UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Reply
 
Thread Tools
Old 24th Sep 2019, 1:43 pm   #41
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

These are 50uf caps with a working voltage of 225v only. The original cap that came out of the can was 25mm diameter by 40mm tall the rest of the 90mm can had tar and an air gap.
Now:
Spec sheet for the caps I've used are Panasonic CD Type A if you type this in you should get the pdf specification sheet.
They are
high ripple current
endurance at 105c 8000 to 10000 hours. I hope this helps shed some light on your concerns regarding the ripple current of the capacitors I've used.

Lawrence both resistors are measuring 2.62k is that of any help? Measured cold as you said.

Cheers Chris
cdm1christopher is offline   Reply With Quote
Old 24th Sep 2019, 1:59 pm   #42
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,373
Default Re: Philips BX281U20 valve radio

Quote:
Originally Posted by cdm1christopher View Post
Lawrence both resistors are measuring 2.62k is that of any help? Measured cold as you said.
If they are in the heater circuit they're looking like thermistors, eg: if they were resistors then 0.1*2,620 = 262 volts.

Lawrence.

Last edited by ms660; 24th Sep 2019 at 2:11 pm. Reason: clarify
ms660 is offline   Reply With Quote
Old 24th Sep 2019, 2:14 pm   #43
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Ah thanks for that Lawrence
cdm1christopher is offline   Reply With Quote
Old 24th Sep 2019, 2:29 pm   #44
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,373
Default Re: Philips BX281U20 valve radio

VA1009 is the nearest spec I can find that seems to fit the bill.....2.5k +-0.75k @ 25C.....200 to 250 ohms @ 0.1 amp:

http://www.electrojumble.org/DATA/Mu...o%20VA1040.pdf

Lawrence.
ms660 is offline   Reply With Quote
Old 24th Sep 2019, 3:13 pm   #45
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Nice one have a look later.
cdm1christopher is offline   Reply With Quote
Old 24th Sep 2019, 7:16 pm   #46
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Well this is what it says about r30.
This resistor serves to limit the burn-out of the scale lighting lamp. In the event of a renewal, R30 must be placed in the middle between the axis of the volume control and C85

Lost me as it's not in that position so does that mean you have to move it?
cdm1christopher is offline   Reply With Quote
Old 24th Sep 2019, 7:37 pm   #47
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Em this is odd I have another sheet which gives the ohms readings for R30 and R44.
R30 is 170ohm and R44 is 300ohm. Odd!!! pic attached of sheet spec.
Attached Thumbnails
Click image for larger version

Name:	20190924_193704.jpg
Views:	20
Size:	33.6 KB
ID:	190775  
cdm1christopher is offline   Reply With Quote
Old 24th Sep 2019, 7:46 pm   #48
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,373
Default Re: Philips BX281U20 valve radio

Yours uses thermistors, you can position them where you like as long as the effect of the heat from them affecting any other components is kept to a minimum.

The values you have just highlighted have been in the manual I posted a link to all the time.....

Lawrence.
ms660 is offline   Reply With Quote
Old 24th Sep 2019, 7:53 pm   #49
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Oh deary me I'm focusing on too many things at once as opposed to sticking to one then move on. What a willy wonker but it is late that's my excuse ha.
cdm1christopher is offline   Reply With Quote
Old 27th Sep 2019, 2:54 pm   #50
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

well this is turning out to be a job and a half. Access to the underside nightmare. I've replaced all caps apart from one I'm waiting for. Those thermistor need replacing as both have heat damage but I'm having trouble finding replacements
Also had to replace some wiring again what a nightmare everything is just so cramped in their probably why don't find any refurbed I think.

The main resistors and small caps I'm leaving in place for now as readings okay. I'll wait and see when I get a chance to fire her up.
The tunning cap needs an additional bolt to secure it to chassis as its wobbly stupid design. Its sitting on rubber mounts two of which are secured with screws the other nothing so will need to drill hole in chassis then use a nylon bolt nut and washer for that. Also protects any ground connection potential.

R1 power resistor fine and the dropper also readings still spot on.

