Help me troubleshoot Philips Valve radio 15RB505 - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Hiten123 · 19th May 2020, 12:26 pm

Hello,
I have cleaned as much as possible and cleaned Valve pin contacts too. Now as mentioned by members will replace three capacitors.

A minor confusion and need to confirm

Capacitor C20
in schematic Manual is mentioned as (100 K pf)
Should I read that value as 100000pf (In nanofarad it will be 100nf or in microfarad 0.1uf) Correct ? (Because my multimeter has mf and nf settings.) Please see attached picture. left side is C20. This is mustard capacitor and are known to be everlasting. Do I need to change this ? Are they also known to be robust or should I change it.

Capacitor C24
in schematic manual is mentioned as (10 pf )
so in nanofarad it will be 0.01nf) Correct ?
Also Please see attached picture. On right circled is C24. One end is connected to chassis (Ground) Looks same as C36. Should I change it or keep it. ?

Capacitor C36
in schematic manual is mentioned as (8K2 pf )
is that value as 8200pf (In nanofarad it will be 8.2nf) Correct ?
Please see attached second picture. This is C36. What type of capacitor is this ?

For learning purpose. please tell me function of all three capacitors. What function they do and how critical are they.

So far after cleaning the radio is playing fine. No mishap or such thing after cleaning.

AC/HL · 19th May 2020, 3:27 pm

The schematic is available from radiomuseum on an individual basis for anyone wishing to see it.

GeoffK · 19th May 2020, 5:13 pm

C20 decouples the screen grid of the mixer/oscillator valve B1. C24 gives some negative feedback to B2 and signal to the magic eye tuning indicator. C36 the audio coupling to the output stage part of the ECL82 valve. C24 and C36 seem to be ceramic type capacitors and should be left in place. C20 is a mustard type that are reliable but could be replaced with a polyester or polypropylene type, of suitable voltage rating.

Hiten123 · 20th May 2020, 7:48 am

Thanks GeoffK.
so I presume the ceramic types C24 and C36 need not be changed ? I mean they are robust and longlife not to have any leakage ? Will look for C20 which is 0.1uf. in polyester film type. There is also one more electrolytic capacitor of value 25uf (25V) from pin 2 of the ECL82 valve to the ground (A 375 ohms resistor parallel to it) As it was on the bottom of the chassis I didn't checked it. It his Philips blue film type. like picture from internet attached.

Sample blue sleeve Capacitor

Thanks very much again

GeoffK · 20th May 2020, 12:14 pm

Smaller ceramic capacitors seldom need any attention, especially as they are mainly found in the RF, IF stages and are chosen to give accurate tuning and changing them for no good reason can adversely affect the tuned stages. The capacitor to the audio output valve control grid usually needs changing if it is a wax covered or metal type such as TCC but the ceramic type should be more reliable and it is an unusual value of 8n2 chosen for that particular circuit. The 25uF electrolytic capacitor is the cathode bypass for the ECL82 and could be changed but the low voltage Philips capacitors are fairly reliable. A read up on valve radio technology would help you understand the workings of the radio better, there is plenty of online information.

Hiten123 · 21st May 2020, 12:25 pm

Thanks GeoffK. I bought new caps but as of now I will keep original caps as it is and start reassembling.
Regards

Hiten123 · 5th Jun 2020, 3:17 pm

Hello everyone,
I have put back together the radio. And for almost 2 weeks have been listening to it on and off for about 20 mins. It is working fine with most of the original parts. The Place I stay is about 40/50 km from the radio station. couple of questions I would like to ask are...

1) The CD Player line out to Pickup input plays fine no hum or interferance. But Being far from radio station I only get one AM Radio Station with little interferance. Is there any way to reduce the AM intereferance ?

2) While turning on there is No Pop or spike noise but while turning off the radio produces pop/spike sound. Is there a solution to it ?

3) being 50 year old The dial glass plate has developed air bubbles between glass and color (Probably screen printed) I though putting some solution overnight might dissolve the paint and reduce air bubbles. I have used Kerosene, Acetone, Iso Propyl Alcohol but the paint is hardened and have no effect. Any other way to lightly dissolve the paint so air bubbles are reduced ? light restoration of original would be good.

Thanks very much and best regards.

