Toroidal Transformer Failed In Cambridge DVD Player
Make and Model: Cambridge Audio – Azur 540C
Problem reported: Dead
Preliminary observation: Checked and found that the fuse was blown and the primary winding of the toroidal transformer was open.
Rectification done: Took clear snaps of the connections of the transformer and its measurements. Removed it and tried to get it rewound. Since the cost of rewinding was almost three times more than that of making a new normal transformer, got a new one made matching the output voltages and without the 110V winding in the primary, after obtaining the consent of the customer. The secondary had two outputs. One was 16-0-16 0.5A and another was 0-10V 2A. Also ensured that the size of the transformer did not exceed the limits. Replaced the fuse and connected the transformer without fixing it inside the cabinet and applied power. Found the DVD player working well. Then fixed the Transformer inside the cabinet using tags, for which I had to drill a couple of holes at the bottom. The player was working very well when checked continuously. Satisfaction got added to its collection.
Caution: The tray was so flimsy that if we push it in by hand, it will go out of alignment! So, we should only use its remote or panel controls for ejecting or loading. Once it got misaligned, the player would show error. It is very difficult to put it back in its original track. I do not know whether it was a problem in this set due to wearing out or a design problem!
Here are the pictures:
This article was prepared for you by Parasuraman Subramanian from India. He is 70 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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https://jestineyong.com/dry-solder-caused-no-light-in-mr-light-emergency-light/
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Waleed Rishmawi
June 16, 2020 at 6:05 pm
very interesting to see this kind of transformers in a DVD player. Usually I find them in Amplifiers. thanks for sharing my friend. your articles always have something new and exciting. have a blessed day
Parasuraman S
June 16, 2020 at 9:37 pm
Many thanks dear friend!
JACKY TANG
June 17, 2020 at 3:29 pm
Hi brother, may i know the tranformer primary, the brown n blue colour were 230 voltage, and the black n blue colour cables were 110 voltage? Not the black colour cable was neutral(0 v) , and the blue n brown colour cables were live? Thanks
JACKY TANG
June 17, 2020 at 3:33 pm
This type of dvd player always the platic gear wore out, need to replace it, becos i have done so many this type of dvd repairs before, the cambridge audio always have the tranformer problem due to quality built, recently i just repaired one with tranformer problem..hahaha..
Albert van Bemmelen
June 16, 2020 at 6:29 pm
Good to know that rewinding a transformer is still about 3 times as expensive than buying a new one. So in that case it doesn't really matter that such service does not exist im my country. And I always buy new transformers if need be. Most defect transformers I need though have many different voltages and can't be replaced by common ones that are standard. Also because of their different sizes. Like the ones used in old Philips DVP620VR/00 DVD/VHS combi sets. And even if I could still buy those at a reasonable price it could be a power dissipation design flaw in those smps transformers. Why they go bad and that could make them go bad a second time too?
Paris Azis
June 16, 2020 at 7:32 pm
Hey Albert
Up to now and during my entire professionally active life, I can hardly remember 4 cases of defective smps transformers.
They usually are beyond suspicion during troubleshooting power supplies. I have found all types of other failures with these supplies except the power transformers.
Your statement is very impressive to me.
Lately I am finding, relatively often, shorted output chokes in cheap Chinese designs, which have their coil made of aluminum instead of copper. In fact they usually are totally toasted. Perhaps the coil material is the cause, although there is no proof about it. But, as I remember,this type of failure was unknown 30 years ago.
Even in computer power supplies of high wattage, I have never encountered such a failure, no matter if everything in the primary side was blown out. The smps transformer was always intact.
The only exception about this topic refers to CRT TV horizontal output transformers, especially those working with vacuum tubes and therefore with much higher voltages than their "siblings" working on transistorised circuitry.
Where did you find such failures? It would be good to know that.
Parasuraman S
June 16, 2020 at 9:40 pm
YEs very true!
Albert van Bemmelen
June 16, 2020 at 11:32 pm
I will try to find the schematic on ElektroTanya if I can't find it on my backup dvd's. And I will mail that power supply schematic if that is okay. And another bad power supply with bad transformer was probably in the also Philips HTS5560/12 Bluray Home theater set that failed to supply about 42V DC to the audio amplifier endstage. And you surely remember the time I found a bad smps transformer in a multi-voltage selectable Laptop Power supply after you told me in the commends to just rewind the transformer.
Parasuraman S
June 16, 2020 at 9:39 pm
There are some manufacturing defects which kills the product as it is a mass production. But when you do only one, utmost care is taken and chances of its failure is remote.
