Author Topic: CM14 Issues  (Read 3374 times)

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Offline tjohnson

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CM14 Issues
« on: 12:43, 30 September 20 »
Probably one for @Bryce .
I just pulled my CM14 out of storage (the garage) and when I switched it on the picture was trapizoidal, after a short while it when back to normal shape.  There has been a bit of distortion there after.  Probably not powered up for well over a year.
What do you think re-cap in order?
Cheers Trevor
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Offline tjohnson

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Re: CM14 Issues
« Reply #1 on: 12:52, 30 September 20 »
Oops spoke to soon.  Left it running, came down could smell distinct burning smell.  Picture had distorted (see attached). played with brightness and picture vanished and replaced with high pitch whine.
No picture displayed at all now.

« Last Edit: 13:07, 30 September 20 by tjohnson »
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Offline Bryce

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Re: CM14 Issues
« Reply #2 on: 14:23, 30 September 20 »
Unfortunately, you possibly could have avoided this. If you bring in electronics from the garage, you should leave it for a day or two before turning it on. The damp / difference in temperature can cause condensation on the PCB. That together with old caps can cause other things to fail. In your case you have probably damaged the high voltage section.

Bryce.
 
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Offline tjohnson

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Re: CM14 Issues
« Reply #3 on: 14:28, 30 September 20 »
Yeah I did think that but my bad I decided I couldn't be bothered and maybe suffered the consequences as a result.  It's quite mild here, slight dampness could be more of an issue.
Might take the back off see if anything obviously burnt out, then probably just take to the dump.
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Offline tjohnson

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Re: CM14 Issues
« Reply #4 on: 14:56, 30 September 20 »
Yep noise certainly sounds like its coming from the HT section

https://youtu.be/Um3ZVOni_q0

https://youtu.be/kohekEyQR1s
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Offline tjohnson

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Re: CM14 Issues
« Reply #5 on: 19:39, 15 November 20 »
Small update on this, @ComSoft6128 sent me a spare PCB which I installed yesterday, unfortunately the flyback on the spare PCB wasn't useable so I swapped the flyback from the original pcb onto the board.  Upon powering on there was a definite pop sound and a small flash and then nothing.

This afternoon I've been trying to diagnose the issue with zero knowledge of how this thing works.  I've found that ICP501 (ICP-N20) seems to be blown on both boards (open on multimeter), this seems to be some sort of current limiting fuse that sits on a +103v line that goes into the FB and the horizontal drive transformer.  Annoying that I didn't find this on the original board before fitting the one from ComSoft6128 and it seems to be quite expensive to buy.  Neither has any visible physical damage. 

 What I've then then found is that there seems to be a short on both boards between the base-emitter on the big main horizontal output driver transistor Q405 (2SD1877). which I don't think is right, so I guess if this has blown on both boards it would pull large current through and blow this current limiting device.  Again this doesn't seem to have any physcial damage and is a large transistor, 2sd1877 which seems to be quite an expensive part to buy.  I've no idea if the replacement PCB was good before fitting so I'm kind of in the dark on this.

Anyone have tips on testing the flyback?  My main concern is that the FB is faulty and this is causing these components to blow.


« Last Edit: 19:44, 15 November 20 by tjohnson »
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Offline Bryce

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Re: CM14 Issues
« Reply #6 on: 19:59, 15 November 20 »
If there was a pop and a visible flash, then there's a pretty good chance that there's a crack in the HT cable insulation (that big cable coming out of the flyback transformer). Unfortunately, that can indeed result in fried components as the current is (theoretically) infinite. Inspect the cable before you replace any parts.

Bryce.
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Offline tjohnson

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Re: CM14 Issues
« Reply #7 on: 22:43, 15 November 20 »
If there was a pop and a visible flash, then there's a pretty good chance that there's a crack in the HT cable insulation (that big cable coming out of the flyback transformer). Unfortunately, that can indeed result in fried components as the current is (theoretically) infinite. Inspect the cable before you replace any parts.

