Thanks for that video Stuart.. You don't see Super Sonics much as they seem to be very reliable and not prone to the usual faults of other amps from this manufacturer. Did I spot a double sided PCB ? It certainly looked solid. Thanks also for pointing out an alternative method of biasing without the need for a bias meter.
Hi. Thanks for making this video, excellent! I have a SS 22 which looked very similar inside except obviously it uses 6V6 power tubes. Few questions please. Does the difference on plate voltage between the two euro tubes probes indicate an inaccuracy in the probes? Could you have used a warmer grade of 6L6 tubes to get the 40ma you were wanting as opposed to soldering a resistor? Did I see a jumper cable in the effects loop, if so why? All the best and thanks again for the video.
Hi. Here are my answers as best I can. Yes after making this video I checked the calibration of my two meters and they were a few mA different. I adjusted them to be the same! Well spotted. Yes you could use a 'hotter' tube rather than change the resistor. I can;t recall what I did now but often jumper out the effects llop if I suspect the jacks might be playing up. I probably did a quick test and then forgot to remove the jumper.
@@stuartukguitarampguy5830 Hi. Many thanks for the reply. I have the same euro tubes bias probes, x1 with the plate voltage (like yours) and x3 of the bias only probes. My testing in about 8 amps some with their own test points, show an error of 1-3ma for the bias and the plate voltage when compared to reading off pin 3 directly is about 8-15 volts lower than at the pin. To be honest I expected a higher accuracy given their price. Regards.
I have a Fender super sonic 60.does some strange and loud pop noise from time to time. Will send it to the fender repair shop. Tubes:Guess that's what I will have to do next time. Waitet to see where the bias points are.
Fender bias these amps cold from the factory. According to the schematic, they want you to bias to 32 mA. Probably explains why you ran out of adjustment on the pot.
This is incorrect. The Eurotubes bias meter is showing plate current, not bias. You should make a calculation using the plate voltage to figure the bias current. This amp is being way over biased and tubes will fail.
Steve. Not sure I'm following you. Yes you do a calculation to work out what the bias current should be for a given plate volktage and tube type. I use the bias calculator on Ted Weber site. Let's say 40mA for 450V. Then it's just a question of adjusting the bias to give this current (say 40mA) on the Eurotubes bias meter.
I find myself watching again as I enjoy your expertise. Thanks again Stuart.
Chers Michael!
I'm loving these 'How to Bias' videos as this is a common question I get asked about! Very clear videos!
Thank you. Your channel is very informative and deserves more subscribers most definitely.
Once again you provide wonderful information; thanks.
Thanks Michael!
Thanks for that video Stuart.. You don't see Super Sonics much as they seem to be very reliable and not prone to the usual faults of other amps from this manufacturer. Did I spot a double sided PCB ? It certainly looked solid. Thanks also for pointing out an alternative method of biasing without the need for a bias meter.
Glad you enjoyed it Pete!
You don't need a bias meter. The service manual has a procedure using a regular dmm across a series resistor to adjust.
Hi. Thanks for making this video, excellent! I have a SS 22 which looked very similar inside except obviously it uses 6V6 power tubes. Few questions please. Does the difference on plate voltage between the two euro tubes probes indicate an inaccuracy in the probes? Could you have used a warmer grade of 6L6 tubes to get the 40ma you were wanting as opposed to soldering a resistor? Did I see a jumper cable in the effects loop, if so why? All the best and thanks again for the video.
Hi. Here are my answers as best I can. Yes after making this video I checked the calibration of my two meters and they were a few mA different. I adjusted them to be the same! Well spotted. Yes you could use a 'hotter' tube rather than change the resistor. I can;t recall what I did now but often jumper out the effects llop if I suspect the jacks might be playing up. I probably did a quick test and then forgot to remove the jumper.
@@stuartukguitarampguy5830 Hi. Many thanks for the reply. I have the same euro tubes bias probes, x1 with the plate voltage (like yours) and x3 of the bias only probes. My testing in about 8 amps some with their own test points, show an error of 1-3ma for the bias and the plate voltage when compared to reading off pin 3 directly is about 8-15 volts lower than at the pin. To be honest I expected a higher accuracy given their price. Regards.
@@irf888 Agreed. If you open them up there are two trimpots inside which I used to calibrate mine.
How many watts should the parallel resistor be?
I have a Fender super sonic 60.does some strange and loud pop noise from time to time. Will send it to the fender repair shop. Tubes:Guess that's what I will have to do next time. Waitet to see where the bias points are.
That resistor takes very low current so anything like 1/4 Watt is fine. It doesn;t need to be a power resistor.
Man if I need to fool with a resistor to add current in a thousand dollar amp,,,,Something really wrong. Gonna get a monoprice
Yeah it's totally CRAZY! Only about 10% of manufacturers put a bias pot inside. They cost pennies. I honestly don't get it.
Fender bias these amps cold from the factory. According to the schematic, they want you to bias to 32 mA. Probably explains why you ran out of adjustment on the pot.
Ah, interesting thanks Eric
you don't specify witch model supersonic you have here. wouldn't the bias be different being SS 60 having 2 6LS's and SS 22 having 5 6V6'S
correction 2 6V6's
This is the SS 60. Scrub to :30 seconds on the video and shows you on the back plate of the amplifier above the power tubes.
This is incorrect. The Eurotubes bias meter is showing plate current, not bias. You should make a calculation using the plate voltage to figure the bias current. This amp is being way over biased and tubes will fail.
Steve. Not sure I'm following you. Yes you do a calculation to work out what the bias current should be for a given plate volktage and tube type. I use the bias calculator on Ted Weber site. Let's say 40mA for 450V. Then it's just a question of adjusting the bias to give this current (say 40mA) on the Eurotubes bias meter.