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Model 18 Scope Troubleshooting

bktheking said:
There was something strange about the pinout , I think. looking down at the board it's ECB but the tip's are BCE. Like I said, it's been a while. You may want to go with something with a ECB pinout or get into some interesting lead bending- don't forget to insulate the case.
Click to expand...

Does this TIP47 transistor #511-TIP47 not have the recommended ECB pinout? If not, what is the impact? Will wires be crossing each other?
 
I use 2SC2611 for the scope, work fine.
Simply need to be installed under the heatsink:

a871eb18-8464-4f75-96f0-03a2ad32a95a.jpg
 
Did a search and found that others have substituted three additional parts for the Marantz scope transistors bringing the total to four that have been tried. (Marantz part number 34-1006.)

  • 2sc2611
  • 2sc2371
  • KSC3503
  • TIP47 (511-TIP47)
Of the 4 transistors above, are there any that are most suited or ideal for use on the Marantz 18 scope board?

bktheking said:
Here are a couple I subbed in the 18.

34-1006 can be replaced with a 2sc2611 or 2sc2371
Click to expand...

avionic said:
KSC3503-------- http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/KSC3503CS/?qs=JV7lzlMm3yK9EH5vUFWV%2biiSbMEPig00OhIAO5ffQqs=
Click to expand...
 
I have been thinking about using a VTL5C3 vactrol to switch the 200V.

The 200V supply and the two feed lines to the tuner boards would be across the opto-resistor rather than the switch.

Pull a wire from the +12 regulated supply and place a resistor in line with it to limit current and connect it to one side of the switch. Connect the other side of the switch to the anode of the LED and the other side to ground.

When the switch is closed the led would illuminate and cause the resistance of the opto-resistor to drop and allow current to flow through the 200V circuit.
 
txturbo said:
I have been thinking about using a VTL5C3 vactrol to switch the 200V.

The 200V supply and the two feed lines to the tuner boards would be across the opto-resistor rather than the switch.

Pull a wire from the +12 regulated supply and place a resistor in line with it to limit current and connect it to one side of the switch. Connect the other side of the switch to the anode of the LED and the other side to ground.

When the switch is closed the led would illuminate and cause the resistance of the opto-resistor to drop and allow current to flow through the 200V circuit.
Click to expand...

Very cool idea. This would eliminate the switch pop and extend the life of the neon lamps as they wouldn't be always on.
 
When removing the screws from the 4 scope transistors, are there nuts the bottom side of the heat sink? In other words, can I just unscrew the screws from the old transistors and then screw back in the screws to hold down the new transistors? OR do I need to remove the heat sync and fasten nuts on the underside of the heat sync when screws are put back to hold in place the new transistors? Also, are the screws holding down the transistors Torx/star heads are will a jewelers Philips head screwdriver work?

Fhamre's unit below for reference:

index.php
 
Last edited:
A question for an expert on Model 18 (bktheking):

On one of my model 18, I have a little problem with the scope:
-First, dot is centered.
-When I press Audio display, audio display scope signal is perfectly centered.
-when I depress audio Display for FM tuning, FM tuning work, but the scope signal is completely at right.

On my other Model 18, Audio Display and FM tuning signals are perfectly centered.

Any idea?
 
IIRC it's an adjustment, i'll pull my unit down tonight cause I have to do something to it and i'll check to see.
 
Thank.
I suspected also an adjustment, on the Limiter or MPX OSC boards, but I found nothing concrete...
 
It's either the horizontal or vertical adjustment on the limiter or mpx- try either one, it will either move side to side or up and down, you can't really mess up the unit with those pots, only correct it.
 
I tried with R505 on mpx osc board, and R325 & R327 on Limiter board, don't solve the problem.
 
R505 expanded horizontal signal, but does not affect the centering.
R325 & R327 modifies the signal to the vertical.
 
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