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Old 31st Jul 2020, 1:35 pm   #1
DonaldStott
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Default Philips 141U

Just started on this Philips 141U a.k.a. 'rust bucket' and already a couple of the bolts holding on the back panel and bottom panel broke when trying to unscrew them!

A lot of rust to treat but I'm particularly concerned about the valves which are all rusted in and wont budge: -

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Don't want to force them and would welcome any advice on the best way to extract the valves - don't want to start chucking Hammerite Kurust at them for fear of clogging up the valve pins!

This one looks like another 'doozy' as the big black Philips capacitor across the mains has clearly suffered a traumatic event in the past! Time will tell if that event has taken out anything else so I'll be looking for the usual suspects?
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Old 31st Jul 2020, 2:02 pm   #2
dave_n_t
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Default Re: Philips 141U

Donald,
when I've have rimlocks rusted in like that I've done 2 things (and, so far, have been 100% successful!)


i) spray with WD40 (or any other 'lubricating/drying spray); while this is soaking in (for an hour or so)

ii) carefully, gently, bend out both side tabs on the holder that form a 'locating slot' for the glass pip on the side of the valves. Try not to use the glass of the valve as a fulcrum for whatever small implement you use (I use a small watchmaker's screwdriver)

After an hour or so, gently 'wobble' the valve to freedom, being careful not to knock off the glass pip.

good luck!

dave
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Old 31st Jul 2020, 2:24 pm   #3
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Default Re: Philips 141U

They don't look too bad. At least they have glass bases rather than metal. I bet if you gently rock them they will move, and you can then ease them out.
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Old 31st Jul 2020, 7:29 pm   #4
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Default Re: Philips 141U

Quote:
Originally Posted by paulsherwin View Post
They don't look too bad. At least they have glass bases rather than metal. I bet if you gently rock them they will move, and you can then ease them out.
They don't look too bad in that picture but the rust is mainly between the valve bases and the holders - they are stuck really tight.

I've given them all a small squirt of PlusGas which I'll leave overnight.

I am, of course, on glass pip high alert!
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Old 1st Aug 2020, 11:19 am   #5
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Default Re: Philips 141U

... and they're all out - well done again PlusGas!
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Old 2nd Aug 2020, 9:57 am   #6
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Default Re: Philips 141U

Here are the remains of C32, the mains filter capacitor, which blew its top in some catastrophic event - the Service Manual lists this as 33,000pF 600V. If I decide to replace this (?) I will, of course, use a Type-X capacitor.

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Fortunately both the Primary and Secondary of the Output Transformer measure ok but not so good news about V5 (UY41 - Mains Recti9fier) and V4 (UL41 - Power amplifier). In the absence of a valve tester I've checked the heater continuity (Pin 1 to Pin 8) on all valves and V5 and V4 seem completely dead!

Any other tests I can do with my DMM while the valves are out?

Other issues to investigate: -

1. Dropper - while the R3 and R4 sections of the dropper are measuring ok there is nothing whatsoever across R2.

2. Smoothing and Reservoir electrolytics - this is a dual can 50 + 50uF and one cap is measuring 57uF while the other one is 105uF.

3. Loudspeaker - can't find anything in the documentation on the Service Data DVD that lists a value for the speaker?

4. Philips black capacitors - while these all look ok physically I'm inclined to replace these on sight - not a fan of blanket replacements but it may be appropriate here? I'll measure each one as I progress.

5. Tuning Control/Wave Change Switch - this assembly is completely seized!

6. Bulb - of course the 19V 0.09A bulb has blown so I've ordered up a 24V 116mA E10 (MES) bulb. I'm assuming that as it will be slightly under-run then this will increase reliability? The slight difference in voltage shouldn't make a difference so no need for a resistor?
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Old 2nd Aug 2020, 10:45 am   #7
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Default Re: Philips 141U

It's very unusual for two valves to have open circuit heaters in a radio of this type. Normally one fails and that protects all the others. It may be worth double checking this. Maybe the previous owner overran the valves after the dropper section failed.

You might as well replace all the Philips 'black pitch' caps - they will all be leaky.

Try Plus-Gas on the wavechange switch.

The replacement bulb should be OK.
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Old 2nd Aug 2020, 3:53 pm   #8
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Default Re: Philips 141U

Quote:
Originally Posted by paulsherwin View Post
It's very unusual for two valves to have open circuit heaters in a radio of this type. Normally one fails and that protects all the others. It may be worth double checking this.
Paul, you are correct of course - a bit of very light sanding on Pins 1 and 8 of both valves and I now have heater continuity on the UY41.

The UL41 is still showing no heater continuity!

Looking at the capacitors that need to be replaced i.e. the Philips 'black pitch' caps, I have most of them in my stock but would like advice on two of them: -

1. C32, the mains filter capacitor, is listed as 0.33uF - can I replace that with a 0.22uF X-Class capacitor?

2. C37, associated with the on/off/volume control, is listed as 0.015uF - can I replace that with a 0.022uF?

As for the Tuning Knob/Waveband Switch, it still seems to be stuck solid. I've no idea how the black switch component fits onto the tuning spindle and don't want to force it!

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Old 2nd Aug 2020, 4:00 pm   #9
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Default Re: Philips 141U

The caps you suggest should be fine.

As for the switch arrangement, you may need to dismantle it if it's really gummed up.
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Old 2nd Aug 2020, 6:03 pm   #10
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Default Re: Philips 141U

Quote:
Originally Posted by paulsherwin View Post
The caps you suggest should be fine.
Thanks for confirming.

