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HEy Folks,
I am asking a question in general. I am wondering about cathode bias systems and the resistor used to bias the output tubes.
As I understand it, if you increase the bias resistor, you also increase the voltage at the cathode. Correct?
I also...
Started by Jcricket on
, 13 posts
by 6 people.
Answer Snippets (Read the full thread at audiokarma):
This make sense so: : HEy Folks....
Here again, increasing the bias resistor will increase the b+, etc in the power supply along with the correct cathode bias resistor to get everything to work.
The voltages at the power supply.
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I got some new Tung-Sol reissue 6550s for my VBA 400, and I was wondering if anyone has biased one of these amps before, and if it's much different than biasing a 70s Marshall.
I understand there are is a bias pot for each quad, for a total of 2 bias ...
Started by Clammy on
, 17 posts
by 6 people.
Answer Snippets (Read the full thread at talkbass):
Bias....
If it's a phase inverter balance manufacturer's data sheet).
If it's a phase inverter balance like on an SVT warmed up and their bias is stabilized for at least 20 minutes.
And their bias is stabilized for at least 20 minutes.
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Hi all,
As you know I've been working on this amp for a while, the 299A
model 2 and was wondering what is your opinion on the two
bias supply caps, do they go bad, so far everything seems to be
working good with them. I did get some Nichicon 100uf 100...
Started by tube-a-lou on
, 12 posts
by 5 people.
Answer Snippets (Read the full thread at audiokarma):
I forget....
I believe the second generation looks a lot like-wound resistor .
And was wondering what is your opinion on the two
bias supply caps, do they go bad, so far everything seems Here is the bias section of my first generation 299.
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I am working on an A-27, and the manual shows bias to bee 88mv. It sounded fine and ran cool when I first started on it, but found the bias was set to 35mv on both channels. I cranked it up to 88mv and now it gets quite warm at idle.
Any thoughts on this...
Started by Robisme on
, 12 posts
by 4 people.
Answer Snippets (Read the full thread at audiokarma):
Thanks for the input A-27's...the bias....
I doubt if it's audible though...
I wonder if the bias distortion will increase a bit (your 35 mV bias).
And the M-25 are good for up to 30 watts in class A before switching over to class B .
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Guys, can I use the test points without the scope?
I mean I biased a dozen of amps using kind of Weber bias meter (attached between tube and a socket) + voltage meter and calculated bias from known formulas. And wanted to know if the SVT's test points...
Started by boroman on
, 20 posts
by 7 people.
Answer Snippets (Read the full thread at talkbass):
At that time they were not as prized as today un-modded? to bias an SVT, all you need I'll need to replaced ....
Having as a bias pot.
MV=mA on the cathodes.
A 1 ohm resistor between cathode and ground.
Circuit as a "Bias King" uses.
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Noticed my 7868s in my 400 (serial # 27776 P) glowing a bit too orange recently, and started trying to diagnose the problem. I am a beginner, so please bear that in mind!
One tube red-plated completely and then died. I replaced it with another used one...
Started by pborten on
, 15 posts
by 5 people.
Answer Snippets (Read the full thread at audiokarma):
Bar resistor between the new diode bridge and ground the selenium rectifier ... .
A few things to check.
Is that I'm only getting about -16 VDC bias supply right at the new silicone bridge output, before it hits got a bias problem.
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I am rebuilding my JTM-45 Reissue, installed a turrent board that I drilled and staked and populated, new Mercury OT. When doing the testing as per Georges instructions, the bias will only go to -37VDC, the instructions say it should reach -45 VDC. Can...
Started by kansas-terry on
, 15 posts
by 3 people.
Answer Snippets (Read the full thread at metroamp):
If they bias too hot and you don't have enough range on the bias pot to bring the ....
See if the tubes will bias okay first.
It can vary a lot with different tubes.
The negative bias voltage on charts is just a rough guide.
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I have my old amp I bought in Nam in 68, I gave it to my brother in law years ago to change the finals in it to have more output.
Lost brother in law years ago and haven't messed with it, but last time I played it one side was alot louder than the other...
Started by Dudly on
, 11 posts
by 4 people.
Answer Snippets (Read the full thread at audiokarma):
Procedures....
In the meantime I don't want that I have found in the manual .
I have looked at every post I can work on the balance part of it if the bias and current are right.
To know where to hook my meter up so I can adjust the bias and current.
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I have a 50wt plexi with a PPIMV that has lost bias ref on one tube.
V4 reads -38.8mv and V5 shows as .001mv. I have traced the MV circuit and all appears ok there. Very confusing. The grid feeds with the master wide open read the same.
When the amp is...
Started by Reeltarded on
, 15 posts
by 5 people.
Answer Snippets (Read the full thread at metroamp):
If those are okay be missing ....
Umm there is a "board componentsAre you using 1 ohm resistors to measure bias? Check voltage on V5 pin 3 and 4.
Not the resistors where you check bias, the actual bias SUPPLY resistor.
No no.
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So I'm rebuilding the entire power supply on the Bandmaster I'm learning lots of neat stuff about rectification, filtering, and negative bias voltage supply.
I have no idea what I just said but learning about it is cool Check out my deal and what I am...
Started by mortatort on
, 14 posts
by 8 people.
Answer Snippets (Read the full thread at harmony-central):
I have no idea what I just said but learning about it is cool
Rectifiers .
And negative bias voltage supply.
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