MoJo Brit 800 Build: At My Wits End!!!!
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- pompeiisneaks
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Re: MoJo Brit 800 Build: At My Wits End!!!!
It is so mind boggling to me to have someone come to a forum asking for help to then go on being rude to people and acting like they know already how to resolve the problem. Your skill with electronic circuits in general doesn't directly easily apply to tubes, OR you're not as skilled as you think you are.
I'm pretty new to this, only been doing it for a few years and see many of your assumptions are way off base. I also see you being testy to people that know about 100 times what you do about this subject.
How would you feel as a certified aircraft mechanic to have me coming and asking you for help and telling you that i know how planes work because I once flew on one, and have done flight sims...
And then being testy to you because you don't answer my non clear, uninformed questions perfectly and immediately out of the goodness of your heart for free?
I think you should ask yourself why you think people would want to help someone that doesn't respect the time and effort they put in for free, to be berated for not doing it 'right'?
~Phil
I'm pretty new to this, only been doing it for a few years and see many of your assumptions are way off base. I also see you being testy to people that know about 100 times what you do about this subject.
How would you feel as a certified aircraft mechanic to have me coming and asking you for help and telling you that i know how planes work because I once flew on one, and have done flight sims...
And then being testy to you because you don't answer my non clear, uninformed questions perfectly and immediately out of the goodness of your heart for free?
I think you should ask yourself why you think people would want to help someone that doesn't respect the time and effort they put in for free, to be berated for not doing it 'right'?
~Phil
tUber Nerd!
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Re: MoJo Brit 800 Build: At My Wits End!!!!
First off a kt77 is much more like a 5881 in terms of its 25 watt rating.
Second, the tube data sheet for a kt77 with about 400 volts on its plate and screen calls for -31 volts with a 25% up or down range.
I would want you to get at least a - 38 volts to show up on pin 5 of each output tube socket before you even try to pop the output tubes back in.
Next the filament voltage of 5.6 vac is not good!
With the output tubes yanked out you should have very close to 6.8 volts, that’s over 20% low !
A acceptable voltage range is 6.3 + or - 10%.
Second, the tube data sheet for a kt77 with about 400 volts on its plate and screen calls for -31 volts with a 25% up or down range.
I would want you to get at least a - 38 volts to show up on pin 5 of each output tube socket before you even try to pop the output tubes back in.
Next the filament voltage of 5.6 vac is not good!
With the output tubes yanked out you should have very close to 6.8 volts, that’s over 20% low !
A acceptable voltage range is 6.3 + or - 10%.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: MoJo Brit 800 Build: At My Wits End!!!!
I had the exact same problem when turning the key on my Tweed Super: insufficient bias voltage. I had no sound and lowered heater voltages across the board. Once I got the voltage range correct and properly adjusted the bias, all was well.
Another thing to look for is an incorrectly wired bias adjustment pot. Mine was wired backwards once on a PR build in the source diagram and it limited the bias adjustment too much and I risked frying those output tubes. Correctly wiring the adjustment pot saved my bacon.
Another thing to look for is an incorrectly wired bias adjustment pot. Mine was wired backwards once on a PR build in the source diagram and it limited the bias adjustment too much and I risked frying those output tubes. Correctly wiring the adjustment pot saved my bacon.
Just plug it in, man.
Re: MoJo Brit 800 Build: At My Wits End!!!!
Don't think your comments are appropriate...I am frustrated that this doesn't work and I've got 20 different replies that are giving assumptions/advice and not answers. Same as in your analogy, if you asked me how to change a spark plug in a reciprocating engine, I would assist with step-by-step directions, not just tell you "I think you need plugs and a socket wrench". I do know how circuits work but when you do not obtain the readings you are expecting it gets a bit weird. I do appreciate the help but wish it were a bit clearer.pompeiisneaks wrote: ↑Sun Sep 12, 2021 10:07 pm It is so mind boggling to me to have someone come to a forum asking for help to then go on being rude to people and acting like they know already how to resolve the problem. Your skill with electronic circuits in general doesn't directly easily apply to tubes, OR you're not as skilled as you think you are.
