Bush AC11, whistling humming and deaf. - UK Vintage Radio Repair and Restoration Discussion Forum

jay_oldstuff · 10th Jun 2012, 11:49 pm

Hi all,

I'm having some trouble with an AC11 chassis. I've sorted a number of issues relating to the paxolin sockets tracking, replaced all waxies and the HT electrolytics which were shot.

The set now basically works on MW but with lots of whistles and howls whilst tuning. Tuning is also very critical and just touching the dial upsets the set. LW is the same but very deaf the only station I can get is R4 and only on my 100' long wire aerial. SW is dead, there is also more mains hum than I was expecting.

HT measures fine at 260V at C33 and 120V at C27. I've tried subbing valves with known good ones with no improvement.

Jay

Steve_P · 11th Jun 2012, 5:20 pm

I assume you are using the trader sheet here.

If so, the first place I would look is R21. If you've tried the rectifier from another set, have you tried the rectifier from this set in another one?

Check the metal paint on the valves, because if it's severely scratched all sorts of funnies can occur.

Clean the wavechange switch as these are the root of all evil.

If the tuning is that sensitive, I wonder if the IF or RF has been tweaked at some time?

Cheers,

Steve P.

jay_oldstuff · 11th Jun 2012, 7:52 pm

Yes. I'm on the trader sheet sorry should of stated. I've already replaced R21 it had failed due to the tracking fault. All valves are B8A so no metalised coating, valve lineup is the classic UY41 UL41 UCH42 UBC41 UF41.
Wave change switch has been given a thorough going over.
I really do hope it's not a case of someone having a tweak as I hate doing alignment.

Jay

Steve_P · 11th Jun 2012, 8:08 pm

Squirt 465 kHz at it and see what that's like? Are there any signs of it being messed with?

Cheers,

Steve P.

jay_oldstuff · 11th Jun 2012, 9:29 pm

Guess I will have to dust off the signal generator then. I don't think the trimmers have been messed with as they are still sealed with white paint. I've just been back through all the caps I've changed and double checked for errors but have found none. This one is going to be a ****** I know it.

Jay

10th Jun 2012, 11:49 pm	#1
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Bush AC11, whistling humming and deaf. Hi all, I'm having some trouble with an AC11 chassis. I've sorted a number of issues relating to the paxolin sockets tracking, replaced all waxies and the HT electrolytics which were shot. The set now basically works on MW but with lots of whistles and howls whilst tuning. Tuning is also very critical and just touching the dial upsets the set. LW is the same but very deaf the only station I can get is R4 and only on my 100' long wire aerial. SW is dead, there is also more mains hum than I was expecting. HT measures fine at 260V at C33 and 120V at C27. I've tried subbing valves with known good ones with no improvement. Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

11th Jun 2012, 5:20 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Bush AC11, whistling humming and deaf. I assume you are using the trader sheet here. If so, the first place I would look is R21. If you've tried the rectifier from another set, have you tried the rectifier from this set in another one? Check the metal paint on the valves, because if it's severely scratched all sorts of funnies can occur. Clean the wavechange switch as these are the root of all evil. If the tuning is that sensitive, I wonder if the IF or RF has been tweaked at some time? 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...?

11th Jun 2012, 7:52 pm	#3
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Bush AC11, whistling humming and deaf. Yes. I'm on the trader sheet sorry should of stated. I've already replaced R21 it had failed due to the tracking fault. All valves are B8A so no metalised coating, valve lineup is the classic UY41 UL41 UCH42 UBC41 UF41. Wave change switch has been given a thorough going over. I really do hope it's not a case of someone having a tweak as I hate doing alignment. Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

11th Jun 2012, 8:08 pm	#4
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Bush AC11, whistling humming and deaf. Squirt 465 kHz at it and see what that's like? Are there any signs of it being messed with? 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...?

11th Jun 2012, 9:29 pm	#5
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Bush AC11, whistling humming and deaf. Guess I will have to dust off the signal generator then. I don't think the trimmers have been messed with as they are still sealed with white paint. I've just been back through all the caps I've changed and double checked for errors but have found none. This one is going to be a ****** I know it. Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train