Dear,
My AUDIOLAB 8000C preamp burns its input fuse ( T1A 5x20mm ).
Because its transformer ( a Nuvotem Teo ) has its primary shorted.
Alas, I could not find the diagram for the 8000C.
So, impossible for me to know the characteristics of its transformer.
And especially the voltage at its secondary output.
In order to chise a new trasfo
Hence my question...
If One of You had :
- this diagram with this voltage value ?
- or knew these voltages ?
And if he agrees to tell me,
I would be infinitely grateful to him !!
My greetings from France,
Raymond
My AUDIOLAB 8000C preamp burns its input fuse ( T1A 5x20mm ).
Because its transformer ( a Nuvotem Teo ) has its primary shorted.
Alas, I could not find the diagram for the 8000C.
So, impossible for me to know the characteristics of its transformer.
And especially the voltage at its secondary output.
In order to chise a new trasfo
Hence my question...
If One of You had :
- this diagram with this voltage value ?
- or knew these voltages ?
And if he agrees to tell me,
I would be infinitely grateful to him !!
My greetings from France,
Raymond
Attachments
This one is not easy.
From what I know there are no complete service manuals for this preamp (and other gear from Audiolab) but there may be a way around it if you know some basic electronics.
From what I seen in other pictures the relay (mute?) near the power supply rectifier/regulator is 24V (DC?) so I would guess a transformer secondary of 18Vac and since Talema "code"P2S2 translates to 2 primaries (2 x 115V) and 2 secondaries (18/0/18/0) and I think around 50VA (check marking on the back of unit).
Just one stupid question is the 1Amp fuse before or after the transformer ?
Wish you good luck.
From what I know there are no complete service manuals for this preamp (and other gear from Audiolab) but there may be a way around it if you know some basic electronics.
From what I seen in other pictures the relay (mute?) near the power supply rectifier/regulator is 24V (DC?) so I would guess a transformer secondary of 18Vac and since Talema "code"P2S2 translates to 2 primaries (2 x 115V) and 2 secondaries (18/0/18/0) and I think around 50VA (check marking on the back of unit).
Just one stupid question is the 1Amp fuse before or after the transformer ?
Wish you good luck.
Yes, and check the transformer VA rating by comparing the core with other brands.
Don't undersize it.
In the 8000A, the supply voltages are +30V/0V for line and MM, and +10V/0V for MC.
(No negative supply voltages.)
Here is the audio circuit schematic for the 8000C.
Don't undersize it.
In the 8000A, the supply voltages are +30V/0V for line and MM, and +10V/0V for MC.
(No negative supply voltages.)
Here is the audio circuit schematic for the 8000C.
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Please don't just get a new transformer. The chance of a Talema burning trough the primary, just for fun is very, very low.
In most cases a rectifier and/ or a capacitor are the primary cause.
First disconect the transformer from the unit and check it all allone, for Ohms on primary and secondary side. Best remove it from the chassis.
Then post again.
The 18-0-18-0 Volt, 50 VA guess seems right to me. a usual value for pre-amps. You don't need to buy exactly the same, so a 240V version may be simpler to get than 120-120V.
In most cases a rectifier and/ or a capacitor are the primary cause.
First disconect the transformer from the unit and check it all allone, for Ohms on primary and secondary side. Best remove it from the chassis.
Then post again.
The 18-0-18-0 Volt, 50 VA guess seems right to me. a usual value for pre-amps. You don't need to buy exactly the same, so a 240V version may be simpler to get than 120-120V.
Thank you very much for your answers.
But unfortunately I still do not know the the secondary voltage of its transformer,
The only thing I have to know for buying an other transformer.
Sure, the T1A fuse is before the transformer, and as I unsoldered its secondary, so the transformer is the culprit !
At the secondary output, there are 3 wires so it is a winding with a midpoint for the 0 volt.
Thinking a little, and taking the service manual of the 8000A ( a preamp-amp ), the Power Supply output has +/-44vcc.
