Need some help to identify the torroidal tranformer found in my audiolab 8000a amplifier . Transfomer ,"Talema" made in Ireland
1) Part no 9802-P1S2 (talema) .What is the VA value, sec voltage and amp.
2) Existing secondary , three wires ; black, yellow and orange .What color code do they represent?
3) Can I use a 4 wired (2 sec rails transformer for a replacement?
Any information will be most grateful.
1) Part no 9802-P1S2 (talema) .What is the VA value, sec voltage and amp.
2) Existing secondary , three wires ; black, yellow and orange .What color code do they represent?
3) Can I use a 4 wired (2 sec rails transformer for a replacement?
Any information will be most grateful.
Hi,
the 8000a probably had a toroid between ~160VA and ~250VA fitted.
Any dual secondary can be converted to centre tapped.
The diodes should identify positive and negative. The other ends take the AC from the transformer.
The transformer windings in a centre tapped are in series. Measure the resistance of each pair. Two pairs will be almost identical, 0r2 or so, the third pair will be about double ~0r4.
The higher resistance pair exclude the centre tap, so it becomes easy to identify. This wire should be connected to the power zero volts common connection that goes to the centre of the pair of smoothing caps. Have they leaked all over the PCB yet?
If replacing I would suggest that 160VA is too small.
try 200VA to 300VA. Physical size is the most important criteria. It must fit the space available.
I think Talema are still in existence.
the 8000a probably had a toroid between ~160VA and ~250VA fitted.
Any dual secondary can be converted to centre tapped.
The diodes should identify positive and negative. The other ends take the AC from the transformer.
The transformer windings in a centre tapped are in series. Measure the resistance of each pair. Two pairs will be almost identical, 0r2 or so, the third pair will be about double ~0r4.
The higher resistance pair exclude the centre tap, so it becomes easy to identify. This wire should be connected to the power zero volts common connection that goes to the centre of the pair of smoothing caps. Have they leaked all over the PCB yet?
If replacing I would suggest that 160VA is too small.
try 200VA to 300VA. Physical size is the most important criteria. It must fit the space available.
I think Talema are still in existence.
Thanks for the quick response Andrew .I have written to Talema and so far there is no response from them. I did open the bottom cover and there is indeed a layer of brown oil. It comes from the transformer?
The transformer is "kaput" no readings "mvolts" only between the 3 sec wires when AC 220 is switched on. I done a search on the archive and I think Arbi44 from New Zealand has replace similar model with 225ac and duel 30vc sec with some success. I weighed the existing transformer around 2kg. Talema spec on 225Ac is 1.9kg.That also confirm recommendation within the range you recommend. The talema has two models withins this spec 225AC-2x30AC 3.75 amp and 225AC-2x55AC 2.045amp.The power supply AC has 2.5 amp which of these two models do you recommend.I do a quick check on the capacitors and majority are 50V.
My next problem will be to find which of the three existing wires(yellow,black and orange) is a zero reference. The yellow and black welded and disappear into the PCB board the orange is welded into the center of 2 10,000uf 50v capacitors connected within two cap terminals.(No negative marking on capacitors,cannot tell if cap are connected in parallel or in series.) I guess the yellow and black are AC sec going into the rectification diodes. I guess also it doesnot matters if I swasp the so call sec +VAC and -VAC .The rectifications diodes configuration will produce the postiveDC and negative DC anyway.I am really elementary in electronic. Now the orange wire connect to middle pair of 10000 uf cap's terminal,I found in some 8000A models which has duel secondary output has 2 wire(orange and red) connected to these pair of cap.I guess this orange wire should be the zero reference.And a few green wires from this point go the binding post (black) on the terminals for speaker connection. Thanks again for your help and any advice will be grateful.
The transformer is "kaput" no readings "mvolts" only between the 3 sec wires when AC 220 is switched on. I done a search on the archive and I think Arbi44 from New Zealand has replace similar model with 225ac and duel 30vc sec with some success. I weighed the existing transformer around 2kg. Talema spec on 225Ac is 1.9kg.That also confirm recommendation within the range you recommend. The talema has two models withins this spec 225AC-2x30AC 3.75 amp and 225AC-2x55AC 2.045amp.The power supply AC has 2.5 amp which of these two models do you recommend.I do a quick check on the capacitors and majority are 50V.
My next problem will be to find which of the three existing wires(yellow,black and orange) is a zero reference. The yellow and black welded and disappear into the PCB board the orange is welded into the center of 2 10,000uf 50v capacitors connected within two cap terminals.(No negative marking on capacitors,cannot tell if cap are connected in parallel or in series.) I guess the yellow and black are AC sec going into the rectification diodes. I guess also it doesnot matters if I swasp the so call sec +VAC and -VAC .The rectifications diodes configuration will produce the postiveDC and negative DC anyway.I am really elementary in electronic. Now the orange wire connect to middle pair of 10000 uf cap's terminal,I found in some 8000A models which has duel secondary output has 2 wire(orange and red) connected to these pair of cap.I guess this orange wire should be the zero reference.And a few green wires from this point go the binding post (black) on the terminals for speaker connection. Thanks again for your help and any advice will be grateful.
Hi Tank,
the zero volt between the smoothing capacitors is NOT the reference for the signal stages.
Zero volt connects to the transformer centre tap. It then goes to another ground point. This second ground point is, from memory, a star arrangement. This star is the reference.
