Philips N4520 pushbuttons

[mickyfinn]

The deck is in working order except for sticking transport buttons.Apparently a common fault with these decks is that with the age the old lubricant on the bank of 5 push switches dries out causing them to fail to latch,they are joined by a spring assisted latch bar so pressing one releases another etc.The functions work ok but only if the buttons are held in.
Removal of the assembly(theres not enough space to get at it in situ)and cleaning/oiling hasnt been successful.I got in touch with another forum member who had posted a similar problem with the same deck in this section.He very kindly offered to take a look at the assembly in the hope of finding something I missed.Far too heavy to post the deck so the 30 odd wires were cut.After a couple of weeks he had got it to the stage where although certainly better than I had managed to do,after rejoining the wires there is still a problem of erratic operation,sometimes works fine,sometimes no latching,sometimes a switch has to be pulled out to make it switch off.It seems there must be excess wear or damage inside one or more of the switch housings.Reason for this post is to ask if anyone possibly recognises the switch bank being used in another maybe more common deck?Failing that any ideas of a fix/bodge/miracle to make the machine useable?At the moment I can't really see any point of reinstalling the assembly into the machine.Have attached pics to illustrate.
Thanks
Mick

[jim221]

hello Mick, I have the Philips 4520 and if it was me I would be looking at replacing the individual switches. I think Mouser electronics do very similar switches. i think the switches are self latching which means that they stay where they are for one press and then press again to unlatch. it would not be a big job to replace them(i think). If I can find them I will give you the pt numbers. Thinking back to when I first got my 4520 I had problems with the switches but that was a build up of dirt on the switch blades themselves.This was occurring on where they went thro the plastic surrounds. I took the pc boards out and then cleaned the switch operators ad lubricated them with a very thin smear of grease and they have not been a problem since. I am fairly sure that is your problem not with the switches themselves. Best of luck
Jim

[mickyfinn]

Thanks for the reply Jim.Wish it was that simple.All 5 switches are joined by a metal latching bar,when one is locked in and another is pressed the latch bar moves to unlock the first one.I hoped that the dried gunge was the fault but it turned out not to be.
Mick

[stevehertz]

Hi Mick, I had a similar situation with the latched and linked pushbuttons on a Tandberg receiver. The problem I had seems to be the opposite of what you have; yours won't latch, mine wouldn't pop back out! Anyway, FYI the problem and the fix is described here that I posted to the 'tips' section: http://vintage-radio.net/forum/showthread.php?t=130341
It may serve as background info re the way the switches are built and can change with age. Otherwise if I were you I would try saturating the switches with Servisol 10.

[mickyfinn]

Many thanks for that Steve,well worth having a go at.Switches do look quite similar.Cheers!
Mick

[ben]

Sounds like the spring tension on the latching bar is too weak. I'd be looking there.

[mickyfinn]

A stronger spring was tried, this resulted in the switches not unlatching.
Mick