Help on new #40 build
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Re: Help on new #40 build
I do have a variac at my disposal . Would this help? Maybe I should just remove the limiter and chance it, or remove limiter and bring her up slowly with the variac.
Just worried about the voltages on the preamp tubes. If there is no voltage drop across the dropping resistor strings, then these tube swill be seeing 400+ volts on the plates.
Just worried about the voltages on the preamp tubes. If there is no voltage drop across the dropping resistor strings, then these tube swill be seeing 400+ volts on the plates.
If it sounds good, it is good! Trust your ears
- martin manning
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Re: Help on new #40 build
If you are still in standby mode, then the voltages down the rail will all be about the same since there is no current draw (unless you have a bleeder resistor somewhere). Switch into play mode and remeasure. I also recommend a 60W bulb.andresound wrote:However, the volltages (with bulb limiter) at the B+ = 196, then B2 - B5 are all 183v !!! Shouldn't they be dropping in increments?
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Re: Help on new #40 build
My voltages with limiter in circuit.
Secondary = 300.7 v ac
B+1 = 186.5 v
B+2 = 185.7 v
B+3a = 149.4 v
B+3b = 152.5 v
PI = 183.8 v
V2 = 183 v
V1 = 182.8 v
Regards Andre
Secondary = 300.7 v ac
B+1 = 186.5 v
B+2 = 185.7 v
B+3a = 149.4 v
B+3b = 152.5 v
PI = 183.8 v
V2 = 183 v
V1 = 182.8 v
Regards Andre
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If it sounds good, it is good! Trust your ears
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Re: Help on new #40 build
These are the voltages I am aiming for. Just oposted the pic for viewing of dropping resistors
Andre
Andre
If it sounds good, it is good! Trust your ears
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Re: Help on new #40 build
I thought $%£@! it! And removed the bulb limiter. Been on for 30 min and no smoke! Transformers are cool. Heater supply is 6.2v ac. Bias is - 48v pin 5
Secondary = 639 ac
B+ = 424v
Voltages are high on preamp!!
V1 pin 1 409.4 v
V1 pin 3 6.52 v
V1 pin 6 409 v
V1 pin 8 6.52 v
V2 pin1 410 v
V2 pin 3 8.92 v
V2 pin 6 411,5 v
V2 pin 8 8.97 v
PI pin 2 297.3 v
PI pin 3 & 8 106.1 v
PI pin 6 277.7 v
PI pin 7 66.9 v
Something wrong here guys!! Any ideas? Amp is very quiet and no sound with an input. Highly imbarresed
Secondary = 639 ac
B+ = 424v
Voltages are high on preamp!!
V1 pin 1 409.4 v
V1 pin 3 6.52 v
V1 pin 6 409 v
V1 pin 8 6.52 v
V2 pin1 410 v
V2 pin 3 8.92 v
V2 pin 6 411,5 v
V2 pin 8 8.97 v
PI pin 2 297.3 v
PI pin 3 & 8 106.1 v
PI pin 6 277.7 v
PI pin 7 66.9 v
Something wrong here guys!! Any ideas? Amp is very quiet and no sound with an input. Highly imbarresed
If it sounds good, it is good! Trust your ears
- martin manning
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Re: Help on new #40 build
Missing cathode ground?
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Re: Help on new #40 build
Thanks Martin,
Will check now.
Will check now.
If it sounds good, it is good! Trust your ears
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Re: Help on new #40 build
Martin, you are the MAN!!
Cathodes for V1 & V2 not grounded. BUT still no sound!!! Voltages have improved But still to high on preamp.
Secondary 646 ac
B+1 429.8
B+2 428.5
B+3b 241.7
B+3a 223.9
PI 409.1
V2 297.8
V1 293.9
Valves biased at -49.4
Andre
Cathodes for V1 & V2 not grounded. BUT still no sound!!! Voltages have improved But still to high on preamp.
