#1
so a couple weeks ago i got a b52 at100 and i think the rectifier tube died on me today. i just retubed it too. the amp works fine in solid state rectification but i get no sound in tube ab1 and tube a rectification. so here are a few questions

1. can i still run the amp safely in solid state rectification mode without any damage being done to it?
2. can i just buy a rectifier tube that matches that one and do a swap or do i have to check my bias.
3. since the rectifier is part of the power section of the amp is it still treated like a regular tube? ie: can i remove it clean the pins with detoxit and replace it without risking frying myself from the voltage?

thanks as always guys and gals
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#2
Quote by iheartgun
so a couple weeks ago i got a b52 at100 and i think the rectifier tube died on me today. i just retubed it too. the amp works fine in solid state rectification but i get no sound in tube ab1 and tube a rectification. so here are a few questions

1. can i still run the amp safely in solid state rectification mode without any damage being done to it? YES
2. can i just buy a rectifier tube that matches that one and do a swap or do i have to check my bias. Yes No need to bias a Rectifier tube.
3. since the rectifier is part of the power section of the amp is it still treated like a regular tube? ie: can i remove it clean the pins with detoxit and replace it without risking frying myself from the voltage?Yes you can remove it and clean it. Make sure that the amp is turned off.

thanks as always guys and gals


Answers in bold
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#3
cool, thanks for the help and the knowledge! i pulled it used detoxit and threw it back in and it works fine now. the only reason why i didnt do that from the get go is the fact that ive never dealt with a rectifier tube before
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It is NOT trash metal it is tHrash metal...get it right
#4
Rectifier tubes are cheap - buy a spare.
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#5
the rectifies are part of the power supply....not necessarily the power section. The rectifies are configured to convert the AC voltage coming from the power transformer into a steady DC voltage signal that can be fed to all of the vacuum tubes (b/c they all need about 300VDC to operate).

A rectifier/diode at its fundamental level is a cathode and anode. A heater transfers heat to the cathode which causes it to emit electrons which flow towards the positively charged anode. The current (electron flow) can only move in ONE direction. A common configuration is a rectifier bridge where four rectifiers are attached end to end in order to take a AC signal and convert it to DC. Then after the bridge you have a network of capacitors that smooth out the signal so that it is fairly steady.

A diode is a very simple component and therefore does not need biasing. Typically only power tubes need biasing. Most times preamp tubes are designed to be self biasing. I think they might do it for power tubes in some cases. To clear up any confusion...the bias is just the idle state of the tube...like the idle speed of the car. You are basically setting how much current is flowing through the tube when it is not being driven (i.e. no input signal). The bias setting depends on the design of the stage and the users personal taste (though there are strict guidelines which are based on the gain stage design).

Again preamp tubes are usually self biasing so you can change them freely AS LONG AS you replace it with the SAME TYPE of tube (i.e. 12AX7, 12AT7, 12AU7, etc.). Each of these tubes behave differently in a gain stage...a gain stage circuit is typically NOT one size fits all. Amp designers optimize the circuit for the chosen preamp tube which is typically a 12AX7. Some clean amps may use some of the other kinds and i believe that some phase interters use 12AT7's. Basically a phase inverter is the final stage of the preamp before the power amp. It is only used in push pull power amps (as far as i know).

The solid state rectification mode is using solid state diodes to convert the voltage. The other mode uses vacuum tube rectifiers. I haven't studied power supplies enough to tell you the perceivable difference between the two kinds but the general difference is that one uses solid state components while the other uses tubes. But all this section is doing is providing a supply voltage to the preamp and power tubes. I could go on about preamps and power amps but it is beyond the scope of this topic (besides i have already gone a little too far). Sorry for the overload of information...i am very passionate about the subject. I hope you (or anyone) finds this info helpful.
"If A is a success in life, then A equals x + y + z. Work = x; y = play; and z = keeping your mouth shut."
--Einstein

"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
--Einstein
#6
"Self biasing" normally just means cathode biased. They don't actually self bias, they have a resistor limiting current and elevating the cathode to a DC offset - the bias. When you cathode bias, a tube has to be way off spec to not be biased in a safe region for that tube.
Some of us even bias cathode biased amps at times. I use radically different 6V6 tubes in my Champ at times so I actually go in and measure what's going on. I have mine biased slightly cold to extend the life of rare NOS tubes. I have considered adding a switch to swap between the two resistors I've found to provide the best compromise of bias currents.
Truly self biasing amps do exist but are very rare. It's something I've always wanted to try. Stick an LM317 regulator on the cathode configured as a current regulator. Bypass it with a nice expensive capacitor and bada bing bada boom, a true self biasing power amp. I imagine that it's never done because people would cry about SS stuff in the path of the output signal, even though it's bypassed. When you consider how much SS stuff actually gets thrown in what are supposed to be tube amps these days I'm surprised such a thing isn't more common.
Gilchrist custom
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Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#7
if you are using tube rectification and the tube blows will there be any over current going to from the power section to the rest of the amp? in my mind there would be but would it be enough to blow a transformer per se?