Output tranny readings also okay.

All main capacitors well out of spec by 50% plus.

Got new running screen coming plus new tunning dial kit springs cord etc.

The cabinet needs a clean and I'll replace the old aluminium sheet with new.

Then the case will need a clean then job done.

Be a while yet.
Attached Thumbnails
Click image for larger version

Name:	20190927_143751.jpg
Views:	56
Size:	53.7 KB
ID:	190898   Click image for larger version

Name:	15695923952405333683039216297428.jpg
Views:	55
Size:	79.4 KB
ID:	190899   Click image for larger version

Name:	1569592418338153958672949163015.jpg
Views:	52
Size:	79.9 KB
ID:	190900  
cdm1christopher is offline   Reply With Quote
Old 29th Sep 2019, 12:17 pm   #51
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Hi guys
can anyone tell me what and how this antenna clip works on the pic you will see it says cap antenna and this is screwed to the inside of the cabinet as shown in the picture. Now it is supposed to have a wire attached. Now what I cannot work out is it does not connect to anything in the cabinet!!
The foil is beside it but theres no evidence of it being connected to the foil at all. I did move clip so it was touching the foil but there's no continuity?

But the foil has a ohm reading of 0.50 ohms not sure how that is?

Thanks
Attached Thumbnails
Click image for larger version

Name:	20190929_120651.jpg
Views:	35
Size:	31.8 KB
ID:	191022   Click image for larger version

Name:	20190929_120658.jpg
Views:	35
Size:	48.5 KB
ID:	191023  
cdm1christopher is offline   Reply With Quote
Old 29th Sep 2019, 12:38 pm   #52
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,373
Default Re: Philips BX281U20 valve radio

It looks like it's not been fitted properly, looking at the photo undo the screw that secures it then solder a connecting wire between the end where the fixing hole is and the antenna socket then orientate it so that it's pointing upwards (in context of the photo) with the belly of the contact in contact with the foil then put the screw back to secure it.

13th photo:

https://www.pa3esy.nl/Philips/ontvan...bx281_set.html

Lawrence.

Last edited by ms660; 29th Sep 2019 at 12:55 pm. Reason: link and re-write
ms660 is offline   Reply With Quote
Old 29th Sep 2019, 1:18 pm   #53
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Wow thanks Lawrence not sure how you get this info I was looking for couple days and could not find any decent pictures. But I did think it must touch the foil otherwise why was it there.

Oh and I see where this part goes now as it was floating at front of cabinet. On mains horar trying to figure that out for a week

Thanks
Attached Thumbnails
Click image for larger version

Name:	20190929_131929.jpg
Views:	34
Size:	26.6 KB
ID:	191030  
cdm1christopher is offline   Reply With Quote
Old 29th Sep 2019, 4:40 pm   #54
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 13,641
Default Re: Philips BX281U20 valve radio

Quote:
Originally Posted by cdm1christopher View Post
Those thermistor need replacing as both have heat damage but I'm having trouble finding replacements

Just because thermistors look cooked doesn't necessarily mean they're defunct. Do they show sensible resistance readings cold and hot?


You may well be able to get away with just resistors if you experiment a bit and don't mind dimmish panel lights.
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is offline   Reply With Quote
Old 29th Sep 2019, 7:57 pm   #55
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Yeah I think your right. Yes their readings are pretty much similar cold have not tested them hot as Im still waiting for a few parts. But the cases look in pretty good shape it's just small parts of the end caps bit metallic looking as if they have been hot. Once I've got the parts I'll fire her up slowly then take some readings. I must admit all other resistors are more or less within spec some spot on some around 10% out but I know these are prob 20% resistors. The caps where way out all of them. The 100uf was reading 475uf!!!. A Couple of the the tar ones just crumbled and fell off. The dual 50uf can one was reading 4.64uf the other 6.92uf. Could be why thermistors where getting hot just a thought.