Bryce.
I've just had a look and can't see any obvious cracks in the big fat cable going to the suction cup like thing.
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Offline tjohnson

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Re: CM14 Issues
« Reply #8 on: 20:46, 17 November 20 »
Well I've had a look at the the spare PCB and found a crack on it in the power supply section so I guess that is scrap them.
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Offline tjohnson

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Re: CM14 Issues
« Reply #9 on: 23:10, 18 November 20 »
Small update on this.  Bryce you were right.  The fault was caused by the monitor being stored in a garage. Apparently these are known for this issue, there are rubber wedges that absorb water and then cause corrosion on the deflection coils.  I took out the wedges and they were visibly damp.  After removing the coil there is some corrosion on it and can see burning where it was arcing.  I'm not sure I'm going to be able to repair this tbh, so looks like storing it in a garage was a bad idea.


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Offline Bryce

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Re: CM14 Issues
« Reply #10 on: 10:36, 19 November 20 »
Yup, unfortunately there are many polymers that absorb water and can cause issues. This can happen even inside the house, but it happens much faster if the monitor is stored somewhere with higher amounts of moisture in the air like a garage.

Bryce.
 
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Offline tjohnson

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Re: CM14 Issues
« Reply #11 on: 18:58, 01 December 20 »
I have some things to try to get the monitor working again, I picked up a TV locally and might be able to swap the tube and yoke in, will see how I get on with that.
On a different note I pulled my CTM644 out the garage where it was also stored.  I left it for a couple of days inside to aclimatise and it seems fine.   

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Online dragon

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Re: CM14 Issues
« Reply #12 on: 04:14, 02 December 20 »
I have this problem but with my ctm 644. And stored into my house.


Thats why open a page try to make a database of the tubes and the yokes that used amstrad. To find the equivalency with moderns tubes.




I found in her day in a book  of electronics a part of the nomenclature of the code of the deflection coils. And I locate some specs of modern yoke.


Unfortunly in her day I can't find the exact specification of the orion yokes to find a modern equivalence. It just need one that use the same parameters...





So first take a picture of the code and search it in google. I don't know if amstrad user diferentes yokes in the cm 14 that in the ctm 644.

If you have lucky and can  find the specification maybe you can find a modern replacement that have the same parameters..





« Last Edit: 04:29, 02 December 20 by dragon »
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Offline tjohnson

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Re: CM14 Issues
« Reply #13 on: 17:06, 02 December 20 »
The tube in my CM14 is a A34AGT13X
According to this site http://tubular.atomized.org/
It is Heater 6.3v G1 50v and a CR-31 neck
I was also told to measure the resistance on the horizontal and vertical coils and seek to match as closely as possible with the coils on any replacement.
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Offline Bryce

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Re: CM14 Issues
« Reply #14 on: 19:29, 02 December 20 »
The chances of finding a suitable yoke for a tube is more or less zero. The coils physical dimensions - curvature, magnetic properties and electrical properties would all have to match exactly and that's not going to happen. There's more chance of finding a boxed CM14 with Alan Sugars signature on the lid.

Bryce.
 
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Online dragon

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Offline tjohnson

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Re: CM14 Issues
« Reply #16 on: 19:52, 02 December 20 »
My CM14 has a DSE-1422BL I measure 13.7ohm vertical and 5.0ohm horizontal but since the horizontal is burnt I wouldn't trust that reading.
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Online dragon

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Re: CM14 Issues
« Reply #17 on: 20:03, 02 December 20 »
Oh that's very interesting it's the same yoke that died in my ctm 644. :picard:


Iv view In her day same tube diferent yokes.




Orion Tube 3702B22-TC20Yoke deflection coil: semco dse-1422BL BECCpcwiki:Orion Tube: R70BV1BK1A-TC10Yoke deflection coil:KYS? -60096 ggdk.


