PANASONIC SE-405 CD-4 DEMODULATOR

[J. PUPSTER]

I recently got a Panasonic SE-405 Demod. in that looked to be in pretty good condition (pics below.) I still haven't hooked it up and tried it yet.

This is my first Panasonic Demod. ( I also have tried the Marantz CD-400B and the JVC 4DD-5.) The thing that's different with the Panasonic, is it has a rear button to select between Semi-conductor and MM carts. I only have MM carts. so far. First thing I did when setting it up was to hit that cart button for MM usage; however it seems to me to be locked into the SC (pushed in) position. I can't seem to get it to bounce back out. So what I'm looking for here, is anyone that knows about or has this model or one that's similar, how these buttons should function and have they had any issues with it sticking? Also, of course any potential solutions for how to get it unstuck would be helpful. I'm not used to getting deep into the mechanical or electronics of gear like this; and it's also not in a place that's easy to access, so any help would be appreciated.

Someone sent me the owners manual and (service manual - seemed very light to me BTW.) but nothing specific in them to suggest a solution.

Or finally perhaps it's something simple i.e. (only operates once plugged into power, but I doubt that.)

Thanks for any help on this!

 

[Sonik Wiz]

That switch is in tough spot. You can't really get it very well from top or bottom. It's hard to tell from the pic but inside the spring there should be a tab that is actually part of the switch, the button and spring being external parts. Is that white piece of plastic broken off? If so it will be challenge to figure out what to do next.

If it looks like it's all intact try taking a small flat head screwdriver & and apply to the black button, from inside, and try to nudge it into the "out" position.

 

[Sonik Wiz]

I'm back. I took a pic of what I'm talking about in my SE-405:

This in the out/MM position to show that white plastic coming out of the actual switch part. I can't see it in your shot but maybe that's just because the spring is compressed? Otherwise that might be the broken part.

The switch on my unit functions fine and, no, you do not need to have the power on to operate the switch.

 

[Doug G.]

Spray some Deoxit or other lubricating cleaner into the switch from the inside of the unit and work the switch to free it up. It's just stuck from sitting around or remaining in the same position for a long time.

Doug

 

[user 19847]

If you do not have a copy of the owners or service manuals and schematic you can find them here:

https://www.vinylengine.com/library/panasonic/se-405.shtml
The Technics SH-400 also has a front panel selection for SC and MM, and the Technics manual states that if the wrong position is selected for the cartridge type you are using, it could damage the cartridge. I did not see any note like this in the SE-405 owners manual, but I would recommend you not use this demodulator until you get the button working.

 

[jupp369]

Thanks for any help on this!

Do you have a Panasonic SC ? and a good needle?
That stupid switch also don't want to do a good contact in mine! I tried contact spray but it get's more worse.
I only had an old SC system from '74 - no more good, so I cut the traces and soldering those for MM. (could be rebuild)
Now it's playing very well again.
Have only the part of the plan with input here, but if you want to do it also, I can show you what to cut and want to connect at S1.
Simply ignore the blue lines, they are only for recording CD-4.

 

[J. PUPSTER]

Do you have a Panasonic SC ? and a good needle?
That stupid switch also don't want to do a good contact in mine! I tried contact spray but it get's more worse.
I only had an old SC system from '74 - no more good, so I cut the traces and soldering those for MM. (could be rebuild)
Now it's playing very well again.
Have only the part of the plan with input here, but if you want to do it also, I can show you what to cut and want to connect at S1.
Simply ignore the blue lines, they are only for recording CD-4.

Appreciate the offer but that’s way over my abilities. I don’t do electronics repair, probably another reason so few folks get into CD-4 as it’s become a major PITA. I’m now on my third demodulator of different types and still trying to get one to work cleanly, but I will not give in and be denied, I have way too many LP’s to still listen to!

I’ll give it a good Deoxit spray tomorrow as Dougy suggested and see what happens.

Although it would be helpful to know how that switch functions internally so maybe I could nudge it at a particular angle to get it unstuck?

Also so far no SC carts for me, only MM, don’t know anything about SC carts.

And if I could find a good SH-400 I’d probably give that a try also.

 

[proufo]

Pull it and push it again.

 

[MidiMagic]

The SC cartridge position applies something similar to phantom power for a condenser or semiconductor microphone. It applies a voltage to the cartridge leads to power the semiconductors. This power could damage a magnetic cartridge.

 

[Sonik Wiz]

I’ll give it a good Deoxit spray tomorrow as Dougy suggested and see what happens.

Although it would be helpful to know how that switch functions internally so maybe I could nudge it at a particular angle to get it unstuck?

Deoxit is a very good contact cleaner but I doubt the problem is dirty contacts. Also the switch is sealed so good luck getting any spray stuff inside. Still, let us know how this goes.

Knowing how the switch functions can be found in the schematic above. I don't think that will help you fix it unless you want to get out the soldering iron & hard wire it into MM selection.

 

[J. PUPSTER]

Deoxit is a very good contact cleaner but I doubt the problem is dirty contacts. Also the switch is sealed so good luck getting any spray stuff inside. Still, let us know how this goes.

Knowing how the switch functions can be found in the schematic above. I don't think that will help you fix it unless you want to get out the soldering iron & hard wire it into MM selection.

How does the schematic show me how it works mechanically to unlock it? In other words how does the switch lock (pushed in) and unlock when pushed in again. I assume the spring is there to apply rebound force after pushing in the second time to unlock at the pushed-in position.

