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46
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Ceriatone / Overtone / Re: Problem with Overtone Special
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on: May 19, 2011, 11:13:31 AM
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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.
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. |
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48
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Ceriatone / Overtone / Re: Problem with Overtone Special
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on: May 19, 2011, 10:22:39 AM
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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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49
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Ceriatone / Overtone / Re: Customized OTS 50W (Bluesmaster Clean) First impression
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on: April 12, 2011, 09:43:08 PM
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SRY guys I'm not sending schematics anymore.
I do this mod or a complete built around this mod as a commercial activity.
What do you mean by commercial activity? Im guessing that means not free? That's very simple; I got requests for this schematic/mod and then someone else did do the mods for the guy who requested the schematic and get payed. I figured out I could do this myself and get payed. I also like working out modding requests, like Steven's, and being creative within the OTS design. PS. Van Weelden is lightyears beyond me... |
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52
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Ceriatone / Overtone / Re: How to set the PI balance using scope
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on: March 21, 2011, 10:31:43 PM
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Hi Hywell, If you have a 50w OTS and a DMM you also can use the 2 red bias points to measure. Insert 1kHz signal in the Fxloop and set your DMM for dc voltage. This method is more accurate because it takes the imbalance of the power tubes in account. Your actually measuring cathode balance of the power tubes in this method. For you 100w guys; the red testing probes have to be tied together for tube v4 and v5. V6 and v7 also have to be tied together. And in this way you also have 2 measuring points were you can measure ac balance. One other thing: just like when biasing; leave the amp 15 min on before measuring, sometimes tube heat changes the response of tubes. I read the thread on ampgarage and spent a while trying to set mine, but without a scope found it frustrating. I did post some info here http://ceriatoneforum.com/index.php?topic=3428.msg16597#msg16597but I'm not sure I know what I'm doing to be honest I know I need to achieve AC 0v on the PI, but so many of my tubes were way out even the one I bought as 'balanced'. Couple with that and the fact the trimmer made very little difference to the AC balance makes me think my meter is just too crap!. SO my first question is, if I order another 'balanced' Sovtek LPS tube what do I need to ask for? Balanced gain? which is what I think I got or balanced transconductance? (If I knew what it was I'd be better informed when I go to the shop!) Secondly how accurate does my meter have to be to achieve this 0v AC? +- 1mV? or better? Not sure if mine is good enough but I'd like to try it again. Cheers guys. |
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53
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Ceriatone / Overtone / Re: How to set the PI balance using scope
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on: March 21, 2011, 06:09:02 PM
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Hello all
back to the infamous PI pot this thread leaves me wondering what I am missing.
Mcinku for those of us that dont have access to an O-scope, what difference in tone are you noticing once you have it set properly?
I am just wondering if this will be a necessary adjustment for my amp since right now it sounds great. Although I want to get the most out of the amp too.
Would you be able to tell the differennce between an OTS that has PI setup and 1 that has not by ear?
Thanks
Todd
Perfect balance is not the aim; when it's set slightly out of balance, harmonics and bloom will be more present. You need a balanced tube to get the best out of the amp. |
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55
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Ceriatone / Overtone / Re: loud hum, no signal
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on: March 16, 2011, 09:32:05 AM
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Just bend the wires, it's the EMI from the heater wires that causes a degenerating tone.
Voltages are a bit high but that could also be your wallpower; when 120 is 125v, you get these voltages on the tube side(like in your chart).
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56
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Ceriatone / Overtone / Re: loud hum, no signal
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on: March 15, 2011, 08:35:47 AM
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Can you measure(amp off!) the resistance between First node of the filtering and the Ot secondaries?
And then measure resistance between all filter nodes to their respective plate resistor leads.
Measure all cathode to ground resistance.
The voltages at v2 , v3 are scary; it looks like there is no grounding for the cathode resistor and bypass cap for v2 and v3.
Other things:
*edit*
At the power tubes; keep the grid wires away from the screen resistors.
At the pre amp tubes: keep grid, anode and cathode wires away from the heater wires.
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57
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Ceriatone / Overtone / Re: OTS FM50 kit in transit
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on: February 26, 2011, 08:28:58 AM
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You also need heatshrink, some extra hook-up wire(in case you screw up, don't ask).
A soldering station is very handy when it comes at soldering a buss bar(hotter). and capacitors(less hot).
Long flat pliers are a charm to work with, especially when the built is half completed. Don''t use leadfree solder it's a pain in the *ss.
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58
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Ceriatone / Overtone / Re: Modern Eagle Mod?
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on: February 18, 2011, 08:47:02 AM
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Slope 100k, coupling cap after v1a 0.001uF(together with the mid cap 285pF), 10M PAB resistor.
My guess is that the amp has a more responsive tonestack; less mid heavy and the PAB has less volume jump and is overall less bright(33pF master bright) compared to the Ford Mustang.
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59
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Ceriatone / Overtone / Re: Customized OTS 50W (Bluesmaster Clean) First impression
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on: February 10, 2011, 12:53:18 PM
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No problem Jeff! The OD and clean is with the same tonesetting. Erwin,
Thank you so much. That clean patch sounds nice and warm to me. When you switch back and forth from OD to clean, do you have to change all of the tone settings to get a good tone? Thanks again and sorry, I don't mean to hijack the thread.
Best Regards,
Jeff
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to keep the forums alive.
... 1kHz freq is not a lot of fun to listen to