F-2B weirdness

[edwin]

One channel of my F2B is behaving oddly. Just moving the volume makes crackles and the speaker also has considerable motion.


Any ideas where to start?


TIA


Edwin

[lbpesq]

Sounds weird, alright.  I'd suggest exercising the pots (with power off, of course), but I suspect you've already tried that approach.

Bill, tgo

[StephenR]

Can't make any suggestions other than obvious ones like checking the solder points, making sure the tube is seated properly etc. Since you just changed the tubes did you try putting the old tube back in the now wonky channel? Weird symptoms.

SR

[rv_bass]

I had a similar thing happen with both of my F-1X preamps.  The speaker crackled when I turned up the volume on the amp or preamp.  Turned out the cord from the preamp to the amp was bad.  I replaced it with an new cord and it hasn't happened since.

[gtrguy]

I I remember right, there are jacks with contact points in there that can sometimes get dirty. A few passes with fine folded over bit of 1000/1500 wet/dry sandpaper or a matchbook striking surface will clean them up.

[edwin]

It was a tube. I have a pair of Bugle Boys in there, so I was loathe to take them out, but it did the trick. Oh well, I have a 5751 in there now, but need to find a 12AX7 that matches reasonably to the remaining Bugle Boy.

[sonicus]

I have tried a pair of  smooth plate Telefunken ECC83 tubes in mine . I enjoyed the smooth articulation . I also tried a  pair of FETRON #TR1009 just to see how they would sound . The FETRON TR1009/12AX7 solid state substitution units were common in some of the early MESA -BOOGIE circuits  in some gain stages . As expected the Telefunkens were less harsh .

[edwin]

Wow, I didn't even know you could get something like that. If I were going to do something like that, it would make sense to just design it from the ground up to be solid state and then make it really small.

[gtrguy]

I did a sorta study on some tubes in the F-2B a while back:

http://club.alembic.com/index.php?topic=22299.msg225055#msg225055

[edwin]

I did a sorta study on some tubes in the F-2B a while back:

http://club.alembic.com/index.php?topic=22299.msg225055#msg225055

Thanks for the link! I remember that. Are there any tubes which you'd give a glowing (see what I did there?) review? You didn't seem all that excited about any of the ones you tried.

Just for the record, I thought the Bugle Boys sounded great.

[gtrguy]

I would buy new JJs. They are great tubes and last a long time.

My review was written pretty dry, but my conclusion that tubes are like car tires and will 'wear' down over time was good advice.

I have a couple Bugle Boys for my guitar amps and they are great! Since my review I also acquired a 'Holy Grail' vintage Genalex Gold Lion
(Not the new 'reissue') 12AX7 and it is by far the best sounding preamp tube for guitar I have owned. I find a lot of my tubes at the Goodwill Outlet stores (sold by the pound!) and many of them are lurking inside old movie projectors that have sound.

[gtrguy]

As far as old tubes go, It is pretty hard to beat a good old 12AX7 RCA tube. My opinion is that they were the best of the made in USA tubes, good sounding and robust.


One funny trait of made in Europe or England tubes is that they flare up when first turned on with a bright flash. This can be disconcerting unless one realizes they are supposed to do that.


Many tubes were re-branded by various companies, and you can find rare Mullards etc, with different labeling on them, often with the original brands still there.


https://www.vivatubes.com/identifying-vintage-nos-vacuum-tubes-by-brand-country-and-eia-code/

[elwoodblue]

One funny trait of made in Europe or England tubes is that they flare up when first turned on with a bright flash. This can be disconcerting unless one realizes they are supposed to do that.

I have a bugle boy that does that, I always thought it was a fluke and that it might fail soon...thanks for the peace of mind