Toroidal Transformer - Repair possible ?

[[email protected]]

Hi,

I have a 400w amplifier with a faulty mains transformer. ...or at
least I'm pretty sure it's faulty !

It's a split primary (115/230v) toroid with the secondaries at 21v,
44v and 51v. There is some scorching near the entry point of one of
the primaries, and I get 15.3k ohms across one primary winding and
just 1 single ohm across the other. I presume this means it's
faulty ?

(please excuse my ignorance, I'm pretty certain it's screwed, I just
wanted a confirmation of my diagnosis ! )

So.... presuming there's a short in there somewhere, is it possible to
get it repaired ? ...or would that be financial insanity ?

Lastly, failing the repair option, does this look like a regular 'off
the shelf' part (i.e. are these secondaries standard) ?

If it helps, it's made by Toroid International Ltd., Part
No:-TI-65801E. I can't say what VA rating it is.

Many thanks in advance,

Cheers,

Kev.

 

[Jerry G.]

The company in the link below are transformer rebuilders. You would have to
call them to see if they will do a toroidal type transformer. This requires
a specific type of winding system to do this.

http://www.wardtransformer.com/rebuilt.htm

--

Jerry G. GLG Technologies GLG
==========================


Hi,

I have a 400w amplifier with a faulty mains transformer. ...or at
least I'm pretty sure it's faulty !

It's a split primary (115/230v) toroid with the secondaries at 21v,
44v and 51v. There is some scorching near the entry point of one of
the primaries, and I get 15.3k ohms across one primary winding and
just 1 single ohm across the other. I presume this means it's
faulty ?

(please excuse my ignorance, I'm pretty certain it's screwed, I just
wanted a confirmation of my diagnosis ! )

So.... presuming there's a short in there somewhere, is it possible to
get it repaired ? ...or would that be financial insanity ?

Lastly, failing the repair option, does this look like a regular 'off
the shelf' part (i.e. are these secondaries standard) ?

If it helps, it's made by Toroid International Ltd., Part
No:-TI-65801E. I can't say what VA rating it is.

Many thanks in advance,

Cheers,

Kev.

 

[James Sweet]

Hi,

I have a 400w amplifier with a faulty mains transformer. ...or at
least I'm pretty sure it's faulty !

It's a split primary (115/230v) toroid with the secondaries at 21v,
44v and 51v. There is some scorching near the entry point of one of
the primaries, and I get 15.3k ohms across one primary winding and
just 1 single ohm across the other. I presume this means it's
faulty ?

(please excuse my ignorance, I'm pretty certain it's screwed, I just
wanted a confirmation of my diagnosis ! )

So.... presuming there's a short in there somewhere, is it possible to
get it repaired ? ...or would that be financial insanity ?

Lastly, failing the repair option, does this look like a regular 'off
the shelf' part (i.e. are these secondaries standard) ?

If it helps, it's made by Toroid International Ltd., Part
No:-TI-65801E. I can't say what VA rating it is.

Many thanks in advance,

Cheers,

Kev.

Sounds to me like it's bad, though it wouldn't hurt to do some careful
exploratory surgury to see if the shorted winding is right at the surface,
might be something you can fix yourself. Failing that, have you tried
contacting the manufacture of the amp? Be prepared for sticker shock but it
doesn't hurt to check.

 

[Anon]

Sounds to me like it's bad, though it wouldn't hurt to do some careful

exploratory surgury to see if the shorted winding is right at the surface,
might be something you can fix yourself. Failing that, have you tried
contacting the manufacture of the amp? Be prepared for sticker shock but it
doesn't hurt to check.

I've been trying to do exactly that, but the damn thing has the centre
(about 1 3/4" dia) filled with potting compound, which isn't gonna
some out without some serious, and potentially destructive, drilling.
:-( So frustrating, as the small bit of scorching on the tape is just
where one of the primary wires enter, suggesting that the fault *is*
near the outside.

 

[[email protected]]

I've been trying to do exactly that, but the damn thing has the centre

(about 1 3/4" dia) filled with potting compound, which isn't gonna
some out without some serious, and potentially destructive, drilling.
:-( So frustrating, as the small bit of scorching on the tape is just
where one of the primary wires enter, suggesting that the fault *is*
near the outside.

