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Retro-Fitting the Muter BMR95 CRT tester..

 
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Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Wed Feb 19, 2014 10:50 pm

Hi all,

I'm made mindful of the classic line from "Apollo 13" where the 'guys on the ground' are instructed to come up with method of adapting one type of air-scrubber to work in liue of another "We've gotta make this, using nothing but that".

I was given the Muter by Marc, some moons ago, and although it came with a range of CRT bases, it had none to suit our vintage sets.

So the hunt (the scrounge) was on for the parts I needed to build an adapter to suit B12A and B8H CRTs.. First off was the B12, which was donated by Trevor "Murphy V310".

This would have been "it" asa far as I was concerned, and I would have mmodified one of the existing adapters to take the B12, but then I thought it would make more sense to make a purpose built adapter for the job.. This led to the search for a B9A plug to make the connection to the Muter, and sure enough, VRATs to the rescue, in the form of Dave "Framer Dave" who donated just the perfect plug, with plastic shield, and pre-wired, so that saved me a job.

Now that could have been as far as it would have gone, but having a couple of B8H CRTs, and since there could be more in future, it seemed logical to include one of these too, and sure enough, another VRAT rescue, courtesy of Rob "Glowing Anode".

So.. Now I had the "Make one of these" challenges, and I also had the "out of nothing but that" pile of parts.

The next part of the puzzle was map out the wiring of the Muter, using data for the only CRT that I had; A) the CRT data, and B) an original adapter to work from, in order to cross referrence the wiring from the Muter, to the "known" CRT, and onto the B12 and B8 bases.. Fortunately I am in possession of small number of Mullard "Data Books", and as luck would have it, they were just old enough to have the data I needed, or so I thought.

I was easily able to sort out most of the wiring, but fell foul of my old foible of failing to recognise that in colour CRT terminology, A1 and G2 are the same thing, just different referrences! :ccb

I had a PM from Marc, and a reply from Mike "Cathovisor" in my "Cross-referencing CRT base connections for CRT tester.." thread, both giving me the same advice "A1 = G2", only that Mike went one step further in pointing out that "A2 = G3" in this equation.. See thread, viewtopic.php?f=15&t=7611

So now I had everything I needed to make a start.

First order of business was to remove all remnants of old wiring and miscelaneous components from the CRT bases, then drawing out a plan/map of the wiring, and at the same time, cross mapping these with existing wiring on Rob's B9 plug.. Once I'd got that sorted, I was able to wire up the B12.. I tested this 'first phase' on a known B12 CRT, and what a (pleasant) surprise, it works! At first, I thought there was an error in my work (the "Short G1-G2" indicator on the Muter was glowing, very dimly, but glowing) however, setting up the Muter, and taking the readings, went exactly as per the instruction manual, and were more or less plausible.. Next, I needed to find some suitable wiring to connect the B8, and guess what? I struck lucky with some multicore signal wiring from an ancient cooling module from a computer server, so I whipped off a length of that!

Cross referencing to the B8 was a straightforward job, complicated only by my breaking off a solder lug from the B8, so a little bit of surgery was needed to transplant a redundant connector from the B8, into the place of the broken one.

Once I'd got the wiring job done, another test to check that it was working, and Bob's your uncle! :aad All that remained was to tidy up the overall wiring and neatness of the job.

Here are a few pictures of the progress....

DSCN0427.jpg
"From nothing but that"...


DSCN0429.jpg
Cleared of surplus wiring etc..


DSCN0436.jpg
"We have a problem"..


DSCN0440.jpg
Wired - the B12A


DSCN0441.jpg
Wired - the B8H


DSCN0442.jpg
The end product - Almost.


DSCN0443.jpg
Don't try this at home..


Now... Looking at this last photo, you can perhaps get an idea of my disorganised style of working, but belive it or not, all the data I needed is now contained within this picture, but I'll defy any to decode it and get it right. :qq1 :aaj

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Framer Dave » Thu Feb 20, 2014 12:57 am

Congratulations Marion! So glad you've got some use out of that plug. It's been in my spares box for so long that I've forgotten where it came from.

