UK Vintage Radio Repair and Restoration Discussion Forum

UK Vintage Radio Repair and Restoration Discussion Forum (https://www.vintage-radio.net/forum/index.php)
-   Vintage Radio (domestic) (https://www.vintage-radio.net/forum/forumdisplay.php?f=20)
-   -   GEC BC402 receiver. (https://www.vintage-radio.net/forum/showthread.php?t=181189)

Dorian27 17th Jun 2021 8:04 pm

GEC BC402 receiver.
 
I am very much a novice so I need help I have the above radio and I think the smoothing capacitor has gone on this model it has four connections and it is 50uf+50uf +50uf 275v could any one tell me where I could get hold of one of these please.

Herald1360 18th Jun 2021 9:20 am

Re: Gec bc402
 
Wrong thread? This one is for giving info on where sets and parts can be found AFAIK.

Anyway, you may not find any exact drop in replacement but you may be able to gut and restuff the can with four suitable modern 47uF parts or if function takes priority over form you could simply use four individual capacitors under the chassis leaving the (disconnected) original in place for appearance sake.

HamishBoxer 18th Jun 2021 9:58 am

Re: Gec bc402
 
What makes you think the cap has failed? Is it hum?.

Dorian27 18th Jun 2021 10:01 am

Re: Gec bc402
 
It is a valve radio. All valves light up but absolutely no sound at all. I think the output transformer is ok

ms660 18th Jun 2021 10:24 am

Re: Gec bc402
 
Quote:

Originally Posted by Dorian27 (Post 1383461)
It is a valve radio. All valves light up but absolutely no sound at all. I think the output transformer is ok

Loudspeaker or its connections? Voltages?

Lawrence.

Sideband 18th Jun 2021 10:27 am

Re: Gec bc402
 
Quote:

Originally Posted by Dorian27 (Post 1383461)
It is a valve radio. All valves light up but absolutely no sound at all.

That hardly points the finger of guilt at the smoothing capacitor! The output transformer COULD be the culprit but you say it's OK. So please tell us what checks you have made and as a result of these checks, what conclusions you have come to.

Voltage checks are the key point here. Tell us what you have measured otherwise we are all guessing. Triple 50uF caps are still available from specialist suppliers but they are not cheap. You don't want to change on guesswork just because you think it might be faulty. Most times, they would fail O/C and cause a very loud hum.

ms660 18th Jun 2021 10:36 am

Re: Gec bc402
 
Wrong section anyways for parts needed info.

Lawrence.

Dorian27 18th Jun 2021 10:37 am

Re: Gec bc402
 
When I connect my multy meter to the input terminals on the output transformer I get a crackle noise in speaker. So I assume it is OK. I have replaced all valves with good ones apart from that I don't now where to go I am a novice I assumed then it was the smoothing capacitor =

HamishBoxer 18th Jun 2021 10:42 am

Re: Gec bc402
 
Certainly not smoothing cap at this point. Needs basic checks for starters. Just take care, lethal voltages.

ms660 18th Jun 2021 10:45 am

Re: Gec bc402
 
Quote:

Originally Posted by Dorian27 (Post 1383477)
When I connect my multy meter to the input terminals on the output transformer I get a crackle noise in speaker. So I assume it is OK. I have replaced all valves with good ones apart from that I don't now where to go I am a novice I assumed then it was the smoothing capacitor =

If the all valve heaters are lit then measure the DC voltage on pin 3 of the rectifiers valve socket first.

Lawrence.

Dorian27 18th Jun 2021 12:18 pm

Re: Gec bc402
 
Voltage on pin3 is 547 to 577

HamishBoxer 18th Jun 2021 12:23 pm

Re: Gec bc402
 
Sounds a bit high even without a load, if for instance a feed res was o/c.

ms660 18th Jun 2021 12:24 pm

Re: Gec bc402
 
Quote:

Originally Posted by Dorian27 (Post 1383503)
Voltage on pin3 is 547 to 577

If that's DC volts with respect to chassis try again.

Lawrence.

HamishBoxer 18th Jun 2021 12:27 pm

Re: Gec bc402
 
Check what is on either side R36 and if needed the circuit is at the top of this page RHS.

Dorian27 18th Jun 2021 12:47 pm

Re: Gec bc402
 
477 voltage on pin 3 DC

Dorian27 18th Jun 2021 12:52 pm

Re: Gec bc402
 
R36 reads 560 one end 580 other dcv

Dorian27 18th Jun 2021 12:58 pm

Re: Gec bc402
 
I think I've got R36 wrong I have 2 service sheets for this model and R36 is different on both is R36 according to you on smoothing capacitor or on dropper please

Dorian27 18th Jun 2021 3:40 pm

Re: Gec bc402
 
Quote:

Originally Posted by Dorian27 (Post 1383518)
477 voltage on pin 3 DC

Sorry I think I have been reading my meter wrong . 48v on pin3 of rectifier.

Sideband 18th Jun 2021 6:30 pm

Re: Gec bc402
 
Quote:

Originally Posted by Dorian27 (Post 1383587)
Quote:

Originally Posted by Dorian27 (Post 1383518)
477 voltage on pin 3 DC

Sorry I think I have been reading my meter wrong . 48v on pin3 of rectifier.

Well if you are now reading the meter correctly and you only have 48V on pin 3 look at the circuit diagram and find out what the voltage SHOULD be. Don't try and do these things blind (without a circuit) or you will learn nothing, get frustrated and give up. Firstly get familiar with your meter and learn how to read it.

You'll need to do some more voltage checks. I'm not trying to be unhelpful but the only way to learn, is by doing and looking at the circuit. Clue...the radio needs a LOT more than 48 volts HT to operate. So what does it say on the circuit? Your move.....

I'm looking at the Trader sheet and there is a table showing all voltages.

Dorian27 18th Jun 2021 7:10 pm

Re: Gec bc402
 
I am very grateful for your help. I will start again tomorrow. And re check if I am reading things correctly and let you now when I get some decent results


All times are GMT. The time now is 2:47 am.

Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.