MCS 3275 Restoration - backlight issues

P

P. S.

Active Member
Hi,


This is my first post on this forum. I am a noob who recently went into the vintage audio “business” ;-) and this forum has proved very helpful for me.


I recently purchased an MCS 3275 receiver on an estate sale. It had some issues with scratchy knobs, lack of balance across the channels etc.


I disassembled it and cleaned pots and knobs with deoxit D5 followed by application of deoxit gold. Did this according to the procedure described in sticky thread on this forum.


The sound problems got resolved after that (yay!) but other problems of cosmetic nature showed up. After the cleaning process the backlight of the radio scale stopped working. Obviously I blame my clumsy hands and lack of experience with vintage electronics for that. I tried to wiggle the cables, applied some more deoxit onto the lamp circuits but no good results.


Now I got a noob question - what do you think might be the reason that caused the lights go out? Also - does anybody have a link to MCS 3275 service manual handy? Tried to google this document but could not find anything.


Any help/feedback would be appreciated.


-Piotr
 
Register to hide this ad
Blown fuse that protects the lamps?
Fuse blown by being wet, or the lamps being wet (deoxit?) and the deoxit not being fully dry before power was applied?
 
Ha - that might be fuses indeed. In the cleaning process I found 3 fuses (besides the main fuse at the back). I took them out and deoxit-ed. I will reinspect the fuses themselves and fuse contacts. Weird thing is that only the radio lights do not work. The power meters are working fine. Might be the case they are on different fuses?

UPDATE - just learned that the lamp "bulb" is simply a fuse. Seems like I need to open up the lamp and replace this
 
Last edited:
Hope that works.
If not, sometimes there are fuses on the bottom of the receiver as well. May have to remove the bottom cover to access them.
 
From the schematic, there is a fuse that protects the lamps. Fuse "FU503" is for the lamps and its rated 125V at 3A. The back lamp fuse lamps are 12V at 5W and the meter lamps are 12V at 50mA.
Also, the lamp circuit is 10.1 Volts AC!. Make sure your DVOM is set correctly.
I use lamps from an auto parts store are they are the same style.
 
Hi,

Thank you all for help on this. The bulbs finally arrived and I was able to get the back plate lamps up and running. MCS Guy do you know what type of lamps go inside the meters? Also how do you ensure you don't damage the delicate meters when changing the bulbs?
 
P. S. said:
Hi,

Thank you all for help on this. The bulbs finally arrived and I was able to get the back plate lamps up and running. MCS Guy do you know what type of lamps go inside the meters? Also how do you ensure you don't damage the delicate meters when changing the bulbs?
Click to expand...

I'm afraid I don't remember exactly what kind of lamps where in the meters. But I seem to recall they were grain bulbs pushed into a rubber grommet on the top or bottom. Similar to this https://www.parts-express.com/12v-70ma-lead-lamp-02-dia--070-105

I don't think they were a problem changing them out, its was getting to them to change them.
 
MCS Guy thanks a lot for the info. Can the meters be accessed by pulling off the front panel or you need to reach from the back?
 
I think I got them from the back, but I remember taking the faceplate off to move the selector switch board below it to have access.
 
You must log in or register to reply here.
Back
Top Bottom