Marantz 1200 pilot lamp
- Thread starter Marcantz
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ChrisMarantz
Super Member
I believe the correct bulb is a #1829
Marcantz
Member
Thank you dgwojo !
you sent to me this link:
http://audiokarma.org/forums/showthread.php?t=74423
What i understand is #757 work for the Marantz 1200 but is not the exact bulb model.
I can change bulbs on amps but don't know anything about electronic repair so , that is why i prefer put the correct bulb.I just don't want some parts like resistor have stress because i can't test or repair by myself.
you sent to me this link:
http://audiokarma.org/forums/showthread.php?t=74423
What i understand is #757 work for the Marantz 1200 but is not the exact bulb model.
I can change bulbs on amps but don't know anything about electronic repair so , that is why i prefer put the correct bulb.I just don't want some parts like resistor have stress because i can't test or repair by myself.
hurricanestv
Member
this explains the relay board trouble i had with a badly repaired resistor, lifted traces and general rough appearance of that board.
With the stock resistor on the relay board, you get 48V to that bulb. I'd bet someone put a #47 or some lower voltage bulb in mine and cooked the board.
I think you can find 48V bulbs that will fit. I had done a quick google on that base style with 48V and came up with several options.
I ripped all that out and put in 8 LED's (any fewer and the inline resistor i used would get smoking hot).
With the stock resistor on the relay board, you get 48V to that bulb. I'd bet someone put a #47 or some lower voltage bulb in mine and cooked the board.
I think you can find 48V bulbs that will fit. I had done a quick google on that base style with 48V and came up with several options.
I ripped all that out and put in 8 LED's (any fewer and the inline resistor i used would get smoking hot).
hurricanestv
Member
yup, bayonet ba9s. here are two LED options i ran across.
https://www.jkllamps.com/files/TELEPHONE BAYONET T-2 1_21.pdf
http://www.ledtronics.com/products/ProductsDetails.aspx?WP=C307K1076
Marcantz
Member
The amp work perfectly without bulb ,no heat no burn smell and i hope it will work with the correct lamp.I have try with #47 lamp because i have read in a post that it was the good one but when i have seen that the amp relay board was too hot ,15 minutes after it was on then i turned it off.
hurricanestv
Member
I'd say you ran a lot of current through the resistor on the relay board. In the attached picture, you can see the position of the resistor in question because the previous owner put four 1W resistors in series/parallel configuration to replace the original (5W is original). I assume he burned up the original by putting a bulb like you did into it.
If you have a multimeter, just check voltage at the bulb socket (red and black wires). If you're getting 48V, then it is likely that you DID NOT burn up the resistor. If you aren't getting 48V, replace that resistor. Won't take long and it is inexpensive.
Good luck!
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hurricanestv
Member
Volts DC
skibjr
Super Member
Guess I'm missing something here - why would the circuit design call for 48V to a 28V bulb??
hurricanestv
Member
It's a good question...when I went looking for bulb information here and elsewhere, I got a lot of recommendations for bulb types, including suggestions that ALL marantz bulbs should be 6V. The service manual does not list the part number for the bulb, but 6V is obviously wrong. I bet the 28V bulb runs that resistor hot, but maybe not hot enough to damage anything. I cannot verify that the 28V bulb is actually what was original (mine was missing). So unless an original owner who knows for a fact which bulb was supplied with the unit chimes in, we're all sort of guessing.
The only thing that I could absolutely verify is that you get 48V to the socket with the relay board populated with original spec parts.
ChrisMarantz
Super Member
The schematic for the model 30 integrated amplifier shows 28 volts at the bulb. The model 30 uses the same basic power supply circuit as the 1200. In my copy of the model 30 service manual, the bulb number 747 has been written in.
I don't remember exactly where I found the lamp number 1829 for my 1200, however I do know that I purchased it new when I refurbished the unit.
I will look tonight trough my notes and see what I find
I don't remember exactly where I found the lamp number 1829 for my 1200, however I do know that I purchased it new when I refurbished the unit.
I will look tonight trough my notes and see what I find
skibjr
Super Member
I pulled out my 1200 service manual, and naturally, it just gives the Marantz part number for the bulb - no voltage/current spec or manufacturer number. :thumbsdn:
Looking at the circuit, the bulb is powered directly off of one of the 51V rails, in series with a 220 Ohm resistor. So, measuring the open circuit at the empty socket should indeed yield 51VDC, which you've confirmed. My GE 757 bulb measures about 35 Ohms across the filament, which means (if I have my math right), there's 7 volts at 200mA flowing though the bulb. Guess running the bulb at a quarter of it's rated voltage = long life!