Cheers Chris
cdm1christopher is offline   Reply With Quote
Old 30th Sep 2019, 12:05 am   #56
Croozer
Pentode
 
Join Date: Jul 2016
Location: Edinburgh, Scotland, UK.
Posts: 101
Default Re: Philips BX281U20 valve radio

Thermistors of this type and for this purpose are generally designed to run hot.
Generally when a metal is cold it's resistance is low compared with when it's hot. So at first switch on, the cold valve heaters have a low resistance permitting a high current to flow through them until they reach working temperature and their resistance increases. The thermistor is intended to so the direct opposite of this, with a high resistance when cold, and low when it has heated up. Thus the valve heaters are protected from flaring at switch on - a sort of 'soft start'
Croozer is offline   Reply With Quote
Old 1st Oct 2019, 1:44 pm   #57
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Hi guys
I've added couple of pics.
The foil has been renewed and with the help of Lawrence you can now see how the aerial clip is attached to the foil. Just in case your refurbing one and had same problem as me as on how it was to be connected.
I have also taped the speaker wires to the metal cone as they are just tied off and flying around. So to reduce the strain I thought tape would reduce the chance of the wires pulling off the speaker coil.
I also used some lock nut on the speaker threads to make sure they don't come loose due to speaker vibrabtion.

Seems all bit trivial but hopefully the info maybe of some help to someone. The speaker ohms is 3.8 so just in case you need to replace a dud one and had no readings.

Cleaned up cabinet which I must say is immaculate no scratches damage at all. Probably because it was stored in the case. Found out why these did not usually come with cases. Probably for travelling salesman promoting the product.

Still waiting on these caps

Cheers Chris
Attached Thumbnails
Click image for larger version

Name:	20191001_132627.jpg
Views:	56
Size:	65.5 KB
ID:	191140   Click image for larger version

Name:	20191001_132636.jpg
Views:	52
Size:	38.9 KB
ID:	191141   Click image for larger version

Name:	20191001_132659.jpg
Views:	55
Size:	81.8 KB
ID:	191142  
cdm1christopher is offline   Reply With Quote
Old 2nd Oct 2019, 3:07 pm   #58
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

New safety caps added for aerial connection.
Pics attached.
Attached Thumbnails
Click image for larger version

Name:	20191002_150336.jpg
Views:	32
Size:	38.4 KB
ID:	191182   Click image for larger version

Name:	20191002_150345.jpg
Views:	24
Size:	27.1 KB
ID:	191183  
cdm1christopher is offline   Reply With Quote
Old 4th Oct 2019, 5:51 pm   #59
cdm1christopher
Pentode
 
Join Date: Apr 2019
Location: Birchington, Kent, UK.
Posts: 114
Default Re: Philips BX281U20 valve radio

Well managed to get her working not took any voltage readings yet.
Bit concerned as there is a lot of static and now and again the bulb and unit go out with rather large hiss and comes back on.
Noticed also the aerial if you move it around again lots of static. So maybe I've wired it up wrong plus using those y2 safety caps causing problem? Usually you can plug in unplug and normally move it around the aerial and it's just quiet. From previous units used.
Picking up stations okay.
So maybe it's a ground problem somewhere?
Valves lighting up fine and the bulb is nice and bright.
So think I'm gonna have to check everything plus the RF is very close to tuning cap and the main chassis mounted capacitor can. Not sure if that would cause any problems such as hissing and static just a thought.
Any ideas much appreciated.

Many thanks Chris
cdm1christopher is offline   Reply With Quote
Old 4th Oct 2019, 8:26 pm   #60
Croozer
Pentode
 
Join Date: Jul 2016
Location: Edinburgh, Scotland, UK.
Posts: 101
Default Re: Philips BX281U20 valve radio

Congratulations on getting it going!
If it is designed as a continental set/220V mains, it may be that the scale lamp runs bright on higher UK mains. Heater voltages of the valves would quickly indicate how close to spec. in the printed manual your voltage checks should be. Eg the UBL21 should have 55V across the heater.

PS please remember this is a live chassis set so observe the safety precautions necessary - especially ensuring that the mains are connected right way round so chassis potential is close to the earthed side of the mains and not the live side.
Croozer is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 5:31 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.