Barker 88. AZ4G problems. - UK Vintage Radio Repair and Restoration Discussion Forum

Ian B · 9th Jan 2007, 10:12 am

Hi All,

I bought a Barker 88 at the last Wootton Bassett auction. All there but very rough. Speaker field coil o/c but a large choke had been fitted neatly on top of the chassis.

I replaced all the wax caps, reformed the electrolytics, connected a speaker to the op trans terminals and switched on. Checked voltages, all seemed close to those given in the Trader sheet. Could only get strong stations on MW. Checked frequency changer & IF amp - both very low, found a couple of better ones, repaired broken connection to LW aerial coil, applied switch cleaner to wavechange switch, now working on all bands.

Left on soak for a couple of hours, all seemed ok. Repaired & repolished cabinet. Now looks worth the tenner I paid for it!

However, having replaced the chassis I left it on further soak and after about 2 hours it just went silent. All valve heaters still lit, but a smell of something rather hot, and a faint "bubbling" noise. Having got it all apart again I found that the rectifier heater winding had gone short circuit. Managed to find a replacement transformer, and decided to check the rectifier (AZ4G); only one anode working.

My question is (sorry about the long preamble): did the transformer short kill the rectifier, or did a dud rectifier overload the transformer? Or is it just coincidence? It seems fine now, but I'd just like to know!
Thanks in anticipation,

Ian Blackbourn.

Steve_P · 9th Jan 2007, 6:08 pm

Probably not linked. Had this one before.

The Heater Winding was probably dodgy to begin with. I've had these rectifiers (AZ4G) do this before, just one section of the heater goes O/C, and the radio will keep running, sometimes still working!

You've changed them both, so clap the back on and forget it - just use the thing!!

Cheers,

Steve P

PJL · 10th Jan 2007, 12:08 am

Ian, I think I would vote for rectifier killing transformer as half wave would result in more heat dissipated in the transformer as well as localising it to one winding...but as Steve points out - the nightmare is over!

Ian B · 10th Jan 2007, 10:50 am

Thanks gents, I'll just sit back & enjoy it now!

Ian

9th Jan 2007, 10:12 am	#1
Ian B Hexode Join Date: May 2006 Location: Arlesey, Bedfordshire, UK. Posts: 401	Barker 88. AZ4G problems. Hi All, I bought a Barker 88 at the last Wootton Bassett auction. All there but very rough. Speaker field coil o/c but a large choke had been fitted neatly on top of the chassis. I replaced all the wax caps, reformed the electrolytics, connected a speaker to the op trans terminals and switched on. Checked voltages, all seemed close to those given in the Trader sheet. Could only get strong stations on MW. Checked frequency changer & IF amp - both very low, found a couple of better ones, repaired broken connection to LW aerial coil, applied switch cleaner to wavechange switch, now working on all bands. Left on soak for a couple of hours, all seemed ok. Repaired & repolished cabinet. Now looks worth the tenner I paid for it! However, having replaced the chassis I left it on further soak and after about 2 hours it just went silent. All valve heaters still lit, but a smell of something rather hot, and a faint "bubbling" noise. Having got it all apart again I found that the rectifier heater winding had gone short circuit. Managed to find a replacement transformer, and decided to check the rectifier (AZ4G); only one anode working. My question is (sorry about the long preamble): did the transformer short kill the rectifier, or did a dud rectifier overload the transformer? Or is it just coincidence? It seems fine now, but I'd just like to know! Thanks in anticipation, Ian Blackbourn. Last edited by Darren-UK; 8th Aug 2007 at 10:48 am. Reason: General tidying.

9th Jan 2007, 6:08 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Barker 88 Probably not linked. Had this one before. The Heater Winding was probably dodgy to begin with. I've had these rectifiers (AZ4G) do this before, just one section of the heater goes O/C, and the radio will keep running, sometimes still working! You've changed them both, so clap the back on and forget it - just use the thing!! 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...?

10th Jan 2007, 12:08 am	#3
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Barker 88 Ian, I think I would vote for rectifier killing transformer as half wave would result in more heat dissipated in the transformer as well as localising it to one winding...but as Steve points out - the nightmare is over!

10th Jan 2007, 10:50 am	#4
Ian B Hexode Join Date: May 2006 Location: Arlesey, Bedfordshire, UK. Posts: 401	Re: Barker 88 Thanks gents, I'll just sit back & enjoy it now! Ian