Philips PM5324-Replacement push switches-Where from? - UK Vintage Radio Repair and Restoration Discussion Forum

djsbriscoe · 29th Dec 2019, 2:37 pm

Hi,
I might have to replace at least 3 of the push button switches (or all of the same bank if I can get them).
First how do these switches work? Are there any simple explanations explaining the pins and what happens when the button is pushed? I know how a normal switch works but I've forgotten how these push types work in detail.
I'd like to know, so I can figure out if they even need replacing.
Is there anywhere that still sells a suitable replacement? Can they be bought as a kit?
I hope someone can help. Thanks.

David.

Chris55000 · 29th Dec 2019, 7:08 pm

Evening Dave!

These PB switch banks are a common type that used to be sold by Maplin and I think you can still get them from RS, Farnell or Mouser!

If you look on towards the end of the PM5324 manual, Fig. 40 indicates the joints you need to unsolder to remove the switch–bank from the PCB, then once you've removed the assembly, you can bend up the small bent–over tabs on the metal u shaped channel each switch slides into, and then lift the individual switch from the rest of the switchback module.

If you pull up the little springy metal clip from the front of each switch–bank, you can then withdraw the front shaft containing two phosphor–bronze sliding contacts that slide across the switch mounting–pins, which form the fixed contacts!

(Do watch to make sure you don't lose the sliding contacts tho! If you do decide to dismantle the switch–bank, don't forget to get some proper contact–grease for reassembly – I used to know it as Electrolube's MS4 but I'm not sure what it's sold as these days!)

I don't have one of these switch–assemblies to hand to take pictures I'm afraid, but you should be able to work it out from the description I've given and the Philips PM5324 bookwork!

(A reasonably nicely scanned 60 page one is available free from "Manuals Lib".)

Replacement switch modules of this type with various numbers of poles can also be found on eBay from time to time – another source of them is any old 1980's radio (e.g., Old Roberts or Thorn/BRC sets) or piece of test gear with a row of press–button switches about 15–20 mm apart!

Chris Williams

OldTechFan96 · 29th Dec 2019, 7:57 pm

Hello,

Would these be of any use? They are from an early 70's English oscilloscope. They are of the latching variety bar the single one, which is momentary.

Chris55000 · 29th Dec 2019, 9:02 pm

Hi!

Yes, if the pin spacing matches the original types!

Chris Williams

OldTechFan96 · 29th Dec 2019, 11:03 pm

Just made some measurements:

W: 10mm
H: 8mm
D: 19mm (switch body, does not include shaft)

Can't see any branding on the latching switches.

Diabolical Artificer · 30th Dec 2019, 7:38 am

I have some of these if you need any. These type were used in some Telequipment scopes as well as loads of other test gear. They look complicated but are essentially lots of DPST sw's in one body

Andy.

djsbriscoe · 30th Dec 2019, 8:47 pm

Thanks for all your helpful replies.
I will look at the switches later on if they need attention. And I have to figure out how to test them properly before I start removing parts needlessly without suitable replacements.

I've just ordered a full set of all 18 of the electrolytic capacitors in the instrument. Cost me £24.37 off Farnell including free delivery. It will have nice new set of modern Vishay capacitors fitted to it. I'm hoping that this will solve the original problem and prevent any others cropping up.

I will supply the capacitor details later on if anyone is interested (and if there is an improvement).

I suspect that the original problem (unstable HF Oscillator) is a faulty capacitor in the voltage/amplitude stabilization section of same. We shall see. More later.

David.

P.S This is a lovely instrument to work on. Everything easy to get to and the manual is very clear and descriptive.

Diabolical Artificer · 31st Dec 2019, 9:16 am

"P.S This is a lovely instrument to work on. Everything easy to get to and the manual is very clear and descriptive." Yep, it does help if a bit of gear is designed with repair in mind, I always offer thanks to the designers when they put access panels in etc and a good well written manual is unfortunately a thing of the past.

Andy.

stuarth · 31st Dec 2019, 9:27 am

Before you go too far with difficult jobs like switch or widespread capacitor replacement, it’s worth checking the power supply voltage.

Mine had an odd fault many years ago, so I don’t remember exact details, but it affected output levels. The problem turned out to be the power supply, the unit is very sensitive to errors on the internal supply rails.