19th May 2020, 12:26 pm	#21
Hiten123 Triode Join Date: Apr 2020 Location: Mumbai, India Posts: 13	Re: Help me troubleshoot Philips Valve radio 15RB505 Hello, I have cleaned as much as possible and cleaned Valve pin contacts too. Now as mentioned by members will replace three capacitors. A minor confusion and need to confirm Capacitor C20 in schematic Manual is mentioned as (100 K pf) Should I read that value as 100000pf (In nanofarad it will be 100nf or in microfarad 0.1uf) Correct ? (Because my multimeter has mf and nf settings.) Please see attached picture. left side is C20. This is mustard capacitor and are known to be everlasting. Do I need to change this ? Are they also known to be robust or should I change it. Capacitor C24 in schematic manual is mentioned as (10 pf ) so in nanofarad it will be 0.01nf) Correct ? Also Please see attached picture. On right circled is C24. One end is connected to chassis (Ground) Looks same as C36. Should I change it or keep it. ? Capacitor C36 in schematic manual is mentioned as (8K2 pf ) is that value as 8200pf (In nanofarad it will be 8.2nf) Correct ? Please see attached second picture. This is C36. What type of capacitor is this ? For learning purpose. please tell me function of all three capacitors. What function they do and how critical are they. So far after cleaning the radio is playing fine. No mishap or such thing after cleaning. Attached Thumbnails

19th May 2020, 3:27 pm	#22
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Help me troubleshoot Philips Valve radio 15RB505 The schematic is available from radiomuseum on an individual basis for anyone wishing to see it.

19th May 2020, 5:13 pm	#23
GeoffK Heptode Join Date: Mar 2016 Location: Essex, UK. Posts: 602	Re: Help me troubleshoot Philips Valve radio 15RB505 C20 decouples the screen grid of the mixer/oscillator valve B1. C24 gives some negative feedback to B2 and signal to the magic eye tuning indicator. C36 the audio coupling to the output stage part of the ECL82 valve. C24 and C36 seem to be ceramic type capacitors and should be left in place. C20 is a mustard type that are reliable but could be replaced with a polyester or polypropylene type, of suitable voltage rating. __________________ *Geoff*

20th May 2020, 7:48 am	#24
Hiten123 Triode Join Date: Apr 2020 Location: Mumbai, India Posts: 13	Re: Help me troubleshoot Philips Valve radio 15RB505 Thanks GeoffK. so I presume the ceramic types C24 and C36 need not be changed ? I mean they are robust and longlife not to have any leakage ? Will look for C20 which is 0.1uf. in polyester film type. There is also one more electrolytic capacitor of value 25uf (25V) from pin 2 of the ECL82 valve to the ground (A 375 ohms resistor parallel to it) As it was on the bottom of the chassis I didn't checked it. It his Philips blue film type. like picture from internet attached. Sample blue sleeve Capacitor Thanks very much again

20th May 2020, 12:14 pm	#25
GeoffK Heptode Join Date: Mar 2016 Location: Essex, UK. Posts: 602	Re: Help me troubleshoot Philips Valve radio 15RB505 Smaller ceramic capacitors seldom need any attention, especially as they are mainly found in the RF, IF stages and are chosen to give accurate tuning and changing them for no good reason can adversely affect the tuned stages. The capacitor to the audio output valve control grid usually needs changing if it is a wax covered or metal type such as TCC but the ceramic type should be more reliable and it is an unusual value of 8n2 chosen for that particular circuit. The 25uF electrolytic capacitor is the cathode bypass for the ECL82 and could be changed but the low voltage Philips capacitors are fairly reliable. A read up on valve radio technology would help you understand the workings of the radio better, there is plenty of online information. __________________ *Geoff*

21st May 2020, 12:25 pm	#26
Hiten123 Triode Join Date: Apr 2020 Location: Mumbai, India Posts: 13	Re: Help me troubleshoot Philips Valve radio 15RB505 Thanks GeoffK. I bought new caps but as of now I will keep original caps as it is and start reassembling. Regards

5th Jun 2020, 3:17 pm	#27
Hiten123 Triode Join Date: Apr 2020 Location: Mumbai, India Posts: 13	Re: Help me troubleshoot Philips Valve radio 15RB505 Hello everyone, I have put back together the radio. And for almost 2 weeks have been listening to it on and off for about 20 mins. It is working fine with most of the original parts. The Place I stay is about 40/50 km from the radio station. couple of questions I would like to ask are... 1) The CD Player line out to Pickup input plays fine no hum or interferance. But Being far from radio station I only get one AM Radio Station with little interferance. Is there any way to reduce the AM intereferance ? 2) While turning on there is No Pop or spike noise but while turning off the radio produces pop/spike sound. Is there a solution to it ? 3) being 50 year old The dial glass plate has developed air bubbles between glass and color (Probably screen printed) I though putting some solution overnight might dissolve the paint and reduce air bubbles. I have used Kerosene, Acetone, Iso Propyl Alcohol but the paint is hardened and have no effect. Any other way to lightly dissolve the paint so air bubbles are reduced ? light restoration of original would be good. Thanks very much and best regards.