also would squealing be the result of a 12ax7 in place of a 12at7 in lets say a reverb driver position?

oh and cath you really should write a book man your knowledge is intense. lol
Live Rig
Michael Kelly Custom Shop Plum Telecaster
Michael Kelly Custom Shop Plum Patriot


EVH 5153 50w
Jet City 2x12
Custom Board

It is NOT trash metal it is tHrash metal...get it right
#8
No. If the tube blows all voltage to the tubes apart from the heaters disappears. It's the same as hitting the standby switch.

Squealing is most often a microphonic tube. Try gently tapping them one by one with a pencil and listen to what comes out of the speaker. A little microphonics is fairly normal but if the tapping comes out loud and clear replace that tube.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#9
Quote by Cathbard
"Self biasing" normally just means cathode biased. They don't actually self bias, they have a resistor limiting current and elevating the cathode to a DC offset - the bias. When you cathode bias, a tube has to be way off spec to not be biased in a safe region for that tube.
Some of us even bias cathode biased amps at times. I use radically different 6V6 tubes in my Champ at times so I actually go in and measure what's going on. I have mine biased slightly cold to extend the life of rare NOS tubes. I have considered adding a switch to swap between the two resistors I've found to provide the best compromise of bias currents.
Truly self biasing amps do exist but are very rare. It's something I've always wanted to try. Stick an LM317 regulator on the cathode configured as a current regulator. Bypass it with a nice expensive capacitor and bada bing bada boom, a true self biasing power amp. I imagine that it's never done because people would cry about SS stuff in the path of the output signal, even though it's bypassed. When you consider how much SS stuff actually gets thrown in what are supposed to be tube amps these days I'm surprised such a thing isn't more common.

yes i know that. i didn't explain it b/c my post was already getting too long.

using and SS component in the cathode bias circuit might not be as bad as people think. It might affect the frequency response some but that is something that can be fixed elsewhere. if SS components can be used to keep the cathode voltage constant (or within a few milivolts) then it would actually improve the gain of the amplifier. A problem with traditional cathode bias amps is that the voltage at the cathode will fluctuate when the input signal hits the grid. A bypass capacitor can be used to reduce the fluctuations but it won't completely go away. Though maybe if tuned right that configuration can have some interesting and desirable results. But the point is that if SS components in the cathode bias circuit can keep the reference voltage at the cathode constant then the gain of the amplifier will increase...maybe not by much for the specific gain stage but a net increase across the board might be noticeable. Also realize i am only talking about preamp tubes. Power tubes are a different beast and i haven't studies too much on them yet. I know how pentodes and power beam tetrodes work but i haven't learned a whole lot about power amps yet. I don't get much time to read the books i got...i have college work keeping me busy.
"If A is a success in life, then A equals x + y + z. Work = x; y = play; and z = keeping your mouth shut."
--Einstein

"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
--Einstein
#10
If I were to do it I would only do it on the power valves. Set a constant current for DC and bypass the whole circuit for AC with a decent cap. I don't see why it wouldn't work quite well. Maybe one day. Too busy building classic circuits to sell atm ..... but one day maybe. It would be fun to see how well it actually works in a guitar amp I reckon.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#11
Quote by Cathbard
If I were to do it I would only do it on the power valves. Set a constant current for DC and bypass the whole circuit for AC with a decent cap. I don't see why it wouldn't work quite well. Maybe one day. Too busy building classic circuits to sell atm ..... but one day maybe. It would be fun to see how well it actually works in a guitar amp I reckon.

ya i may look into it some day myself. i am too busy right now. when i get a break in December i am going to continue to study tube amps and one day when i am in a financially stable position i will start experimenting. I have several boxes of old vacuum tubes i'd like to mess around with. Most probably won't work but it should be fun. Though my first project will be a multi channel variable DC power supply to use as a design tool. I am thinking about having about 4 channels that output 0-500VDC as well as several auxiliary outputs of 5V, 6V, and 12V. Should be a fun project.
"If A is a success in life, then A equals x + y + z. Work = x; y = play; and z = keeping your mouth shut."
--Einstein