Secondary 646 ac
B+1 429.8
B+2 428.5
B+3b 241.7
B+3a 223.9
PI 409.1
V2 297.8
V1 293.9
Valves biased at -49.4
Andre
If it sounds good, it is good! Trust your ears
Re: Help on new #40 build
I find that 40W bulbs glow too bright for larger amps (50W and 100W). While it isn't as safe, I typically use a 60W bulb in my limiter so I can tell the difference between normal current draw and s short.
- martin manning
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Re: Help on new #40 build
Well, that's some progress anyway. Can you post or point to the schematic you are using, and post voltages for pins 1, 2, 3, and 6, 7, 8 for the preamp tubes, and 3, 4, 5, and 8 for the power tubes?
Re: Help on new #40 build
Check your 27k dropping string resistor to make sure it's not 2.7k.
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Re: Help on new #40 build
Secondry 652v acmartin manning wrote:Well, that's some progress anyway. Can you post or point to the schematic you are using, and post voltages for pins 1, 2, 3, and 6, 7, 8 for the preamp tubes, and 3, 4, 5, and 8 for the power tubes?
V1 pin1 301.2
pin2 0
pin3 1.467
pin6 202
pin7 0
pin8 1.451
V2 pin1 210.9
pin2 0
pin3 1.395
pin6 205.7
pin7 0
pin8 1.483
PI pin1 278.9
pin2 66
pin3 103.6
pin6 279.5
pin7 70
pin8 103.6
V4 pin3 427.7
pin4 426.8
pin5 - 47.7
pin8 .035
V5 pin3 428.8
pin4 427.5
pin5 - 47.8
pin8 .036
FX pin1 240.7
pin2 8.22
pin3 13.02
pin6 222.3
pin7 0
pin8 1.718
Andre
If it sounds good, it is good! Trust your ears
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Re: Help on new #40 build
sorry herewith schematic of #40 v1.16
and relay connection
and normster FX loop
and relay connection
and normster FX loop
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If it sounds good, it is good! Trust your ears
- martin manning
- Posts: 13376
- Joined: Sun Jul 06, 2008 12:43 am
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Re: Help on new #40 build
Your voltages look reasonable except for the loop send stage. Pin 2 should be about 28V and pin 3 should be about 30V. Check the wiring and component values around there.
To see if that's where your signal is dying you can try jumping over the FX loop by pulling that tube and connecting a clip lead from the input side of the send pot to the input of the master volume (Level) pot. Turn the send and return pots all the way up.
Can you post a link to the schematic? The image above is fuzzy.
To see if that's where your signal is dying you can try jumping over the FX loop by pulling that tube and connecting a clip lead from the input side of the send pot to the input of the master volume (Level) pot. Turn the send and return pots all the way up.
Can you post a link to the schematic? The image above is fuzzy.
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Re: Help on new #40 build
Thanks Martin,
Checked my wiring for the 1000th time and reveresd some faults. I now have sound coming through (very soft). The return pot of the FX loop is acting like a master volume. The send pot makes no difference.
The tone stack seems to work.
The drive pot of the OD introduces a wired sound that (if the drive pot is not full open), and i put a finger on the blue cable from the relay board to the 0.01uf, the wired noise goes away. Also if I play a note, the wired sound seems to follow the fequency of the note played The higher I turn the drive pot, the lower in frequency the wired sound becomes!
Will try bypassing the FX loop. So just to be clear, clip lead from wiper (centre lug?) of send pot, to wiper of i meg level pot (OD master?).
Please excuse the ignorance.
Checked my wiring for the 1000th time and reveresd some faults. I now have sound coming through (very soft). The return pot of the FX loop is acting like a master volume. The send pot makes no difference.
The tone stack seems to work.
The drive pot of the OD introduces a wired sound that (if the drive pot is not full open), and i put a finger on the blue cable from the relay board to the 0.01uf, the wired noise goes away. Also if I play a note, the wired sound seems to follow the fequency of the note played The higher I turn the drive pot, the lower in frequency the wired sound becomes!
Will try bypassing the FX loop. So just to be clear, clip lead from wiper (centre lug?) of send pot, to wiper of i meg level pot (OD master?).
Please excuse the ignorance.
If it sounds good, it is good! Trust your ears