MY one and only ORANGE Super Bass JMP 100 Mk 2

Sysco, I mean what do u use instead of SHUNT?

I have a nice plastic tool set to make the physical adjustment of the trim pot. So yeah mebbe,,,,,,,,, do u use a contraption, a different method or what?
 
Hopefully this will make up for ripping Session 5 off on his ORANGE amps


This video is a priceless resource
 
Last edited:
chilipeppermaniac said:
Sysco, I mean what do u use instead of SHUNT?

I have a nice plastic tool set to make the physical adjustment of the trim pot. So yeah mebbe,,,,,,,,, do u use a contraption, a different method or what?
Click to expand...
For the last six years I have relied on the COMPU BIAS Automatic Vacuum Tube Bias and Balance Meter. An amazing bias reading system, but at a price. The meter displays plate voltages, cathode current, and real-time tube dissipation in watts. As long as you know what the specs of your power tubes are, just adjust the bias trimpot within the ranges and suit to taste.
It looks like this:
Bias Check (1).JPG

The adapters that fit in between the tubes and the chassis' power tubes sockets:
Bias Check (2).JPG


I've used it many times and feel confident it was worth it. Unfortunately, I don't think this manufacturer is around and building these metering tools anymore. That being said, all you really need is the meter and the ability to probe the different power tube pins on a fully live amp.
 
syscokid said:
That being said, all you really need is the meter and the ability to probe the different power tube pins on a fully live amp.
Click to expand...

Yup, this is basically what I have done since a former member in here encouraged me with faith I COULD learn to understand and gain the knowledge to actually diagnose and fix my own amps. It has been a fruitful pursuit since 2016 /17
 
chilipeppermaniac said:
Yup...
Click to expand...
I just thought of something you need to add and install in order to use your meter and its probes to measure the bias voltage at Pin #8 of all power tubes. Here's another look at your amp. See the red circle at V7? Within the red circle is a ground lug that is connected to pin #1, then pin #8:
Superbass Ashdown.jpg


You will need to install a 1 ohm metal oxide resistor with a 1 watt rating, in between the ground lug and pin #1, and still retain the connection between pin 1 and pin 8:
1 ohm bias probe resistor.png
When you will be checking and adjusting the bias voltage, you're going to probe pin #8 as shown in the pic above.

You'll need to do this to all four power tube sockets:
bIAS PROBE RESISTORS 4 SOCKETS.png



The other method around this is to get a bias socket adapter like this:
IMG_3182.jpg
With something like this, you won't need to add that 1 ohm resistor because these adapters already have it inside. Cheapies, direct from China, will cost about $20 each. You only need one, but you'll have to install it on each tube to verify the bias of each tube.

Now if you want something fancier, Weber makes the Bias Rite. The version that comes with four octal tube adapters is the Bias Rite BR-4, and cost $141 plus whatever for shipping. A nice advantage to the Weber is it also provides the plate voltages besides the bias idle current voltages:
untitled.png


Obviously the most economic method is to add those 1 ohm resistors, but it is also the most dangerous method too.
 
Bdon, Great news so far with my efforts last week and a house to myself tonight, I had a chance to play my orange Marsh for about 1 hour hooked up to my 1960A. Gave it the good sound test with my 1990 Strat and 3 knob SG. Now I am fairly confident we have the amp out of the woods danger wise. Removing that dangerous tube and installing and biasing the 4 new 6550's and a 12 ax7 has sorted things out. No terrible odd noises or shocking flashes and fuses poppin.
 
Suggestions from SoloDallas

57620825_605369503301407_3420101817360607124_n.jpg


⁣⁣Well yes, Ladies & Gents, this is an actual screen shot of Mal’s amplifier settings. This was from one of his @marshallamps_uk Superbass amplifiers. Use it well - this is how the Master of Rhythm Tone did himself.

************

SoloDallas once told me Angus set his 2203/2204 eq's with TMB on 5 Presence on 2. Worked on my 2204.
 
Cool One MDub. My current situation is my amp is neither 100% Superlead nor 100% Superbass, as some of the Caps and Resistors are mixed values in the various stages.
 
Speaking of that, Adrian. I miss where the whole combo meals were $3.14 including tax instead of needing a mortgage just to pay twice as much for the same combo nowadays. Oh and go over to a machine to select it and place the order instead of dealing with a human being. We all know this is because of all the extra costs the owners of the establishments must incur to make a machine cheaper than a human like $15 minimum wages, high property taxes, etc etc.
 
syscokid said:
For the last six years I have relied on the COMPU BIAS Automatic Vacuum Tube Bias and Balance Meter. An amazing bias reading system, but at a price. The meter displays plate voltages, cathode current, and real-time tube dissipation in watts. As long as you know what the specs of your power tubes are, just adjust the bias trimpot within the ranges and suit to taste.
It looks like this:
View attachment 24365

The adapters that fit in between the tubes and the chassis' power tubes sockets:
View attachment 24366


I've used it many times and feel confident it was worth it. Unfortunately, I don't think this manufacturer is around and building these metering tools anymore. That being said, all you really need is the meter and the ability to probe the different power tube pins on a fully live amp.
Click to expand...

Nice probe Sysco. Does it read plate current directly or use current sensing resistors?
I don't make use of 1 ohm current sensing resistors inserted between the cathode & ground. Aside from them practically never being exactly 1 ohm, they actually show the "cathode" current which comprises plate & screen current, meaning your tubes are biased cooler than you think they are.
I prefer to use the "voltage drop across OT primary half divided by (DC) resistance of OT primary half" method of calculating plate current & do the same to calculate each tubes screen current.
I do have a simple probe.IMG_20190512_100836.jpg
This is hooked to a mA meter, the meter being inserted between the tubes plate & the OT, giving "just that tubes" plate current. I use this for juggling tubes in a quad & the like.
Good to hear that you have your amp up & running Chilli. Cheers
 
You must log in or register to reply here.
Back
Top