#1
I bought my Marshall TSl601 combo brand new 1 year ago.

2 days ago (when I last used the amp) i noticed a few strange buzzing and popping/crackling sounds that soon went away. I turned on my amp today and it started buzzing really loudly, then there were some popping sounds, then it died.

It is not a power problem or fuse as the amp still turns on, and I can switch between channles.

It is not a blown speaker As i plugged my zoom multi straight into the speaker and it worked.

The amp now turns on, but no sounds is produced at all through any of the channels.

I have not replaced the valves/tubes since i bought it new last year, but I have not used the amp the much.

I took the back cover off, and both power amp tubes still have ornage glows, but now blue glow at all.

How can I tell if one or more of the valves has blown? cold it be something else?

Any help is appreciated.
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#3
my tsl100 did that and it was a fuse.
my gear: ibanez destroyer( with gibson 500t pickup), epiphone les paul plus,ampeg electric, marshall jcm2000 triple super lead half stack
#4
It might be power tubes going dead.
I don't give a shit if you listen to me or not
#7
There is a fuse under the chassis along with the mains fuse at the back of the amp. It could be the one causing problems, but don't start messing around inside the amp unless you know whats going on. Bring it to a tech.
#8
Teh thing is the power seems to be working fine, so I guess it cant be a fuse then?
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#9
Quote by Leper_Messiah_
Teh thing is the power seems to be working fine, so I guess it cant be a fuse then?


Sure it can. You're thinking about the mains fuse. You can blow the HT fuse under the chassis and still get power to the amp. I had a similar scenario a few months ago where I shorted a tube socket during testing on my amp build, blew the fuse, and didn't realize because the amp still turned on, and if I remember correctly, didn't kill the current going to the heaters, so the tubes would still glow. I maybe wrong and would have to see the schematic again to be sure.
Last edited by al112987 at Sep 2, 2008,
#12
Quote by al112987
Sure it can. You're thinking about the mains fuse. You can blow the HT fuse under the chassis and still get power to the amp. I had a similar scenario a few months ago where I shorted a tube socket during testing on my amp build, blew the fuse, and didn't realize because the amp still turned on, and if I remember correctly, didn't kill the current going to the heaters, so the tubes would still glow. I maybe wrong and would have to see the schematic again to be sure.


Ok, on my amp the HT fuse is next to the mains fuse so ill open her up and have a look.

I guess my main concern is finding out why the fuse blew, because replacing it may very end with the same result
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#13
Quote by Leper_Messiah_
Ok, on my amp the HT fuse is next to the mains fuse so ill open her up and have a look.

I guess my main concern is finding out why the fuse blew, because replacing it may very end with the same result



So you can remove the HT fuse without lifting the chassis? If so, then check it and replace it. Its very cheap to do. There are a lot of things that can cause it to blow. Most common is a tube short. Did you have any redplating or indication of a bad tube before this happened?

But don't open the chassis if you don't know what you're doing.
#15
Seriously, those blue filter caps store charge, even when the amp is unplugged and 300 VDC will most likely kill you if its put across your body.
#16
Quote by 311ZOSOVHJH
ampy unpluggy


I'm still laughing... Sorry - That just hit me head on... Still laughing...
TS - change the fuses, insert coin, try again.
#17
Quote by al112987
So you can remove the HT fuse without lifting the chassis? If so, then check it and replace it. Its very cheap to do. There are a lot of things that can cause it to blow. Most common is a tube short. Did you have any redplating or indication of a bad tube before this happened?

But don't open the chassis if you don't know what you're doing.


Yeah the fuses access is near the speaker plugs, you can access without opening p the amp
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#18
Quote by gregs1020
I'm still laughing... Sorry - That just hit me head on... Still laughing...
TS - change the fuses, insert coin, try again.

ha....

well, i only said that there may be more than one fuse and to double check amp is unplugged before starting to explore...


...i pictured some kid poking around looking for a fuse to change and never coming back here to report what happened.
#19
I have taken out the HT fuse and it is indeed blown. How this for a plan of attack:

1) Ill put another fuse in and see what happens. If it blows again I will replace the two power tubes. They are EL34, do I need to bias them?

The only amp repair place in my city want to charge $70 per valve to bias and install, not including the cost of the valve, and said it can take up to 3 weeks.
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#20
Quote by 311ZOSOVHJH
ha....

well, i only said that there may be more than one fuse and to double check amp is unplugged before starting to explore...


...i pictured some kid poking around looking for a fuse to change and never coming back here to report what happened.

My thoughts exactly, its just what I thought. I was totally on board with what and why you were telling him that. It's the manner that you used to deliver the message that killed me.
Edit: To TS, replace that fuse and lets see what happens. You may be fine, it could be something as little as a power surge. But try it. Tubes are one thing to consider, IF it blows right away but who knows, crap happens... Let's see if that fixes your issue first.
Last edited by gregs1020 at Sep 3, 2008,
#21
Quote by Leper_Messiah_
I have taken out the HT fuse and it is indeed blown. How this for a plan of attack:

1) Ill put another fuse in and see what happens. If it blows again I will replace the two power tubes. They are EL34, do I need to bias them?

