Amplifier Problems

[Liam Thompson]

My two amp have both bit the dust this week.

When I turned my valve head on at a gig a couple of weeks ago no sound came out but the LEDs and valves were glowing. I turned off the amp and I changed all speaker cables, guitar leads and tried two guitars but still no sound. Then smoke came bellowing out of the amp so I quickly turned it off. I checked the fuse on the back and that had blown. I took the amp home had a look inside to check if any other fuses had blown and everything seemed ok. I replaced the fuse and connected everything back together. This time it went up in a smoke and sparks after a couple of seconds with molten solder dripping from the chassis. The standby switch now just wobbles about and doesn't click on or off anymore, the whole amp is balck inside, the amp doesn't come an anymore and the fuse hasn't blown. I've given hope of this amp ever being able to be fixed

I turned up to to a gig with my hybrid combo with the intention of unplugging the the built in speaker and just connecting a 4X12 to the output. I turned the amp on and nothing, no lights or anything. My combo needs 4 ohms minumum load. I suspect the cab may have been 8 or 16 ohms as it didn't have anything to say so on the back and only had one input.

If it was a 16 ohm cab would this be too much for a hybrid amp, could this be the reason my amp no longer works? I have checked all the fuses they were all ok but I replaced them anyway and still nothing.

Could the transformer have blown?

Also does anyone know of a surge protector or any piece of eqipment I could use to prevent this kind of thing happening again?

Sorry for the long post and all the questions. Any help is greaty appreciated.

 

[egan.]

Here's a not very helpful answer. Take your amp to a tech. He should be able to tell you what failed on the amp and possible causes....and fix it. Every answer you'll get here will be 100% speculation on what made your amp short or overheat-- Not very helpful info when you'll have to take it to a tech to get it fixed anyway.

 

[Frank'nfurter]

Hi Liam

Sorry to say that, but you have waisted your tube amp!! After the first signs of trouble you had not switch on it again! Maybe now the overall damage is much more increased (and the repair costs)
Looks like a damaged output transformer and even one of the load capacitors and one of the line resistors (Standby switch too). The reason for all this mess could be a brocken power diode from the high voltage rectifier. That means that all following devices had get AC instead of DC and that will blow one or two of them.
Remark for the next time: If a fuse is gone, there is a reason for it!!! Call a technican!!!!

After all, have you checkt all the speaker cables? Seems there is on with a short circuit in one of them, or even worser one of the speakers in the cab is damaged.
I know, bad news but hey, thats all possibilities.

 

[Liam Thompson]

Yeah I know exactly what your saying, I just haven't made myself clear enough after reading through my post again, by going on so much about my amps.

I mainly want to know what equipmentment, surge protecters and what not, can stop this kind of thing happening again. Secondly I wanted to know if anyone had any ideas what went wrong with my amps.

Thanks for your time anyway Egan. Can you believe I live in one of the largest cities in England and there isn't one guy who can fix amps properly in Sunderland. I think I shall have to travel 20 miles to Newcastle to get someone to even look at it!

Here's a not very helpful answer. Take your amp to a tech. He should be able to tell you what failed on the amp and possible causes....and fix it. Every answer you'll get here will be 100% speculation on what made your amp short or overheat-- Not very helpful info when you'll have to take it to a tech to get it fixed anyway.

 

[Liam Thompson]

Hi Frank,

Yeah, I have no intention of even trying to fix the valve head lol. It was a very old Fender Bassman 100 (made about 1973-76 I was told), maybe it was just time for it to go to amp heaven/hell. It once fell out of the back of the van at 20mph , IN THE RAIN, and smashed to bits on the floor (I have no luck). Couldn't believe when I fixed the housing, tried some new valves and re-biased them and it still worked fine.

As for the combo, it wasn't my cab or speaker cables it was the venue's so maybe they were to blame.

Hi Liam

Sorry to say that, but you have waisted your tube amp!! After the first signs of trouble you had not switch on it again! Maybe now the overall damage is much more increased (and the repair costs)
Looks like a damaged output transformer and even one of the load capacitors and one of the line resistors (Standby switch too). The reason for all this mess could be a brocken power diode from the high voltage rectifier. That means that all following devices had get AC instead of DC and that will blow one or two of them.
Remark for the next time: If a fuse is gone, there is a reason for it!!! Call a technican!!!!

