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Specs needed on Philips LX700/21S

 
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John Bennett
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PostPosted: Tue Jul 15, 2008 12:29 pm    Post subject: Specs needed on Philips LX700/21S Reply with quote

Hi. I have a Philips LX700/21S with a dead transformer - part T902 on the drawings. This part is no longer available and I need to know the voltage and current specs for the 2 secondary windings - or at least the voltage - so that I can look for a substitute. If anyone has this info or has access to this model to measure the voltage, that would be greatly appreciated. Thanks, John
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stijnsg



Joined: 27 Mar 2009
Posts: 13

PostPosted: Sat Nov 07, 2009 4:07 am    Post subject: Re: Specs needed on Philips LX700/21S Reply with quote

John Bennett wrote:
Hi. I have a Philips LX700/21S with a dead transformer - part T902 on the drawings. This part is no longer available and I need to know the voltage and current specs for the 2 secondary windings - or at least the voltage - so that I can look for a substitute.


Hi John,

I have just encountered the same problem. Did you ever manage to find out what the specs. of that transformer are? Thanks.

Regards,
stijnsg
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stijnsg



Joined: 27 Mar 2009
Posts: 13

PostPosted: Sat Nov 07, 2009 12:13 pm    Post subject: Reply with quote

Forgot to mention the following:

*the Philips part number (12 NC code) of this transformer: 9965 000 17391
*I noticed that my transformer had a blown thermal fuse. To get access to this fuse, you will have to desolder the transformer from the printed circuit board and cut away (at the bottom of the transformer) 1 sheet of the blue insulation tape that covers the windings. Just measure the resistance across the thermal fuse. In my case it was open circuited. In case I can not get hold of the transformer itself, I could try to find a thermal fuse with identical spec: Tf=130 C (Celsius), a M33 type (radial).

Still I am hoping anyone could let me know the spec. of the transformer. Thanks.

Regards,
stijnsg
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sat Nov 07, 2009 8:44 pm    Post subject: Reply with quote

stijnsg wrote:
Forgot to mention the following:

*the Philips part number (12 NC code) of this transformer: 9965 000 17391
*I noticed that my transformer had a blown thermal fuse. To get access to this fuse, you will have to desolder the transformer from the printed circuit board and cut away (at the bottom of the transformer) 1 sheet of the blue insulation tape that covers the windings. Just measure the resistance across the thermal fuse. In my case it was open circuited. In case I can not get hold of the transformer itself, I could try to find a thermal fuse with identical spec: Tf=130 C (Celsius), a M33 type (radial).

Still I am hoping anyone could let me know the spec. of the transformer. Thanks.

Regards,
stijnsg


I used to come across many similar situations with open primary on a transformer caused by an internal thermal fuse. If the windings are not damaged/overheated, it is a safe bet that a replacement thermal fuse will be sufficient. On many occasions, the opening of the thermal fuse may be due to a surge in the primary current or over-driving the circuit that supplies it. OR simply an under rated design issue. For example, on a certain Denon receiver, it was a very common problem where it would open the internal thermal fuse simply by playing the unit at high volume for a short period of time.
Provided you have the technical ability as you are working around hazardous input voltage you can try this;
Remove the transformer from the circuit, temporarily replace the thermal protector(depending on the design,some easy, some very difficult or even impossible to get to) with a 2~3 amp inline fuse and apply the primary AC with a test cord. If there is no further damage, while fuse should remain intact, there should be no warming of the windings and for reference you can measure the secondaries. There is also a reference of EI-35 for the transformer in the parts list which I think was manufactured by Sumida.
I am not familiar with the specific unit but In looking at the schematic, it appears that T902 is used to provide a dual reference for some sort of a display and a 12 volt supply which also supplies relay coil RL901. If all else fails, a replacement should not be too difficult to find of course depending on what part of the world you are.

