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Old 7th April 2014, 07:42 AM   #1
mdamp is offline mdamp  Australia
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Default 6L6 6SJ7 Amp please pick faults if any

Hi all me again can anybody see a problem with the schematics I made this amp from schematics on here I changed pin 4 from the original schematics from here and put 240v through a 560ohm resistor as from the original it seems to have too much voltage going to pin 4 and reading the data on 6L6 the max volts to the screen is 250v and I was getting 275volts. if I should put it back the way it was from the original supply supply schematics it to me would have to high voltage to pin 4? any input would be great thanks. the sound like the EL34B my other diy is tight and deep bass and can turn amp volume to 3/4 and Ipod at 94% without any distortion to my ears.
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Old 7th April 2014, 09:22 AM   #2
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6L6-GC Substitutes Close or identical STR387, STR415, SV6L6GC Different rating or performance 6L6, 6L6G, 6L6GA, 6L6GB, 6L6GT, 6L6WGA, 6L6WGB, 6L6WGC, CV1286, CV1947, CV1948, CV586, EL37, VT115, VT115A Different pinout 5B245M, 6BG6, 6BG6G, 6BG6GA, 807, 807W, ATS25, ATS25A, CV1060, CV124, CV1364, CV1374, CV1572, CV2796, CV2817, CV3618, CV3809, CV428, QV0525, VT100, VT100A, VT60(RAF), VT60A(RAF) Different filament voltage 19BG6G, 19BG6GA Warning: Substitutes are given as a guide only - please refer to original manufacturers data sheets to ensure that a substitute is safe and appropriate for your application.

6L6-GC Ratings Vh Ih VaMax Vg2Max VhkMax PaMax Pg2Max 6.3 0.9 500 500 +/-200 30 5

So Screen Grid may have up to 500V as can the Anode.
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Old 7th April 2014, 11:18 AM   #3
mdamp is offline mdamp  Australia
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Quote:
Originally Posted by JonSnell Electronic View Post
6L6-GC Substitutes Close or identical STR387, STR415, SV6L6GC Different rating or performance 6L6, 6L6G, 6L6GA, 6L6GB, 6L6GT, 6L6WGA, 6L6WGB, 6L6WGC, CV1286, CV1947, CV1948, CV586, EL37, VT115, VT115A Different pinout 5B245M, 6BG6, 6BG6G, 6BG6GA, 807, 807W, ATS25, ATS25A, CV1060, CV124, CV1364, CV1374, CV1572, CV2796, CV2817, CV3618, CV3809, CV428, QV0525, VT100, VT100A, VT60(RAF), VT60A(RAF) Different filament voltage 19BG6G, 19BG6GA Warning: Substitutes are given as a guide only - please refer to original manufacturers data sheets to ensure that a substitute is safe and appropriate for your application.

6L6-GC Ratings Vh Ih VaMax Vg2Max VhkMax PaMax Pg2Max 6.3 0.9 500 500 +/-200 30 5

So Screen Grid may have up to 500V as can the Anode.
Thanks I have just discovered these 6L6 tubes I'm using are Russian 6N3C and they are close to 6L6G info I googled so Am I right to believe it is safe to run the Anode and screen at 300v will be acceptable?? or should I just run both at 250v to be safe? any input would be grateful
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Old 7th April 2014, 11:52 AM   #4
mdamp is offline mdamp  Australia
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Quote:
Originally Posted by JonSnell Electronic View Post
6L6-GC Substitutes Close or identical STR387, STR415, SV6L6GC Different rating or performance 6L6, 6L6G, 6L6GA, 6L6GB, 6L6GT, 6L6WGA, 6L6WGB, 6L6WGC, CV1286, CV1947, CV1948, CV586, EL37, VT115, VT115A Different pinout 5B245M, 6BG6, 6BG6G, 6BG6GA, 807, 807W, ATS25, ATS25A, CV1060, CV124, CV1364, CV1374, CV1572, CV2796, CV2817, CV3618, CV3809, CV428, QV0525, VT100, VT100A, VT60(RAF), VT60A(RAF) Different filament voltage 19BG6G, 19BG6GA Warning: Substitutes are given as a guide only - please refer to original manufacturers data sheets to ensure that a substitute is safe and appropriate for your application.

