2265B Selector Switch Carbon

Fhamre

Super Member
I have been trying to fix my dead fm. It could well be the selector switch as there is no voltage from the pin (J431)on the phono/switch board that comes from the FM portion of the switch. I have a good 2265B so I have been comparing voltages .
In this section of the switch I can see a large carbon like deposit where the switch needs to make contact. I have hit it hard with Deoxit a number of times, including using a mix with some Comet. But that junk is not moving.I even tired gently prodding it off with the tinest of screwdriver. No luck.
Any suggestions. I have never taken a rotary switch apart but that looks like one solution. I would hate to do all that work and screw up the switch or find out it wasn't the problem.
Yes, I have a service manual. In fm mode the unit has no static or signal of any kind. It just lights up.
 
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Carbon deposit, like in something burnt?
Its looks grey and attached to the contact like a blob of whatever.

HTML:
Could be the power supply section that powers the tuner board.
Common problem.
Every other function of this unit works to spec, just a dead FM section.
 
Not sure if I could capture it in a picture.
Sorry I'm a bit of a newb so I may not use the correct terms. To see the deposit I have been using my magnified light to see into the first section of the switch. On the end of one of the small tabs this deposit resides. Right where it makes contact once the switch is turned to FM. From the schem I know this is the FM portion of the switch.
Of course this is only a semi educated assumption that this is my problem. But I know other parts of the switch have this deposit and their corresponding voltages are good.
 
Well I took a picture through my magnifying light. Can't quite make out the deposit. But its on the end of the little contact tab in that front first section of the switch. the pin above it J431 should have 9V, its 0V.
 

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Fhamre;1373471 Every other function of this unit works to spec said:
That's right. The power supply is more than just one output.
Check for power on the tuner board.
I have had that issue with Marantz receivers. They work great except for the FM. It was a power supply issue. I think it was a regulator I replaced.
If you have the schematic, look for the connection between the power supply and tuner board and see if you have the proper voltage.

Rob
 
Fhamre,

Try what Rob suggests. He is a lot more experienced and smarter than me. In the meantime don't try removing anything you might think is a deposit. It may have been put there for a reason.

Carl
 
PHP:
Check for power on the tuner board.

I know the tuner board is getting some power. I have checked every pin on the board and compared them to the good unit. The biggest variance is with the pin connected to the switch specifically J431. That being said I will check the supply coming from P800 the power supply board to ensure its correct. One little challenge is the fact that the 2265B went through at least two major changes to the circuitry in the tuner. My service manual has copies of the two service bulletins. Sure enough both my units apply to the last update.
Regardless the schematic is not totally accurate. But I have two units so I should be able to sort it out, tonight, hopefully.
 
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I checked all the connections from the power supply to the tuner board everything checks out.Still the only issue I can find is that pin J306 on the tuner board should read 9v, its 0v.That pin is connected to the switch/phono board at pin J431 it should read 9v, mine has 0v. J431 is connected to the first section of the switch which is the fm portion.
That so called carbon deposit I was seeing may be just solder on the tip of the tab in the switch.
I don't have many more hairs to pull out.
 
Hey Fhamre,

I finally got my 2265B opened up. I don't see any kind of "carbon" deposits. on mine.

Do you see anything?
2265B_s1.jpg

2265B_s2.jpg
 
Damn...I just realized I have an extra selector pot part. It was suppose to be the tone control pot.
Don't understand?
I believe what I am seeing maybe solder on the switch tab tips.
Still can't find the missing voltage source.

you could you just jumper the switch contact and see if the FM comes to life.

Tom
I have pondered Tom's suggestion but not certain which pin to jump to ,to get 9v to J431. I am not that bright and don't want to screw up.
Playing with tuner boards and selector switches is new territory for me.
 
Hey nice quality pics! How did you do that?
No, mine pretty much looks the same.
What to do, what to do?
Thx for the effort and pics.
 
I have blown up the pictures you posted of the switch, and the blobs you see are rivets that were inserted during the manufacturing process (and soldered, by somebody later). The wafer is a printed circuit board with a pattern, and the rivets were supposed to both hold the actual switch contacts in midair and provide an electrical connection between the pc board foil pattern and the switch contacts.

It looks like somebody had trouble with the switch and tried soldering the two together to make a connection.

The actual switch is in deeper.

If somebody could get me a copy of the service manual (pdf or paper) I can help a LOT more...

here is a picture of something similar... no deoxit was applied to this switch, otherwise a bright path would be showing on the rotor.

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Well you might not want to try this.....or you might want to.

But what I have done on rotary switches ... Is spray them with de-oxit, then use a fine blade screw driver and apply a "little" pressure to contact that is having the issue... Then work the switch back & forth..... but be careful! Just a little pressure should do it.

You don't want to deform the contacts....just help them with a little extra pressure...

If you have old stereo or some thing else that has a similar switch and you don't care about it....test the process on that first....


jk
 
Maybe you should just sell it to a busdriver that lives like on the otherside of the country where quality equipment is plentiful..........lol.......kidding
 
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