Aragon 4004 mkii humms

[Loksta]

I just received a aragon Mkii with my new speakers infinity deltas, it humms without anything plugged into it, unfortunately as soon as I plugged the audio research pre amp it's power supply died so I haven't been able to test if it passes through the humm to speakers, any ideas of possible causes? Thanks

 

[savatage1973]

With no speakers or source connected, you are likely hearing a mechanical hum from the huge toroid transformer in that amp. You probably will not hear it in the signal path.

 

[KeithL]

I agree with savatage1973. I own the same amp and there is a mechanical hum from the amplifier, but it does not reach the speakers.

 

[Loksta]

Thanks guys, I didn't know whether to try plug it in or not, was getting sus on it don't want too blow my new speakers just arrived yesterday after a three and a bit month wait. My new audio research pre power supply went up in smoke! So was getting sus on the power coming in. Btw we run 240 volt here in Oz, is there some mod to get rid of the hum or reduce it with power boards or conditioners?

 

[Schurkey]

Hum in the 4004 amps was a problem all during production, but mostly the original versions. They used transformers from several companies.

The later Mark II or Series II had a square of damping material glued to the cover.

My Mark II was silent, but the earlier one had a little hum. It didn't go through to the speakers, it was a mechanical hum in the transformer.

When I called Mondial in '92 or so about transformer hum, I was told that the hum was due to noise on the power supply from the wall outlet. The transformer was essentially "cleaning up" the dirty power.

They also suggested playing with the nut that secures the two transformers. Sometimes a little looser would reduce the hum. Rarely, tightening it would reduce the hum.

I have to assume that your 4004 was set up for 240 volt mains, I don't know how to convert a 120-volt unit to 240 volt operation--although I know it can be done. The later 8008 use a power inlet device that can be removed, turned, and reinstalled to change between 120-volt and 240 volt, as long as the proper fusing is also used.

 

[Loksta]

Thanks shurkey that's answered a lot of questions, but raised a few, it's a 4004 that I was told was upgraded too a mkii, The guy I purchased from converted it too 240 before he shipped it he is pretty knowledgeable, I have a power cleaner on order atm as wiring in this house and mains board is old, on the mains board it states 240 volt 50 hz, back of the amp sticker says 115 vac 60 cps, I have no idea what it is now if a switch inside was switched what it would convert too, it didn't go up in smoke when plugged in so I presume it has been switched. I will open have a look, thanks guys nice to know others do the same.

 

[Loksta]

Btw it isn't a mkii, I forgot I ended up with a 4004, just checked

 

[Loksta]

 

[Loksta]

I'm assuming you mean this big nut

 

[Schurkey]

Yes, that's the big nut. Mark it's position, loosen it an eighth- or quarter-turn and see what happens with the hum.

You could buy a square-foot of dampening material and glue (self-adhesive) to the cover of the amp just above the transformers. That's where they put it on the Mark II.

Do you have Motorola transistors? That'd be an early amp.

http://www.ebay.com/gds/Classic-Aragon-Amps-A-primer-/10000000001149810/g.html

 

[totem]

Have a MKII that played a tune pretty good, did the tighten and loosen thing without any change but what did seem to work was playing it enough to warm it up well and over time it did lost a lot of the hum.

 

[Binkman]

gday;

Schurkey has a good hint on reducing the hum.. I've read from aussie posts and advised couple mates down there who have isolated tranny's with some dampening materials on conventional center tapped trans and had very good results (including dampening endcaps or covers with gaskets). So just an option/ idea. reducing the hum by loosening may help but the best results were with dampening materials.