glad you fixed this for my father. It was his Father’s Day gift! Thanks a lot!

Once again, I want to say thank you to Tony for taking on this project. You, sir, are a gentleman and a scholar!

I like your biasing method for single push pull. i dont like it for stacked push pull as one tube being weaker and one stronger will not show itself .and can lead to an overloaded tube . On stacked tubes i like the anode current method on each individual tube . Great Video Tony

@bishopcullen1819

3 жыл бұрын

you prolly dont care but if you guys are bored like me during the covid times then you can watch pretty much all of the latest movies on InstaFlixxer. Have been watching with my gf for the last couple of days =)

@jaredhudson8145

3 жыл бұрын

@Bishop Cullen Definitely, been watching on InstaFlixxer for years myself :)

I have the schematic for this if you need it. I fixed one about a year ago. Pretty much a variant of a Marshall. See you have the schematic after watching more. Uncle Doug always did this method of bias also( I’ve done it this way also) until someone sent him a bias master or whatever brand with the built in meter to measure amperage and plate voltage. He did multiple comparisons with it to the winding resistance methods and the results were so negligible he uses the gadget all the time now. I have one called bias head our some such thing to plug into my DMM with a switch to toggle between plate voltage and bias current. I use it most of the time. The modern Marshall’s since the late 90’s have 1ohm resistors on the cathode to ground with a common pin and 1 pin per output tube or pair of tubes depending on 50 or 100 watt output. Nice and easy especially on the DSL/TSL models. You don’t have to pull the chassis, adjustment pots are next to the pins. One pot per tube/pair to balance the bias also. All amps should have a balance on the bias circuit. I have added that on a lot of amps I’ve worked on. Most tube are not well balanced half the time even though claim to be. I always run them on my old Hickok 539C to double check transconductance as well as plate current. This changes as the tubes wear also. I re-bias my own amps every 6 months if I’ve gigged a lot of hours on the tubes. You can make a nice bias socket probe from an old tube base or buy a blank base. Just put a lead from the plate and cathode pin with some banana plugs and use you meter on the amperage plugs. Get an accurate reading with no resistor voltage drop. Just make sure it’s plugged into the meter or you have a nice 500v lead dangling around. I guess that’s why they use the resistor for the sake of safety.

Hi Tony! I wish someone had shown me how to do this when I started out. I learned this process along the way, but the way you explain it is going to help a lot of newcomers. Looking forward to part two - what a splendid way to relax :) thanks for uploading mate!

The amp in the thumbnail is the aor series II model amp. I have a 1989 series II and although everyone says they break, I’ve had mine for 25 yrs and occassionally gigged it and other than changes of valves it’s still going.

Love the way you slowly but diligently walked through the bias process. Really made it easy to understand. My best friend is a long time amp tech/builder so I have absorbed years of amp repair knowledge and yet also it’s all only on a pretty surface level understanding. It’s like, I knew how to bias a set of tubes and have done it several times but also feel like I have a more legitimate understanding of it now? Like when you finally find that comfy spot on that couch and sink into it lol. An internal click sounded off. Thanks for posting this!

I know very little about this stuff, learned over the years from videos like this and just from poking around in vintage amps I was playing (swapping tubes and such). I just picked up the 50w version of this exact head, transformer dates it to Jan 22 1986, pretty low serial #. Its giving me some signs of worn out tubes so I opened it up to find the tubes are all pretty new looking GT, all 4 12ax7 and both el43, so my assumption is they arent very old. However whether it was biased accordingly or they just got plopped in i cant say. That being said, I believe it has the original big caps, and now I think theyll need replacing after over 35yrs. This video was a really great way to learn about a somewhat mysterious amp. Really awesome of you! I wont be servicing it myself but I like to know what to expect and this helped a lot!

That has some nice iron I have been collecting transformers and tubes for years and finally made my own single Se amp thanks to your videos I have the parts to build a amp like this I just don’t have the knowledge yet

Excellent video, thanks for posting this.

Excellent video, thanks Tony. Bring on the distortion!

Awe man I gotta wait for the next video. Lol Great video and explanation of how bias works. Thank you.

Caps ,clean pots, check for drifty resisters in the power supply. Nice work man.

Thanks for sharing Tony

Hello Tony, You might want to open up that Uni T power meter (1010) because the internals could do with an electrical "safety tidy up" as it may have exposed mains terminations inside and I know how much you value doing things correctly. The Martin P you tube video teardown is what I am referring to. It might even make an interesting (safety) video in-of-itself.

54:00 - You could also swap tubes to get matching 'totals' on each side!

I like to bias my Marshalls with a multimeter or a bias probe. But I fine tune the bias by ear while playing my favorite guitar with my favorite strings and favorite amp settings. I tend to bias a little colder than Marshall recommends. It just sounds better to my ears. I.e. more crunch and clarity. I use the multimeter or bias probe to keep me out of the danger zone so to speak. I once biased my Marshall 100 watt master volume to 48.5% dissipation and it sounded good. I would have tried to bias the four EL34s higher but my bias potentiometer was maxed out.

Wurth bias caps. I used Wurth electrolytic on the board. Nice long life and high temp rating.

