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)


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

Closed Thread
Thread Tools
Old 4th Dec 2017, 11:14 am   #1
Join Date: Sep 2007
Location: Brentwood, Essex, UK.
Posts: 409
Default GEC BC 4750 Fault

Hello All,
I am getting a strange fault on this GEC BC4750 that I wondered if anyone else had experienced.
I changed the faulty HT Smoothing and output valve grid coupling caps and powered it up, even without an aerial it was getting the strongest MW Stations quite well - this is going to be an easy one I thought (mistake)

The weird thing is connecting up the usual 15ft of wire that I use actually makes reception worse, or at best on some stations a very slight improvement, on many it drops the volume level.

I noticed by accident that a finger, or the length of wire, touched on the SW Aerial trimmer (C26 on trader sheet 919 ) makes reception quite good on MW with plenty of volume.
I thought possibly switching problems so have cleaned the wave change switches with no improvement.
I think I had something similar with a GEC BC4850 years ago and never found out what it was!
music-centre is offline  
Old 4th Dec 2017, 12:30 pm   #2
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 876
Default Re: GEC BC 4750 Fault

It could be a high resistance connection or short on one of the trimmer capacitors.

Try moving the adjustment screw and then return it to the original position.
Silicon is online now  
Old 4th Dec 2017, 12:31 pm   #3
Radio Tech
Radio Tech's Avatar
Join Date: Dec 2012
Location: Bocking, near Braintree, Essex, UK.
Posts: 1,377
Default Re: GEC BC 4750 Fault

Hi Steve

it might be worth checking to see if any of the wafer switches have defective contacts and some of the coupling and de-coupling capacitors. I personally have not come across this with sets but there it is.

Best wishes

Radio Tech is offline  
Old 4th Dec 2017, 1:05 pm   #4
ukcol's Avatar
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,930
Default Re: GEC BC 4750 Fault

Originally Posted by Radio Tech View Post
....and some of the coupling and de-coupling capacitors.
Yes, change ALL the paper dielectric capacitors. They will all be leaky to a greater or lesser degree. Leaky decouples can alter the DC conditions on valves causing various symptoms and the AGC function can also be defeated by leaky capacitors.

I always change all the paper capacitors in a set and they always test leaky at their working voltage.
Best Regards,
Colin McLaughlin
BVWS Member
ukcol is online now  
Closed Thread

Thread Tools

All times are GMT +1. The time now is 11:52 pm.

All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at
Failure to heed this warning may result in death or serious injury to yourself and/or others.

Powered by vBulletin®
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.