Stuart

29th Dec 2019, 7:08 pm	#2
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,874	Re: Philips PM5324-Replacement push switches-Where from? Evening Dave! These PB switch banks are a common type that used to be sold by Maplin and I think you can still get them from RS, Farnell or Mouser! If you look on towards the end of the PM5324 manual, Fig. 40 indicates the joints you need to unsolder to remove the switch–bank from the PCB, then once you've removed the assembly, you can bend up the small bent–over tabs on the metal u shaped channel each switch slides into, and then lift the individual switch from the rest of the switchback module. If you pull up the little springy metal clip from the front of each switch–bank, you can then withdraw the front shaft containing two phosphor–bronze sliding contacts that slide across the switch mounting–pins, which form the fixed contacts! (Do watch to make sure you don't lose the sliding contacts tho! If you do decide to dismantle the switch–bank, don't forget to get some proper contact–grease for reassembly – I used to know it as Electrolube's MS4 but I'm not sure what it's sold as these days!) I don't have one of these switch–assemblies to hand to take pictures I'm afraid, but you should be able to work it out from the description I've given and the Philips PM5324 bookwork! (A reasonably nicely scanned 60 page one is available free from "Manuals Lib".) Replacement switch modules of this type with various numbers of poles can also be found on eBay from time to time – another source of them is any old 1980's radio (e.g., Old Roberts or Thorn/BRC sets) or piece of test gear with a row of press–button switches about 15–20 mm apart! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! Last edited by Chris55000; 29th Dec 2019 at 7:19 pm.

29th Dec 2019, 7:57 pm	#3
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Philips PM5324-Replacement push switches-Where from? Hello, Would these be of any use? They are from an early 70's English oscilloscope. They are of the latching variety bar the single one, which is momentary. Attached Thumbnails

29th Dec 2019, 9:02 pm	#4
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,874	Re: Philips PM5324-Replacement push switches-Where from? Hi! Yes, if the pin spacing matches the original types! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

29th Dec 2019, 11:03 pm	#5
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Philips PM5324-Replacement push switches-Where from? Just made some measurements: W: 10mm H: 8mm D: 19mm (switch body, does not include shaft) Can't see any branding on the latching switches.

30th Dec 2019, 7:38 am	#6
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,669	Re: Philips PM5324-Replacement push switches-Where from? I have some of these if you need any. These type were used in some Telequipment scopes as well as loads of other test gear. They look complicated but are essentially lots of DPST sw's in one body Andy. __________________ Curiosity hasn't killed this cat...so far.

30th Dec 2019, 8:47 pm	#7
djsbriscoe Pentode Join Date: May 2015 Location: Hemel Hempstead, Hertfordshire, UK. Posts: 133	Re: Philips PM5324-Replacement push switches-Where from? Thanks for all your helpful replies. I will look at the switches later on if they need attention. And I have to figure out how to test them properly before I start removing parts needlessly without suitable replacements. I've just ordered a full set of all 18 of the electrolytic capacitors in the instrument. Cost me £24.37 off Farnell including free delivery. It will have nice new set of modern Vishay capacitors fitted to it. I'm hoping that this will solve the original problem and prevent any others cropping up. I will supply the capacitor details later on if anyone is interested (and if there is an improvement). I suspect that the original problem (unstable HF Oscillator) is a faulty capacitor in the voltage/amplitude stabilization section of same. We shall see. More later. David. P.S This is a lovely instrument to work on. Everything easy to get to and the manual is very clear and descriptive. Last edited by djsbriscoe; 30th Dec 2019 at 8:57 pm.

31st Dec 2019, 9:16 am	#8
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,669	Re: Philips PM5324-Replacement push switches-Where from? "P.S This is a lovely instrument to work on. Everything easy to get to and the manual is very clear and descriptive." Yep, it does help if a bit of gear is designed with repair in mind, I always offer thanks to the designers when they put access panels in etc and a good well written manual is unfortunately a thing of the past. Andy. __________________ Curiosity hasn't killed this cat...so far.

31st Dec 2019, 9:27 am	#9
stuarth Heptode Join Date: Feb 2010 Location: Heysham, Lancashire, UK. Posts: 669	Re: Philips PM5324-Replacement push switches-Where from? Before you go too far with difficult jobs like switch or widespread capacitor replacement, it’s worth checking the power supply voltage. Mine had an odd fault many years ago, so I don’t remember exact details, but it affected output levels. The problem turned out to be the power supply, the unit is very sensitive to errors on the internal supply rails. Stuart