6L6-GC Ratings Vh Ih VaMax Vg2Max VhkMax PaMax Pg2Max 6.3 0.9 500 500 +/-200 30 5

So Screen Grid may have up to 500V as can the Anode.
ok this is what search I did for this tube
(6n3C, 6n3C-E)

General
Tetrode, used in output stages of low frequency amplifiers.
Envelope: glass, with octal base.
Mass 70 g.

General characteristics:

Type 6P3S 6P3S-E 6n3ce
Filament voltage, Volt 6.3 6.3
Anode voltage, Volt 250 250
1st grid voltage, Volt -14 -14
2nd grid voltage, Volt 250 250
Type 6P3S 6P3S-E
Filament (heater) current, mA 90090 88040
Anode current, mA 7218 7313
2nd grid current, mA no more than 9 no more than 6
1st grid reverse current, mkA 3 0.5
Cathode current, mA no less than 275 -
Output power, W no less than 5.4 no less than 5.8
Mutual conductance, mA/V 5.2 to 6.8 5.2 to 6.8
Internal resistance, kΩ 25 no more than 65
Inter electrode capacitance, pF:
input 112 11
output 8.21.5 6.7
transfer no more than 1 no more than 1
Operation time, h 1000 5000
Limited operating values:

Type 6P3S 6P3S-E
Filament voltage, V 5,7-7 6-6.6
Anode voltage, V 375 250
2nd grid voltage, V 300 250
Cathode - heater voltage, V 100 90 / -200
Cathode current, mA - 90
Anode dissipation, W 20 20.5
2nd grid dissipation, W 2.75 2
Resistance in 1st grid circuit, kΩ 500 150
Operating environmental conditions :

Type 6P3S 6P3S-E
Acceleration of vibration loads, g 1.5 3
by frequencies, Hz 50 5 to 300
Acceleration of multiple impacts, g - 12
Acceleration of single impact, g - 100
Continuos acceleration, g - 100
Ambient temperature, С -60 to +70 -60 to +160
Relative humidity at up to 40C, % 98 98
Plate and plate-grid curves
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Old 7th April 2014, 03:34 PM   #5
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I have used soviet 6p3s for years with 450 V at UL push-pull amplifier and without any problem.

Click the image to open in full size.



So your +Ub 300 V is fully OK.
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Old 7th April 2014, 03:50 PM   #6
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I use 6n3c-E from the Svetlana Factory.They are equivalent to 5881 and have a slightly higher spec than 6L6. The 6L6 GT are much smaller in power handling.
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Old 7th April 2014, 09:18 PM   #7
mdamp is offline mdamp  Australia
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Quote:
Originally Posted by artosalo View Post
I have used soviet 6p3s for years with 450 V at UL push-pull amplifier and without any problem.

Click the image to open in full size.



So your +Ub 300 V is fully OK.
WOW nice little unit thanks for the input will leave the amp as is, seeing 300v is fine, How do you like the tone control in your amp I was thinking about it in mine but steered away from it as others said it muddy the tone?
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Old 7th April 2014, 09:22 PM   #8
mdamp is offline mdamp  Australia
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Quote:
Originally Posted by JonSnell Electronic View Post
I use 6n3c-E from the Svetlana Factory.They are equivalent to 5881 and have a slightly higher spec than 6L6. The 6L6 GT are much smaller in power handling.
Thanks the schematics I use did say the design is for 6L6 / 5881 SE so all should be good, I need now to change my other DIY EL34B amp power as I was told 355v was at the top and should to save the valve cut power down to 320v
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Old 8th April 2014, 06:05 AM   #9
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Quote:
Originally Posted by mdamp View Post
...How do you like the tone control in your amp I was thinking about it in mine but steered away from it as others said it muddy the tone?
That tone control is active Baxandall and works really well.
One can create a muddy tone control if he does not know what he is doing.

For the same reason some tubes are told to be "bad sounding" tubes.
From almost any tube a bad and good sounding circuit can be done, but the latter is much demanding task.
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Old 8th April 2014, 08:51 AM   #10
mdamp is offline mdamp  Australia
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Quote:
Originally Posted by artosalo View Post
That tone control is active Baxandall and works really well.
One can create a muddy tone control if he does not know what he is doing.

For the same reason some tubes are told to be "bad sounding" tubes.
From almost any tube a bad and good sounding circuit can be done, but the latter is much demanding task.
Yes true, will after many searches I have come to a decision the I will run the Plate voltage from 300v - 350v and Screen from 250v - 270v with all this reading I think 300v plate and 250v screen is the best way to get the right balance from these tubes. Will rewire power source and see how it runs.
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