Possible that the transformer secondary is 44v x 1/1.414 = 30v
But not sure at all because there are zener diodes.
This is why I need You !!!
Thanks again,
Raymond
But unfortunately I still do not know the the secondary voltage of its transformer,
The only thing I have to know for buying an other transformer.
Sure, the T1A fuse is before the transformer, and as I unsoldered its secondary, so the transformer is the culprit !
At the secondary output, there are 3 wires so it is a winding with a midpoint for the 0 volt.
Thinking a little, and taking the service manual of the 8000A ( a preamp-amp ), the Power Supply output has +/-44vcc.
Possible that the transformer secondary is 44v x 1/1.414 = 30v
But not sure at all because there are zener diodes.
This is why I need You !!!
Thanks again,
Raymond
Alas Rayma !!!
On your diagram ( thanks for giving me it ! ), there il all schematics, except its Power Supply
And it is what I am looking for
Raymond
For BETTER sound: Do use only ONE secondary winding.
Re-solder all solder joints: desolder and re-solder with MINIMAL solder. You must be able to look through the holes of the board.
;-)
Cool circuits. DO sound much much better than the most big and expensive amps;-)
Re-solder all solder joints: desolder and re-solder with MINIMAL solder. You must be able to look through the holes of the board.
;-)
Cool circuits. DO sound much much better than the most big and expensive amps;-)
;-)
8000A: fine pre amps, but horrible power amps;-)
Replace the poweramps with simple pp-followers;-)
8000A: fine pre amps, but horrible power amps;-)
Replace the poweramps with simple pp-followers;-)
Maybe so but they are completely different beasts the "A" has a symmetrical/dual power supply and the "C" has a single voltage power and as far we ( I ) know they can be completely different (or not) in voltage.
Without any prove otherwise I'm going to shut up and keep an eye to see where this is going.
Without any prove otherwise I'm going to shut up and keep an eye to see where this is going.
Unless someone can measure their 8000A for the secondary voltages, this is all that we can do.
Power supply schematics are not available. The regulated DC voltage is +30VDC, with the MC
stage further regulated down to +10VDC.
Power supply schematics are not available. The regulated DC voltage is +30VDC, with the MC
stage further regulated down to +10VDC.
My idea was, the "A", of course different, has the same preamp section as the "C".
Then it makes sense to compare them.
But, as with the "A" the Power supply is not schematized, I am still not enlightened.
If I am telling the truth thinking that only one wire on the primary is dead ( it is a 2 x 115v )...
It would be possible to power my preamp with a 115v variac to measure the secondary output voltage ??
Raymond
Then it makes sense to compare them.
But, as with the "A" the Power supply is not schematized, I am still not enlightened.
If I am telling the truth thinking that only one wire on the primary is dead ( it is a 2 x 115v )...
It would be possible to power my preamp with a 115v variac to measure the secondary output voltage ??
Raymond
It doesn't work that way
If you power only 1 primary winding you will not get the proper output voltage, normally for 110/120Vac primaries the winding are connected in parallel but hey if it is already damaged what do you have to lose ?
Edit just to say that if you feed the "good" primary winding it's going to induce voltage on the "shorted" one and blow the fuse anyway...
If you power only 1 primary winding you will not get the proper output voltage, normally for 110/120Vac primaries the winding are connected in parallel but hey if it is already damaged what do you have to lose ?
Edit just to say that if you feed the "good" primary winding it's going to induce voltage on the "shorted" one and blow the fuse anyway...
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If the fuse still blows with the transformer secondary unconnected,
this fault could also damage the Variac itself.
Photograph and document all the connections, and then remove the toroid from the chassis.
Measure all the windings for continuity, and post the results here.
Then we can decide whether it is safe to power the transformer separately.
this fault could also damage the Variac itself.
Photograph and document all the connections, and then remove the toroid from the chassis.
Measure all the windings for continuity, and post the results here.
