Recent Posts

1

Stereomour II / Re: Stereomour II mods

« Last post by 2wo on Today at 05:34:14 PM »

"Hot time, summer in the city"

2

Kaiju Stereo 300B amp / Re: driver testing

« Last post by joralieu on Today at 02:25:45 PM »

Would a bad 431 regulator on that side cause this?

3

Kaiju Stereo 300B amp / Re: driver testing

« Last post by joralieu on Today at 12:43:29 PM »

I get O ohms there

4

Mainline / Re: Voltage check issue / page 52 / 6.3vDC reading [resolved]

« Last post by N72826 on Today at 12:16:06 PM »

Hello, I am having the same issue. I have tried resoldering the 124 and 499 ohm resistors as well as every other pad on the board. I receive a reading of 12.1 on the 6.3vDC solder pads while the 275v solder pads are within the expected range.

5

Crack / Re: Tube Rolling w/Crack

« Last post by watonwak on Today at 11:22:08 AM »

Thanks Paul, good to know!

6

Crack / Re: Turntable-like static in left channel only (not volume dependent)

« Last post by big_n8_dawg on Today at 11:12:04 AM »

You can also try cleaning the pins of the tubes, as oxidation on the pins can sound like crackling.

Thanks Paul,

Please pardon my ignorance, but if it was oxidation on the tube pins, would it be not be restricted to that particular tube? I'm happy to clean them, just curious.

I'll go ahead and clean the pins on a couple different sets of tubes. Would contact-cleaner and a brush be sufficient?

While I'm at it, should I also clean the sockets? If so, any suggestions on how to best do it? Maybe some sort of small cosmetic brush?

Thanks,
Nate G.

7

Crack / Re: Turntable-like static in left channel only (not volume dependent)

« Last post by Paul Birkeland on Today at 10:37:55 AM »

You can also try cleaning the pins of the tubes, as oxidation on the pins can sound like crackling.

8

Crack / Re: Tube Rolling w/Crack

« Last post by Paul Birkeland on Today at 10:26:21 AM »

Any tips on deciphering these readings? what values indicate a good vs bad tube?

With the Speedball installed, the stronger a 12AU7 is, the lower the plate voltage will tend to be (within reason).  A 12AU7 that's trending towards death will rise up more toward 100V.  This is a lot harder to do with the 6080 since the circuit is directly coupled.

9

Crack / Re: Tube Rolling w/Crack

« Last post by watonwak on Today at 09:34:31 AM »

This is a near-new 12AU7.

Any tips on deciphering these readings? what values indicate a good vs bad tube? also, can we do the same to the 6080 to check its health?

10

Crack / Re: Turntable-like static in left channel only (not volume dependent)

« Last post by big_n8_dawg on Today at 08:56:09 AM »

The upper green wires at B7 and B8 don't look to be well soldered.
5L doesn't look well soldered.
6L doesn't look well soldered.
B1 needs more heat/more solder.

Poking around with the chopstick is the correct method to isolate this issue, but you need to poke at everything in the circuit, not just the components for the offending channel.

780F is not too hot for soldering, and it could be too cold depending on how long you're holding the iron against the joints.  (For reference, I solder at 900 degrees F)

Paul,

I re-soldered the connections you pointed out (at 875F), and initially it appeared to have resolved, but it did come back after about a minute, though it did "seem" quieter than it was.

Since I thought I perceived an improvement, I re-soldered them one more time, and then went ahead and re-soldered most of the other connections on the amp to be a little more sure. (I have attached updated pics - please let me know if you would like to see any other angles or pieces of the circuit.) Again, it seemed much better at first, and was quite quiet for a few minutes, but it did eventually return, so I rechecked everything with the chopstick, on both sides of the circuit, but there was no discernable change to the noise at any component, wire, or solder point.

(Also, for clarification regarding my prior concern about potentially overheating components - during the initial build, I used a flakey old 35w soldering iron that I really shouldn't have (actual temperature unknown), and it took quite some time to get enough heat into some of the component legs for soldering. This is why I was wondering if I might have overheated something.)

Thanks Again,
Nate G.