Blown TTS Decoder - what did I do wrong?

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NedFlanders
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Blown TTS Decoder - what did I do wrong?

Postby NedFlanders » Tue Dec 11, 2018 3:33 pm

Hi all,

being laid up at the moment I decided to finally fit the A3 TTS decoder to Flying Scotsman. I had previously discovered that the speaker would not fit in the loco so I had picked up a sugar cube 8ohm speaker.

Before
Image

I look the Lenz chip out of scotsman, soldered in an 8 pin socket so that i could swap decoders easier later and connected the tts chip, having soldered on the Sugar cube speaker.

Nearly there
Image

Tidied up
Image

On my z21 system she would respond to commands sent to loco ID 3 and move forwards/backwards but apart from a clicking noise that was the only sound I got from it. Attempts to program it on the z21 came to naught.

previously I had found that the Hornby eLink would program some locos that the z21 wouldn't so I cranked it up - sat scotsman on the programming track and it kept coming back with a loco id of 255 and what appeared to be spurious results as well to any other cv. also previously, I had seen issues until I set a loco ID explicitly on the eLink so I set the loco to 72 - it appeared to accept that. I then went out of the software - back in - and proceeded to get spurious results again to any cv inquiry.

hmmmm,, ok - I put it back on the z21 to see if i would get an different results after it having been on the eLink. Nope - faint clicking noise still there, responding to forward and back commands sent to loco 3 until.... silence! Nada, nothing. no response.

Ah yes, there it was, the faint acrid smell of electronics having a bad hair day. I stripped out the decoder and there was one of the chips on the board having melted its way through the tape I had put around the decoder ( as recommended by the hornby sheet with the decoder- although they did say Sellotape and I used Scotch magic tape) it melted the hole extremely neatly but melted nonetheless.

burnout ( red arrow)
Image

So , any thoughts on what I did wrong? did i just get a dud one? i checked the sugar cube speaker and couldnt see that the solder had shorted in any way - all wire joints were insulated/heatshrink.

The Flying Scotsman is one that came with a hornby set within the last 10 years. It has previous form in that it misbehaved with a Hattons chip, sometimes only responding when another loco was running. once i put the lenz chip in place it settled down. The "Small Controller" wanted sound for Scotsman so I thought the Hornby TTS would be the way to go....

The TTS chip was a present last Christmas - no idea where it came from at this stage. The sugarcube is an 8ohm ESU

Our two other TTS locos (factory fitted) work away with the z21. I am well bamboozled by this working and then gradually expiring - does that point to the loco being the issue? I would have expected the chip to die immediately with a short.

Any thoughts/suggestions welcomed as I'm sure that the Small Controller will be asking pertinent questions.... ;)

Having another one to fit before Christmas I am nervous now. I think I will test any 8pin chip in a working loco first in future - e.g. Hornby's Ketley Hall. at least that way I can rule (ish) out the chip if something happens afterwards

Ned.
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Bufferstop
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Re: Blown TTS Decoder - what did I do wrong?

Postby Bufferstop » Tue Dec 11, 2018 5:01 pm

Do TTS chips require an 8ohm speaker? If you powered it down whilst the tape was still melting there's a chance the hot chip will have survived. I'd try reconnecting the original speaker just to see if anything works.
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Flashbang
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Re: Blown TTS Decoder - what did I do wrong?

Postby Flashbang » Tue Dec 11, 2018 5:53 pm

Hi
Two things.
1) As its a tender drive you should have the loco connected to the tender when programming and running as the loco provides a path to one sides rails.
2) When the original wires were removed from the silver coloured brush strips did you carry out a continuity test between the left brush strip and all tender wheels and any metal of the tender chassis. There must not be any continuity noted. If there is, you must remove the cause before applying DCC power.

Finally, I assume the loco ran faultlessly on DC rail power before conversion? No hesitancy to start or general poor running experienced. As a poor running loco on DC will become far worse on DCC.
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Broken? It was working correctly when I left it.

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RAF96
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Re: Blown TTS Decoder - what did I do wrong?

Postby RAF96 » Tue Dec 11, 2018 6:32 pm

...soldered in an 8-pin socket...


I would be looking there first. Poor socket, solder bridge, pin touching metal, wrong connection, etc, especially with a ringfield.
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Paul-H
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Re: Blown TTS Decoder - what did I do wrong?

Postby Paul-H » Tue Dec 11, 2018 7:34 pm

Also ignore the instructions about wrapping the decoder in tape, they get hot and need air, I once used a bit of loose fitting un-shrunk heat shrink and after 5 minutes running it had started to shrink, it got that hot.

Paul

NedFlanders
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Re: Blown TTS Decoder - what did I do wrong?

Postby NedFlanders » Tue Dec 11, 2018 8:39 pm

Bufferstop wrote:Do TTS chips require an 8ohm speaker? If you powered it down whilst the tape was still melting there's a chance the hot chip will have survived. I'd try reconnecting the original speaker just to see if anything works.


Yes, 8ohms is the requirement for the speaker.

I'll give the original speaker a go later in the week.

Cheers.
Getting back into railways, one step at a time.

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NedFlanders
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Re: Blown TTS Decoder - what did I do wrong?

