ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades RCA 45EY 2 record player

What kind of inverter is it? Personally, I wouldn't be happy with anything but a true sinewave output in this application.

I've built and used square wave solid state and vibrator inverters to run things for years; one of which was a valve radiogram. The low power synchronous motor isn't terribly fussed by waveform. From my experience, and your description of noise, it's an amplifier issue.
Being an AC/DC supply, these are more prone to mains borne 'interference', which in this case will be the very rapid change in voltage from the modified square wave, rather than a gradual change as per sine wave.
Generally a low value capacitor, say around .1uF rated at 250VAC will cure the problem if placed at the input to the amplifier supply.
Also, another thing to try is a capacitor across the rectifier's anode-cathode. Try .01uF 250VAC.
You can also try an inline mains filter.
Reversing the mains plug may also help.
Other things to look at are earthing issues.
Not knowing if the output of the inverter is isolated, I won't say try earthing one side of it, but earthing the 12V input can also help.

Thanks for your response aussie but i was using the inverter off a car battery not the household mains........I have now also tried a stepdown transformer and the amp works perfectly so i say its not an amp problem for obvious reasons in regard to the motor i would rather use the inverter, as the motor runs very hot off the stepdown any ideas???

It's sounds as though it's the output of the inverter. Whether square-wave (worst) or modified sinewave (not so bad), those steep transients are rich in harmonics and can cause interference.

Although I'd still prefer to start with pure sinewave, I'd agree that with suitable filtering you should be able to eliminate most of the noise.

Cowabbi,
All the suggestions I made were for running off inverter...as Paul says, the square wave supply is rich in harmonics; in otherwords, there's more than just a 60 cycle supply feeding your gramophone. 60 cycles is the fundamental frequency doing the work, but there's many multiples of this frequency which extend into the audio spectrum (and no doubt RF) which is why you can hear the buzzing. You need to incorporate filtering between the inverter and the 120VAC input of the amplifier which will round off the edges of the square wave. Earthing can also help if the interference is getting in by some other stray path.
When I posted my previous reply I forgot to ask if you had changed all the leaky capacitors, high resistors, and dried out electrolytics, but as you've mentioned the sine wave supply runs the amp ok then that's not the problem.
As the amplifier is only of moderate gain (one triode and one pentode) I don't think it would be too difficult to solve the problem.
By the way, does the inverter noise vary with the volume? If so, it indicates it's being picked up around the amplifier input.
As for the motor running hot on the transformer (ie. 50 cycle supply), maybe it is the lower frequency causing that, but would be a sign of a motor made with as few turns of wire (ie. cost cutting) as they could get away with. The other thing is the actual transformer...one of my stepdown transformers is actually 220 to 120V, so with 240-250V fed into it and a very light load on the secondary the voltage is rather high ~135v. I don't use it for lamps or things with valve heaters.
One other thing also with AC/DC gear, because of the way the valve heaters are supplied, the heater to cathode insulation can be fairly stressed depending where certain valves are in the heater chain, and if this starts to fail you'll get evidence of hum.

Hi there Aussie....Ive checked and indeed the noise goes up and down with the volume.
Ive also noticed that when you near the pick up or motor board the noise gets louder too.
Can you please please give me any suggestions.
Kind regards

It sounds as though the noise is being picked up on the tonearm wiring and/or the turntable chassis. I take it this is a unit with only a 2-wire supply cord and no ground on the deck?

Yes Paul you are quite right this player was built in 1951.....but I still dont understand why it only plays up on the inverter?
What can I do?

By the way....Im using a modified sine inverter
regards

Because the voltage waveform coming from the inverter is not the same as that which comes out of a domestic power point. To put it bluntly, it's horrible and noisy, but cheap to generate. A modified sine wave is merely a square wave with the same peak voltage as the mains voltage but with reduced duty cycle so the RMS (ie. the power that does the work...more correctly the equivalent heating power) is the same.
It is still full of nasty harmonics that find their way into everything. Hence the extra filtering and possible earthing required.