Ceriatone Forum

I wonder if anyone could help me......

My new Ceriatone OTS was built for me by a well respected amp builder here in the UK. I've played through it for a few months with all kinds of guitars and setups, never let me down and I always look after my gear.

So I took the amp one night to a band practice and there was no sound coming out from it!!! It powers up, so it couldn't be the power lead, the PAB pedal lights up as usual, I tried several different guitar cables, also tried swapping my guitars with my friends....still nothing. I changed the tubes even, still nothing.

It might be the 2A slo blow fuse could have blown?? But surely the pilot light on the amp wouldn't be lit??
I've tried turning every dial up to 10, taking it off 'standby' to 'operate' to see if there's any hiss, but nothing.

Could it be the speaker?? It's a V30 and they're built solidly and reliable??

PLEASE HELPP!!!!!!

Do all of your tubes heater filaments light up?
Could be fuses, do you know how to check the fuses?
Do you use a D-lator? I felt pretty stupid one day when nothing was working on my amp and it turned out to be the power cable had disconnected from the K-lator.


There is actually quite a few reasons this could happen , but if you arent technically experienced I would suggest bringing it to a tech ( after checking the easy stuff )

Todd

Sounds like the HT Fuse has blown.

This happened on my OTS early on, the pilot light will illuminate but no HT voltage to tubes.

I replaced this fuse 12 months ago and it's been fine since.

This fuse is not 2 amp.....think it's 500mA IIRC

Yes definitely check the fuses. The pilot light will stay lit even if the HT fuse is blown. Also, I had to go with a Slo Blo in the HT. My layout calls for a Fast Blo, but it was just too sensitive. I asked Nik about this and he said it was OK. I think it has to do with the maker of the fuse. The "fast blo" that came with the kit had a much larger filament. All the ones I can find in the US have a very thin filament in comparison.

Thanks for replies guys.

I have moderate knowledge of amps to be honest. I unscrewed and changed the fuse at the rear of the amp last night to what it says to do - 2A Slo Blo, but still no sound. The tubes were fully burning and lit up, if it's something I could fix, cool. I don't really want to take it to an amp tech to sort it, especially if its something as simple as a fuse. Is there anything internally that could go tits up? I understand there is an internal fuse that could have blown also??

There are only 2 fuses
1 on rear and 1 on bottom
none inside chassis.

Your HT fuse is the one on the bottom by the power tubes!
Unplug your amp before checking these!

If you are not technically experienced with working on amps, I would suggest not opening chassis as you may have heard there could be deadly voltage present even when unplugged!

Todd

Ah I see. What does HT stand for? I'm pretty careful when it comes to electric....learned my lessons! What values should I look at getting as a replacement? Also why would it blow, is there something I should be worried about? Sorry for all the questions and thanks for the help!

I think you said you have the original OTS
http://www.ceriatone.com/images/layoutPic/OvertoneLayout/Overtone-Special-V2.jpg
That is the link to your Layout.
just below the Power Xfrmr you will see HT fuse 0.5amp fast blow.

If you go back a couple post's and read Soundperf's comment on the fuse ( he changed it from fast blow to slow blow per Nik ), that could be the reason it blew. If you put another fuse in and it immediately blows again, at that point I can only recommend bringing it to someone qualified to diagnose. 

Todd

I should also add, that all my voltages internally were checking OK, so when I kept blowing the fast blo's is when I contacted NiK.

Do you have overdrive trimmer on back of amp, maybe turned down by accident? Good luck with your troubles.

You asked what HT was

High Tension Fuse
High Tension is just another way of saying High Voltage.

Todd

Cheers guys, it was the HT fuse.

There's a chicken head knob right between the two 6L6 power tubes (50w OTS), I'm guessing this is the bias control. What must have happened is, the control must have been turned up somehow and therefore over-biasing the power tubes, they probably couldn't handle it, and hence blowing the electronic HT fuse.

I'm quite sure this isn't the OD trimmer because it makes no difference in sound when I turn it. It must be the bias control. As I said, I didn't build the amp, so don't know.

Also it seems the bias test points don't seem to work either. I tried to bias it last night with a digi multimeter, I switched the amp on and let it run a while, inserted the black and red probes and switched on the MM and nothing.....no reading what so ever. I'm sounding like a complete numpty!! ha ha ha

You should ditch the chickenhead for the bias; luckily your HT fuse did it's work. If a amp has been long biased to hot; your Output transformer could be damaged.
Set the DMM to mv for readings.

Thanks Erwin. I hope the tranny isn't damaged, thats all I need. I'm getting the HT fuse tonight to see if it works. I know it's the fuse because when I unscrewed the holder, the fuse fell apart.

Any chance of your Bluesmaster clean/OTS overdrive schematic??

No schematics, but you sent the amp to me: I will be happy to mod it for you.

As long as the Ht fuse is not replaced you can't bias a amp.  Also if you didn't touch the bias pot when the amp got broken, the fault might also be in a failing powertube.

As I understand, you live in Holland? I'm in the UK, so it would be a nightmare to send it to you, without the thought of the costs of shipping etc. I know a good tech that would do it for me, but he costs £££'s. I think it may be a power tube, but I'm not too sure. I will however try and bias it again with it fully operating. Thanks Erwin!

I can't seem to find any 500ma HT fuses. But I do have 1A ones available. Would these be ok to use?

No never use a fuse rated higher than what is called for :o
Or else your amp will just protect the fuse from blowing ;)

Todd

When you say you can't find one, do you mean in your home or from a retailer?

Also, when you say the fuse "fell apart" this sort of makes me wonder if the amp took a hard knock. I would definitely check all the tubes, etc. for damage.

Yes, it's all fine now. 500ma fuse is in and the amp is working and sounding fine. There was a microphonic 12AX7 in V1, which made a horrific noise when on the OD channel and PAB engaged, but that's been changed and all working. The tube must have took a knock also somehow. It's not the most sturdy of amps though. I have a Vibrolux Custom which has been going solid without any problems for years.

Saying that, I can now really tell how touch sensitive the amp is, not even by playing a string. When you move around with the guitar lead, you can hear the signal passing through it, it's wicked. The amp really is ALIVE!!! :D