Regards,

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Fri Feb 21, 2014 11:40 pm

Hi Dave,

Many thanks for it. :aad

That pre-wired plug saved me a lot of time and fiddly soldering. :aad

I have in mind an alteration to the end product, in which it would be shrouded in a piece of plastic fall pipe, and possibly to incorporate a small switch to allow the selection of either, 6V or 12V heater supply.. In the Muter's original wiring, there are both supply voltages available at the same time.. Which voltage is selected, is entirely dependant upon which adapter is in use.. To do this the Muter way would involve making a second, identical adapter with wiring for the alternative heater supply (12V).. It seems logical to me that a switch would avoid the need for that, although care would be needed in ensuring the switch is correctly set before applying any power.

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by freya » Sat Feb 22, 2014 8:09 pm

very tidy looking adapter, well done Marion. Glad someone had the patience to sit down and work it out.

I will endeavour to make one up myself using your sheet. Hopefully it will make sense :bba

Thanks

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Michael Watterson » Sat Feb 22, 2014 8:30 pm

Katie Bush wrote: although care would be needed in ensuring the switch is correctly set before applying any power.


I was working on a GE YTW-1 emission tester on Thursday or Friday. Seriously need to check switches for sockets and heater / filament. It does 0.7 to 117V heater. The charts test all 6.3 + 6.3 heater valves at 12V, so if socket selectors are "wrong" it puts 12V on one (or both in parallel) heater instead of both in series. It has dodgy switches to the sockets. I think I've cooked a 12AU7.

You can later add 2V, 4V etc as well as 6.3 & 12 so maybe a 4 way or 6 way rotary switch? One position can be to short the heater pins together.

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Sat Feb 22, 2014 9:55 pm

freya wrote:very tidy looking adapter, well done Marion. Glad someone had the patience to sit down and work it out.

I will endeavour to make one up myself using your sheet. Hopefully it will make sense :bba

Thanks


Hi Stephen,

If it comes to that, you wouldn't really need all my working out (which was a bit of a head scratcher from the start).. I'm sure I could draw up a much simpler diagram that will give point-to-point connections.

To point of fact, now that I have made one, it's only a matter of copying it, rather than having it all to work out again.. Of course, that wouldn't be true if it were necessary to build up another adapter for a different type of CRT base.

I've made one small improvement to relieve stress on the soldered joints...

DSCN0451.jpg
A minor improvement..

As can be seen, I've tied the wiring loom back to the B12 CRT base.. This helps to take the stress from the wiring and soldered joints.

Marion
Last edited by Katie Bush on Sat Feb 22, 2014 10:02 pm, edited 1 time in total.

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by freya » Sat Feb 22, 2014 10:00 pm

I would have to say yes please for the simplified pin to pin layout, no hurry if your busy with other things though.

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Sat Feb 22, 2014 10:04 pm

Hi Stephen,

Would I be correct in assuming you have the same CRT tester as mine? - Just so that I know were singing from the same songsheet. :qq1 :aa

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Sat Feb 22, 2014 10:19 pm

Here's a couple of pictures showing the tester at work on a B8H based CRT..

DSCN0446.jpg
B8H on test.. Heater; 6V, doesn't look this bright in reality..

The heater looks rather bright, but this is an artefact of the camera, and in reality, it appears quite normal for a 6V heater.

DSCN0445.jpg
Oh dear, that doesn't look so good..

This is what the tester shows when correctly set.. I'm not altogether convinced that the tester is working 100% accurately.. I believe my wiring to be correct, and the tester still shows very low emission readings on other CRTs using one of the Muter's own 'stock' adapters on known to be good CRTs.

I suspect the tester will need looking at, even so, I can get a feel for the state of play with a CRT from the readings I get on this tester, and the differences between 'known to be good' CRTs and 'known to be dud' ones.

Marion

P.S.

The "lads" very easily get bored....

DSCN0453.jpg
Don't let me keep you, fellas!

:aak

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by freya » Sat Feb 22, 2014 10:35 pm

Hi Marion, yes the same

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Sat Feb 22, 2014 11:45 pm

freya wrote:Hi Marion, yes the same


Hi Stephen,

I'll see if I can roll it out for tomorrow evening (Sunday).. If not, it will be as soon as possible after then. :aad

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by marc » Sun Feb 23, 2014 1:13 am

Hi Marion,

It will be interesting to compare results with my B&K when we call over.
Just one question, which adapter fits the units on the third picture ? :bba

Marc.

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Sun Feb 23, 2014 9:12 pm

marc wrote:Hi Marion,

Just one question, which adapter fits the units on the third picture ? :bba

Marc.