The only amp repair place in my city want to charge $70 per valve to bias and install, not including the cost of the valve, and said it can take up to 3 weeks.


holy hell, no way should anyone be paying $70 to install and bias a set of tubes...

most modern Marshalls have a bias trimpot accessible from the top of the chassis.. buy an el34 biasing kit from Groove tubes or something that lets you measure at the appropriate pins without having to lift the chassis. Its very user friendly.

search google to find how the correct operating points of the el34 and bias to those specs. oh, and also, use only one hand at all times when working with the amp and don't touch the glass of the tubes, the oils on your hand are not good for them and can cause premature failure.
#22
Quote by al112987
holy hell, no way should anyone be paying $70 to install and bias a set of tubes...

most modern Marshalls have a bias trimpot accessible from the top of the chassis.. buy an el34 biasing kit from Groove tubes or something that lets you measure at the appropriate pins without having to lift the chassis. Its very user friendly.

search google to find how the correct operating points of the el34 and bias to those specs. oh, and also, use only one hand at all times when working with the amp and don't touch the glass of the tubes, the oils on your hand are not good for them and can cause premature failure.


Thanks for your help.

I have a friend who has the same amp as me and claims that biasing is probably not necessary and that if there's too little current, then the amp will jsut sound bad, and if theres too much they just burn out faster. Is this true?

Is biasing completely necessary in your opinion?
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#23
Update:

I replaced the fuse the amp worked as normal. I used a mutli-meter to check the Bias of the tubes and they were running at 120 mV/mA when they should have been at 80. These are the factory tubes. I am going to buy two mesa boogie el34's and instal and bias them next week.
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#24
get el34 tubes and you probably dont need to bias...wouldnt hurt to replace v1 and v2 preamp tubes
#25
Just42Dave, if the el34s are running at 120mA when they should be running at around 80, that's way too hot. Even without new tubes, he needs to adjust the bias.

Those tubes are probably cooked, even if they are fine now. Did you see any redplating before your amp crapped out? I imagine that there must some.
#26
I didnt really notice any red plating, but i think its odd that they were running at 120 especially when these are the tubes that came with the amp when i bought it new last year.

I adjusted the bias down to 80mV/mA
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#27
the bias in an amp can shift over time. but 120mA as opposed to 80mA... thats 50% over the suggested operating point.

still, if all seems well, then I think they're fine. I'd still watch for any red plating though.
#28
Quote by al112987
the bias in an amp can shift over time. but 120mA as opposed to 80mA... thats 50% over the suggested operating point.

still, if all seems well, then I think they're fine. I'd still watch for any red plating though.


Ok, will do.

I'm still not sure what casued the HT fuse to blow in the first place, perhaps becasue there was too much current running through the tubes?
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#29
It could be anything, tubes running too hot, a power surge, a bad fuse.

Glad to hear you have your amp working and you biased it. I think it's a scam for what techs want to charge to replace tubes.
I don't give a shit if you listen to me or not
#30
Quote by Kevin Saale
It could be anything, tubes running too hot, a power surge, a bad fuse.

Glad to hear you have your amp working and you biased it. I think it's a scam for what techs want to charge to replace tubes.


Indeed, i was originally hesitant to try and learn because of the warnings by everyone saying OMGZ you will be electocuted etc. But the new JCM2000 models are very easy to bias. You dont even have to open them up. Theres a small plate on the back near the speaker out that has the three pins and resistance screw on the inside. All i had to do was apply a multi-meter to the pins and adjust the screw, very easy, anyone can do it.
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#31
That is nice. It wouldn't even be easier with a bias rite.
I don't give a shit if you listen to me or not
#32
Yeah, its a really good option that your amp allows you to do that.

I have to pull my chassis out, hang it upside down on a jig and measure the pins directly with a multimeter and turn the trimpot located on the circuit board.

It makes changing a set of tubes a huge chore, I'm thinking about installing an external biasing control like the JCM2000s have.
#33
Im still at a loss to explain why the stock tubes were running at 60mV a piece from the factory when they are supposed to be at 40mV each
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2
#34
Leper_Messiah

hey, i just wanted to say that i'm happy you got your amp back in order and that i didn't mean to call you a kid earlier but i just didn't know. Rather play it safe then sorry right? I don't know you from adam and didn't bother to check your profile. still haven't, but you obviously know what you are doing.
#35
Bias tends to shift in newer amps, I had problems with my amp after I finished building it where I would bias, play it for a few hours, and have my tubes redplate only to find that the bias had shifted.
#36
Quote by 311ZOSOVHJH
Leper_Messiah

hey, i just wanted to say that i'm happy you got your amp back in order and that i didn't mean to call you a kid earlier but i just didn't know. Rather play it safe then sorry right? I don't know you from adam and didn't bother to check your profile. still haven't, but you obviously know what you are doing.


No probs
Gear:

07 Gibson LP Vintage Mahogany
90-91 Fender MIJ '62 Reissue Strat
Fender Acoustic/Electric
Marshall TSL601 Combo
Crybaby Wah
Ibanez TS-9
Boss Tu-2