Transformer VA and volts question.

nazarene

Good day

Maybe someone here a bit more schooled in electronics can help me with some info.

Ive got a marshall 8080 with a busted transformer, I want to replace the transformer with a toroida but I cant seem to find one with the exact specs of the original one. Ive measured the output from a working marshall 8080 that ive got access to.

It is a 120va transformer and measured 34 0 34 on the secondary. What I want to know is if it would ok to use a toroidal with a rating of 160va and with an output of 35 0 35
Any help/info would be greatly appreciated!

babbalute

As far as I remember you will need to know the current required on the 35V lines. You can get many transformers that will give you 160va and 35-0-35 volt but with various current outputs. So it might be better to contact one of the amp repair people to make sure you get the correct toroidal transformer, I assume you have space to put it instead of the Block transformer ?

nazarene

babbalute wrote: As far as I remember you will need to know the current required on the 35V lines. You can get many transformers that will give you 160va and 35-0-35 volt but with various current outputs. So it might be better to contact one of the amp repair people to make sure you get the correct toroidal transformer, I assume you have space to put it instead of the Block transformer ?

Im just thinking about using a toroidal as it seems impossible to get a replacement transformer for that amp, and also because toroidals should b a bit quieter, every valvestate ive heard had buzzing coming from the power transformer so im hoping that a toroidal will cure that. Oh man I did not know about measuring the amps on the secondary side, I will try and measure that this weekend from a working 8080 combo.
But if its a gamble im sure I can maybe have a new one made that will have the same mounting holes as the original one. I was planning on mounting the toroidal at the bottom of the amps cabinet.

babbalute

You can try this company, he makes any kind of transformer(except toroidal) but if you have a sample it becomes som much easier.
http://www.petersouris.co.za/

peterleroux

babbalute wrote: You can try this company, he makes any kind of transformer(except toroidal) but if you have a sample it becomes som much easier.
http://www.petersouris.co.za/

+1 (for the idea generally, never used this company)
One of the things about living in Gauteng is that we still have a good manufacturing industry, so as long as you have the right spec, chances are you can find a small armature winder who is prepared to sort you out with a transformer

I-M-Biased

The old transformer is 120VA. That means 120 VoltAmps, which for all practical purposes is the same as saying 120 Watts. Now the Volts that it gives out is 34 - 0 - 34 V. The two windings are used so that the earth line is floating in the middle of two 34 Volt streams, one above, and one below. If you add up the two voltages it gives 68 Volt. If you divide 120VoltAmp by 68Volt you get 1.76Amp. (Remember the formula: Volts x Amps = Watts).
Now the new toroidal transformer is rated at 160VA. Divide that by 35 + 35 Volts and you get 2.29 Amps which is more than the original. So the toroidal should be fine. The 2 Volt difference is marginal and shouldn't be a problem for the amplifier.

nazarene

I M Biased wrote: The old transformer is 120VA. That means 120 VoltAmps, which for all practical purposes is the same as saying 120 Watts. Now the Volts that it gives out is 34 - 0 - 34 V. The two windings are used so that the earth line is floating in the middle of two 34 Volt streams, one above, and one below. If you add up the two voltages it gives 68 Volt. If you divide 120VoltAmp by 68Volt you get 1.76Amp. (Remember the formula: Volts x Amps = Watts).
Now the new toroidal transformer is rated at 160VA. Divide that by 35 + 35 Volts and you get 2.29 Amps which is more than the original. So the toroidal should be fine. The 2 Volt difference is marginal and shouldn't be a problem for the amplifier.

awesome! many thanks! exactly what I wanted to know!! ?
thanks again!