Philips B3X16A - No SW band after 10MHz - UK Vintage Radio Repair and Restoration Discussion Forum

renato_enca · 19th Apr 2007, 8:56 pm

Hello, friends.
I have a Philips model B3X16A, the same set that had the magic eye not working. One thing I've noticed is that when I turn on the set, the tuning section (the converter) takes too long to start up, being the IF circuit already running and giving noise.

Also, the other 2 wavebands past 10Mhz (SW2 and SW1) aren't working. Sometimes, the set is silent for more than 5 minutes at power on, then suddenly the station in which it was tuned appears loud and clear. I began working on it, and found a 56k resistor in the converter circuit measuring 400k, changed it but no improvements. It only became VERY more sensitive. Any suggestions?

PJL · 19th Apr 2007, 10:17 pm

It sounds like a problem with the local oscillator. If you have checked the resistance values and replaced the decoupling capacitors, then the next test would be to try a replacement ECH81 as these can cause the local oscillator to fail at high frequencies.

renato_enca · 19th Apr 2007, 10:29 pm

Thanks for the response.
I don't have an ECH81, so what could I use instead?

Steve_P · 19th Apr 2007, 10:42 pm

Check caps and other stuff first, and give the valve pins and base a clean.

Cheers,

Steve P

paulsherwin · 19th Apr 2007, 11:59 pm

Quote:

Originally Posted by renato_enca

Thanks for the response.
I don't have an ECH81......

Many forum members will have a spare ECH81 in the junk box. If you post a request in the 'Parts Wanted' section of the forum, I would expect somebody to send you one (used but good) for the price of the postage if you explain why you want it

An ECH83 (used in car radios) should be OK.

Paul

Mike Phelan · 20th Apr 2007, 7:27 am

Renato
Is the anode voltage on the triode (local osc) of the ECH81 OK, and the HT to it as well? If this is low then the LO will start to stall at higher frequencies.

Paul
Would a 12 volt ECH83 work OK on "normal" HT? Never tried this.

paulsherwin · 20th Apr 2007, 10:20 am

Quote:

Originally Posted by Mike Phelan

Paul
Would a 12 volt ECH83 work OK on "normal" HT? Never tried this.

This has been discussed in the forum before, and the consensus was that ECH83s are just selected ECH81s. I've used one without problems.

Paul

Mike Phelan · 20th Apr 2007, 5:07 pm

Cheers, Paul - I had not come across that before.

renato_enca · 20th Apr 2007, 10:24 pm

Thanks everybody, it was indeed the ECH81 valve too weak. I could find an ECH81 on the very bottom of my junk box, it was a luck being not broken.

Very best regards from

Renato

19th Apr 2007, 8:56 pm	#1
renato_enca Retired Dormant Member Join Date: Feb 2007 Location: Lisbon, Portugal Posts: 51	Philips B3X16A - No SW band after 10MHz Hello, friends. I have a Philips model B3X16A, the same set that had the magic eye not working. One thing I've noticed is that when I turn on the set, the tuning section (the converter) takes too long to start up, being the IF circuit already running and giving noise. Also, the other 2 wavebands past 10Mhz (SW2 and SW1) aren't working. Sometimes, the set is silent for more than 5 minutes at power on, then suddenly the station in which it was tuned appears loud and clear. I began working on it, and found a 56k resistor in the converter circuit measuring 400k, changed it but no improvements. It only became VERY more sensitive. Any suggestions?

19th Apr 2007, 10:17 pm	#2
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Philips B3X16A - No SW band after 10MHz It sounds like a problem with the local oscillator. If you have checked the resistance values and replaced the decoupling capacitors, then the next test would be to try a replacement ECH81 as these can cause the local oscillator to fail at high frequencies.

19th Apr 2007, 10:29 pm	#3
renato_enca Retired Dormant Member Join Date: Feb 2007 Location: Lisbon, Portugal Posts: 51	Re: Philips B3X16A - No SW band after 10MHz Thanks for the response. I don't have an ECH81, so what could I use instead? Last edited by Darren-UK; 6th Oct 2007 at 12:45 pm. Reason: Accordance with other edits.

19th Apr 2007, 10:42 pm	#4
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Philips B3X16A - No SW band after 10MHz Check caps and other stuff first, and give the valve pins and base a clean. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...? Last edited by Darren-UK; 6th Oct 2007 at 12:45 pm. Reason: Accordance with other edits.

20th Apr 2007, 7:27 am	#6
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Philips B3X16A - No SW band after 10MHz Renato Is the anode voltage on the triode (local osc) of the ECH81 OK, and the HT to it as well? If this is low then the LO will start to stall at higher frequencies. Paul Would a 12 volt ECH83 work OK on "normal" HT? Never tried this. __________________ Mike.

20th Apr 2007, 5:07 pm	#8
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Philips B3X16A - No SW band after 10MHz Cheers, Paul - I had not come across that before. __________________ Mike.

20th Apr 2007, 10:24 pm	#9
renato_enca Retired Dormant Member Join Date: Feb 2007 Location: Lisbon, Portugal Posts: 51	Re: Philips B3X16A - No SW band after 10MHz Thanks everybody, it was indeed the ECH81 valve too weak. I could find an ECH81 on the very bottom of my junk box, it was a luck being not broken. Very best regards from Renato