After all, have you checkt all the speaker cables? Seems there is on with a short circuit in one of them, or even worser one of the speakers in the cab is damaged.
I know, bad news but hey, thats all possibilities.

 

[egan.]

Yeah I know exactly what your saying, I just haven't made myself clear enough after reading through my post again, by going on so much about my amps.

I mainly want to know what equipmentment, surge protecters and what not, can stop this kind of thing happening again. Secondly I wanted to know if anyone had any ideas what went wrong with my amps.

Thanks for your time anyway Egan. Can you believe I live in one of the largest cities in England and there isn't one guy who can fix amps properly in Sunderland. I think I shall have to travel 20 miles to Newcastle to get someone to even look at it!

It's hard to find a good tech...sort of like a mechanic. Since Frank seems to have a good handle on things prehaps he can suggest a preventative measure. I would say that it's always a good idea to at least have your gear protected by a surge protector. That said sometimes electronic components just fail and nothing can really prevent it....epecially when they're 30 years old.

 

[Liam Thompson]

Are these surge protecters like the muti-plug extensions you can get for a PC?

This may be a stupid question (especially after the trouble I've had with amps recently) but would it be wise to get a protecter that stops surges as well as drops in power? I've heard that most of these protecters for computers only protect against power spikes rather than drops, which can be just as damaging.

Also, would getting one of those voltage regulators mentioned in a recent post be helpful for me?

It's hard to find a good tech...sort of like a mechanic. Since Frank seems to have a good handle on things prehaps he can suggest a preventative measure. I would say that it's always a good idea to at least have your gear protected by a surge protector. That said sometimes electronic components just fail and nothing can really prevent it....epecially when they're 30 years old.

 

[Frank'nfurter]

What? A old Fender Bassman 100? Please spend the money to the tech and try to get the amp back to live!!
You know that all first Marshalls were nothing else as light modified circuits from the old Fender Bassman?
If you need a schematic for the Bassman, look at this:

http://www.freeinfosociety.com/electronics/schemview.php?id=869
http://www.freeinfosociety.com/electronics/schemview.php?id=870

 

[Liam Thompson]

If its possible to fix I think I will get someone to look at it when I get some more money. It really smells of mass electrical burning and it is very charred inside

I've had the schematics for the amp since I bought it but I don't have a clue about them myself, guitar wiring and amp pot replacements are as far I go.

Frank, I know exactly what your saying about the Fender Bassman 100! My other guitar player uses a 5150 mark 1 and a Marshall 2X12 cab and even he says my POD XT Live (5150 setting) running through the Bassman 100 into the same cab sounds much better, warmer, tighter and it has a lot more bottom end, never mind that the clean tone is awesome. Pus I have/had tonnes of headroom.

What? A old Fender Bassman 100? Please spend the money to the tech and try to get the amp back to live!!
You know that all first Marshalls were nothing else as light modified circuits from the old Fender Bassman?
If you need a schematic for the Bassman, look at this:

http://www.freeinfosociety.com/electronics/schemview.php?id=869
http://www.freeinfosociety.com/electronics/schemview.php?id=870

 

[egan.]

Are these surge protecters like the muti-plug extensions you can get for a PC?

This may be a stupid question (especially after the trouble I've had with amps recently) but would it be wise to get a protecter that stops surges as well as drops in power? I've heard that most of these protecters for computers only protect against power spikes rather than drops, which can be just as damaging.

Also, would getting one of those voltage regulators mentioned in a recent post be helpful for me?

Certainly brownouts (voltage drops) are potentially dangerous to your gear. So in that regard a voltage regualtor could be quite useful. That said, I think you'll find that very few folks drop the extra cash to get a voltage regualtor for use in their live rigs.
Personally I use a rackmount furman which basically just handles spikes. I've not really had any issues, but I guess it's a matter of degrees of safelty. Frankly, I would get the amp fixed before I'd worry about dropping $300us on a voltage regulator.