Quote:
Originally Posted by paulsherwin View Post
As for the switch arrangement, you may need to dismantle it if it's really gummed up.
I'm hoping that I don't need to dismantle this as it would mean tackling the drive cord - something I'd rather avoid! Just can't work out how the black switch component fits onto the tuning spindle?

In an earlier Thread someone has already noted that C30 (tone correction and spike suppression) is wired from the Primary of the Output Transformer to the chassis and not across the two terminals of the OT where it's failure is less likely to cause damage. The advice was to leave the circuit position the same, but use a 1000V rated capacitor? Would one of my 630V Polyester Axial Capacitors be sufficient?

And while we are here I'm assuming that C3 and C34 associated with the aerial sockets need to be Y-class but what voltage?
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Old 2nd Aug 2020, 6:14 pm   #11
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Default Re: Philips 141U

No, this cap will cause serious grief if it fails short circuit. You can get some seriously high AC voltages on output valve anodes, especially if the speaker is disconnected. Modern plastic film caps are much less likely to fail short circuit, but they still need to be adequately rated.

The actual value of the tone correction cap isn't all that critical. The original value tends to result in excessive top cut to modern ears. It's worth buying a bag of 0.01uF caps rated at 1kV or higher specifically for this application.
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Old 2nd Aug 2020, 7:11 pm   #12
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Default Re: Philips 141U

Thanks again Paul - that gives me enough to be getting on with for the time being!
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Old 4th Aug 2020, 8:01 pm   #13
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Default Re: Philips 141U

In Post #8 above I said "I've no idea how the black switch component fits onto the tuning spindle and don't want to force it!"

And of course after several nights using PlusGas with no progress I did decide to exert a bit more pressure and guess what - although I now have some movement of the tuning spindle independently of this black switch component I did also manage to crack the thing and two of the 'teeth' broke off!

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If ever there was a candidate for 3D printing then this must be it - any volunteers? Superglue or Epoxy will hold them back in place but will that be enough to withstand the rigours of waveband switching?

As I mentioned I have some movement but turning the tuning spindle is still extremely difficult and tight so I'm hoping another couple of nights of PlusGas might help?

I was hoping that a Forum member who has restored one of these sets might be able to offer some advice, guidance and insight?
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Old 5th Aug 2020, 4:27 pm   #14
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Default Re: Philips 141U

Tuning spindle has loosened up considerably following another night of PlusGas treatment.

Today I used a cotton bud to carefully apply a few drops of light penetrating oil to the tuning spindle - my oil of choice in such situations is used for Trombone Slides as recommended some time ago by boxdoctor - thanks Tony.

Still need to know what I should do with those broken teeth?

I should have added that only Philips could make such a simple thing as a waveband switch so complicated with 5 x phosphor bronze leaf springs, a steel ball bearing, moulded operating gear, brackets and clips, among other parts, as part of the mechanism - see my picture in Post #8 above!

Following a small diversion by way of the rusted bulb holder which will probably need replaced we can now move on to the electronics - hopefully?
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Old 5th Aug 2020, 5:44 pm   #15
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Default Re: Philips 141U

If you free up the wavechange switch it shouldn't need too much torque to operate it, so the first thing to try is to glue the teeth back on with good glue, either superglue or epoxy (I've always been an epoxy man, but opinions differ). Don't use Poundland specials for this. If that fails you will need to reform the gear teeth with a Dremel type tool and some brass, nylon or plastic.

I agree that the arrangement is needlessly complicated, but the radio is a pretty design, influenced by the European 'Philetta' models.
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Old 5th Aug 2020, 5:51 pm   #16
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Default Re: Philips 141U

I would suggest removing most of the bronze leaf springs in order to weaken the detent. This will reduce the loading on your repaired teeth. A detent is really superfluous on a 2 position wave change switch anyway - the KB FB10 manages perfectly well without one.

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Old 5th Aug 2020, 9:28 pm   #17
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Default Re: Philips 141U

Thanks Paul - I have some Plastic Padding Super Steel epoxy that should do the job.

Thanks Leon - I hadn't thought of removing some of the bronze leaf springs in order to weaken the detent but I'll now give it a go.
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Old 6th Aug 2020, 11:19 am   #18
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Default Re: Philips 141U

Hello Donald,

I don't know if the 131U is identical to the 141U, but I have a scrap 131U which I cannibalised to fix my 141U several years ago. The switches are still present and not broken, so if you want the set for parts, I'd be happy to send it to you.

Gus.
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Old 6th Aug 2020, 11:44 am   #19
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Default Re: Philips 141U

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I don't know if the 131U is identical to the 141U, but I have a scrap 131U which I cannibalised to fix my 141U several years ago. The switches are still present and not broken, so if you want the set for parts, I'd be happy to send it to you.

Thanks Gus - PM sent.
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Old 12th Aug 2020, 10:08 am   #20
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Default Re: Philips 141U

Good progress with all the Philips 'black pitch' caps now replaced - X and Y type caps used of course in the appropriate places!

Only five of the resistors measured over tolerance with the remainder remarkably within 5%.

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I mentioned earlier that one section of the Dropper was giving no readings so that will be replaced by a 240ohm 10W ceramic cement resistor.

All valve pins and sockets cleaned along with the waveband switches and I've obtained a replacement UL41 thanks to Norman Raeburn. Some parts also replaced from scrap 131U set acquired from westcliff - thanks Gus.

Getting close to first trial switch on with Lamp Limiter ...!
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