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What in Thorens TD 320 could cause a Transformer To Burn??!

Discussion in 'Turntables' started by Jadran, Mar 11, 2017.

  1. Jadran

    Jadran Off The Record

    Messages:
    1,181
    Location:
    Tesla's birthland
    Great idea, ralphfcooke. Thanks! I was looking to buy this tool some time ago, it seems that now is that moment.
     
  2. petehall347

    petehall347 the brandy coffee man Subscriber

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    22,450
    Location:
    uk.. the middle bit
    just read through this quickly and am surprised that it hasn't been suggested to disconnect the motor and see what happens .
     
  3. cdk99

    cdk99 Well-Known Member

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    863
    Location:
    SaguaroLand
    Would it be possible to tell something from feeling wire and connection temps with fingers?
     
  4. Thunderbox

    Thunderbox AK Subscriber Subscriber

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    290
    Location:
    Saskatoon, Saskatchewan
    I would check to make sure the turntable is actually set for 220V and not 120V. That would double all current and could be the problem.
     
  5. ralphfcooke

    ralphfcooke New Member

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    18
    This turntable uses an external transformer, stepping the local mains supply down to around 16V AC.
    All the rectification, regulation is done within the turntable, and pretty much all of those components have been checked/changed.
    All that is left is the oscillator/power circuit that drives the motor, or the motor itself.
    The service manual here is available at Vinyl Engine, after free registration
    https://www.vinylengine.com/ve_down...td316_318_320_321_phantasie_service_en_de.pdf
     
  6. Jadran

    Jadran Off The Record

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    1,181
    Location:
    Tesla's birthland
    OMG!!! Before I explain what happened at the end, I would like to thank to everyone who contributed to the thread, while looking for a solution to this problem!

    Now, it is actually so stupid, simple, and at the front of my nose from the very beginning, but...
    I trusted the seller in Germany, who gave this turntable to his friend ('electrician'?) prior shipping to me, and that guy has changed the broken original input connector with this crap...
    [​IMG]
    I had no idea there is the source of all this trouble. Nothing has showed a sign, current flow was correct, so were values checked by V-meter, no heating downstream to the turntable's board, nothing.
    So today I found at home one of those China made simple plug-in connector,
    [​IMG]
    and voilà, here's the solution to the problem it shouldn't be blown out of proportion at the first place, if I just knew. WOW what a lesson! That fuse holder won't be needed, here is just for a case if something goes wrong.
    Here is the image that shows how current is 15 V on the entrance. Motor runs smoothly and the most important - transformer stays cool, barely warm after one hour!!!
    [​IMG]
    Now just have to drill through the existing hole on the metal chassis to make it wider, as the new female connector does not fit, and I will certainly not going to buy the original, and spend additional 12€ !

    Once again, thank you all who were jumping in with the ideas willing to help! Respect :bowdown:
    Sometimes solutions are so simple that is so hard to find them :bigok:
     
    Last edited: Mar 21, 2017
    ranch 22b likes this.
  7. ralphfcooke

    ralphfcooke New Member

    Messages:
    18
    Be careful when you fit the new connector to the chassis. it looks like one of the connections goes to the outer, metal shell. If this is the case and you fit it without insulation I suspect the problem will come back!

    The input to the turntable is ~16V AC, which is then fed through the rectifier and smoothed via the 1000uF capacitor, BUT, and its a big BUT, the negative side of the DC will very likely be connected to the metal chassis of the turntable.
    If this is indeed the case then you will be shorting out one of the diodes of the bridge, and causing too much current to flow from the transformer. I would recommend that you either get a completely insulated input socket, or drill out the hole and fit a piece of insulating material to allow the socket to be fitted with no risk of a short circuit between the socket and the metal chassis.

    Looking at the socket previously fitted, I think you might be better off reusing it, but check which of the connections is correct, as I suspect this wasn't done properly before.
     
    Jadran likes this.
  8. Jadran

    Jadran Off The Record

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    1,181
    Location:
    Tesla's birthland
    Yes, thank you Ralf. I'm aware of this, it's no rush and I'll be doing it slowly now, when I know what was the problem. Maybe just another isolated female power plug-in that will fit in existing hole will do the trick. If I don't find one maybe I'll go through the wooden base, glue it there and be safe. Drilling the metal is never my favorite option anyway, and can always cover the old hole.

    edit: the problematic one was obviously not new when mounted, and it has two (broken) holes for screws, for which chassis has been additionally drilled. I'm not going to play with this one anymore, it's for the trash bin.
     