Then we can decide whether it is safe to power the transformer separately.
This thread got a little confusing.
Maybe we should point to the fact that anyone with serious knowledge about audio electronics would need less than 10 minutes to aproximate a perfect exchange transformer. The thread starter may have the impression this is a really huge problem. It isn't!
OK, here we go: As this pre amp is so simple, it doesn's matter we have no schematics.
First I would cut the transformer wires to the amp, leaving about 4cm at the transformer. This is for measuring and possible re-use of the transformer, while having the connections 100% clear (wire colors!).
Later it will be 100% OK to use screw connectors to the new transformer. No need to solder the AC wires.
Then measure the resistance of the transformer windings. Make a sketch with wire colors. Post.
Next do a handfull of good pictures of the amp, it's board and wires/ components connected to the now missing transformer.
Use a lot of light, so the pictures can be enlarged. This way we can reconstruct the power supply and find out what AC input it needs.
@dray177 this is a very simple amp with no secrets. If you do not skip any step wise people advise you to take, it will be an easy repair.
Please do not decide by your self what to do next. Let people analyse until the end what the problem is and only reconnect it to 230V when there is an OK.
As said in the beginning, transformer need a cause to burn through. They don't just fail after years of service.
So there might be some other simple parts to replace, my guess is the large capacitor and the rectifier that seems to be hidden behind the wires.
Calculate about 70€ of parts for the worst, including postage and your amp should do for the next 20 years to come.
Maybe we should point to the fact that anyone with serious knowledge about audio electronics would need less than 10 minutes to aproximate a perfect exchange transformer. The thread starter may have the impression this is a really huge problem. It isn't!
OK, here we go: As this pre amp is so simple, it doesn's matter we have no schematics.
First I would cut the transformer wires to the amp, leaving about 4cm at the transformer. This is for measuring and possible re-use of the transformer, while having the connections 100% clear (wire colors!).
Later it will be 100% OK to use screw connectors to the new transformer. No need to solder the AC wires.
Then measure the resistance of the transformer windings. Make a sketch with wire colors. Post.
Next do a handfull of good pictures of the amp, it's board and wires/ components connected to the now missing transformer.
Use a lot of light, so the pictures can be enlarged. This way we can reconstruct the power supply and find out what AC input it needs.
@dray177 this is a very simple amp with no secrets. If you do not skip any step wise people advise you to take, it will be an easy repair.
Please do not decide by your self what to do next. Let people analyse until the end what the problem is and only reconnect it to 230V when there is an OK.
As said in the beginning, transformer need a cause to burn through. They don't just fail after years of service.
So there might be some other simple parts to replace, my guess is the large capacitor and the rectifier that seems to be hidden behind the wires.
Calculate about 70€ of parts for the worst, including postage and your amp should do for the next 20 years to come.
PS Raymont, you made some guesses from a wrong schematic which would instandly blow your pre. Please, you are not the very best electonics repair man in France 😉 ,use the help that some offer you!
Please don't "just buy a transformer" and hope for the best. Let us do it step by step to save your amp (and a lot of money compared to a repair shop).
PPS please, pictures, pictures, pictures. From all sides and perspectives in HD
Please don't "just buy a transformer" and hope for the best. Let us do it step by step to save your amp (and a lot of money compared to a repair shop).
PPS please, pictures, pictures, pictures. From all sides and perspectives in HD
This thread is not at all confusing as you think Turbowatch2.
Here, I am simply asking a requesr for helping me :
Is there a happy Owner of this 8000c preamp who agrees to measure the output voltage at the secondary of its transformer ?
That would be enough for me to repair it.
With my thanks...
Raymond
Here, I am simply asking a requesr for helping me :
Is there a happy Owner of this 8000c preamp who agrees to measure the output voltage at the secondary of its transformer ?
That would be enough for me to repair it.
With my thanks...
Raymond
No it wouldn't. You don't know what's wrong yet. You only have a symptom so far.