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Bottlehead Kits => Crack => Topic started by: BillN150 on April 18, 2021, 08:55:05 AM

Title: I heard a very loud pop on my AKG 240s [resolved]
Post by: BillN150 on April 18, 2021, 08:55:05 AM

Last night I was listening when I heard a loud pop on the left side of my headphones. After that I got terrible distortion so I turned it off. To day I noticed that the white wire leaving my Alps and going too the 12AU7 was touching with the LED that connects with the next terminal on the socket, that is the terminals were touching. I got the two terminals apart then I  replaced the the 12AU7 with another one, checked the speedballs voltages, everything is okay and tried listening and the hum is very bad and gets worse when you turn up the volume. I'm wondering what else I screwed up, perhaps the capacitors in the power supply? I haven't checked the voltages on the transformer yet because I lost my manual and can't seem to find a new one 

Title: Re: I heard a very loud pop on my AKG 240s
Post by: Paul Birkeland on April 18, 2021, 09:33:20 AM

When you installed the Alps, did you mount it to a PC board?  If you just mounted the wires right to the pins on the Alps, it's very easy to just snap the pins off, then you need to start over with a different pot.

You do not have failed power supply capacitors.

Title: Re: I heard a very loud pop on my AKG 240s
Post by: BillN150 on April 18, 2021, 10:31:32 AM

No, I mounted them to a PC board and checked them with a meter, they seem to be fine.

I now have a manual, where should I start

I modified it with a Speedball, an Alps and Mega Audyn Caps (output) and it was unbelievable for a few songs, then Pfft

Last night was the audition of the Caps, I don't see how  it could have operated with the terminals touching but it did

 

Title: Re: I heard a very loud pop on my AKG 240s
Post by: Paul Birkeland on April 18, 2021, 11:52:49 AM

Can you put the old caps back in?

Title: Re: I heard a very loud pop on my AKG 240s
Post by: BillN150 on April 18, 2021, 12:06:38 PM

I suppose...   It will be a while before I get back to you

Title: Re: I heard a very loud pop on my AKG 240s
Post by: BillN150 on April 18, 2021, 02:42:06 PM

What I'm hearing now is a distorted humming from both channels that doesn't get louder as I turn the pot.

Then the left channel gets another distortion as I turn the pot about halfway

This is with the old Caps

I hope this helps

Title: Re: I heard a very loud pop on my AKG 240s
Post by: Paul Birkeland on April 18, 2021, 03:39:48 PM

What are the DC voltages on terminals 1-10?

Title: Re: I heard a very loud pop on my AKG 240s
Post by: BillN150 on April 18, 2021, 04:56:56 PM

I'll get back to you tomorrow with that...

Title: Re: I heard a very loud pop on my AKG 240s
Post by: BillN150 on April 19, 2021, 06:32:56 AM

Here they are:  1 73v
                       2 183v
                       3 0v
                       4 183v
                       5 74v

                       6 0v
                       7 106
                       8 0v
                       9 106
                      10 0v

Title: Re: I heard a very loud pop on my AKG 240s
Post by: Paul Birkeland on April 19, 2021, 06:35:43 AM

That's a working set of voltages.  I would recommend looking for broken wires or loose connections around the input or output wiring.

Title: Re: I heard a very loud pop on my AKG 240s
Post by: BillN150 on April 19, 2021, 08:23:15 AM

Your right on AGAIN!!!  I resoldered the black going from the input to the jack, the red wire going to no. 6 i believe, and

for good measure the white on the output on the alps... dead quiet, when I turn it up halfway all I hear is Keiths piano!!!

                                                                      Thank you much.