Postby NedFlanders » Tue Dec 11, 2018 8:46 pm

Flashbang wrote:Hi
Two things.
1) As its a tender drive you should have the loco connected to the tender when programming and running as the loco provides a path to one sides rails.
2). did you carry out a continuity test between the left brush strip and all tender wheels and any metal of the tender chassis. There must not be any continuity noted.......

Finally, I assume the loco ran faultlessly on DC rail power before conversion?


Hi there,
Yes, tender and loco connected when on the track.

I did no continuity test - i will take a look.

Yes, it ran fine on Dc. Misbehaved on its first chip - a Hatton chip. Worked fine on the lenz. Then as I was going for the TTS chip I decided to put in the 8pin socket to facilitate any further changes. So it's been working on the lenz chip for 18-24 months.

Thanks.
Getting back into railways, one step at a time.

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triuph1050
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Re: Blown TTS Decoder - what did I do wrong?

Postby triuph1050 » Tue Dec 11, 2018 8:47 pm

I too lost a decoder because I wrapped it in tape, ran well for about 15 mins then stopped and I got error message. Now I if I have to protect the chip I cover what it might touch instead of the chip.

NedFlanders
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Re: Blown TTS Decoder - what did I do wrong?

Postby NedFlanders » Tue Dec 11, 2018 8:55 pm

RAFHAAA96 wrote:
...soldered in an 8-pin socket...


I would be looking there first. Poor socket, solder bridge, pin touching metal, wrong connection, etc, especially with a ringfield.
Rob


I will check the continuity there too. I have already used on of the sockets (from a pack, and they have have the wires already attached) in a class 58 without any issue.that said, it is using a cheapie Hatton decoder and not a TTS chip. There is, I suppose, no guaranteeing the quality control applied to the sockets.

Thank you.
Getting back into railways, one step at a time.

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NedFlanders
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Re: Blown TTS Decoder - what did I do wrong?

Postby NedFlanders » Tue Dec 11, 2018 8:56 pm

Paul-H wrote:Also ignore the instructions about wrapping the decoder in tape, they get hot and need air, I once used a bit of loose fitting un-shrunk heat shrink and after 5 minutes running it had started to shrink, it got that hot.

Paul


For the lenz one I hadn't wrapped it, because the hornby one said it was ok - I did. You live and learn.

Thanks.
Getting back into railways, one step at a time.

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NedFlanders
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Re: Blown TTS Decoder - what did I do wrong?

Postby NedFlanders » Tue Dec 11, 2018 8:59 pm

triuph1050 wrote:I too lost a decoder because I wrapped it in tape, ran well for about 15 mins then stopped and I got error message. Now I if I have to protect the chip I cover what it might touch instead of the chip.


Mine was misbehaving straightaway which initially suggested to me that it was either mildly knackered to begin with ( for whatever reason) or needed a reset. I will stick with the chips "al fresco" in future.

Thanks.
Getting back into railways, one step at a time.

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RAF96
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Re: Blown TTS Decoder - what did I do wrong?

Postby RAF96 » Wed Dec 12, 2018 10:01 am

You could invoke the new TTS warranty which includes accidental damage.
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Bigmet
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Re: Blown TTS Decoder - what did I do wrong?

Postby Bigmet » Wed Dec 12, 2018 10:45 am

NedFlanders wrote:...it ran fine on DC. Misbehaved on its first chip - a Hatton chip. Worked fine on the lenz. Then as I was going for the TTS chip I decided to put in the 8pin socket to facilitate any further changes. So it's been working on the lenz chip for 18-24 months...

Have you measured the stalled current draw of the motor on 12V DC?

That the Hattons decoder 'misbehaved', but it was fine with the Lenz would lead me to the thought that the superior current output of the Lenz was sufficient to run the motor.

This motor may have too large a current draw for the TTS decoder.

NedFlanders
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Re: Blown TTS Decoder - what did I do wrong?

Postby NedFlanders » Thu Dec 13, 2018 4:31 pm

RAFHAAA96 wrote:
...soldered in an 8-pin socket...


I would be looking there first. Poor socket, solder bridge, pin touching metal, wrong connection, etc, especially with a ringfield.
Rob


Ok, this one is hurting my head - the orange and grey wires go from the socket to the Motor contacts.

Test at the Motor contacts - no beep from the Multimeter.

Test the Orange and Grey Pin holes on the socket - Beep! ????

The orange and grey pin holes are at the opposite ends of the socket - where could a bridged connection be coming from? If I get a beep at the pin holes surely I should get a beep at the motor contacts?

Image

How is that test result even possible? The loco did respond to commands for moving forwards and backwards so the motor must have been getting current - yet the continuity test suggests there should be a short at the socket?????

I've tested other sockets that are still in the packet and none of them beep, also the Class 56 that I fitted one to already is working away fine ( must test that socket), although that's just got a Hattons chip in it, not a TTS.

This is where the mysteries of electrickery lose me. :D

Ned.
Getting back into railways, one step at a time.

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Roger (RJ)
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Re: Blown TTS Decoder - what did I do wrong?

Postby Roger (RJ) » Thu Dec 13, 2018 5:15 pm

Test each wire individually from the socket to the motor contact to see if there is a loss of continuity.


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