New Microvitec CUB Monitor Tripler

[Slo]

I can only find one supplier on google and its in ireland but its £19.18 including fees and postage to uk has anyone bought one of these?

at less than £20 delivered its got to be worth getting one for any cub regardless of the resolution surely.

http://www.donberg.co.uk/catalogue/tv_m ... 241bp.html

I definately need one as ive just bought two cubs and one is mega blurred unless you turn the brightness right down.

[george.h]

Worth a go, as if the focus control on the tripler doesn't make enough difference (focus still way out) then it sounds like the tripler is cattle trucked. The main difference between the various resolutions of CUB was the dot pitch of the CRT. Might have been slight differences in the video amp/driver chain (better bandwidth) but certainly not in the tripler (worth checking visually that both look the same if they are differnt resolutions).

If you've worked on CRT displays before you'll know the usual precautions.

If not be very very careful with the EHT lead and it's socket in the CRT - 25KV - and it can hold that charge for a long time after switch off.

George

[retroclinic]

Good find! Last few I baught out of Germany were the "exact" type, and were about £40 a pop, but for £12ea for these compatibles, that makes even the 1431s worth fixing - and I've got a fair few of those with beer-o-vison.

Mark.

EDIT: Just placed an order for 2 - so I'll let you know how they go....hopefully not bang!

[Slo]

beer-o-vision lol love it. now that someone as established (if you can say that) as retroclinic has placed an order im gonna buy 2 as well

If this turns out to be worthwhile i got a sneaky feeling that this company is going to sell a shedload of these parts from here and that the price may go up accordingly!

[george.h]

....hopefully not bang!

Only if you do the same trick as my dad did once - was too busy leaning over a TVs main board checking voltages and his head (bald patch to be precise!) made contact with the tube base

As far as I know his b'patch still has a lovely imprint of the tube base PCB's track layout on it

[station240]

Nice find there, friend over here says he has a monitor that is rather blury, said I can have it. Hmm will find out if its a CUB.

[Slo]

George.H Ive swapped a few of these in the past but last time was a long time ago and i always arced out the lead with something to the case and the plug plugged in (but with the fuse removed obviously) is this the best way round this? Ive had small tingles before but nothing what these things are capable of. What are yout thoughts?


Andrew

[retroclinic]

It may not be the best way, but I use 2 large screwdrivers - while holding the insulated handles (!) push one under the anode cap, put the other on the tube ground and touch them together and hold for 10 seconds. Leave it 10 secs, remove the anode cap, then do it again, that usually works.

Mark.

[1024MAK]

It may not be the best way, but I use 2 large screwdrivers - while holding the insulated handles (!) push one under the anode cap, put the other on the tube ground and touch them together and hold for 10 seconds. Leave it 10 secs, remove the anode cap, then do it again, that usually works.

Mark.

Sounds like you like the sparks!
Once I saw an engineer with a special tool he had made up. Alas I forget now what he made it out of
I have seen one guy use a large screwdriver with a heavy duty lead attached between the screwdriver shaft and the tube "ground" (there is a name for this, as not all TV sets had ground connected to the tube metalwork, but I forget it now - I'm sure George will remember).

Mark

[george.h]

Mark (Retro Mark that is lol) pretty well summed up the usual way - couple of chunky screwdrivers to ground the anode cap and discharge the final anode of the tube to earthing strap/braid of the "dag" (the gray coating on the outside of the rear of the tube). They all should have one as part of X-ray protection - yep CRTs can produce X-rays! Important to remember to do both the cap and the tube itself.

I remember seeing one of those "special tools" once, looked something like an EHT probe.

The official Microvitec way is to touch the EHT cap to the chassis metalwork first, then short the tube final anode to the "dag". All while unplugged from the mains of course (officially), but I'm happier having the thing earthed to earth if you know what I mean

You also need to give the PSU a few mins to discharge after switch off.

George

[retroclinic]

Triplers arrived today. Looking at them compared with the original, there is an extra wire, and the colour coding is all up the spout.

IMG_2656.JPG (67.03 KiB) Viewed 4219 times

(New one on the left, original on right)

The following math then usually applies:

Unexpected terminals + guess at where they go = large explosion

However, looking at the wiring diagram they supply on their site, and the schems of the mictovitec, I "suspect" the wiring should be:

White - To LOPT
Yellow and Blue to Ground

Whereas originally the Red was to the LOPT and the black was to ground. The wire coming from the focus pot is clearly ground on both units.

However, I've NOT tested this yet, so if anyone else has got theirs, don't connect it like that and blame me if things go up in smoke! I'll try one out in a day or so when I've got some free space on the bench and report back.

Mark.

EDIT: To add photo

[station240]

There is a circuit diagram on their website, like the extra wire is a connection to D6 (yellow wire).

