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Author Topic: Problem with Overtone Special  (Read 15014 times)
babybear2011
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« on: May 17, 2011, 12:52:54 PM »
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!!!!!!
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T Wilcox
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« Reply #1 on: May 17, 2011, 02:15:28 PM »
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
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exocet
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« Reply #2 on: May 17, 2011, 03:55:49 PM »
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
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SoundPerf
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« Reply #3 on: May 17, 2011, 06:26:33 PM »
Quote from: exocet on May 17, 2011, 03:55:49 PM
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.
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Chris

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babybear2011
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« Reply #4 on: May 18, 2011, 11:55:37 AM »
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??
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T Wilcox
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« Reply #5 on: May 18, 2011, 01:05:22 PM »
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
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babybear2011
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« Reply #6 on: May 18, 2011, 01:09:29 PM »
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!
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T Wilcox
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« Reply #7 on: May 18, 2011, 01:24:19 PM »
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
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SoundPerf
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« Reply #8 on: May 18, 2011, 05:46:45 PM »
Quote from: T Wilcox on May 18, 2011, 01:24:19 PM
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.
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Chris

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« Reply #9 on: May 18, 2011, 10:03:20 PM »
Do you have overdrive trimmer on back of amp, maybe turned down by accident? Good luck with your troubles.
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T Wilcox
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« Reply #10 on: May 19, 2011, 03:15:22 AM »
You asked what HT was

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

Todd
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babybear2011
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« Reply #11 on: May 19, 2011, 10:17:31 AM »
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
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erwin_ve
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« Reply #12 on: May 19, 2011, 10:22:39 AM »
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.
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babybear2011
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« Reply #13 on: May 19, 2011, 10:57:04 AM »
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??
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erwin_ve
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« Reply #14 on: May 19, 2011, 11:08:45 AM »
Quote from: babybear2011 on May 19, 2011, 10:57:04 AM
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.
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