    Last edited: Mar 21, 2017
  9. cdk99

    cdk99 Well-Known Member

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    863
    Location:
    SaguaroLand
    Interesting, thank you for keeping at it and sharing the result. I wonder sometimes how many tons of perfectly good audio equipment are scrapped for minor things like connectors or caps.
     
    Jadran likes this.
  10. Tubologic

    Tubologic Well-Known Member

    Messages:
    578
    Good to know you have found the problem at last. A pity that you ruined three transformers in the process...

    Please note that i have already mentioned this possibility in my previous posts #9 and #16:

    " ... Though it may seems obvious, also check the AC power input connector on the pc board for a possible intermittent short due to a mechanical damage, these parts are not of the highest quality and can fail..."

    " ...Repeat the same test as above but with your protection fuse removed. Leave the cable and connector connected to the turntable to exclude any possible short or leakage in the connector ahead of your fuse. (very unlikely but possible)"

    As your protection fuse didn't failed it was obvious to me that the problem was not inside the turntable but ahead of the fuse.
     
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  11. lini

    lini just me...

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    5,129
    Location:
    Munich, Bavaria
    Jadran likes this.
  12. Jadran

    Jadran Off The Record

    Messages:
    1,181
    Location:
    Tesla's birthland
    Yes I know, you did it, and thank you again for that!
    However, there was no other way to actually check how that plug-in is heating up a transformer and has an intermittent short when + was + and - was - showing a correct current at the Voltmeter?! So removing it was the only way, and as I said - an electrician(?) ( the seller's friend) in Germany made that mod just a day before the TT was shipped to me, he did check the thing and I trusted them. Now I see it was just my mistake! He's probably turned the TT on for a minute, saw it's spinning the platter and that was all.
    A big lesson for me - never trust a seller, no matter how sweet talking might sound!
    Nevertheless, I learned much more about Thorens and its electronic with this case, thanks to this and the other forums, where i picked up a lot of informations. With some mods on top (new switchers), and a lot of new components on the board I could easily sell this TT for more money than I paid on that auction. If not to earn much extras, but just to refund what a spend on the new components so far ;)
    Cheers
     
    Last edited: Mar 22, 2017
  13. Jadran

    Jadran Off The Record

    Messages:
    1,181
    Location:
    Tesla's birthland
    Yes Manfred, that's it. It's on the sale for over 12€ (postage incl.) on the ebay. I don't see the price here, but doubt it would be much cheaper!? For example; all three OP AMP chips (Texas inst.) didn't cost me that much!
     
  14. lini

    lini just me...

    Messages:
    5,129
    Location:
    Munich, Bavaria
    Jadran: I can hardly imagine that that jack should be that expensive, unless the postage would make 90 % of those 12 Euro. Otherwise the vendor pobably just likes to make a good buck by selling what actually is a comparatively inexpensive standard part as if it was an expensive special part (as I've already also seen a few vendors of Thorens replacement wall-warts do, offering generic 15 or 16 V(AC) wall-wart types with standard barrel plug (5.0/2.1 or 5.5/2.1 mm), one could elsewhere get for ~ 10 Euro, for at least 30 Euro, without even swapping the regular barrel plug for the actually correct DIN 45323 type plug (available for ~ 1 Euro)).

    Anyway, Buerklin over here offers quite a few of those Roka 520 family DIN 45323 jack variants, but unfortunately apparently not the one you'd need - and those other variants all are between ca. 0.75 and 1.20 Euro. Hence I'd suggest to contact Roka directly, tell 'em about your problem and that you can't find a source for their 520 2551 type and ask for their advice. In addition I'd suggest you to include your postal address with something like "In case you'd rather reply via conventional mail, here's my address:" - because then they'd already have everything they'd need, in case they'd feel inclined to send you one of these jacks for free...

    Greetings from Munich!

    Manfred / lini
     
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  15. Jadran

    Jadran Off The Record

    Messages:
    1,181
    Location:
    Tesla's birthland
    Thank you Manfred for these suggestions! Appreciate it.
    Yes, everything that could be linked to Thorens has a good chance to be overpriced. So is this ''Netzteil-Buchse'' that is not even original! But I tend to understand the sellers and why everything is pricey on eBay, since the fees both PayPal and eBay charge are far from fair trade! But there are always similar options out there too, or I will simply contact Roka, and see if there is a luck. Thanks :beerchug:
     
    Last edited: Mar 23, 2017
  16. scoville

    scoville AK Subscriber Subscriber

    Messages:
    285
    Location:
    The First West Coast
    I've been following your thread with a bit of alarm as this is my daily table, very happy you figured it out and I'm sure you will be rewarded with many years of vinyl bliss! It's not a table for trading out carts, so find your sweet spot, and let it roll!
     
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