Wonderful video! I learned to bias from you and it has made a great difference in my amps. I too use the eurotubes meters at your recommendation; they are excellent. It is good to see you putting out new material. Thanks again for an entertaining informative lesson.
I have a Blackstar 40w club amp and Blackstar don't say how to bias the EL34 valves but from another channel here on YT I found their little secret, next to the tubes through the chassis there are 2 trim pots one for each valve and there are 2 LED's per valve one green and one red, adjusting the pot for no glow from either green or red LED the bias is set for one tube and just repeat the same for the other tube.
Yes, a 2205. I own one of these from 1985. Michael Schenker’s amp of choice. I love mine, has a much better rock tone than the 2203,04 800’s. They are a bit brash and brittle for me. These have more gain and are just a joy to play without paint peeling volume to get a good tone.
I have an 18 watt marshall clone head. I've seen people add a potentiometer to the board to make a self biasing amp.....biasable. It's done by people who want to use variac voltage regulator. They run the amp on 90 volts and use the installed potentiometer to bias the tubes hot. This creates a sag in the or certain EVH sound. What do think about this mad science?
Nice video, have two JCM800s, a 2210 and 4210. Probably will get the Eurotubes probe but please clarify me one thing: is one probe enough with a matched pair (or quad), and if so, does it matter under which tube the probe is mounted?
Hi If you know the pair/quad is well matched then in theory you just need the probe under one valve and adjust the bias. The others should be good. BUT... it's probably best to use the probe under each valve just to double check.
Great demonstration of how to bias this Marshall model. It's a pity that Marshall don't go one step further and fit an external adjustment that only requires a bog standard digital multimeter and small screwdriver like some on the Fender's have got. Hope you've managed to take advantage of the flying conditions of late 😅🛩
Yes had a nice day out on Isle of Wight yesterday! I think the reason they don't do this is because they really don't want people twiddling. Not one guitarist in 100 knows anything about biasing but will certainly respond to a forum post which goes: "Hey, Anyone else know this awesome Fender hack? There's a screwdriver slot on the top of the chassis, just turn it up to MAX and you'll get this AWESOME tone! Enjoy my dudes!".
this is a great tutorial. quick question though. When you buy a set of tubes and they write a number for the bias point. in my case i have a set of kt88's with 33 written on them. do they mean for me to treat that as the max dissipation instead of the blanket 35w given to kt88's?
My guess is that this is the bias current 33mA which these tubes drew under certain test conditions. Not really useful apart from matching. E.g. you want 2 x 33 or 4 x 33 tubes to be matched pair or quad.
i have a marshal jcm800 2203 that sounds fine while playing 10-30 minutes then eventually i get about 25-50% volume reduction and the tone gets fuzzier. does this sound like a power tube issue or Output Transformer issue? thank you for this video.
Good to see a new episode, Stuart. I imagine that the Lead Series are extremely noisy due to the proximity of the power transformer , to the output transformer. What is your experience with them?
Tampoco son tan ruidosos..ten en cuenta que los transformadores están colocados de una forma estratégica para anular el ruido. Uno mira al sur, y el otro mira al oeste.
Lo causa el gasto normal de las valvulas con su uso. Es cierto que no se sabe de que medida partíamos.. por eso hay que bajar el pote y luego reajustar con un juego nuevo de valvulas.
It's very hard to say as I do not know the history here. It could be a lot of things. I doubt that the bias has drifted that low though. Maybe someone put in different tubes and didn't bias?
@@stuartukguitarampguy5830 I was playing the amp loud one day and it just went silent. Bought a set of new tubes, made no difference. All of them light up. Someone said it may be the output speaker transformer.
@@stuartukguitarampguy5830 I have some test equipment. Audio Generator, Variac, Oscilloscope, Fluke. I'm going to send a signal through the output transformer see if I get anything.
Hi Stuart. This is the jcm 800 model 2210. I had one of these. I regret selling it. Best jcm 800 ever. Thanks for the video.
Yes they are good amps and easy to work on.
Wonderful video! I learned to bias from you and it has made a great difference in my amps. I too use the eurotubes meters at your recommendation; they are excellent.
It is good to see you putting out new material.
Thanks again for an entertaining informative lesson.
Thanks Michael.
The EL34’s have no legend on them because YOU are a legend Stuart! Thanks for the video.
Aw, you are too kind!
I have a Blackstar 40w club amp and Blackstar don't say how to bias the EL34 valves but from another channel here on YT I found their little secret, next to the tubes through the chassis there are 2 trim pots one for each valve and there are 2 LED's per valve one green and one red, adjusting the pot for no glow from either green or red LED the bias is set for one tube and just repeat the same for the other tube.
Yes, a 2205. I own one of these from 1985. Michael Schenker’s amp of choice. I love mine, has a much better rock tone than the 2203,04 800’s. They are a bit brash and brittle for me. These have more gain and are just a joy to play without paint peeling volume to get a good tone.
Always love those tasty, heavy guitar lick intros to your videos.
If you feel like waffling on, you go right ahead Mr. Stuart.
Thanks! They were done by a customer of mine. My playing isn't that good!
Hey Stuart, another great explanatory video for us newbies..More info and procedures learned..Thanks for sharing..Ed..uk..😀
Thanks Ed
I have an 18 watt marshall clone head.