I'm pretty new to this, only been doing it for a few years and see many of your assumptions are way off base. I also see you being testy to people that know about 100 times what you do about this subject.
How would you feel as a certified aircraft mechanic to have me coming and asking you for help and telling you that i know how planes work because I once flew on one, and have done flight sims...
And then being testy to you because you don't answer my non clear, uninformed questions perfectly and immediately out of the goodness of your heart for free?
I think you should ask yourself why you think people would want to help someone that doesn't respect the time and effort they put in for free, to be berated for not doing it 'right'?
~Phil
Re: MoJo Brit 800 Build: At My Wits End!!!!
This is some strong guidance...I will make the changes tomorrow on the bias resistor.Stevem wrote: ↑Sun Sep 12, 2021 10:20 pm First off a kt77 is much more like a 5881 in terms of its 25 watt rating.
Second, the tube data sheet for a kt77 with about 400 volts on its plate and screen calls for -31 volts with a 25% up or down range.
I would want you to get at least a - 38 volts to show up on pin 5 of each output tube socket before you even try to pop the output tubes back in.
Next the filament voltage of 5.6 vac is not good!
With the output tubes yanked out you should have very close to 6.8 volts, that’s over 20% low !
A acceptable voltage range is 6.3 + or - 10%.
- pompeiisneaks
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Re: MoJo Brit 800 Build: At My Wits End!!!!
I think my comments are very appropriate. I'm the forum admin/moderator and it's my job to try and keep people civil. So far your tone has been way less than civil. Just because YOU think a reply is 'advice/assumption and not answers' doesn't mean it isn't. The best attempts were made with the minimum information given. If you want to continue asking people to help but make sure they fit your narrow definition of 'proper help' then you're not going to last long online my friend.nflrage wrote: ↑Mon Sep 13, 2021 1:10 amDon't think your comments are appropriate...I am frustrated that this doesn't work and I've got 20 different replies that are giving assumptions/advice and not answers. Same as in your analogy, if you asked me how to change a spark plug in a reciprocating engine, I would assist with step-by-step directions, not just tell you "I think you need plugs and a socket wrench". I do know how circuits work but when you do not obtain the readings you are expecting it gets a bit weird. I do appreciate the help but wish it were a bit clearer.pompeiisneaks wrote: ↑Sun Sep 12, 2021 10:07 pm It is so mind boggling to me to have someone come to a forum asking for help to then go on being rude to people and acting like they know already how to resolve the problem. Your skill with electronic circuits in general doesn't directly easily apply to tubes, OR you're not as skilled as you think you are.
I'm pretty new to this, only been doing it for a few years and see many of your assumptions are way off base. I also see you being testy to people that know about 100 times what you do about this subject.
How would you feel as a certified aircraft mechanic to have me coming and asking you for help and telling you that i know how planes work because I once flew on one, and have done flight sims...
And then being testy to you because you don't answer my non clear, uninformed questions perfectly and immediately out of the goodness of your heart for free?
I think you should ask yourself why you think people would want to help someone that doesn't respect the time and effort they put in for free, to be berated for not doing it 'right'?
~Phil
~Phil
tUber Nerd!
Re: MoJo Brit 800 Build: At My Wits End!!!!
i'm reading the topis and see the problem. it is impossible for you to fix that, sorry all answers you get allready. you need to measure current through the output valves, and reduce it with the bias voltage (put more negative, bias is the "regulator for the flow through the valve") and some of your problems can be fixed. but others will permanently remain..
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Re: MoJo Brit 800 Build: At My Wits End!!!!
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- pompeiisneaks
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Re: MoJo Brit 800 Build: At My Wits End!!!!
Other than the abusive post, I'm thinking leaving this thread as a cautionary tale for those that think coming to a forum and acting like a jerk is the right way to do it... will not be the right way to do it.
I do now understand why his username was nflrage
username checks out.
If others think I should just nuke the thread, I can.
~Phil
I do now understand why his username was nflrage
username checks out.
If others think I should just nuke the thread, I can.
~Phil
tUber Nerd!