"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
--Einstein
#12
im considering picking up one of those kits just so i can get my hands into it and learn something.
Live Rig
Michael Kelly Custom Shop Plum Telecaster
Michael Kelly Custom Shop Plum Patriot


EVH 5153 50w
Jet City 2x12
Custom Board

It is NOT trash metal it is tHrash metal...get it right
#13
Quote by iheartgun
im considering picking up one of those kits just so i can get my hands into it and learn something.

thats a good idea though i would suggest reading up on the theory and design of tube amps before you get into. Make sure you know about the basic circuit components and how they work in a circuit. It can get kinda difficult but it is necessary information if you want to know how it works and how to build them yourself. Here are some good internet sources i have found:

http://www.freewebs.com/valvewizard/index.html (click on "triode gain stage" on the left side to download the first chapter of his book on preamps. full of great information)

http://www.pentalaboratories.com/tubeworks.html

http://www.aikenamps.com/CommonCathode.htm

http://www.radau5.ch/basics_1.html

http://www.aikenamps.com/

http://www.ampbooks.com/home/books/preamps/

http://www.vias.org/crowhurstba/index.html

Those are just a few. I suggest if you are really interested in learning about this stuff then buy the books offered by the Merlin Blencowe (first link) and Richard Kuehnel (sixth link). I got them and they have been very useful.

Take Care,
John
"If A is a success in life, then A equals x + y + z. Work = x; y = play; and z = keeping your mouth shut."
--Einstein

"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
--Einstein
#14
i have a decent understanding of electronics from my military days but i have yet to actually look into amp building and how my electronics knowledge will apply. these titles you have given me will surely help though. my main fear or dabbling in this is electricity due to the gun system i worked on and some bad experiences various electrical components in it. Thanks!
Live Rig
Michael Kelly Custom Shop Plum Telecaster
Michael Kelly Custom Shop Plum Patriot


EVH 5153 50w
Jet City 2x12
Custom Board

It is NOT trash metal it is tHrash metal...get it right
#15
Quote by iheartgun
i have a decent understanding of electronics from my military days but i have yet to actually look into amp building and how my electronics knowledge will apply. these titles you have given me will surely help though. my main fear or dabbling in this is electricity due to the gun system i worked on and some bad experiences various electrical components in it. Thanks!

i haven't had any hands on time with tube amps so i can't really help you there. I know a decent amount of design and theory. I am sure there are plenty of people here on the forum and elsewhere as well as other websites that can help you. Cathbard obviously has experience with building amps so there is at least one source.

as far as basic electronics go there are plenty of online resources but if you want i can find a way to send you a PDF of a college level circuits book i used. it is pretty good. it goes over everything from voltage, current and power to basic DC resistor networks and circuit analysis techniques as well as phasor and laplace transform techniques for AC circuits. It also has Fourier transform and fliters (passive and active).
"If A is a success in life, then A equals x + y + z. Work = x; y = play; and z = keeping your mouth shut."
--Einstein

"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
--Einstein
#16
Ill have a look on the interwebz and see what there is. i already understand basic electronics and know how to read long line electrical diagrams as well as solder and do minor repairs. but ill have a start at the very beginning just to refresh myself
Live Rig
Michael Kelly Custom Shop Plum Telecaster
Michael Kelly Custom Shop Plum Patriot


EVH 5153 50w
Jet City 2x12
Custom Board

It is NOT trash metal it is tHrash metal...get it right
#17
Kits?
This is where I buy my transformers. They do kits as well using the same trannies. It will save you a bit of money because the trannies are the most expensive part. It's an old tranny factory in Chicago. Good but cheap. The kits come with pretty high grade components. Like, you can choose between Mallory and Sprague Orange Drop signal caps; F&T, JJ or Sprague Atom filter caps. all good stuff at decent prices.
As a first amp to cut your teeth on I'd recommend this:
http://triodeelectronics.com/5f1kit.html
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#18
holy crap thats cheap thanks Cath!
yeah i was looking into ceriatone but they are expensive as hell as well as the MOD 102. but i think ill go with the 5f1 tweed.

Christmas may come early this year.
Live Rig
Michael Kelly Custom Shop Plum Telecaster
Michael Kelly Custom Shop Plum Patriot


EVH 5153 50w
Jet City 2x12
Custom Board

It is NOT trash metal it is tHrash metal...get it right
#19
Damn, I would love to build that with an EL34 power tube.
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