...sorry, that last post *was* from me - I haven't woke up yet ;-) ,
For some reason I had my software set to show '[email protected]' instead
of my proper address.

 

[Frithiof Andreas Jensen]

It's a split primary (115/230v) toroid with the secondaries at 21v,
44v and 51v. There is some scorching near the entry point of one of
the primaries, and I get 15.3k ohms across one primary winding and
just 1 single ohm across the other. I presume this means it's
faulty ?

The one Ohm is likely to be the good winding, the 15.3 kOhm is likely to be
Open and thus broken.

So.... presuming there's a short in there somewhere, is it possible to
get it repaired ? ...or would that be financial insanity ?

Usually not worth it if an off-the-shelf device can be had; but IF the
primary is the outer winding PERHAPS you can get someone to rewind it (for
the price of a Cornea or maybe a left Kidney ..;-) There are shops that do
just that, if you ask them for a quote it might be reasonable enough,
actually.

Lastly, failing the repair option, does this look like a regular 'off
the shelf' part (i.e. are these secondaries standard) ?

No - Usually the secondaries are duplicate windings of the same voltage,
f.ex. 2 x 44 V. This "looks" custom.

If it helps, it's made by Toroid International Ltd., Part
No:-TI-65801E. I can't say what VA rating it is.

Does " Toroid International Ltd" have datasheets or do they sell spares?

Failing everything, you can get one of the afforementioned winding shops to
make a new one - it will cost about 3-4 times the price of a factory unit in
the same power range - but they can work out the VA rating based on the old
design. For a quick guess, if you should run into a compatible device in
some manufaturers catalogue, the weight of the thing is a good guide:
Transformers with the same VA rating weighs about the same.

 

[[email protected]]

Well, I took the plunge and started to dismantle it. It's beyond
repair as the primary coils are on the inside - and I've taken the
secondaries off it. I've contacted the manufacturer and they can't
supply a replacement, but they are emailing me the specs to see if I
can get one made up. But I think that's a no-go as the cost would be
uneconomical compared to the value of the amp. :-(

Oh well, that's a lesson in buying faulty gear off Ebay !

 

[James Sweet]

Well, I took the plunge and started to dismantle it. It's beyond
repair as the primary coils are on the inside - and I've taken the
secondaries off it. I've contacted the manufacturer and they can't
supply a replacement, but they are emailing me the specs to see if I
can get one made up. But I think that's a no-go as the cost would be
uneconomical compared to the value of the amp. :-(

Oh well, that's a lesson in buying faulty gear off Ebay !

Maybe you can find a surplus transformer that'll work? Amps usually aren't
super critical, just find something that'll get you similar voltages at
adaquate current. You can use multiple smaller transformers in
series/parallel if nessesary.

 

[mike]

Hi,

I have a 400w amplifier with a faulty mains transformer. ...or at
least I'm pretty sure it's faulty !

It's a split primary (115/230v) toroid with the secondaries at 21v,
44v and 51v. There is some scorching near the entry point of one of
the primaries, and I get 15.3k ohms across one primary winding and
just 1 single ohm across the other. I presume this means it's
faulty ?

(please excuse my ignorance, I'm pretty certain it's screwed, I just
wanted a confirmation of my diagnosis ! )

So.... presuming there's a short in there somewhere, is it possible to
get it repaired ? ...or would that be financial insanity ?

Lastly, failing the repair option, does this look like a regular 'off
the shelf' part (i.e. are these secondaries standard) ?

If it helps, it's made by Toroid International Ltd., Part
No:-TI-65801E. I can't say what VA rating it is.

Many thanks in advance,

Cheers,

Kev.

Sometimes a transformer has a fusible/thermal overtemp link
in series with the primary and thermally coupled inside the
transformer. If you can find it, that may be the cause.
Just fixed a drill charger with that problem.

Failing that, I'd figger out which secondary winding has the most current
and parallel it with another transformer of the same voltage
rated for the TOTAL power of the system. Assumes the faulty primary
doesn't overheat when you do that.
mike

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[John]

x-no-archive: yes

Well, I took the plunge and started to dismantle it. It's beyond
repair as the primary coils are on the inside - and I've taken the
secondaries off it. I've contacted the manufacturer and they can't
supply a replacement, but they are emailing me the specs to see if I
can get one made up. But I think that's a no-go as the cost would be
uneconomical compared to the value of the amp. :-(

Oh well, that's a lesson in buying faulty gear off Ebay !

