01-11-2018, 09:19 PM
Hi. My 835 is back on the bench (see long thread in 50's section). I was prepared to call it done. After installing the Weber speaker and breaking it in for a few hours, the amp played beautifully. Very clean, of course, but it has a bell-like clarity (especially once you get the volume up a bit) that I really like. Particularly with my Parker, with which I had no trouble finding some very nice sounds. Not quite so much with my strat. In short, this amp seems to match up with my guitars very much like my R-12-R. So, I like it.
I was going to have a bass player friend over this weekend to really give it a go. But alas, it isn't ready.
Here's the thing: I've noticed that it only sounds good it's good and hot. For the first 15-30 minutes it has a very annoying rattle. Not a cabinet rattle; this comes out of the speaker. I assumes that it was a tube, so I ran through a rather large sample of 6SL7s and 6SN7s (many of which actually were microphonic
) but the problem persisted. I even swapped out the rectifier, just because. Finally, with great reluctance, I matched up and installed another pair of EL37s, but the problem remained. (Whew! I really didn't want to give up on those super-expensive power tubes.)
So, now I'm looking for suggestions. I have *no idea* where the problem is. I've pulled the lower chassis out of the cabinet and went banging around with a chopstick, but there was nothing that made any real noise and everything seemed OK. Tomorrow I'll pull the upper chassis and see if anything there is suspect.
My plan goes like this:
1. Pull both chassis and try to identify a microphonic resistor or capacitor with a chopstick.
2. Reflow all the solder joints (sigh).
3. See if noise is identifiable using a tone generator. If it is, scope it. (It would be a lot harder to scope a signal that I have to generate with a guitar.
4. Um, I don't have a 4th idea. Looking for suggestions.
OK, actually I do have a 4th idea, and that is to buy a couple OC3 tubes. It's the only tube I haven't replaced. I *think* I have one *somewhere*, but so far haven't found it. My Hickok 600A doesn't have a setting for OC3, so I can' test it. At least not that way. Is there a way to test it in amp? I only vaguely know what it does.
Anyway, I know that there are people here with way more experience that me, so toss some ideas my way? Thanks!
I was going to have a bass player friend over this weekend to really give it a go. But alas, it isn't ready.
Here's the thing: I've noticed that it only sounds good it's good and hot. For the first 15-30 minutes it has a very annoying rattle. Not a cabinet rattle; this comes out of the speaker. I assumes that it was a tube, so I ran through a rather large sample of 6SL7s and 6SN7s (many of which actually were microphonic
) but the problem persisted. I even swapped out the rectifier, just because. Finally, with great reluctance, I matched up and installed another pair of EL37s, but the problem remained. (Whew! I really didn't want to give up on those super-expensive power tubes.)So, now I'm looking for suggestions. I have *no idea* where the problem is. I've pulled the lower chassis out of the cabinet and went banging around with a chopstick, but there was nothing that made any real noise and everything seemed OK. Tomorrow I'll pull the upper chassis and see if anything there is suspect.
My plan goes like this:
1. Pull both chassis and try to identify a microphonic resistor or capacitor with a chopstick.
2. Reflow all the solder joints (sigh).
3. See if noise is identifiable using a tone generator. If it is, scope it. (It would be a lot harder to scope a signal that I have to generate with a guitar.
4. Um, I don't have a 4th idea. Looking for suggestions.
OK, actually I do have a 4th idea, and that is to buy a couple OC3 tubes. It's the only tube I haven't replaced. I *think* I have one *somewhere*, but so far haven't found it. My Hickok 600A doesn't have a setting for OC3, so I can' test it. At least not that way. Is there a way to test it in amp? I only vaguely know what it does.
Anyway, I know that there are people here with way more experience that me, so toss some ideas my way? Thanks!