It should be very easy to follow the PCB traces that connect the transformer centre tap to the two zero volt connections to the smoothing capacitors, then to find the star reference.
That brown stain cannot come from the transformer. It is almost certainly the contents of the capacitors. They are now very old.
Change them for new ones. 10mF 63V will do.
It might be worth trying 15mF 63V. I think if you can get them to fit the space, you may get slightly improved performance. Some of the higher quality versions may deliver better performance but they tend to be slightly larger so the highest value that will fit the space may be 10mF or even 8mF, but this is really too small for good bass.
The 55Vac transformer is NOT suitable.
You MUST match the transformer voltage. Use only 30Vac.
The power rating of the transformer has a bit of flexibility. Any manufacturer's 225VA (the power rating) sounds about right. But 250VA or 300VA would do just as well and maybe better IF THEY CAN FIT THE SPACE. Some sell specific AUDIO transformers, Again they perform well, but always seem to cost a lot more for the few bits and bobs they add on.
When you get your transformer you can measure the secondary voltage. It will measure more than the rated voltage. The output from the transformer depends on the mains input voltage AND the turns ratio. This measured AC voltage is the open circuit voltage. The rated voltage for your transformer will be about 6% less and takes account of the voltage when delivering rated current into a resistor AND when driven from the correct mains input voltage. Expect to get about 31.8Vac +-6% from the secondaries.
the zero volt between the smoothing capacitors is NOT the reference for the signal stages.
Zero volt connects to the transformer centre tap. It then goes to another ground point. This second ground point is, from memory, a star arrangement. This star is the reference.
It should be very easy to follow the PCB traces that connect the transformer centre tap to the two zero volt connections to the smoothing capacitors, then to find the star reference.
That brown stain cannot come from the transformer. It is almost certainly the contents of the capacitors. They are now very old.
Change them for new ones. 10mF 63V will do.
It might be worth trying 15mF 63V. I think if you can get them to fit the space, you may get slightly improved performance. Some of the higher quality versions may deliver better performance but they tend to be slightly larger so the highest value that will fit the space may be 10mF or even 8mF, but this is really too small for good bass.
The 55Vac transformer is NOT suitable.
You MUST match the transformer voltage. Use only 30Vac.
The power rating of the transformer has a bit of flexibility. Any manufacturer's 225VA (the power rating) sounds about right. But 250VA or 300VA would do just as well and maybe better IF THEY CAN FIT THE SPACE. Some sell specific AUDIO transformers, Again they perform well, but always seem to cost a lot more for the few bits and bobs they add on.
When you get your transformer you can measure the secondary voltage. It will measure more than the rated voltage. The output from the transformer depends on the mains input voltage AND the turns ratio. This measured AC voltage is the open circuit voltage. The rated voltage for your transformer will be about 6% less and takes account of the voltage when delivering rated current into a resistor AND when driven from the correct mains input voltage. Expect to get about 31.8Vac +-6% from the secondaries.
Thanks for your reply. The new tranformer I need to order will have to fit into the tight space of the 8000A housing. I need to do some work to source around for right physical size and VAC value.The capacitors I need will also need to fit into the tight space . Previously seen some member replacing them with Nichicon 63V 15000 uf and that should be my first option for me now that you mention that it can enhance performance/bass.
Now I got the spec of the torroidal tranformer sorted out, not sure how I can replace the existing capacitor one for one as the existing has no -ve marking on the outside. I really lost you in the beginning on "star reference". Are you refering to ground/earth?Thanks for your patience.
Now I got the spec of the torroidal tranformer sorted out, not sure how I can replace the existing capacitor one for one as the existing has no -ve marking on the outside. I really lost you in the beginning on "star reference". Are you refering to ground/earth?Thanks for your patience.
Hi,
have the smoothing caps got a wide painted stripe down one side?
That stripe indicates the negative side. The stripe often has - marks in it to confirm negative (-ve).
The two stripes will both be towards one side of the case.
I seem to recall that the pair of caps lie side by side above the PCB. The four tags have short drop links down to the PCB.
The order of the tags will be +ve, -ve, +ve, -ve.
The two middle ones are the power zero volts. There should be a trace from zero volts going back to the transformer centre tap.
I cannot recall whether the caps have +ve towards the back or front of the chassis.
Hope this helps.
Is there a pic on the Forum? that may solve a problem or two.
have the smoothing caps got a wide painted stripe down one side?
That stripe indicates the negative side. The stripe often has - marks in it to confirm negative (-ve).
The two stripes will both be towards one side of the case.
I seem to recall that the pair of caps lie side by side above the PCB. The four tags have short drop links down to the PCB.
The order of the tags will be +ve, -ve, +ve, -ve.
The two middle ones are the power zero volts. There should be a trace from zero volts going back to the transformer centre tap.
I cannot recall whether the caps have +ve towards the back or front of the chassis.
Hope this helps.
Is there a pic on the Forum? that may solve a problem or two.
hi Andrew, I took out one side of the ELNA cap last night and it indeed has a black dot marking hidened on one of the terminal and the side label say it is the negative. The caps are arranged in series with center tapped sec feeding them.So I have all the items sorted out and thanks to your on line response. I will be out of West Africa in a week time to Singapore on routine rotation .And when I get back I will refurbish the A8000 vintage. Bye2
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