If you really need to you can rewind it yourself. You've already removed
the secondary windings (and kept a record of the number of turns). Now do
the same with the primary. You may be lucky and find the problem in the
outer primary. Rewinding will take time and effort to not kink the wire as
you pass it through the core but if you really need to re-wind it yourself
by hand, you can. Done it several times.

 

[[email protected]]

If you really need to you can rewind it yourself. You've already removed
the secondary windings (and kept a record of the number of turns). Now do
the same with the primary. You may be lucky and find the problem in the
outer primary. Rewinding will take time and effort to not kink the wire as
you pass it through the core but if you really need to re-wind it yourself
by hand, you can. Done it several times.

Hmmm... As masochistic as it may sound, I rather like the idea of
rewinding it by hand - sort of an " I did this ! " thing

The problem I have is that I have no idea of the number of turns on
any of the windings, as I just demolished it All I have left is a
bare toroid former

HOWEVER ! - I *do* have the original manufacturers data sheet which
gives details on voltages and currents etc - but oddly, not the number
of turns. I've copied it below (use Courier or other fixed pitch font
to view).

Would it be possible to work out the number of turns from this ?
The guy at the manufacturers said this would be all that a rewinder
would need to rebuild it.

I'd have to locate the tape stuff they wrapped around the toroid core,
and between the windings etc, but if I get the right gauge wire, is it
possible to rewind this thing by hand ? ....and get it right ?

Cheers,

Kev.


+------------------------------------------------------------------+
¦ Transformer TI-65801E Issue:2 Date 06/08/99 ¦
+------------------------------------------------------------------¦
¦ PRIMARY SECONDARY ¦
¦ ¦
¦ Whi 220mm 18AWG Ora 340mm 20AWG 51.1V No Load ¦
¦ 120 V o-----------------+ +-----------------o 49.0V 0.10A ¦
¦ ¦ ¦ ¦
¦ P1 ¦ ¦ S1 ¦
¦ Blk 220mm 18AWG ¦ ¦ Blu 340mm 16AWG 44.5V No Load ¦
¦ 0 V o-----------------+ ¦-----------------o 42.6V 3.5A ¦
¦ ¦ ¦
¦ ¦ S2 ¦
¦ Red 220mm 18AWG ¦ Vio 340mm 20AWG 21.0V No Load ¦
¦ 120 V o-----------------+ ¦-----------------o 20.0V 0.50A ¦
¦ ¦ ¦ ¦
¦ P2 ¦ ¦ S3 ¦
¦ Gry 220mm 18AWG ¦ ¦ Yel 370mm 16AWG ¦
¦ 0 V o-----------------+ ¦-----------------o 0 V ¦
¦ ¦ ¦
¦ ¦ S4 ¦
¦ Yel 550mm 24AWG ¦ Vio 340mm 20AWG ¦
¦ o-----------------+ ¦-----------------o 20.0V 0.50A ¦
¦ S01 130 deg C¦ ¦ 21.0V No Load ¦
¦ ¦ ¦ S5 ¦
¦ Yel 550mm 24AWG ¦ ¦ Blu 340mm 16AWG ¦
¦ o-----------------+ ¦-----------------o 42.6V 3.5A ¦
¦ ¦ 44.4V No Load ¦
¦ ¦ S6 ¦
¦ ¦ Ora 340mm 20AWG ¦
¦ +-----------------o 49.0V O.10A ¦
¦ 51.1V No Load ¦
¦ ¦
¦ All leads from UL3266 cable. ¦
¦ ¦
¦ S1/S6 wound with 0.95 mm wire ¦
¦ ¦
+------------------------------------------------------------------¦
¦ Nominal dimensions/weight: Mounting method: ¦
¦ (information only) ¦
¦ diameter 125 mm 1) Center filled with foam pad, ¦
¦ height 54 mm 2) bottom recess (18/35/6 mm), M6 ¦
¦ weight 3.0 kg insert and extra 120mm rubber pad ¦
¦ mounting excluded ¦
¦ 1) Maximum 128 mm, 90 deg to leads ¦
¦ Pri/Sec leads: 180° 2) Maximum 56 mm ¦
+------------------------------------------------------------------¦
¦ Comments: ¦
¦ 1. Primary resistance: 2x1.8 ohm ¦
¦ 2. Secondary resistance: 2x0.16 ohm (S2/S5), 2x0.12 ohm (S3/S4), ¦
¦ 2x0.11 ohm (S1/S6) ¦
¦ 3. Calculated temperature rise at 300VA load: 34 deg C ¦
¦ 4. Including perpheral and top/bottom magnetic shield ¦
+------------------------------------------------------------------¦
¦ Label: + + ¦
¦ Toroid International Ltd ¦
¦ ¦
¦ P/N: TI-65801E ¦
¦ Prosound: TFRFE31, Iss 6 ¦
¦ ¦
¦ + +batch code + ¦
+------------------------------------------------------------------+

