ACCORDING TO ML-336 SERVICE MANUAL. THE ENG DESIGNED THE WHITE CUSTOM MADE WIRE WOUND RESISTORS INCASE THERE IS A SHORT OR HUGE INRUSH CURRENT OR CAP FAILURE IT WILL OPEN SO IT PROTECTS OTHER PARTS.
THEY ARE $15 EACH MADE IN USA. THEY WILL NOT SELL ANY PARTS. ML SERVICE CENTER YOU HAVE TO SEND IT THERE FOR ANY REPAIR.
THE RIEDON SP-1976 THE PART I DESIGNED WITH HIGHER JOULES AT 290 IS $22 MADE IN USA.
THE VISHAY DALE RH05010R00FC02 TUBEOMAN 10 OHMS 50 WATT. $ 5 EACH MADE IN MEXICO. DATA SHEET SHOWING NO JOULES.
Tubeoman. I JUST SEND A PRIVATE EMAIL SO I CAN SEND THE SERVICE MAUAL FOR ML-336.
THANKS
THEY ARE $15 EACH MADE IN USA. THEY WILL NOT SELL ANY PARTS. ML SERVICE CENTER YOU HAVE TO SEND IT THERE FOR ANY REPAIR.
THE RIEDON SP-1976 THE PART I DESIGNED WITH HIGHER JOULES AT 290 IS $22 MADE IN USA.
THE VISHAY DALE RH05010R00FC02 TUBEOMAN 10 OHMS 50 WATT. $ 5 EACH MADE IN MEXICO. DATA SHEET SHOWING NO JOULES.
Tubeoman. I JUST SEND A PRIVATE EMAIL SO I CAN SEND THE SERVICE MAUAL FOR ML-336.
THANKS
Renjay651
I fully understand your remarks on Mark Levinson specifying the RIEDON SP-1976 surge resistors, which has an energy pulse rating of 290 Joules stated in their data sheet. You are also correct that the Vishay Dale resistor, I have chosen instead, does not have a specific energy pulse rating listed in the data sheet.
However, you can calculate the maximum energy pulse rating for both resistors using the stated short-term power rating. So, let’s do that.
RIEDON SP-1976
From the data sheet you can read the following.
Nominal Power Rating: 10W
Short Term Overload: 5 x Rated Power for 5 sec
The short-term energy pulse rating can be calculated as:
Epulse = 5 x 10W x 5s = 250 Joules
The good folks at RIEDON have chosen to up-spec their resistor to 290 Joules maybe due to real measurements or due to requirements from Mark Levinson.
Vishay Dale RH050 10R
From the data sheet you can read the following.
Nominal Power Rating: 50W
Short Term Overload: 5 x Rated Power for 5 sec
The short-term energy pulse rating can be calculated as:
Epulse = 5 x 50W x 5s = 1250 Joules
The Vishay Dale 50W resistor can thus withstand a higher energy pulse than the RIEDON resistor.
ML-336 (240V version)
After doing measurement and simulations in PSpice of the total mains surge resistors, transformer, rectifiers and large capacitor banks, I find that the energy dissipated in each surge resistor is over 255 Joules and if the big capacitor banks are at their +20% tolerance specification the energy pulse will be over 310 Joules.
It is clear that the RIEDON resistors are working right at their energy pulse limit and it seems that their resistive wire element slowly is getting longer and longer over the years. The wire will eventually become very loosely coupled to the ceramic body and finally it will open circuit, even with a perfectly working amplifier like mine. This is my finding anyway. See the photos in my pervious posts and compare it to a photo taken in May 2014 attached in this post. In 2014 the RIEDON surge resistors already began to deteriorate.
If the RIEDON resistors will provide additional fuse-like protection is difficult to say. For sure compared with the old original ML surge resistors.
My Vishay Dale solution is difficult to implement, but in my mind, it will last much longer. And again, this is how I see it – you may have other and better arguments.
