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Marantz 4400 Scope heater supply

Camman

Camman

Active Member
Why would the Marantz designers apply power to the heater elements of the Hatachi 50TB1 even with the scope power button in the off position?:scratch2:
Kinda defeats the purpose trying to maintain tube longevity. Heater voltage is not simple connected through the power switch.:no:
Anyone understand the purpose/theory of the complicated connections? Reading the schematic is at best difficult.
Heating the cathode with no power can cause cathode posioning. Might as well leave power applied with the intensity control turned down to barly visible.

Camman
 
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Same with my Marantz 2130. The scope filiments are always on. I have a 4400 in for repair at the moment. The scope tube filiments are on as long as the receiver is on. The power supply switch turns the power supply on when power is applied.
 
Maybe it was made, that the scope turns on immediately after pressing the scope on button. No need to wait until it has warmed up.

Just guessing.
 
yes - all Marantz scope units have the heater voltage turned on at all times. To avoid that, one should mount a separate switch between the trafo and the heater - would be a hassle IMO. That would imploy three switches before you could watch the scope in action. Power on / heater on / scope on (B+).

regards
Freddy
 
Don't have schematic for 4400 but on 2500 and 2600 schematic, both have always running heater while receiver is on by design. Sucks.
 
fredmarantz said:
yes - all Marantz scope units have the heater voltage turned on at all times. To avoid that, one should mount a separate switch between the trafo and the heater - would be a hassle IMO. That would imploy three switches before you could watch the scope in action. Power on / heater on / scope on (B+).

regards
Freddy
Click to expand...

I thought about doing that years ago to save the scope tube. You're right, a PIA. Bottom line is that I bought the 2130 in 1978. Have logged MANY hours on it. The scope still works. You won't damage the tube with this design.
BTW. Is the scope tube in the 4400 the 50TB31?
 
jblmar said:
BTW. Is the scope tube in the 4400 the 50TB31?
Click to expand...

scope2.jpg


Above shows what CRT is in my 4400 serial #2016.
I would think a simple on-off switch in the heater supply mounted unobtrusively on back of unit would work.:thmbsp:
camman
 
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