Now compare that circuit to a standard Voltage Tripler circuit, say the one at the bottom of the page at http://www.play-hookey.com/ac_theory/ps ... liers.html.

The HRT 241BP has the same D1 - D3 and C1,C4,C5, plus to extra stages consisting of D4-5 and C2-3. D6 is the odd one out, I'd say its for protection of the something driving the tripler, but seems to not be needed, but I'd tie it to the ground (blue wire) like Mark said.

Its not technically a Tripler (3 stage CW multiplier), but a 5 stage Cockcroft Walton Multiplier, but that is just splitting hairs.

Basic idea is an input of 5kv AC X 5 stages = 25 KV, then subtract for losses and its 23kv. Now this is important as if you feed it 5V AC it will produce a much safer to play with 23V instead of 23 thousand volts. So you can skip the for testing it first.

[Slo]

I also got mine today exactly the same with extra wire aaargghhhhhhhh! bloomin charmin.

[1024MAK]

Err, before you all go blowing everything up, I have a question which I would like you to think about
Is there a capacitor on the main PCB between the ac supply and the connection to the "white" wire on the new HRT 241BP (red wire on the old tripler)
If not, then if the "blue" wire going to C5 in the HRT 241BP diagram is ground and you also connect the "yellow" wire going to D6 to ground, with the "white" wire being the ac input, I would have thought that D6 would half wave rectify the ac signal by shorting it out for one half cycle Not the intended effect that you want
I don't have a diagram of a CUB to hand, so if I am talking rubbish, put me down gently

Mark K.

[retroclinic]

Okay, here's a comparison, with the HRT diagram, and part of the CUB schem...

comparison.jpg (59.71 KiB) Viewed 4193 times

You can see on the microvitec schem that D6 is infact there, and the anode of it connects to ground (Brown), so that "should" be right.

Mark.

[retroclinic]

Okay, there was only ever going to be one way to know for sure.....

IMG_2682.JPG (66.1 KiB) Viewed 4189 times

No explosions!!! (yet!)

Nice picture, sharp focus slap bang in the middle of the pot range, looking good so far! As a bonus, there are infact 2 holes on the right hand side of where the tripler sits for the yellow and blue wires, so maybe this was all thought of beforehand?

That is a 1431 (albeit in a plastic case, it's the same circuit as the metal ones). Next test would be to fit it to a 1441 I've got one that also has beer-o-vision...

So go for it now slo

Mark.

[1024MAK]

Ahh! It's been a (long) while since I looked at CRT drive circuits...
The EHT winding is not directly connected to ground (but via a capacitor / resistor network) so my comments about D6 in my earlier post are not a concern.

Mark (RetroC) Now that I can see the circuit, I agree that your proposed connection "should" be okay.

EDIT: - and now that you have burnt the midnight oil, we all have a nice picture showing that it does indeed work

Mark K.

[Slo]

*Fires up soldering iron again*

[Slo]

Oh me oh my I cant believe my eyes this monitor was almost cataracted (if thats a word lol) seeing is believing and bloody hell its crystal clear like new in fact.

Well done me for finding the tripler and well done mark for taking the plunge

Just one thing on yours mark it says to make the wires as short as possible and I can see you havent I dont know what difference that would make tho.

Extremely happy at the minute

Andy

[retroclinic]

Aye well done to you indeed! Last 2 I baught were from Germany, admittedly they were genuine EROs, but they were over £30 each.

And so it's journey goes on....

http://cgi.ebay.co.uk/120718531121

Which is where it was meant to be about a month ago, before I soak tested it and found the duff tripler in the first place!

Mark.

[paulv]

Congrats to you both...

@Mark Does this mean you'll be buying more Triplers and fixing up more CUBs? I only have one Acorn monitor to share between 7 machines at the mo so my SCART switch box gets some serious usage..

Wish I had the pennies (and space) for a couple more screens Maybe in a month or two

[retroclinic]

Hi Paul.

I've probably got a dozen or so CUBs in various stages of operation between nice picture and b-all. I know I've got at least another 3 with duff triplers, including a 1441, and my own test bench beloved 1441 with the mitsubishi diamond black tube, to which I had fitted one of the expensive triplers, then threw a hissy fit and blew something in the frame circuit, so that needs fixing too.

So to answer your question, yes, I'll have some for sale, and they will be less than eBay price if you want one direct.

Mark.

[george.h]

Well done that man (Mark) and glad to see if was only the midnight oil that went up in smoke!

George

[1980s_john]

I can only find one supplier on google and its in ireland but its £19.18 including fees and postage to uk has anyone bought one of these?

at less than £20 delivered its got to be worth getting one for any cub regardless of the resolution surely.

http://www.donberg.co.uk/catalogue/tv_m ... 241bp.html

I see these are still available, now priced £9.59 + £6.31 postage (for 1). Any feedback please on long term reliability?