Tubeoman
I fully understand your remarks on Mark Levinson specifying the RIEDON SP-1976 surge resistors, which has an energy pulse rating of 290 Joules stated in their data sheet. You are also correct that the Vishay Dale resistor, I have chosen instead, does not have a specific energy pulse rating listed in the data sheet.
However, you can calculate the maximum energy pulse rating for both resistors using the stated short-term power rating. So, let’s do that.
RIEDON SP-1976
From the data sheet you can read the following.
Nominal Power Rating: 10W
Short Term Overload: 5 x Rated Power for 5 sec
The short-term energy pulse rating can be calculated as:
Epulse = 5 x 10W x 5s = 250 Joules
The good folks at RIEDON have chosen to up-spec their resistor to 290 Joules maybe due to real measurements or due to requirements from Mark Levinson.
Vishay Dale RH050 10R
From the data sheet you can read the following.
Nominal Power Rating: 50W
Short Term Overload: 5 x Rated Power for 5 sec
The short-term energy pulse rating can be calculated as:
Epulse = 5 x 50W x 5s = 1250 Joules
The Vishay Dale 50W resistor can thus withstand a higher energy pulse than the RIEDON resistor.
ML-336 (240V version)
After doing measurement and simulations in PSpice of the total mains surge resistors, transformer, rectifiers and large capacitor banks, I find that the energy dissipated in each surge resistor is over 255 Joules and if the big capacitor banks are at their +20% tolerance specification the energy pulse will be over 310 Joules.
It is clear that the RIEDON resistors are working right at their energy pulse limit and it seems that their resistive wire element slowly is getting longer and longer over the years. The wire will eventually become very loosely coupled to the ceramic body and finally it will open circuit, even with a perfectly working amplifier like mine. This is my finding anyway. See the photos in my pervious posts and compare it to a photo taken in May 2014 attached in this post. In 2014 the RIEDON surge resistors already began to deteriorate.
If the RIEDON resistors will provide additional fuse-like protection is difficult to say. For sure compared with the old original ML surge resistors.
My Vishay Dale solution is difficult to implement, but in my mind, it will last much longer. And again, this is how I see it – you may have other and better arguments.
Tubeoman
Attachments
Ametherm ICL MS35 3R030
3 ohm 30A 750J steady, 1250J instant rating. They are $13 each at DigiKey,in stock.You only need 1 instead of 3 resistors.
https://www.ametherm.com/datasheetspdf/MS353R030.pdf
3 ohm 30A 750J steady, 1250J instant rating. They are $13 each at DigiKey,in stock.You only need 1 instead of 3 resistors.
https://www.ametherm.com/datasheetspdf/MS353R030.pdf
Last edited:
Oreo382
Yes, this might be an option. However, it is not a pure resistor but a power NTC resistor which rapidly will reduce its resistance from 3 Ohm to maybe 0.07 Ohm or less due to the dissipated energy. This will greatly reduce the time it takes to charge the big capacitor banks and may in turn lead to a blown mains fuse in the house.
Yes, this might be an option. However, it is not a pure resistor but a power NTC resistor which rapidly will reduce its resistance from 3 Ohm to maybe 0.07 Ohm or less due to the dissipated energy. This will greatly reduce the time it takes to charge the big capacitor banks and may in turn lead to a blown mains fuse in the house.
You have to charge 4 x 51 mF = 204 mF to 107 Vdc as well as get the primary transformer inductance, Lp, going. Not so fast that that you will burn the 10A mains fuse in the house, and not so slow that the surge resistor shorting relay will burn its contacts when closing.
Also you have to consider that if you switch on the amplifier and switch it off again shortly after and then switch it back on again, the 3 Ohm thermistor may not had time to cool off and then you will switch on with the thermistor at a too low value - say 0.5 Ohm. This may burn the 10 A fuse and stress the large capacitor bank.
I would not take the risk of such a solution.
Also you have to consider that if you switch on the amplifier and switch it off again shortly after and then switch it back on again, the 3 Ohm thermistor may not had time to cool off and then you will switch on with the thermistor at a too low value - say 0.5 Ohm. This may burn the 10 A fuse and stress the large capacitor bank.
I would not take the risk of such a solution.
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