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stijnsg



Joined: 27 Mar 2009
Posts: 13

PostPosted: Sun Nov 08, 2009 5:24 am    Post subject: Reply with quote

[quote="vtech]
There is also a reference of EI-35 for the transformer in the parts list which I think was manufactured by Sumida.
[quote]

Hi vtech,
Good to see that you are still active on this forum. We “met” a while ago when I was repairing my Philips CV/VCD changer which has been working fine ever since.
I noticed the following markings on the transformer’s insulation tape:
*1st line: TTB115331-0020
*2nd line: TD21188FO TENPAO
*3rd line: 0423

From this I conclude that Tenpao is the manufacturer. They have an office in Hong Kong. Their website unfortunately does not provide much help.

I have measured the resistance across the 2 pairs of secondary terminals and have found their resistance not to be equal. From this I conclude that the output voltages at the secondary are probably not intended to be equal either and as such it could very well be a custom designed part by Tenpao for Philips. I will contact Tenpao and see if they are able (and willing) to help me.

The thermal fuse has the following markings:
*1st line: F and a sort of brand symbol
*2nd line: M33
*3rd line: Tf 130 degrees C
*4th line: 030

I do not know the brand name but was able to find this information: http://shop.thiim.com/datasheets/L-MTH-S3M-TS.pdf

On page 2 you can find M33 being listed under “MTM” which (top of page 2) is a 1 A thermal fuse.
Question to vetch: 1 A seems a bit on the low side to me. I am tempted to replace it with a 3 A fuse (with a Tf of 130 degrees C). In my opinion this does not impose a safety risk. Would you agree?

So I have 2 options:
1) Try to get hold of a spare part from Tenpao (or get their data sheet and find an equivalent)
2) Replace the thermal fuse; this seems to be the easiest way forward.

I look forward to hearing from you, vetch.

Regards,
stijnsg
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vtech



Joined: 08 May 2006
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PostPosted: Sun Nov 08, 2009 6:19 am    Post subject: Reply with quote

The EI-35 number is listed in the parts which came up on a search to Sumida Of course Tenpao is what you have.
Either way, I don't see any safety issue as the unit is already fused before with a 3.15 A. While 1 A may be a bit low, a 3A cuttoff should be fine.
Remember with thermal cutoffs, the degree is the most critical factor but in this case there should not be any safety issue as long as you do not exceed the main fuse rating.
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stijnsg



Joined: 27 Mar 2009
Posts: 13

PostPosted: Sun Nov 08, 2009 6:42 am    Post subject: Reply with quote

vtech wrote:
Remember with thermal cutoffs, the degree is the most critical factor but in this case there should not be any safety issue as long as you do not exceed the main fuse rating.


Precisely. Hence my thinking that "upgrading" it from the original 1A to a 3A whilst respecting the specified Tf of 130 degrees C is a valid option. Thanks for the swift reply, vtech! Will let you and other forum readers know how it went once I have a new fuse fitted.

One last question: the original fuse was a one-time fuse. I am tempted to fit a (automatic) resettable fuse. Have you got experience with those? Or would you even advise against it?

Regards,
stijnsg
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sun Nov 08, 2009 3:29 pm    Post subject: Reply with quote

I am sure there is nothing wrong with resettable fuses. It is just I have not used one as a permanent replacement especially when fuses are cheaper and a piece of equipment is going back to an average customer.

As a rule of thumb, unless it is your own equipment, it is not advisable to change a fuse to a resettable.
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stijnsg



Joined: 27 Mar 2009
Posts: 13

PostPosted: Tue Nov 10, 2009 11:16 am    Post subject: Reply with quote

Today I replaced the broken fuse with a 130 degrees C/3 A fuse.

For a small transformer as in the case of LX700/21S, you need to have a bit of patience and steady hands. I had initially one of the transformer winding wires broken but managed to get that too fixed: just had to strip some of the insulation tape to get access to more of that winding wire.

I solder the transformer back in and the amplifier is working as it was before.

Thanks for all the kind advice, vtech!
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vtech



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PostPosted: Wed Nov 11, 2009 2:45 am    Post subject: Reply with quote

Very Happy Your welcome
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