Svt Cl problem

P Daddy Jones · #1 10-06-2011, 11:04 PM

First real posting. I'm guessing late 90's STV CL started to sound flabby after fully warmed up for a hour or so. It would sound nice and tight starting off then go to sh*t. Ok so i did what probably didnt need to be done and retubed it about two months ago. Still sounded like it was going down hill after it fully warmed up. Now I down sized from a 810 to a svt 410hlf. Tested the 410 out at the pawn shop with a combine3 and it was sounding damn good. Turned up to really test it and still sounded good. Turned the bass on the head up from about 1-2o'clock to 4 and it thumbed. Then within seconds it shut off. Thought I saw some flash come from a cheesy old school power strip that was mounted in the road case. Couldnt get it back on until unplugging the head from that strip and plugging it into the power strip at the end of the extension cord. Just figured it worked good for a second and took it home to the Cl. Still the same thing started to happen. Strong start went flabby then started to hear the tubes starting to break up. Turned the bass volume all the way down and checked the lights in the back. Two green lights and one red light on the right side was lit. Hit the standby and turned it back on a few minutes later. Only the green lights lit. Called the tech and said to adjust the bias accordingly and gave me the run down of other possible problems. He said that sometimes he turns down the voltage a couple of clicks past from where the red light just goes off, sometimes due to different sonics(?). So I adjusted both biases in-between where the red light goes off and where the green light goes off. Right in the middle. Just both green lights lit. Let it set for 15-20 and then it started making a sound like I was plugging in the instrument cable into the bass. Shut it down immediately. Guitar player is guessing that a possible switch with wrong speakers in the cab is at fault. From first glance, they look like the originals. Any thoughts on this would be awesome!!

JimmyM · #2 10-07-2011, 05:00 AM

1. Try cleaning the effects loop jack. Sometimes they get corroded if you don't use them, and it causes this sound.

2. Maybe one of your new tubes went ka-flooey.

3. Might be time to replace capacitors, which usually have a 10-15 year life.

Bear in mind I'm not a tech, but these are common problems.

rodl2005 · #3 10-07-2011, 05:09 AM

Is the cab ok? Wired correctly & the correct impedance?

jmpiwonka · #4 10-07-2011, 08:05 AM

i would try a different cabinet
also measure the impedance of the 410 you just got, the svt is going to want to see a 4 or 2 ohm load

like jimmy said check the effects loop jacks, maybe plug a short cable into them.
i had this problem with my head.

P Daddy Jones · #5 10-07-2011, 09:19 AM

The cab has eminence speakers. It's printed on the magnets 4ohm. Seems to be correct. We was thinking about plugging the bass into the fx return to see what happens. My concern with that is the output of the bass being to high for this entry point, 18v carvin. Is it bad on these amps to be running a high output bass into them.

JimmyM · #6 10-07-2011, 03:18 PM

Nope, I've run plenty of high output basses into SVT-CL's and never a problem.

MAMMOTHvolume · #7 10-07-2011, 03:27 PM

Quote:

Originally Posted by P Daddy Jones

The cab has eminence speakers. It's printed on the magnets 4ohm. Seems to be correct. We was thinking about plugging the bass into the fx return to see what happens. My concern with that is the output of the bass being to high for this entry point, 18v carvin. Is it bad on these amps to be running a high output bass into them.

That wont cause it to blow a fuse, my bets on one of the new valves being a dudd. ask for a new set.

coreyfyfe · #8 10-07-2011, 03:45 PM

I had similar noises once with my V4 when I had a power tube going bad. It made a loud booming noise and then a loud dragged out buzz that didn't go away when I put it in stand-by. The amp was fine the next time I ran it but when I tapped on the power tubes I was able to recreate the noise with one of them so I replaced them and all was good to go. I'd second the idea that it could be a bad tube. QC on new production tubes isn't what it used to be and you may have just gotten a bad one that slipped through the cracks.

Alex1984 · #9 10-07-2011, 05:53 PM

+1 to possible bad tubes.

Take it to your tech. The LEDs are more like guidelines, to properly bias them, use a probe and follow the instructions on the back. IIRC, they should be biased off standby but with no signal running through, it's normal for LEDs to come on when you run a signal in to it.

Also, high output isn't a problem, my SVT handles G&Ls no problem.

4StringShooter · #10 10-08-2011, 03:07 PM

Quote:

Originally Posted by JimmyM

1. Try cleaning the effects loop jack. Sometimes they get corroded if you don't use them, and it causes this sound.

2. Maybe one of your new tubes went ka-flooey.

3. Might be time to replace capacitors, which usually have a 10-15 year life.

Bear in mind I'm not a tech, but these are common problems.

