My 'new' ML No 333 amp has a 4 stage on/off switch; push once to power on into standby, wait 10 secs(for everything to stabilise) then push again to turn fully on, press again to go back into standby and press and hold to turn off.
I can hear relays clicking away during each stages of this process.
Here's my problem; There doesn't appear to be any consistency/reliability to the initial power up ie sometimes it comes on and at others its as dead as a brick.
Help!
PS As an aside the amp has a bank of wire wound resistors rather like old electric fire elements that glow orange hot for an instant during stage 2-normal but scared the bejeezus out of me when I first saw it...
RIDEON SP-1976 10 OHM 15 WATT WITH 290 JOULES SPECIAL WIRE MADE BY BOURNES SINCE BOURNES PURCHAED RIDEON 1 YEAR AGO.
IT IS A CUSTOM PART VERY EXPENSIVE $29 EACH MINIMUM ORDER 25 PCS. I DESIGNED THIS PART FOR 331/332/333/334/335/336/33H AND No.33. WITH RIEDON HELP. I HAVE NONE IN STOCK. YOU WILL NOT FIND THIS PART ANY AUTHORIZED VENDOR. I HAVE 25 ON ORDER.12 TO 16 WEEKS TO MAKE IT.
IT IS A CUSTOM PART VERY EXPENSIVE $29 EACH MINIMUM ORDER 25 PCS. I DESIGNED THIS PART FOR 331/332/333/334/335/336/33H AND No.33. WITH RIEDON HELP. I HAVE NONE IN STOCK. YOU WILL NOT FIND THIS PART ANY AUTHORIZED VENDOR. I HAVE 25 ON ORDER.12 TO 16 WEEKS TO MAKE IT.
These are soft start Resistors made with Nichrome wire and are 10 ohms. I would suggest finding some suitable toaster nichrome wire and make your own.
Hello everyone I am repairing the ml 336, its native wire resistors have burned out, please tell me which ones can be replaced? I read about riedon sp-1976 but I can't find them on sale?
They will possibly fail quite quickly as they will have to dissipate about 300 watts of energy in 10 seconds, during the charging cycle, that's why you need Nichrome wire that can run red hot for the duration. Like a heater element.
RIEDON SP-1976 IS NICHROME WIRE.THICKER WIRE THAN THE ORGINAL MARK LEVINSON WIRE AND COATED WITH SILCONE.
RIEDON SP 1976
SPECIFICATION ELECTRICAL SPECIFICATIONS RESISTANCE 10 OHMS RESISTANCE TOLERANCE 1 PERCENT. POWER RATING 15 WATT DIELECTRIC STRENGTH 1500 VAC JOULE RATING 290 JOULES TEMPERATURE RANGE -55C TO +275C MAXIMUM WORKING VOLTAGE 1090V
RIEDON SP 1976
SPECIFICATION ELECTRICAL SPECIFICATIONS RESISTANCE 10 OHMS RESISTANCE TOLERANCE 1 PERCENT. POWER RATING 15 WATT DIELECTRIC STRENGTH 1500 VAC JOULE RATING 290 JOULES TEMPERATURE RANGE -55C TO +275C MAXIMUM WORKING VOLTAGE 1090V
Why don’t you replace these resistors with a thermistor? They have very high energy ratings and handle surges well. After 1-2 seconds, use a relay to short the thermistor out.
Quite why ML went down this route with toaster resistors for in-rush current limiting beats me. It is not a good approach.
https://www.hifisonix.com/projects/imroved-soft-start-dc-blocker-aka-issdcb/
The thermistor to use is
If the in-rush energy is exceptionally high (can’t see why it should be) put a number of thermistors in series.
I have used this technique for about 10 years and on some very big amps and never had a failure.
Quite why ML went down this route with toaster resistors for in-rush current limiting beats me. It is not a good approach.
https://www.hifisonix.com/projects/imroved-soft-start-dc-blocker-aka-issdcb/
The thermistor to use is
If the in-rush energy is exceptionally high (can’t see why it should be) put a number of thermistors in series.
I have used this technique for about 10 years and on some very big amps and never had a failure.
