R965 Controller Fault

[RebGershon]

Hi,

I'm new to the forum but an old model railway man!

I recently inherited a R965 contoller without a power supply that came with some stuff I picked up from an ebay seller.

I connected the input to a 15vac output from my H & M contollers to see if the Hornby contoller would work - it didn't and was making the thermal cutout on the H & M trip. After opening the box I found 3 of the 4 diodes on the rectifier had gone short circuit so I replaced these. I now managed to get 15vac through to the screw terminals but only around 3.5v on the dc output without tripping out the H & M.

On further inspection I noticed a small hole in the front of the triac a 106D1. My controller seems a bit of an odd ball because althought he front cover says made in England, the board is the later Chinese variety from pictures I've seen on the internet.

I ordered a replacement triac which I fiited today. However, I get 20v dc with a voltmeter across the output but the contoller/potentiometer has no effect in reducing the output voltage. Likewise an engine is uncontrollable but goes like a rocket!!

The potentiometer seems to work as the resistance is variable using a meter. There's also 2N6028 transitor which when taken out there's no dc output. The other 2 diodes on the board seem ok but I cna't check the capacitors.

Is it possible there's a fault with the replacement triac or have I missed something else that could have failed?

any suggestions gratefully accepted.

/media/tinymce_upload/cee87a8e1830a836fb03f6cc7783a585.jpg/media/tinymce_upload/32f75556aba7aea39893876242409344.jpgPlease see picures attached. The old triac is laid on top pf the board bottom left corner.

[96RAF]

I have seen a video update to improve the output of these older types of controllers but that involved installing an uprated semi-conductor which oddly was orientated in reverse to the original. That update removed the overheat sensor which this controller does not seem to have. With that in mind have you got the triac legs the right way round, although you come across as knowing exactly what you are doing to have gotten this far.

[Chrissaf]

The R965 'Made in China' Thyristor circuit design is not a voltage controller. It is a current controller. Thus you cannot measure an accurate output voltage. A 20 volt measured output is quite normal as is the speed control not seeming to vary the measured voltage. If you are going to try and measure voltage, you need something to act as a 'motor load' applied to the output to provide something through which current can flow.

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If you have access to a scope, then this is an example of what the output should look like on a working R965 with a 'load' attached.

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/media/tinymce_upload/8e79b7cd03b404ecc941549b43a1ab99.jpg

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Extract from the webpage the image was taken from:

 

"These two pictures of 'on-load' voltage show the controller dynamically changing its delivered power. You can see it switching from modest power on each half-cycle to double power on alternate half-cycles."

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PS - The Made in England 'Margate' version uses a power transistor circuit design to replace the thyristor one in the China made version.

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TIP: As a relatively new poster on the forum, just be aware that the 'Blue Button with the White Arrow' is not a 'Reply to this post' button. If you want to reply to any of the posts, scroll down and write your reply in the reply text box at the bottom of the page and click the Green 'Reply' button.

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Particularly as my reply includes an image, using the 'Blue Button' may result in your reply being held back for image approval, even though it is an existing image.

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See also – further TIPs on how to get the best user experience from this forum.

https://www.hornby.com/uk-en/forum/tips-on-using-the-forum/

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[RebGershon]

Thanks to RAF96 & Chrissaf for your replies.

I'd like to make a couple of points:

1. The oreintation of the new Triac is as per the old one. and as it is the same T092 package one would expect the pin outs to be the same.

2. I understand that with no load connected, the meter will read full voltage.

To reiterate what I wrote in my first post there is still no control of speed via the red speed contoller knob when an engine is on the track, it's either full speed or off with the direction selector switch in the central position irresrpective of the position of the red knob.

So there has to be another reason why there's no variance of speed.

I watched the 1st part of the video about upgrading the controller but that doesn't address the problem I'm having as there's no lack of power to an engine on the track it's just the inability to regulate it.

[96RAF]

Does the reversing switch make any difference?

[RebGershon]

No difference to the speed RAF just reverses the direction.of motion.

[96RAF]

There is likely enough info there for you to draw up a basic schematic of the device so as to try to work put where any short circuiting could occur to give the max-chat scenario described.

 

It is if the triac is being driven to full output regardless of the pot setting. Getting outwith my skill set.

[RebGershon]

I have now replaced both the thyristor and triac but still getting full power only so I'm now beggining the wonder if there's a short on the potentiometer.

For the time being I've decided to leave it alone as it's not worth spending anymore time & effort for something I don't really need.

 

Thanks for all those who answered.

[96RAF]

Having had a look at this again it appears there is probably a fault that emulates if you were trying to power a R965 from a DC source... i.e. you end up with continuous full DC output since there was no zero crossing seen to turn off the Triac/SCR. The answer came to mind when I was recently trying to use a solid state relay module to switch a DC load. The SSR module uses Triac tech to switch AC loads normally.

 

I will have a go at drawing up a schematic for the unit which may help. Maybe I could use it to,write up a Teardown Report on the unit to top up the others I have done before.

 

If required I have a datasheet for the PTC (self resetting fuse link) which lists the initial resistance value.  Measuring this will tell you if the PTC is faulty very quickly. If it is too high it will trigger early or immediately. The usual failures are it going out of spec.

 

 

 

[steve-1218643]

Im having the same problem having replaced the thyristor, transistor and all the capacitors and still no motor speed control. Pot reading ok with a resistance check, all diodes reading ok ....sweat