Shaftesbury 519 amplifier - Page 5 - UK Vintage Radio Repair and Restoration Discussion Forum

Station X · 2nd Sep 2019, 12:22 pm

I'm losing the plot here. Have the smoothers now been reformed using a diode resistor combo?

Guitarist28 · 2nd Sep 2019, 1:09 pm

Graham.

I was checking that the transformer was good to go first. Now I will endeavour to reform the caps.

Best regards

Refugee · 2nd Sep 2019, 1:43 pm

The heaters will most likely drop to about 6.5 volts with the valves in so it should be OK.
It looks like time to reform the caps now.

Guitarist28 · 2nd Sep 2019, 1:46 pm

I have just connected across pins 7 to 3 and switched on.... Immediate buzzing sound. That can't be correct??

Refugee · 2nd Sep 2019, 1:47 pm

I hope that was not with a solid wire.
It should be with the resistor and diode.

Guitarist28 · 2nd Sep 2019, 1:59 pm

With 200kR 2watt and 1n4007 in series?

Refugee · 2nd Sep 2019, 2:05 pm

That is right.

Guitarist28 · 2nd Sep 2019, 2:07 pm

Should it buzz though?? Am I better off starting with a lower voltage through a variac?

Refugee · 2nd Sep 2019, 2:09 pm

It will buzz with a short circuit across the rectifier diode and it is also likely to damage the transformer.

Guitarist28 · 2nd Sep 2019, 2:10 pm

What I am doing incorrectly?

Refugee · 2nd Sep 2019, 2:16 pm

You connected a solid wire where the diode and resister should have been.

Guitarist28 · 2nd Sep 2019, 2:20 pm

You misunderstand, I did use a diode and resistor in series between pins 7 & 3. I'm now at a complete loss what has happened.

Guitarist28 · 2nd Sep 2019, 2:54 pm

Oh dear, its now buzzing without any connections across the rectifier at all.

snowman_al · 2nd Sep 2019, 2:58 pm

Have you got the rectifier the right way round?
The 'cathode' (the band end) Must point to the pin 3. (It does not matter if the diode or resistor goes to pin 1/7 as long as the band points to pin 3.)

Guitarist28 · 2nd Sep 2019, 3:02 pm

It wasnt buzzing before I connected the diode/ resistor. So it appears something has now shorted out...... Where to start!

ms660 · 2nd Sep 2019, 3:12 pm

You had the transformer shrouds off, were the bolts tightened properly when you re-assembled it?

Lawrence.

Guitarist28 · 2nd Sep 2019, 3:14 pm

I think I will have to take it apart again to make sure nothing is shorting out inside... What a pain!

Interesting point thought, it not tripping out my laboratory super fast rcd though??

Station X · 2nd Sep 2019, 3:44 pm

One matter never resolved is the resistance of the primary winding. What does it measure?

Guitarist28 · 2nd Sep 2019, 4:40 pm

Across the 2 purple primary cables.... 78R

Guitarist28 · 2nd Sep 2019, 5:01 pm

What an idiot..... Shrouds were loose, I'd not tighted them fully. It's not buzzing now so shall I try the resistor/diode again?

2nd Sep 2019, 12:22 pm	#81
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Shaftesbury 519 amplifier I'm losing the plot here. Have the smoothers now been reformed using a diode resistor combo? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

2nd Sep 2019, 1:09 pm	#82
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier Graham. I was checking that the transformer was good to go first. Now I will endeavour to reform the caps. Best regards

2nd Sep 2019, 1:43 pm	#83
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Shaftesbury 519 amplifier The heaters will most likely drop to about 6.5 volts with the valves in so it should be OK. It looks like time to reform the caps now.

2nd Sep 2019, 1:46 pm	#84
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier I have just connected across pins 7 to 3 and switched on.... Immediate buzzing sound. That can't be correct??

2nd Sep 2019, 1:47 pm	#85
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Shaftesbury 519 amplifier I hope that was not with a solid wire. It should be with the resistor and diode.

2nd Sep 2019, 1:59 pm	#86
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier With 200kR 2watt and 1n4007 in series?

2nd Sep 2019, 2:05 pm	#87
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Shaftesbury 519 amplifier That is right.

2nd Sep 2019, 2:07 pm	#88
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier Should it buzz though?? Am I better off starting with a lower voltage through a variac?

2nd Sep 2019, 2:09 pm	#89
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Shaftesbury 519 amplifier It will buzz with a short circuit across the rectifier diode and it is also likely to damage the transformer.

2nd Sep 2019, 2:10 pm	#90
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier What I am doing incorrectly?

2nd Sep 2019, 2:16 pm	#91
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Shaftesbury 519 amplifier You connected a solid wire where the diode and resister should have been.

2nd Sep 2019, 2:20 pm	#92
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier You misunderstand, I did use a diode and resistor in series between pins 7 & 3. I'm now at a complete loss what has happened.

2nd Sep 2019, 2:54 pm	#93
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier Oh dear, its now buzzing without any connections across the rectifier at all.

2nd Sep 2019, 2:58 pm	#94
snowman_al Octode Join Date: Dec 2018 Location: Llandeilo, West Wales, UK. Posts: 1,092	Re: Shaftesbury 519 amplifier Have you got the rectifier the right way round? The 'cathode' (the band end) Must point to the pin 3. (It does not matter if the diode or resistor goes to pin 1/7 as long as the band points to pin 3.) __________________ Never Leave Well Enough Alone...

2nd Sep 2019, 3:02 pm	#95
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier It wasnt buzzing before I connected the diode/ resistor. So it appears something has now shorted out...... Where to start!

2nd Sep 2019, 3:12 pm	#96
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Shaftesbury 519 amplifier You had the transformer shrouds off, were the bolts tightened properly when you re-assembled it? Lawrence.

2nd Sep 2019, 3:14 pm	#97
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier I think I will have to take it apart again to make sure nothing is shorting out inside... What a pain! Interesting point thought, it not tripping out my laboratory super fast rcd though??

2nd Sep 2019, 3:44 pm	#98
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Shaftesbury 519 amplifier One matter never resolved is the resistance of the primary winding. What does it measure? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

2nd Sep 2019, 4:40 pm	#99
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier Across the 2 purple primary cables.... 78R

2nd Sep 2019, 5:01 pm	#100
Guitarist28 Heptode Join Date: Dec 2009 Location: Hockley, Essex, UK. Posts: 575	Re: Shaftesbury 519 amplifier What an idiot..... Shrouds were loose, I'd not tighted them fully. It's not buzzing now so shall I try the resistor/diode again?