Help, amp powers on but no tubes glow and no sound

[BG00]

Help me out here, My Laney LC-15R shut down yesterday while i was playing in the afternoon. It was working fine until all the sudden no sound was coming out but the power indicator light was on. I looked at the tubes and none of them were glowing, neither power nor pre. Is this something you have seen before? Maybe a transformer or choke failure?

PS : when i turn it on the power light still goes on and i hear humming from the chassis but no sound from the speaker and no glow in the tubes.

 

[jmh151]

Re: Help, amp powers on but no tubes glow and no sound

I had the same problem on my Marshall. I took it in for repair. They wouldn'[t tell me what the problem was, but they re-tubed and "serviced" the amp- $350 later it worked.

 

[kmcguitars]

Re: Help, amp powers on but no tubes glow and no sound

Does it have a HT fuse? If so check it.

 

[tone4days]

Re: Help, amp powers on but no tubes glow and no sound

check the fuse

if its busted, replace it with the exact correct replacement

if not, time for a service call to the tech

good luck
t4d

 

[ES350]

Re: Help, amp powers on but no tubes glow and no sound

first things first--is the speaker blown? Is it plugged in? Is your cord bad? Is there a standby switch? OK, the tubes don't glow...

No heaters lighting up = possible PT problems...

 

[BG00]

Re: Help, amp powers on but no tubes glow and no sound

Yea, I checked the obvious stuff like speaker, chord, guitar and fuse first, wasn't them. So basically i'm down to power or output transformer or the choke being bad. If it is a transformer do you guys know of any place that sells replacements?

 

[kmcguitars]

Re: Help, amp powers on but no tubes glow and no sound

I'm not familar with your model Laney. They used to use Skot transformers. Don't know if they still do?

 

[ES350]

Re: Help, amp powers on but no tubes glow and no sound

I'm thinking that the '15' designation in the model name indicates an EL 84/6BQ5 output stage ?---in that case, the Blues Jr, AC 15, and even Deluxe Reverb OT's would work. Unless there's a rectifier tube, the Blues Jr. PT would work. None of the above are very expensive and Angela Instruments and AES carry them. Maybe Laney sells a replacement...

 

[WhoFan]

Re: Help, amp powers on but no tubes glow and no sound

just guessing here but is there not other fuses inside amps beside the ones on the back panels... or is that SS amps only? i remember seeing some Fuses inside an amp....

 

[Inferno]

Re: Help, amp powers on but no tubes glow and no sound

That sounds exactly like what happened to my JCM 600 once. It had blown a fuse. You said you checked to see if it was the fuse, but did you check inside the amp? There were 2-3 fuses inside my amp along with the one accessible from the back. It's worth a shot before paying a tech to take a look. Just remember to be careful when opening it up...

:eyecrazy: :scared:

 

[BG00]

Re: Help, amp powers on but no tubes glow and no sound

Thanks for all the response, I have not opened it up yet, I didnt know there were more fuses inside, I will check those tonight and get back to you guys. Also, yes the amp is an EL84 output section, no rectifier. So 15 watt model fender or vox transformer should work?

 

[WhoFan]

Re: Help, amp powers on but no tubes glow and no sound

Thanks for all the response, I have not opened it up yet, I didnt know there were more fuses inside, I will check those tonight and get back to you guys. Also, yes the amp is an EL84 output section, no rectifier. So 15 watt model fender or vox transformer should work?

if it has fuses on the inside they blow for a reason.. so maybe sticking in a new fuse may fix the issue, or it could pop again if something else has trouble... but it's worth seeing if it was just a faulty fuse, or worse issues... but also be extremely careful as opening an amps guts is dangerous to the unskilled, uncluding me.. I really don't know that much about amps myself but i have had to open them and look around myself once in a while... Even with the cord unplugged you could get a nasty zap as the Caps hold a charge... Get zapped in the wrong spot and it could send you into cardiac arrest. Beware

 

[lastwinj]

Re: Help, amp powers on but no tubes glow and no sound

blown heater string fuse, if it has one, blown power tranny, or a connection came loose inside.

 

[ES350]

Re: Help, amp powers on but no tubes glow and no sound

Blues Jr/AC 15/Deluxe Reverb iron will all work for PT or OT...as will the appropriate Heyboer/Hammond types. The DR OT would be an upgrade...

 

[Inferno]

Re: Help, amp powers on but no tubes glow and no sound

...I didnt know there were more fuses inside, I will check those tonight and get back to you guys.

I'm not sure if your specific amp has fuses on the inside, I was speaking from personal experience.

...if it has fuses on the inside they blow for a reason.. so maybe sticking in a new fuse may fix the issue, or it could pop again if something else has trouble...

I agree and disagree. If the fuses are blowing repeatedly then you definitely have a larger problem. I replaced the fuse and haven't had any problems since.

Let us know if you find anything when you open it up!

 

[BG00]

Re: Help, amp powers on but no tubes glow and no sound

Sorry I havent gotten back to you guys about the situation yet. I'll be back home the rest of this week so should be able to open it up. Only reason I havent done it yet is that I'm at college and only have a screwdriver as far as tools go...

 

[BG00]

Re: Help, amp powers on but no tubes glow and no sound

Ok, checked it out today with the help of my electrical engineer father. Funny thing is, we both got shocked by the power cap, and he's supposed to be the pro. So after draining the cap (mostly to our own hands) we took the PC board off and inspected the heater fuses. Sure enough one of them was blown. Now its time to go to radio shack and fix the issue. Thanks for all your help guys. I wouldn't have known where to start looking without you.

 

[fingerace]

Re: Help, amp powers on but no tubes glow and no sound

hope it works out well, without any real major problems...

 

[WhoFan]

Re: Help, amp powers on but no tubes glow and no sound

Ok, checked it out today with the help of my electrical engineer father. Funny thing is, we both got shocked by the power cap, and he's supposed to be the pro. So after draining the cap (mostly to our own hands) we took the PC board off and inspected the heater fuses. Sure enough one of them was blown. Now its time to go to radio shack and fix the issue. Thanks for all your help guys. I wouldn't have known where to start looking without you.

those zaps hurt eh!!!! Hopefully just changing the fuse will fix the problem.. if it blows again i'd take it into a shop ASP... I'm not an expert at all on anything electronic but fuses blow for a reason.. maybe it was just it's time to blow.. you never know... so good luck