Schneider ctm 644 nighfall:Orion Tube:3702B22-TC20Yoke deflection coil:TCD-8701? BEC


Amstrad CTM 644 espaƱolOrion Tube: 3702B22-TC20Yoke deflection coil: TCD-8701 C B C


I remember I found esactly what mean the code.


I'n her day I found one samsung near it. Theorizing can be the same with diferent connector in the pcb.  (six four wires) the samsung dse-1422fl


Dse=Samsung inline, crossarm type tube 29 diameter, 90 grades suitable for 14-20" tv. (pincushion free).


Hey that's very Interesting. This page don't exist last time  I search

http://antel.cn/product_show.asp?CID1=16&CID2=165&ID=3843


Maybe yo can try a inquiry?


Oh these page is new to the specs!.

http://webcache.googleusercontent.com/search?q=cache:jHtL-D53170J:www.szmie.com/product.asp+&cd=5&hl=es&ct=clnk&gl=es&client=ms-android-huawei-rev1
« Last Edit: 20:32, 02 December 20 by dragon »
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Offline Bryce

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Re: CM14 Issues
« Reply #18 on: 20:38, 02 December 20 »
But that's just the problem. There are thousands of variants and "near" isn't good enough, it has to have all of the exact same properties AND then also have the correct dimensions for the tube size.

Bryce.
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Online dragon

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Re: CM14 Issues
« Reply #19 on: 20:45, 02 December 20 »
But some are equal. But we not have all the list variants.


For example dse 1422dl=1422bl



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Offline tjohnson

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Re: CM14 Issues
« Reply #20 on: 21:25, 15 December 20 »
I went ahead and installed the tube and yoke from the philips I picked up locally for free, I also replaced the ICP-N20.
Some success I now have a picture but it's mirrored but it's also quite a bit darker than before so I guess I need to fiddle with some pots somewhere, no idea how I fix the reflected image, could it be the pinout on the tube is different so there will be no easy way of doing this? 

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Offline tjohnson

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Re: CM14 Issues
« Reply #21 on: 01:55, 16 December 20 »
Result, after flipping the connections on the horizontal coils the image is now the right way around.  I also adjusted the sub bright inside the monitor and got an acceptable brightness the service manual refers to putting the monitor into "free-run condition" and then connecting a scope of the collector of Q802 and then obtaining 123-124v but  I had no idea on what it meant by free-run condition, I thought it perhaps means connecting nothing and using my scope I wasn't getting what the manual showed so I did it by eye.  ICP-N20 was blown but the HOT wasn't, I didn't notice that there is an internal diode that made me think they were shorted together.    I need to tweak the horizontal and vertical positions slightly but it looks good, the picture is probably crisper than the old tube, unfortunately there are some surface scratches on the tube but since it was free I can't complain too much and I have a working monitor again.  I measured circa 3ohms on the horizontal coils and 16ohms on the vertical, seems they are close enough to the original to be useable, this tube was from a late model Philips TV, it had an A34AGT13X95 tube in it and apparently made in Glasgow by Chunghwa (CPT) of Taiwan.  Not sure what the coils are will have a look.

« Last Edit: 02:11, 16 December 20 by tjohnson »
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Offline Dr Tiger Ninestein

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Re: CM14 Issues
« Reply #22 on: 11:41, 04 January 21 »
Ive got a cm14 that Im going to have store away for a while and this thread has got me thinking.


It was going to go into the garage or loft but obviously after reading this i think im just going to put it into one of the bedroom cupboards.


Just wondering if it would be worth getting some large silica gel packs and putting them into the cardboard box that the monitor is being stored in?


 

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Offline Bryce

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Re: CM14 Issues
« Reply #23 on: 11:58, 04 January 21 »
Loft would be better than the garage, but simply covering it with a towel or blanket will also keep moisture out.

Bryce.
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Offline Dr Tiger Ninestein

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Re: CM14 Issues
« Reply #24 on: 12:29, 04 January 21 »
I think im going to keep it in one of the bedroom cupboards to be on the safe side.


Do you think it would be worth ordering some large silica gel packs to put in the box with it?
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