I've seen people add a potentiometer to the board to make a self biasing amp.....biasable.
It's done by people who want to use variac voltage regulator.
They run the amp on 90 volts and use the installed potentiometer to bias the tubes hot.
This creates a sag in the or certain EVH sound.
What do think about this mad science?
Wow I haven't heard of that! I guess if it gives the sound they want, then why not?
Great Video. Thank you
I'm glad you enjoyed it.
Nice video, have two JCM800s, a 2210 and 4210. Probably will get the Eurotubes probe but please clarify me one thing: is one probe enough with a matched pair (or quad), and if so, does it matter under which tube the probe is mounted?
Hi If you know the pair/quad is well matched then in theory you just need the probe under one valve and adjust the bias. The others should be good. BUT... it's probably best to use the probe under each valve just to double check.
Great demonstration of how to bias this Marshall model. It's a pity that Marshall don't go one step further and fit an external adjustment that only requires a bog standard digital multimeter and small screwdriver like some on the Fender's have got. Hope you've managed to take advantage of the flying conditions of late 😅🛩
Yes had a nice day out on Isle of Wight yesterday! I think the reason they don't do this is because they really don't want people twiddling. Not one guitarist in 100 knows anything about biasing but will certainly respond to a forum post which goes: "Hey, Anyone else know this awesome Fender hack? There's a screwdriver slot on the top of the chassis, just turn it up to MAX and you'll get this AWESOME tone! Enjoy my dudes!".
😅😅😅😅😅@@stuartukguitarampguy5830
They did on the jcm2000 range but then didn't on the JVM even put the fuses on the board too
Young Stuart! The man!! x
You are most kind sir.
I noticed that the plate voltage increased with your bias adjustment. Should I recalculate the bias current and re-tweak, or is that being too fussy?
Hi Don. Too fussy. THis is not an exact adjustment.
this is a great tutorial. quick question though. When you buy a set of tubes and they write a number for the bias point. in my case i have a set of kt88's with 33 written on them. do they mean for me to treat that as the max dissipation instead of the blanket 35w given to kt88's?
My guess is that this is the bias current 33mA which these tubes drew under certain test conditions. Not really useful apart from matching. E.g. you want 2 x 33 or 4 x 33 tubes to be matched pair or quad.
@@stuartukguitarampguy5830 thank you!
i have a marshal jcm800 2203 that sounds fine while playing 10-30 minutes then eventually i get about 25-50% volume reduction and the tone gets fuzzier. does this sound like a power tube issue or Output Transformer issue? thank you for this video.
Almost certainly not output transformer. I'd replace the power tubes and see if that solves the issue. If not, it's tech time!
@@stuartukguitarampguy5830 okay thank you. will try that first.
Fast job. Thank you.
Thanks Miguel.
Good to see a new episode, Stuart. I imagine that the Lead Series are extremely noisy due to the proximity of the power transformer , to the output transformer. What is your experience with them?
Tampoco son tan ruidosos..ten en cuenta que los transformadores están colocados de una forma estratégica para anular el ruido. Uno mira al sur, y el otro mira al oeste.
I have not found this to be so. As our Italian friend says below, they are priented to cancel out the induced hum.
Hi Stuart, are these Eurotubes only on camera difficult to read? How is the readability in real?
Hi William Yes only on camera. I haven;t had any reliability issues.
My mistake the 2210 was a 100 watt. I think this is the 2205.
This amp looked incredibly clean, inside and out! What year was it made?
I thnk these are 1980s but not too sure tbh.
Stuart, was the bias that low when you received the amp due to the owner swapping out tubes or what would cause the bias to decrease that much?
Lo causa el gasto normal de las valvulas con su uso. Es cierto que no se sabe de que medida partíamos.. por eso hay que bajar el pote y luego reajustar con un juego nuevo de valvulas.
It's very hard to say as I do not know the history here. It could be a lot of things. I doubt that the bias has drifted that low though. Maybe someone put in different tubes and didn't bias?
Si, es muy cierto eso que dices. No soy Italiano. Soy Español. 😉@@stuartukguitarampguy5830
My 800 doesn't make any sound. Tubes are all hot and red. Any idea ?
If by 'red' you mean red plating (glowing cherry red, and not just the small glow from the heater,) then you have a problem in the bias circuit.
@@stuartukguitarampguy5830 small glow.
@@jesse75 It could be so many things. I guess you've checked the HT fuse?
@@stuartukguitarampguy5830 I was playing the amp loud one day and it just went silent.
Bought a set of new tubes, made no difference. All of them light up.
Someone said it may be the output speaker transformer.
@@stuartukguitarampguy5830 I have some test equipment. Audio Generator, Variac, Oscilloscope, Fluke.
I'm going to send a signal through the output transformer see if I get anything.
👍👍
Great video! I made my own bias probes with cheap multimeters, works great. Instructions from youtube. €10 per probe👍
Nice well done. Can you also read plate voltage?
@@stuartukguitarampguy5830 I have a test point on the socket where I can see plate voltage with another multimeter. Made my life so much easier
Hi Stuart. In my jcm800 2203 (1987) is not possible up 20 mv. Cold bias I think😢
Ok. tbh you won't notice THAT much of a difference in sound between 20mA and say 35mA
This is not a "How to" because you didn't even show how to hook up the bias probes. Most people have not idea how to do that.