Hey Tony !!! Got my Groove Tube #8s but decided to bias the Mullards that had been replaced when the transformer smoked by a company in Atlana .... using your method I found that it ended up at 10 watts per pair !!! Waaay off .. .336 volt drop 15 .8 ohm and 464 vdc ... so I adjusted it to 1.15 drop on the red side 1.08 on the blue finally ....I'd swapped them every which way to get them as close to even as possible and they rocked !!! 33.35 watts red 28.79 watts blue... Clear chunky sweet punchy Heaven !! .... put in the new GTs and did the same well I'm gonna swap them back cause the mullards are.... warmer.... sounding ??? The GTs are #8 and a bit IDK......... dry??? Antiseptic maybe .... good but not great, fine when looking for clean punchy clarity ... Thanks for posting this vid ...been back several times to make sure I don't toast my rig ... for a 1985 head I'll put up against ANY make or model ... BTW I'm running it through a 1984 or 5 JCM 800 top cab 412 the bottom is in the house holding up pictures lol

Hi! Thanks for the video ! I own this amp and it started to ring modulate... Any Idea ?

Thanks

WHERE DID YOU GET THAT LANEY SCHEMATIC?!?!? I envy you! (You do great work and keep it simple) I bought my Laney brand new. I am sole owner. They said to send it to them for anything! BAH!

Using Ohm's law to make the calculations also saves you about $100.

I'm curious as to why the bias is so high for a class-AB amp. At 60-70% idle, it seems like it's more of a push-pull class A. It would enter class B only when you're pushing north of 60-70W (about). Yours is not the first video to say this, but I only picked up on that today.

@SIXSTRING63

4 жыл бұрын

Russell Hltn Class A usually runs 100% of the rated plate dissipation. Class A is usually running about half the plate voltage as AB also since they are conducting constantly.

@pauldavies6037

4 жыл бұрын

Each pair of valves are in parallel class A?

@russellhltn1396

4 жыл бұрын

@@pauldavies6037 You can. The class is how the tube conduct during the wave form. In class A, they conduct all the time. The reason I'm raising the question is that it would seem to conduct all the time until the signal level reaches half of full power. Granted, this is class AB, but I'm just surprised at how much it seems to be more like "A" than "B".

@russellhltn1396

4 жыл бұрын

@@pauldavies6037 Yes, the valves are in parallel. they're running class AB.

@SIXSTRING63

4 жыл бұрын

www.valvewizard.co.uk/pp.html

I have a Laney AOR Series 1 Pro Tube Lead 50 Watt model, but I do not have the footswitch for it. Are any of the current Laney footswitches compatible with my amp, or should I contact Laney directly? I couldn't find anything on Reverb. Thanks in advance to anyone that may be able to give me some solid advice.

@voyantcreative

10 ай бұрын

Just snagged the same head! Considering its a simple channel switching type, my guess is any generic single switch will work properly. I know most are the same simple circuit, some dont do it proper and will just cut the signal without sending to ground though which can cause those loud pops. I dont think its dangerous for the head but just annoying and probably puts stress on tubes and speakers.

tony are you still using the power meter in you new bench?

@xraytonyb

3 жыл бұрын

Yes. I actually used it in the last two videos I posted on the Fisher 500. It is connected to my variac.

Looks rectangular to me. 😉

looks like a marshall lay out

Wonder if it is the one I had stollen in BC .. best amp I ever owned.. but mine was stolen .. 😡🤬😠🤔😭

@johnpoyner8823

3 жыл бұрын

Was stolen in 1995.. gone but not forgotten..

@tangotango256

Жыл бұрын

@@johnpoyner8823 might explain the missing sn portion of the rear panel decal ... I'll check mine for a matching number stamping on the insidesurfaces when I reinstall the mullard tubes tonight and rebias ... sorry for your loss brother

57:57 - influencing the circuit? With 1 ohm? In the measuring / calibrating procedure ... Certainly people with close to zero electronical knowledge. Like you don't influence the circuit when measuring everytime ... For me the superior method is the cathode resistor type, with a socket adapter or without, and having two voltmeters you can really do it "on the fly". I just don't see any sensible drawbacks in it. And there is also a chance you will spot a faulty tube (or screen resistor) that way. Your method seemed like a waste of time. But is is true, it took so long also because you went through explaining it - the formula for the calculation is more or less fixed and so you can do this also very quickly, measuring both halves of the primary resistance with the amp off, and then with two voltmeters biasing ... Is it a weak point of your method ... you don't measure individual tubes, but the pairs. What if there is a severe imbalance in the pair? Edit: Seen 2nd part of the video ... oops, screen current, my bad ... Kudos for doing really neat job on this amp!!

.

Would it have been better to have let Bratley the Guitologist fix that Guitar Amplifier.

@xraytonyb

4 жыл бұрын

I'm sure he would have done a great job.

@SteveHacker

4 жыл бұрын

DAVID GREGORY KERR ... BRAD Lenzy...

@jernejkurincic9050

4 жыл бұрын

Nope, he is much more messy

Chicken heads not stock i did the same thing it looks better.