 

[J. PUPSTER]

The SC cartridge position applies something similar to phantom power for a condenser or semiconductor microphone. It applies a voltage to the cartridge leads to power the semiconductors. This power could damage a magnetic cartridge.

I see two issues with this:

1- that would be an easy mistake to make, getting confused on which position is for which cart. type. Or just an accidental bump of the switch.

And

2- if it did damage your MM cart. shouldn’t they have written a warning boldly in the manuals for that very easy mistake?

But one way or the other, not knowing any of this for sure is exactly why this problem stopped me in my tracks to complete the setup.

 

[Sonik Wiz]

How does the schematic show me how it works mechanically to unlock it? In other words how does the switch lock (pushed in) and unlock when pushed in again. I assume the spring is there to apply rebound force after pushing in the second time to unlock at the pushed-in position.

Ah, well, now I understand you. The schematic shows how the switch works electrically. Mechanically switches like this have a little hook latch that snags on a point inside the switch when pushed in and releases when pushed a second time. The spring, as you said, completes the operation & pushes the switch button "out". I've taken switches like this apart before & I don't know how to describe it any better than that with words.

Again I suggest taking a screwdriver & applying it to the button from inside the box & try to work it into the MM position. Or you could take pliers and gently grab the outside of the button & try to work it free back & forth that way.

Agree with Midi, the voltage output for the SC cartridge could damage a MM cart. Fix the switch first & then proceed.

 

[J. PUPSTER]

Ah, well, now I understand you. The schematic shows how the switch works electrically. Mechanically switches like this have a little hook latch that snags on a point inside the switch when pushed in and releases when pushed a second time. The spring, as you said, completes the operation & pushes the switch button "out". I've taken switches like this apart before & I don't know how to describe it any better than that with words.

Again I suggest taking a screwdriver & applying it to the button from inside the box & try to work it into the MM position. Or you could take pliers and gently grab the outside of the button & try to work it free back & forth that way.

Agree with Midi, the voltage output for the SC cartridge could damage a MM cart. Fix the switch first & then proceed.

I will definitely try all those suggestions - thank you all!

Basically I see this as a "Mechanical Engineer" problem rather than an "Electrical Engineer" problem.

I seem to remember seeing the interior of switches similar to this way back in my youth. Isn't there some kind of latching mechanism that has a tiny interior coil spring against the latch and maybe also some small ball bearings? I'm just hoping it's not an internal spring that came out of position and is jamming it up on the inside. I may have to buy a cheap parts unit and take it apart or if I can just find a similar switch to get a look inside

This is such a seemingly small and insignificant situation with this switch; but never forget this old saying:

"For want of a shoe, the horse was lost. For want of a horse, the rider was lost. For want of a rider, the battle was lost. For want of a battle, the kingdom was lost, And all for the want of a horseshoe nail.”

Also, are there still SC carts for CD-4 available anywhere?

 

[J. PUPSTER]

and...

what are the differences in the PANASONIC SE-405 and PANASONIC SE-405H models?

 

[Sonik Wiz]

and...

what are the differences in the PANASONIC SE-405 and PANASONIC SE-405H models?

Wow... didn't even know there was a H version. Lets give a shout out to @Doug G. about this. He seems quite informed on Technics/Panasonic CD-4 stuff.

 

[J. PUPSTER]

Wow... didn't even know there was a H version. Lets give a shout out to @Doug G. about this. He seems quite informed on Technics/Panasonic CD-4 stuff.

Yes indeed @Doug G. - glad to have your knowledge and experience here with us!

 

[quadsearcher]

As for DeOxit, we don't know if any contacts need to be cleaned, but it has a very thin lubricant that stays after it dries. If some could be forced in with the nozzle right at the point where the sliding part meets the stationary housing around it, it might loosen it up (if nothing's broken). Avoid splashback of course. I sort of get the nozzle lined up and held in place, then look away so it can't get in my eyes.
Just a guess, I don't recall seeing a push switch frozen like that.

 

[J. PUPSTER]

As for DeOxit, we don't know if any contacts need to be cleaned, but it has a very thin lubricant that stays after it dries. If some could be forced in with the nozzle right at the point where the sliding part meets the stationary housing around it, it might loosen it up (if nothing's broken). Avoid splashback of course. I sort of get the nozzle lined up and held in place, then look away so it can't get in my eyes.
Just a guess, I don't recall seeing a push switch frozen like that.

I got it unfrozen with the Deoxit

There's a long brown casing for the switch mechanism that has a couple of small holes in the top, so I sprayed those also, after about a minute it started working again. You can see the white inner plastic switch part sliding back and forth inside the brown casing when moving it. (See the arrows for location, sorry my focus wasn't better on the pic!)

Now the really scary part, hooking it up and seeing if it works properly

 

[Sonik Wiz]

I got it unfrozen with the Deoxit 



There's a long brown casing for the switch mechanism that has a couple of small holes in the top, so I sprayed those also, after about a minute it started working again. You can see the white inner plastic switch part sliding back and forth inside the brown casing when moving it. (See the arrows for location, sorry my focus wasn't better on the pic!)



Now the really scary part, hooking it up and seeing if it works properly 





Congratulations! I'm really kinda surprised it fixed that easy, but certainly glad it did. Now, time to smoke test it!

I hate having the pots on the bottom.