Another thing I had done to mine was when the Tech replaced ALL 6 Power Tubes and the Pre Amp tube, he tore down the amp a bit and replaced ALL the grounds to the Powertubes, saying that there were a lot of BAD solder joints there. The Amp sounds like new. Oh yeah, about those " Biasing Lights " in the back. You can NOT trust them for ANY kind of accuracy. After mine came back from the bench, the light on one bank of P{owertubes was far brighter than the other. I didnt dare mess with it, as it sounded brand new.
They run on a "Push-Me-Pull-You " principle.

"Reporting from the Great Bavarian Festival...OCTOBERFEST, in Kitchener-Waterloo, Ontario, Canada ...PROST !!!!!!

Immigrant · #11 10-08-2011, 03:26 PM

Quote:

Originally Posted by P Daddy Jones

The cab has eminence speakers. It's printed on the magnets 4ohm. Seems to be correct. We was thinking about plugging the bass into the fx return to see what happens. My concern with that is the output of the bass being to high for this entry point, 18v carvin. Is it bad on these amps to be running a high output bass into them.

For some reason I thought the 410HLF was loaded with four 16 ohm speakers, and the 810 with 32 ohm speakers. If each speaker is 4 ohms, how could they be wired to achieve a 4 ohm load?

Keep in mind I have no idea what I'm talking about.

BassmanPaul · #12 10-08-2011, 03:32 PM

Series parallel with 4Ω drivers will result in a 4Ω cabinet. Test the cabinet with a 9V battery and check that all the cones are moving in the same direction. Usually with the + terminal to the tip and the negative to the sleeve the cones will move out away from the magnet.

**B-string** · #13 10-08-2011, 03:43 PM

Quote:

Originally Posted by Immigrant

For some reason I thought the 410HLF was loaded with four 16 ohm speakers, and the 810 with 32 ohm speakers. If each speaker is 4 ohms, how could they be wired to achieve a 4 ohm load?

Keep in mind I have no idea what I'm talking about.

Series-paralell wiring, when impedance is the same wire two sets in series Z+Z= twice the impedance. Wire those two groups in paraell Z-Z= half the impedance. 4+4= two 8ohm groups. Wire the two groups in paralell 8-8= 4 ohm load.

**B-string** · #14 10-08-2011, 03:48 PM

Quote:

Originally Posted by JimmyM

1. Try cleaning the effects loop jack. Sometimes they get corroded if you don't use them, and it causes this sound.

2. Maybe one of your new tubes went ka-flooey.

3. Might be time to replace capacitors, which usually have a 10-15 year life.

Bear in mind I'm not a tech, but these are common problems.

My bet is with #2. One output tube has gone soft. Take it back to your tech for proper testing as a support component could cause a good tube to fail.

okcrum · #15 10-08-2011, 04:31 PM

Quote:

Originally Posted by 4StringShooter

Oh yeah, about those " Biasing Lights " in the back. You can NOT trust them for ANY kind of accuracy. After mine came back from the bench, the light on one bank of P{owertubes was far brighter than the other. I didnt dare mess with it, as it sounded brand new.

The brightness of the LED has nothing to do with the accuracy of the bias measuring circuit.

**B-string** · #16 10-08-2011, 05:29 PM

Quote:

Originally Posted by okcrum

The brightness of the LED has nothing to do with the accuracy of the bias measuring circuit.

Interesting choice of words? Even the Ex-SLM engineer on this board says they will get you in a safe bias range if the circuit is working properly, the if was carefully chosen.

JimmyM · #17 10-08-2011, 09:36 PM

Quote:

Originally Posted by B-string

My bet is with #2. One output tube has gone soft. Take it back to your tech for proper testing as a support component could cause a good tube to fail.

Speaking of tubes gone bad, I got off pretty easy with my tech today. I had a light hum in my SVT that wasn't from outside sources. He said the midrange tube and the two 12BH7 driver tubes in my SVT are ka-flooey. I have a spare 12DW7 and I just need to buy a couple 12BH7's, pay the bench charge, and I'm good to go.

**B-string** · #18 10-08-2011, 09:59 PM

Your SVT doesn't use the 6K11 for the mids? They are easy to find still (I believe), 6K11 seem to last forever. WHOLLY MOLLY! I sold two NOS RCA 12BH7s 6 mo. ago for $10 each. I need to check tube prices more often, just saw that AES was selling them for 29.90 each....now out of stock.

JimmyM · #19 10-08-2011, 11:05 PM

Nope, it uses a 12DW7. Hoping my tube store has a better deal than $30 on 12BH7's. I could get new ones for a lot less. Some NOS 12BH7's aren't so bad, though. I don't need the world's best...not for $30 ea

4StringShooter · #20 10-09-2011, 12:26 AM

Quote:

Originally Posted by okcrum

The brightness of the LED has nothing to do with the accuracy of the bias measuring circuit.

I realize that. I was referring to Voltage measurement when Biasing.