I've got a couple of dead Microvitec 1431s which I have yet to look at, so this may be jumping the gun!

On a related note, a friend recommends as a general TV repair tip to remove the tripler first then make sure everything else is working. Does this approach apply to the 1431 please?

Regards,
John

[retroclinic]

Yes, you can disconnect the tripler and run the monitor up. Offer up an INSULATED screwdriver to the output of the LOPT at about 3mm distance, and it should arc across. If not, then you've got a HV problem. The tripler fault mode is usually blurry picture either at turn on, or focus drift that cannot be corrected. I have had one tripler though that went short circuit.

Thx, Mark.

[SmellyGeekBoy]

Hello all,

Sorry to revive such an old thread but I'm sat here with my CUB in bits in front of me, spare tripler in hand, pondering what to do next.

I'm assuming it's the tripler that's at fault, it takes a very long time to warm up and come into focus. Either way I have it now so I might as well change it!

First of all, what's the recommended procedure to discharge these? This CUB hasn't been powered up for a few months so I'm not expecting a big bang when I ground the anode - should I get a specialist tool or is it OK to use a screwdriver and a bit of wire? Does the monitor need to be plugged in (obviously not powered on) to discharge so it has a route to earth? I've done a lot of reading on the subject and watched some videos but I've never actually discharged a CRT before. I'm proficient at soldering and not scared of playing with mains electricity but I'd rather be safe than sorry.

I also found a link to a LOPT in another thread - from the same supplier as the tripler - does it make sense to change both just as a precautionary measure? The inside of this CUB is absolutely disgusting and the original LOPT looks pretty worse for wear. I don't mind paying to get another 30 years of life out of this as the tube seems in good nick (it's a Hitachi FWIW, not sure how many different options there were).

Many Thanks!

[1024MAK]

DON'T plug it in.

It may be an anticlimax seeing as it's been off for over a month...

Get a long flat bladed screwdriver with a metal shaft, but fully insulated handle. Attach a wire from the shaft of the screwdriver to the metal chassis of the CRT tube. Put one hand in your rear pocket, don't lean on or touch the chassis. Now (without damaging it) push the screwdriver under the EHT rubber cap until you firmly touch the metal "socket contact".

Remove the screwdriver, then remove the EHT rubber cap from the CRT tube.

Now you can take your hand out of your pocket

Mark

[Kazzie]

Hi,

I suspect I'm the person from the other thread with the LOPT replacement.

I used the screwdriver and wire technique as Mark just outlined, using a car jumper lead as the wire. (My crocodile clips were too small to fit around the screwdriver's shaft.) My monitor was unplugged and unearthed at the time, and as it'd been unplugged for a month waiting for payday, there was no audible discharge spark or anything. So I just made very sure I'd reached the metal spring before going in myself. (I had more trouble removing the spring than discharging it!)

[paulv]

DON'T plug it in.

It may be an anticlimax seeing as it's been off for over a month...

Get a long flat bladed screwdriver with a metal shaft, but fully insulated handle. Attach a wire from the shaft of the screwdriver to the metal chassis of the CRT tube. Put one hand in your rear pocket, don't lean on or touch the chassis. Now (without damaging it) push the screwdriver under the EHT rubber cap until you firmly touch the metal "socket contact".

Remove the screwdriver, then remove the EHT rubber cap from the CRT tube.

Now you can take your hand out of your pocket

That's a great technique. BITD, we used two wooden handled screwdrivers, one on the earth, one to the tube connector then touch the shafts together. It was quite haphazard and definitely not the a method I would recommend as there was scope for the "earth" screwdriver to slip off the chassis etc. the resulting sparks as the screw driver shafts approached each other however were rather "cool" to see when the TV had only recently been used before needing repair.

Slightly OT but still in the back of a CRT unit that I remember from BITD was the guy that was teaching me about TV repair took a screwdriver and placed it a short distance from the top of a few of the vacuum tubes whilst the TV was on. He was attempting to show me that the High Voltage was "real" by demonstrating the purple/violet arcs from the tips of the tubes to the driver shaft. At the time, I'd been studying physics at GCSE for a year or two and had by then, seen and tinkered with a Jacobs Ladder so I was thinking to myself that he was a nutter doing what he was doing to illustrate the point

Paul

[SmellyGeekBoy]

Thanks for the replies everyone. It was indeed me in the other thread. I think I'm getting some of my terminology confused - I'm fairly new to CRTs and was under the impression that the "tripler" was usually integrated into the same unit as the LOPT. It seems they're separate things in my CUB. I'll do some more reading on the subject.

I've come across the screwdriver technique so that's the route I was going to go down. Glad to hear that it's recommended here. I was kind of half hoping that someone would say that the CUB was self-discharging. Oh well.