at it too long, I get tired, irritable and my head starts to hurt, I've yet to find the balance. I find while I'm in the groove, so to speak, my mind has a good map of the board and I can make good progress. Woe betide I get distracted by a phone call, e-mail, text, or doorbell, then the map in my head goes puff!....... gone.
Well, you're making better progress than me. More glasnost from here and the toner transfer paper was a waste of time, all that happened was the toner stuck on the fuser roller making a mess of subsequent prints. For some reason it appears OKI printers are the goto model for this, cooler fuser temperature I wonder?. My best attempt was my first using nail varnish remover and just ordinary paper, glossy magazine stuff was worse.
Obviously I was a bit niave thinking all those YouTube videos results were not after much experimentation and trial and error. Just for the hell of it I did etch one board (attached) but the lands were quite pock marked as I just couldn't seem to get the toner density right. Surprisingly the narrower tracks have continuity but some of the thicker ones don't.
Does anyone have experience of this product?
In the final stages, this is how I'm keeping track of which components need wiring as a common pad.
Your board brings back memories!
It ain't pretty but it will work.
I used to spend weeks debugging such builds, back in the day. I love the fact that the computer now does it for you. With simulation and design rule checking your prototype usually works first go. It's just as well because BGA parts in particular are difficult to rework.