Identifying Supplied Parts

[Paul Birkeland]

That is the year they were made...

[JosephDuffy]

That is the year they were made...

Well... now I feel silly! Just thought I'd check since the size was slightly off. Better be safe than sorry

But thanks I gave it a Google but couldn't find any answers

[Grainger49]

I'm thinking that the 12 and 13 are date codes, machine codes or batch codes.

[2wo]

Ive heard that 2012 was a good year for French Cabs, er Caps. 

[JosephDuffy]

I've soldered everything on, all my resistance/voltage checks, and they all came out fine. When I first did it I had a "deep hum" in the left channel, so I resoldered the pot and it went away. However, I still have a "buzzy hum", which stays fairly quiet when no audio source is connected, no matter how much I turn up the amp. However, when a source is connected, even without anything being connected at the other end of the cable, a hissing occurs and gets louder the more I turn the amp up (maybe this is just a cabling issue, though) Forgot I had another RCA cable to test. It was indeed a crappy RCA cable.

I know this should be a grounding issue, so I resoldered all the connections that I could see that are ground connections. I've double checked this, and made sure that all other joints are soldered. I must have missed a ground connection somewhere for this to still be happening. The main joint I'm worried about is the ground coming from the power transformer, since it has a lot of connections in one solder. However, I have resoldered this and it looks fine. I have included an image from the instructions, which has circled each of the joints I have resoldered. If I missed any or there's any more debugging I could be doing, please let me know.

[Grainger49]

The center lug on every terminal strip is ground as it is connected to the chassis.  The bottom two terminal strips are used, maybe the two above the tube sockets too.

Check those and rewet them.

[mcandmar]

Is the buzz only on one channel?  If so swap the tubes around and see does it move, i've had a lot of bad luck with noisy tubes. And faint backround hum does seem to get better with time as things burn in.

As for solder points, check the middle post of the main power supply that connects to the transformer, i belive this is the center tap for the heater windings.  And as Grainger says most of the middle posts are used as they are tied to the chassis. The final step i took which cured the hum on mine was to totally dismantle and rebuild the main power supply strip, something in that lot had a bad connection that re flowing didnt cure.  I suspect it was far left post that is also connected to the bottom left corner of the transformer that was at fault. One other i completely missed was the small jumper wire from the headphone jack to the middle post of the bottom right strip.  I fitted aftermarket sockets so i only skimmed through that section of the manual, hence i missed it initially.

Also try turning your soldering iron off while testing.   I'm embarrassed to say this but i re-soldered my earth connections 2-3 times one night trying to cure a bzzzzt noise on one side, only to later find it went silent when i switched the soldering iron off    ..much profanity ensued.

[JosephDuffy]

I'll check some more of the joints in a moment, but I think I resoldered the center joints.

I'd just like to add that the noise gets louder the longer the amp has been on, until about a minute in where it settles. I'm assuming this is still the ground (since the noise is in both channels), but I just thought I'd add that bit of information, just in case.

[mcandmar]

Hold on, has this amp only just been built and powered on for the first time?    If its a loud bzzz that drowns out the music you have a problem, if its just a backround noise/hum then i wouldn't get overly worried about it until everything has had time to settle, especially the tubes.  They do quieten down with a few days use, after about a week everything will be as quite as its going to get IMO.

For example one of my tubes got distinctly upset with me after being run upside down while testing, made all kinds of strange noises for a few power/heat cycles before it settled down again.  I could hear its internals expanding as it heated up making a boing boing boing boing noise, eventually it made a loud POP and has been silent ever since.  Got to love how they all have their own character

Leave it playing for a few hours then listen again and see if it has changed..

[JosephDuffy]

Hold on, has this amp only just been built and powered on for the first time?    If its a loud bzzz that drowns out the music you have a problem, if its just a backround noise/hum then i wouldn't get overly worried about it until everything has had time to settle, especially the tubes.  They do quieten down with a few days use, after about a week everything will be as quite as its going to get IMO.

For example one of my tubes got distinctly upset with me after being run upside down while testing, made all kinds of strange noises for a few power/heat cycles before it settled down again.  I could hear its internals expanding as it heated up making a boing boing boing boing noise, eventually it made a loud POP and has been silent ever since.  Got to love how they all have their own character

Leave it playing for a few hours then listen again and see if it has changed..

This makes sense. I do hear little rattles when I first turn it on/off, and since I'm awaiting a better RCA cable I'll give it a bit of use tonight and tomorrow and then see if the problem has subsided.

[JosephDuffy]

Ok, bad sign: My fuse blew. I was using it last night for an hour or 2, then I turned it off for the night. I came to it now to use it and when I turned it on it didn't turn on at all, and the fuse in the amp is gone. I haven't changed anything and it was working fine last night. It's also plugged into a surge protector and no other fuses have blown. I'll have to buy some more fuses I guess!

Is there anything I can look at now so see why my fuse may have blown? I was still getting the buzzing last night, so it might be linked.

[mcandmar]

Very strange, by my half arsed calculations the load should only be a fraction of the 1amp rating of the fuse.  i.e. a dead short or physical vibration are the only things that should break it.  ...unless it was faulty all along and causing the buzzing

1amps are rare in this part of the world, most stuff is 3,5, or 13.  You could try having a peek inside your multimeter if you want one in a hurry.

[JosephDuffy]

Very strange, by my half arsed calculations the load should only be a fraction of the 1amp rating of the fuse.  i.e. a dead short or physical vibration are the only things that should break it.  ...unless it was faulty all along and causing the buzzing

1amps are rare in this part of the world, most stuff is 3,5, or 13.  You could try having a peek inside your multimeter if you want one in a hurry.

I just popped in to the market and a guy is selling some 1A fuses for 50p, but they're out of stock, so I'll have to go back on Friday when I'm not working. Maybe it was damaged (the US > UK trip is a long one), but I guess we'll see!

The fuse in my multimeter seems to have a 250mA fuse in it, but thanks for the idea!

[Doc B.]

Double check the orientation of the filter capacitors.

[JosephDuffy]

Double check the orientation of the filter capacitors.

Just given these a double and triple check, along with any connections connected to them, and can't see any issues (joints look good, but might be worth resoldering them?)