Strange resistor in my AR-4xa...

[abelpereira]

Hi there!

My name is Abel, and I write from Vigo, in the Northwest coast of Spain.

Recently I bought a pair os AR-4xa, the version with highs pot and strange tweeters with external conductors.

They look great (but I'm going to finish them in walnut wood) and sound good... but comparing with my other pair of Boston Acoustics A40, I find some lack of highs.

I tried to act on the pot, put I didn't feel any difference, so I opened them and I found something strange for me...

I'm not really an expert in electronics, but it seems that th pot is bypassed with a ceramic resistor, isn't it?

What will be happen if I cut out this resistor, or even bypass it with a simple cooper cable? I'm not sure that the pots are working allright, and at the end I just wan to increase the higs level. I can regulate them with the amp.

Thanks in advance for your help, and my apologies for my terrible english...

-- Abel

 

[RoyC]

Hi Abel,

The 10 ohm resistor is not an original AR part. Based on the appearance of the corroded rivets, there is a very good chance the pot is not functional. Consequently, the entire signal is shunting through the resistor resulting in very little high frequency response.

One way to test the tweeters is, as you suggested, to simply replace the resistor with a piece of wire. This should result in strong tweeter output. If the tweeters are OK, replace or refurbish the pot to restore the original tonal balance and crossover point. If the green crusty corrosion is present on the pot's wiper and disk I recommend replacing it. While you are doing this work, take the opportunity to replace the 10uf capacitor.

The above recommendations are made with the assumption the tweeters and woofers are original, and functioning properly.

Roy

 

[abelpereira]

12 hours ago, RoyC said:

Hi Abel,

The 10 ohm resistor is not an original AR part. Based on the appearance of the corroded rivets, there is a very good chance the pot is not functional. Consequently, the entire signal is shunting through the resistor resulting in very little high frequency response.

One way to test the tweeters is, as you suggested, to simply replace the resistor with a piece of wire. This should result in strong tweeter output. If the tweeters are OK, replace or refurbish the pot to restore the original tonal balance and crossover point. If the green crusty corrosion is present on the pot's wiper and disk I recommend replacing it. While you are doing this work, take the opportunity to replace the 10uf capacitor.

The above recommendations are made with the assumption the tweeters and woofers are original, and functioning properly.

Roy

 

Hi Roy,

Thanks for the tip. I followed it, and actually, the pots are not working. I replaced the resistors by two pieces of wire, and now the highs are back. It was a relief to hear them and know the tweeters are OK.

Replacing the capacitors is a good idea, but I'll wait till get a new pair of pots. I think it will be difficult to get the original ones in Europe, so I must decide if I put other ones or want to pay a hug amount of money bringing them from the US.

And yes, woofers and tweeters are original. Not so the grills, which are terribly ugly...

-- Abel

[reza]

 

On 5/30/2022 at 9:10 AM, abelpereira said:

And yes, woofers and tweeters are original. Not so the grills, which are terribly ugly...

 

They are original , they were an option as against linen , these above came from a pair of 2AX's I picked up here in UK 

I changed them