 

[John]

Hmmm... As masochistic as it may sound, I rather like the idea of
rewinding it by hand - sort of an " I did this ! " thing

The problem I have is that I have no idea of the number of turns on
any of the windings, as I just demolished it All I have left is a
bare toroid former

HOWEVER ! - I *do* have the original manufacturers data sheet which
gives details on voltages and currents etc - but oddly, not the number
of turns. I've copied it below (use Courier or other fixed pitch font
to view).

Would it be possible to work out the number of turns from this ?
The guy at the manufacturers said this would be all that a rewinder
would need to rebuild it.

I'd have to locate the tape stuff they wrapped around the toroid core,
and between the windings etc, but if I get the right gauge wire, is it
possible to rewind this thing by hand ? ....and get it right ?

Cheers,

Kev.


+------------------------------------------------------------------+
¦ Transformer TI-65801E Issue:2 Date 06/08/99 ¦
+------------------------------------------------------------------¦
¦ PRIMARY SECONDARY ¦
¦ ¦
¦ Whi 220mm 18AWG Ora 340mm 20AWG 51.1V No Load ¦
¦ 120 V o-----------------+ +-----------------o 49.0V 0.10A ¦
¦ ¦ ¦ ¦
¦ P1 ¦ ¦ S1 ¦
¦ Blk 220mm 18AWG ¦ ¦ Blu 340mm 16AWG 44.5V No Load ¦
¦ 0 V o-----------------+ ¦-----------------o 42.6V 3.5A ¦
¦ ¦ ¦
¦ ¦ S2 ¦
¦ Red 220mm 18AWG ¦ Vio 340mm 20AWG 21.0V No Load ¦
¦ 120 V o-----------------+ ¦-----------------o 20.0V 0.50A ¦
¦ ¦ ¦ ¦
¦ P2 ¦ ¦ S3 ¦
¦ Gry 220mm 18AWG ¦ ¦ Yel 370mm 16AWG ¦
¦ 0 V o-----------------+ ¦-----------------o 0 V ¦
¦ ¦ ¦
¦ ¦ S4 ¦
¦ Yel 550mm 24AWG ¦ Vio 340mm 20AWG ¦
¦ o-----------------+ ¦-----------------o 20.0V 0.50A ¦
¦ S01 130 deg C¦ ¦ 21.0V No Load ¦
¦ ¦ ¦ S5 ¦
¦ Yel 550mm 24AWG ¦ ¦ Blu 340mm 16AWG ¦
¦ o-----------------+ ¦-----------------o 42.6V 3.5A ¦
¦ ¦ 44.4V No Load ¦
¦ ¦ S6 ¦
¦ ¦ Ora 340mm 20AWG ¦
¦ +-----------------o 49.0V O.10A ¦
¦ 51.1V No Load ¦
¦ ¦
¦ All leads from UL3266 cable. ¦
¦ ¦
¦ S1/S6 wound with 0.95 mm wire ¦
¦ ¦
+------------------------------------------------------------------¦
¦ Nominal dimensions/weight: Mounting method: ¦
¦ (information only) ¦
¦ diameter 125 mm 1) Center filled with foam pad, ¦
¦ height 54 mm 2) bottom recess (18/35/6 mm), M6 ¦
¦ weight 3.0 kg insert and extra 120mm rubber pad ¦
¦ mounting excluded ¦
¦ 1) Maximum 128 mm, 90 deg to leads ¦
¦ Pri/Sec leads: 180° 2) Maximum 56 mm ¦
+------------------------------------------------------------------¦
¦ Comments: ¦
¦ 1. Primary resistance: 2x1.8 ohm ¦
¦ 2. Secondary resistance: 2x0.16 ohm (S2/S5), 2x0.12 ohm (S3/S4), ¦
¦ 2x0.11 ohm (S1/S6) ¦
¦ 3. Calculated temperature rise at 300VA load: 34 deg C ¦
¦ 4. Including perpheral and top/bottom magnetic shield ¦
+------------------------------------------------------------------¦
¦ Label: + + ¦
¦ Toroid International Ltd ¦
¦ ¦
¦ P/N: TI-65801E ¦
¦ Prosound: TFRFE31, Iss 6 ¦
¦ ¦
¦ + +batch code + ¦
+------------------------------------------------------------------+