Hi Marc,

Fancy you not being able to figure that one out!

It's a GC3F, of course.. "Ginger Cat, 3, Feline" - Naturally.. :aak

Marion

P.S.

His Stephen,

I've drawn up a plan (rather than circuit diagram) which I think will convey all the information you need.. A point-to-point wiring diagram was going to get way too messy.

I'm just waiting for my camera batteryto charge up, and I'll post it tonight. :aad

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by marc » Sun Feb 23, 2014 10:12 pm

Katie Bush wrote:
marc wrote:Hi Marion,

Just one question, which adapter fits the units on the third picture ? :bba

Marc.


Hi Marc,

Fancy you not being able to figure that one out!

It's a GC3F, of course.. "Ginger Cat, 3, Feline" - Naturally.. :aak

Marion

P.S.

That's a shame, I've only got a PU55 connector ! :aaj

Marc.

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Sun Feb 23, 2014 10:45 pm

Hi Stephen,

Take a look at this, and see if it makes sense to you.


DSCN0455.jpg
Simplified mapping of base pins/connections

I've tried to keep things as simple as I can, and although I have labelled the various pins on the three bases, all you really need to do, is to follow the coloured dots.. There are six coloured dots on each base, in five different colours.

Colour codes to represent coloured wiring..
Black = "h" (both sides)
Pink = "k"
Blue = "g"
Green = "a1"
Red = "a2"

If you take the colours as reperesenting the coloured wiring, it is just a matter of connecting all the pins of a particular colour onto the same lead.

On the B8H base..
The "a2" lead equates to "a3" pin.
There are two "g" pins (I used only only one - pin 2)

On the "Muter B9A Socket" view..
This is the view looking onto the socket itself, or alternatively, looking onto the rear aspect (solder tag side) of the B9A plug, which is why the pin Nos. are reversed.

Hopefully this will be clear from the picture, but if you get stuck, I'll try to make it look more logical.

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Sun Feb 23, 2014 10:50 pm

marc wrote:That's a shame, I've only got a PU55 connector ! :aaj

Marc.


No bother.. They're mutually interchangeable.

Where else do you think all the kittens come from?.. :aak

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Katie Bush » Wed Mar 26, 2014 11:40 pm

Hi Stephen,

How's the adapter coming along? And have you been able to test it? I'm just curious to know if you have 'better' readings that I'm getting. :)

Hi Marc,

Yep, still looking forward to seeing how this compares with your B&K.

I still haven't devised a K1TT3N adapter, so a GC3F/PU55 might have to suffice. :) :aaj

Marion

 
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Re: Retro-Fitting the Muter BMR95 CRT tester..

Post by Alastair » Tue Oct 13, 2015 7:25 pm

Hi Marion--

Perhaps you may find my readings useful for comparison. My Muter looks exactly like yours, but is a 2005, but expect the test readings would be the same.

I had to make up a CRT adaptor for Axx-120X type delta-gun CRT's but fortunately there were two of the same type adaptors for some type that uses 806 Muter adaptor.

--I was able to remove the original tube socket and bung a B12 in its place--but the wiring colour-code in the adaptor was completely different to yours.

All sorted, here's what I found when trying it out. Both CRT are Mullard A56-120X, the old one, a green and orange label, the good one a plain green label.

Tube 1 which gave a bright but foggy/poor focus especially on bright parts, not great grey-scale tracking, (I suspect it may have a little air who knows)--

Red, 0.85mA, Green, 0.8mA Blue, 0.9mA
The Cut-Off is slightly different on all guns.

As this is an old and obviously well-used CRT (Quite silvered down near the base-pins) I tried the two rejuvenating settings. All this did was slightly reduce the readings when re-tested, maybe because I had done the 'non-destructive' to it previously, and it wasn't able to give any more anyway. I have not picture-tested it since its 'Mutering'....

Tube 2 which is quite excellent, sharp bright and good tracking, with a clean glass, no silvering near the pins--

Red, 1.0mA, Green, 1.0mA Blue, 1.1mA.
The Cut-Off compares closely on red and green, but fractionally higher on blue.

The user-manual claims anything over 0.7mA is to be considered 'Good'

IF yours is under-reading--It could be the two 10K inside the thing that the user-manual talks of, a design feature to fail if there's a G2/3 short......


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