 

[NathanSoulfracture]

If your head can handle 4OHMS minimum then using a 16OHM cabinet wont have caused any damage to it, it would have just reduced the output signal, if you had used a Cabinet which had a rating of less than 4OHMS then your head would have overheated.

i think.

 

[Liam Thompson]

Damn I didn't know they cost that much

I think I'll stick with getting something that handles the spikes, I'll look into the Furman stuff.

Luckily I'm not in a hurry to have either amp fixed as I managed to get hold of a Marshall 9000 valve power amp. But I definetly don't want that going up in smoke in the meantime.

I'd given up on the amp ever being able to be fixed but you and Frank have concinced me to get something done, when I get some cash. Knowing half the guys up hear I'll probably be charged £50 for them to even look at it.

Certainly brownouts (voltage drops) are potentially dangerous to your gear. So in that regard a voltage regualtor could be quite useful. That said, I think you'll find that very few folks drop the extra cash to get a voltage regualtor for use in their live rigs.
Personally I use a rackmount furman which basically just handles spikes. I've not really had any issues, but I guess it's a matter of degrees of safelty. Frankly, I would get the amp fixed before I'd worry about dropping $300us on a voltage regulator.

 

[GodslasheR]

Sorry that i am actually straying this topic awaya little.. but the mention of a Fender Bassman really shock me here. I am using a Fender Bassman 350 head, and yes it's true that it sounds much warmer and the amount of bottom end on the Bassman is awesome! I was wondering how does the Bassman 100 differ from the Bassman 350?

 

[Liam Thompson]

The head was 4 ohms and I was using my cab, which is also 4 ohms so that shouldn't have been the problem.

It was the Laney transister combo that was 4 ohms and the cab (which was the venue's) I was using may have been 8 or 16 ohms, so I was wondering if a 16 ohms cab would be too much for a transister amp or whether it would make no difference except I'd have to turn the amp up more?

If your head can handle 4OHMS minimum then using a 16OHM cabinet wont have caused any damage to it, it would have just reduced the output signal, if you had used a Cabinet which had a rating of less than 4OHMS then your head would have overheated.

i think.

 

[Liam Thompson]

Hi,

I've only tried a handful of Bassman 100's but never a 350. I was tempted to buy a Bassman 135 off Ebay when mine exploded. To be honest I've never even heard of a Bassman 350, I can't find any info on the net quickly either.

What does it look like,wattage etc?

Sorry that i am actually straying this topic awaya little.. but the mention of a Fender Bassman really shock me here. I am using a Fender Bassman 350 head, and yes it's true that it sounds much warmer and the amount of bottom end on the Bassman is awesome! I was wondering how does the Bassman 100 differ from the Bassman 350?

 

[Frank'nfurter]

If your head can handle 4OHMS minimum then using a 16OHM cabinet wont have caused any damage to it, it would have just reduced the output signal, if you had used a Cabinet which had a rating of less than 4OHMS then your head would have overheated.

i think.

You think in the right way. That's called "Ohm's law"

 

[Liam Thompson]

Cool I wasn't sure if it was different for transister amps and valve amps. So I know in the future that as long as the cab is equal or of higher ohmage I'm not going to blow anything else up :Spin:

You think in the right way. That's called "Ohm's law"

 

[Frank'nfurter]

Ha, just find the right schematic:

http://www.ampwares.com/ffg/schem/bassman_135_schem.jpg

Sorry. Schematic was to big.

 

[Andy Sneap]

actually, tranny amps can handle impedence difference a little better, so I've always been led to beleive(forgetting to plug cab in etc). If theres smoke, I'll bet money on the output transformer, especially if its a grey/blue with a real nasty plastic type smell.

 

[Liam Thompson]

The tranny amp looks fine inside, the Fender Bassman 100 appears to have two transformers (I think they are both are anyway) and both them and pretty much everything else inside smells of burnt plastic and is grey in colour

actually, tranny amps can handle impedence difference a little better, so I've always been led to beleive(forgetting to plug cab in etc). If theres smoke, I'll bet money on the output transformer, especially if its a grey/blue with a real nasty plastic type smell.