You can rewind it. Some things you will need to consider are:
Keep original 2 x 0-120V windings or just 1
What inductive reactance the primary winding should have at 60 Hz and then
what primary inductance will be. You need to have sufficient inductance on
the primary side so that the no load primary current is kept low. (low
milliamps) If you have too small a primary inductance your no load primary
current will be very high... bang! Too higher primary inductance and your
load regulation will suffer. Do a Google search on Magnetizing Current.

Once you determine primary inductance you need to determine how many turns
this will need on your particular core. If you don't know its AL value, you
can wind say 10 turns on the core, measure the inductance then calculate the
required number of turns needed to achieve you inductance.

Calculate the required turns ratio and required secondary turns needed to
achieve you secondary voltages.

What wire diameter primary and secondary windings should have.

It makes the whole thing a lot simpler, if you note the number of turns of
each of the windings of the transformer as you strip it.

By the way, as you stripped the transformer, what was wrong with it ?

 

[H. Dziardziel]

snip

If it's mangled I would work backwards from the wire size,
primary resistance and an estimated coil-core area.. Wind test
coils for say 24V and 6V, run unloaded, and loaded. Toroidals
don't need much coil winding. Good luck

 

[[email protected]]

You can rewind it. Some things you will need to consider are:

<snip>

Ah. I hadn't figured on there being aspects like inductance and stuff
involved here. Not knowing much about transformers, or inductance for
that matter, I had figured that it was a simple case of turns ratios.

By the way, as you stripped the transformer, what was wrong with it ?

There was a short in the primary windings - there were two layers of
primaries (presumeably the two 120v windings, one on top of the other
?), and a bit of burnt carbon (on the innermost layer of all !) told
me it was done for. Unfortunately, I damaged the secondary windings
whist drilling out the resin plug in the centre. At that point I knew
that I now had damaged primary AND secondary windings and thought
there was no way on earth it could be repaired, so I just ripped it to
bits. (not counting as I went !).

The manufacturer told me that this data sheet would be sufficient to
take to a rewinder and get it rebuilt... so how would they manage it
without this data (as it's not on the data sheet)?

Many thanks,

Kev.

 

[John]

<snip>

Ah. I hadn't figured on there being aspects like inductance and stuff
involved here. Not knowing much about transformers, or inductance for
that matter, I had figured that it was a simple case of turns ratios.


There was a short in the primary windings - there were two layers of
primaries (presumeably the two 120v windings, one on top of the other
?), and a bit of burnt carbon (on the innermost layer of all !) told
me it was done for. Unfortunately, I damaged the secondary windings
whist drilling out the resin plug in the centre. At that point I knew
that I now had damaged primary AND secondary windings and thought
there was no way on earth it could be repaired, so I just ripped it to
bits. (not counting as I went !).

The manufacturer told me that this data sheet would be sufficient to
take to a rewinder and get it rebuilt... so how would they manage it
without this data (as it's not on the data sheet)?

Many thanks,
Kev.

A transformer manufacturer probably wouldn't use your stripped core. They'd
use a new one of roughly (or exactly) the same size which they new the
specification for. From their manufacturing experience they would know that
for example for a single 120V 60 Hz primary, an inductance of say 17 Henrys
on a particular core would have a no load primary current of so many
milliamps (say 20 mA) and that to achieve that inductance would need so many
turns. Once they know primary turns they calculate secondary turns for the
required voltage. Then wire size for the required current. All easy stuff
for a transformer manufacturer.