Philips 4307 - UK Vintage Radio Repair and Restoration Discussion Forum

k.anter · 7th Oct 2018, 12:53 am

Hi everyone, my first post.

I just got what looks to be never used Philips 4307. Got new belts installed (the usual belt goo). Also cleaned all potentiometers heads and started my first play. First was no sound at all, then starting to produce very accurate but very low volume. I noticed that with any touch of the main board it starts to produce cracking sound then finally a correct sound. I tried to check the board for unsoldered components. I noticed that touching what is marked as R448 at the far right end of the board helps. I'm not into electronics that much but I find my way around. what is the replacement part for it. any help would be appreciated.

Attached is a the schematic with the part circled in red.

Thank you.

Station X · 7th Oct 2018, 8:51 am

Hello and welcome to the forums.

R448 is a 100 ohm preset potentiometer. You may find that giving it a squirt of switch cleaner and working it form end stop to end stop several times will cure your problem. Be careful to note the original position though.

ben · 9th Oct 2018, 11:34 am

Probably tin whiskers on the output/driver transistors causing low output. See the other recent thread.

7th Oct 2018, 12:53 am	#1
k.anter Diode Join Date: Oct 2018 Location: Cairo, Egypt Posts: 1	Philips 4307 Hi everyone, my first post. I just got what looks to be never used Philips 4307. Got new belts installed (the usual belt goo). Also cleaned all potentiometers heads and started my first play. First was no sound at all, then starting to produce very accurate but very low volume. I noticed that with any touch of the main board it starts to produce cracking sound then finally a correct sound. I tried to check the board for unsoldered components. I noticed that touching what is marked as R448 at the far right end of the board helps. I'm not into electronics that much but I find my way around. what is the replacement part for it. any help would be appreciated. Attached is a the schematic with the part circled in red. Thank you. Attached Thumbnails

7th Oct 2018, 8:51 am	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Philips 4307 Hello and welcome to the forums. R448 is a 100 ohm preset potentiometer. You may find that giving it a squirt of switch cleaner and working it form end stop to end stop several times will cure your problem. Be careful to note the original position though. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

9th Oct 2018, 11:34 am	#3
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Philips 4307 Probably tin whiskers on the output/driver transistors causing low output. See the other recent thread. __________________ Regards, Ben. Last edited by ben; 9th Oct 2018 at 11:35 am. Reason: link added