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Author Topic: Trouble with new build - help, please!  (Read 11125 times)
vim
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« on: August 04, 2011, 11:09:37 PM »
Well, it had to happen. After having built both a OTS HRM and a 2550, I thought this would be easy. Not so.
When starting the thing up, the 6V6 tubes are glowing with a pulsing blue light, and noice (scratching) is heard loudly through the speaker. I have checked the layout and all solders, and cannot find anything wrong!

Anyone have any idea where to start looking? I´m handy, but no engineer, so I´m a little lost right now...

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« Last Edit: August 05, 2011, 07:20:46 AM by vim » Logged
T Wilcox
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« Reply #1 on: August 05, 2011, 02:04:14 PM »
Can you post pics of the guts here?
Are you sure the 6v6 tubes are good? What are your voltage readings throughout?
I dont know about the tubes pulsing but sometimes the blue glow is just the gas inside the tubes which may not be a problem. In my OTS my NOS 6l6's glow blue a little but my JJ's do not. Pulsing?
Also have you checked all grounding with meter to make sure there is no resistance to ground?

Todd
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Plexi bass 1986 ( build #6 )
Ceriatone Ultra Champ ( build #5 )
TW Express clone ( build #4 )
Ceriatone HRM MK2 ( build #3 )
Ceriatone 2550  ( Build #2 )
Ceriatone OTS FM50 Modern Eagle Mod (Build #1)
EBMM Steve Morse original
50th anniv American Strat
vim
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« Reply #2 on: August 05, 2011, 05:56:20 PM »
Quote from: T Wilcox on August 05, 2011, 02:04:14 PM
Can you post pics of the guts here?
Are you sure the 6v6 tubes are good? What are your voltage readings throughout?
I dont know about the tubes pulsing but sometimes the blue glow is just the gas inside the tubes which may not be a problem. In my OTS my NOS 6l6's glow blue a little but my JJ's do not. Pulsing?
Also have you checked all grounding with meter to make sure there is no resistance to ground?

Todd


Yes, I´ll post pics if I cannot solve it tonight. Thanks.
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plasticvonaband
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« Reply #3 on: August 05, 2011, 06:36:49 PM »
Quote from: vim on August 04, 2011, 11:09:37 PM
Well, it had to happen. After having built both a OTS HRM and a 2550, I thought this would be easy. Not so.
When starting the thing up, the 6V6 tubes are glowing with a pulsing blue light, and noice (scratching) is heard loudly through the speaker. I have checked the layout and all solders, and cannot find anything wrong!

Anyone have any idea where to start looking? I´m handy, but no engineer, so I´m a little lost right now...

 Undecided

Sounds like a problem with the tremolo circuit. if the blue light is pulsing, that means the tremolo is on, if it is a bias type, which i believe Nik's is. If it is flucuating enough it could make the noise you describe as well.

Gregg
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Overdrive is like peanut butter. Some like it crunchy, some like it creamy.
Bluesmaster 50 2x12 combo and some guitars.
vim
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« Reply #4 on: August 05, 2011, 10:57:40 PM »
Some strange readings, and impossible to get a decent reading on V2, pin 1 and 3. Low readings on V3/V4, pin1 & 8.
Could this be a faulty tube (V2?)?



Prinzeton         240V      10/8/10               
                                 
Tube   Type   Pin1   Pin2   Pin3   Pin4   Pin5   Pin6   Pin7   Pin8   Pin9   
                                 
V1   12AX7   145      1,15         165      1,3      JJ
                                 
V2   12AX7   ?       1,6 - 2,6         280      85      Sovtek
                                 
V3   6V6GT   0,2      390   395   39         13      
                                 
V4   6V6GT   0,2       390   395   35         11      
                                 
V5   GZ34            314      332            
                                 
OT CT   408                              
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plasticvonaband
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« Reply #5 on: August 05, 2011, 11:21:18 PM »
sounds like a bad tube to me. much better than my original theory Wink
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Overdrive is like peanut butter. Some like it crunchy, some like it creamy.
Bluesmaster 50 2x12 combo and some guitars.
vim
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« Reply #6 on: August 06, 2011, 08:15:06 PM »
Getting weirder and weirder.
Voltage readings done over again, now with tremolo switched off.  Readings seem to be OK I think, except for V5 Pin 4 at - 40 (should be +313 or something like that). V3 and V4 pin 8 also are low, at 11 and 13 (should be 27).
Also footswitch makes the tremolo effect really weak (almost inaudible) and when switched off the amp starts popping like a machine gun.

I´ve got Nik trying to help. I´m completely lost.
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vim
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« Reply #7 on: August 08, 2011, 06:11:55 PM »
No prob. - no more  Chair Dance

Tube   Type   Pin1   Pin2   Pin3   Pin4   Pin5   Pin6   Pin7   Pin8   Pin9   
                                 
V1   12AX7   142      1,2         150      1,3      JJ
                                 
V2   12AX7   228      2,2         280      76      Sovtek
                                 
V3   6V6GT   37      393   388   -28         37      
                                 
V4   6V6GT   34       394   388   -28         34      
                                 
V5   GZ34            321      330            
                                 
OT CT   399                              

And life is good.
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T Wilcox
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« Reply #8 on: August 08, 2011, 06:26:55 PM »
What did it end up being? Huh?
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Plexi bass 1986 ( build #6 )
Ceriatone Ultra Champ ( build #5 )
TW Express clone ( build #4 )
Ceriatone HRM MK2 ( build #3 )
Ceriatone 2550  ( Build #2 )
Ceriatone OTS FM50 Modern Eagle Mod (Build #1)
EBMM Steve Morse original
50th anniv American Strat
vim
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« Reply #9 on: August 08, 2011, 08:59:25 PM »
I think the original problem must have been that I got solder into one tube soccet. Replaced 3 soccets (got hold of some "good quality" ceramic ones from a friend), and then a few, new problems occured. One soccet was actually broken, so that was changed back to the original.
Also found two wires from the main board to V1, that was partially broken inside the cloth insulation. Replaced these, and now it seems to be fine.
Discovered later tonight that when the amp is cold, I´ve still got a very low scraping sound the forst 30 secs. but after that, it is dead silent. I´ll let it stay this way for now. Bias set at 25 and it sounds sweet!

Must thank Nik for patiently helping with debugging!

I´ll post a few pics in a new thread later tonight.

Thanks!
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vim
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« Reply #10 on: December 30, 2011, 09:06:44 PM »
Guess this is of very little interrest to anybody, but anyway:
The scraping/scratching that was pretty annoying the first seconds/minute or so, suddenly just dissappeared and never came back. I suspect dust of some kind inside a pot that didn't go away until the amp was used for a while. Now it is 100% - and then some.
Great amp!
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