Parasuraman S
June 17, 2020 at 2:11 pm
Because of mass production, there will be some percentage of inherent defects which ultimately fail in due course of time. Anyhow, for us, electronic enthusiasts, such 'contribution' from the manufacturers are welcome! (LOL)
Tayo
June 16, 2020 at 7:24 pm
As a aspiring novice hobbyist repairman i have no appreciable experience with fixing transformers. Over here in the United States fixing a transformer is basically not an option. I marvel at videos i see on Youtube of some guys in far off countries unwinding them and fixing them by hand. I have power supplies sitting on my to-do shelf with bad transformers and no place to source new ones. Basically making the device useless unless i get the transformer rewound.
Parasuraman S
June 16, 2020 at 9:41 pm
That is very unfortunate.
Paris Azis
June 17, 2020 at 4:25 pm
Hey Tayo
If you are interested in rewinding yourself your linear transformers, for your hobby or your own satisfaction, try to find my relevant article, here, in this blog. All the necessary data are included therein. You can also modify a blown transformer to suit a given need of yours.
Moreover, switching transformers are much more easier to rewind them provided that you can open their ferrite cores without breaking them. They are easier because they have much less turns than their linear counterparts.
The big pain is to rewind a toroidal transformer by hand. This is real torture! They have many many turns in their primary coil and the total length of the wire must pass through their internal hole once per each turn. If you can do that, you are an extraordinary human being!!
Parasuraman S
June 18, 2020 at 1:28 am
Yes, you have a very valid point there. I have seen SMPS TX failing and had to replace these in many CRT Tvs and a few other devices. But never succeeded in opening a Ferrite Cored Tx as it always broke!
Humberto
June 17, 2020 at 11:02 am
I´ve enjoyed a lot reading how you fixed this DVD Player.
Parasuraman S
June 18, 2020 at 1:15 am
Many thanks!
Paris Azis
June 17, 2020 at 5:12 pm
Hey Parasuraman
You have confused me with these toroidal transformers dear!
Everyone knows that they are more robust than the ordinary laminated transformers and can tolerate much wider variations in the load side or in their primaries.
Is that one the same brand with the one of your previous article, where you put the soft start circuit?
Is there any connection between the two cases? I can hardly believe that these transformers fail so easily!
This one here, for example, faces a load demand of 36V.A. (10V x 2A = 20V.A, plus 32V x 0,5A = 16V.A, making a total of 36V.A).
Obviously a 50V.A power transformer covers fully this demand and I believe that the original you replaced was of that nominal power.
Anyway, if you encounter the same failure once again, please do me the favour and measure the idling (magnetising) current. It would be good to know the percentage of the ratio of the nominal power to its idling power.
And if you are so patient and have the means for that measurement, take a temperature measurement after one hour of idling operation.
In any case, if this last measurement shows more than 50 degrees Celsius, then, for sure, the turns calculation is wrong.
In this case, we call the product a "potato" in my country!
Another crucial thing is (again if you have the patience) to remove the windings and see the colouring of the enameled wire of the primary.
I am saying this because if the primary coil keeps its natural colour, there is a chance that the manufacturer uses an internally installed thermal fuse, which you will find it open.
A have many times repaired such transformers just by bridging the thermal fuse. I was lucky, in these cases, because the fuse was installed at the end of the primary coil. I just had to rewind a new secondary (by hand of course)!
If the fuse is at the beginning of the primary, there are such cases as well, there is nothing you can do about it (by hand work)!
And it seems that many manufacturers use this method, which puts a certain death date to the transformer for the obvious reason that the fuse opens much more easily if it detects the core temperature instead of the windings'one...!! We know that as "programmed obsolescence" as someone of my readers had written in one of my articles...
Just remember my request in your next, always interesting, article!
Parasuraman S
June 18, 2020 at 1:25 am
1) My experience is that the toroidal transformers are failing in may devices that I have handled. Probably the electrical condition here might be one of the reasons. 2) No it is not the same brand. That was an audio Amp and this is different! 3) The power rating has been taken care of 4) I have not checked the Transformer for idling current and the nominal current. Shall do so if it all it comes back with a complaint. 5) Ok. Shall take care of your advice, which is very valuable 6) I am fully aware of such thermal fuses inside the Transformers which are quite common in Philips. There is no such fuse inside this Tx 7) My experience is that if the thermal fuse starts failing, the health of the TX is not good and it is always better to replace it.
Many, many thanks for a detailed feedback with a lot of new ideas. It helps a lot!
Paris Azis
June 22, 2020 at 12:40 pm
Thank you too Parasuraman for your detailed feedback.