Sinclair PZ6 PSU - UK Vintage Radio Repair and Restoration Discussion Forum

ajs37 · 17th Feb 2020, 5:35 pm

I am trying to sort this PSU out as it is not working - I saw that the bridge rectifier (BR1 on the circuit diagram) had been replaced, according to the polarity on the diagram. Now it is possible to insert the rectifier the wrong way round, so this may be the problem. Looking at the printed circuit diagram (see photo) I am beginning to think I am going doolally. I think BR1 is shown incorrectly in the photo - am I correct, or am I really going soft in the head?
Thanks - all help received gratefully!
Cheers
Andy

ajgriff · 17th Feb 2020, 5:47 pm

The circuit diagram looks ok to me but it might be me who's losing the plot.

Alan

TonyDuell · 17th Feb 2020, 5:47 pm

The diagram looks OK to me.

ajs37 · 17th Feb 2020, 6:10 pm

ok - it's just me then! I always had problems with diode polarity going back to school physics lessons!

Thanks very much!
Andy

llama · 17th Feb 2020, 6:22 pm

I feel your pain! It's always seemed a bit odd that the positive supply comes out of a cathode - valve or semiconductor. But I rationalise it in my head by thinking of the direction the current flows. It has to be more positive at the diode anode in order to flow as a positive supply into the load. Makes it make sense to me, anyway!
Graham

ajgriff · 17th Feb 2020, 6:55 pm

If it's any consolation Andy I think we all have brain cell failure over things like this from time to time. When it happens to me I usually resort to 'googling' in an attempt to prove my sanity.

Alan

ajs37 · 17th Feb 2020, 11:00 pm

thanks for the supportive comments chaps!

crackle · 18th Feb 2020, 8:06 am

The way I look at a bridge rectifier schematic is; the arrow of each diode points in the way that the current flows, so the 2 diodes in the upper half of the bridge with the arrow pointing up are pointing to the +. In the traditional sense the current flows from the + to the -, so the 2 diodes in the bottom of the bridge are also pointing up to allow the current back to the transformer after it has flowed around the circuit..

Mike

Craig Sawyers · 18th Feb 2020, 8:38 am

One of the nonsenses with electronics in general is that "conventional" current flow is from + to -. However the actual electrons flow from - to +.

The best example is with a valve, where conventional current flows from anode to cathode, but of course the electrons move from cathode to anode.

Craig

'LIVEWIRE?' · 18th Feb 2020, 9:59 am

Craig, I remember being taught the 'fiction' about 'conventional current' back in 1971, so some things don't change with the passing years!

Craig Sawyers · 18th Feb 2020, 10:33 am

The clue alas is in the word "conventional". Dates back to Benjamin Franklin in the early 1700s, way before anyone knew about the electron and its charge.

Franklin arbitrarily came up with the idea that electricity flowed as a result of excess electrical fluid (+) and a deficit (-). And that is where we get the idea of conventional current. And because it was a convention that everyone used, it was not redefined once Millikan and JJ Thompson determined that negative charge on the electron.

Craig

Craig Sawyers · 18th Feb 2020, 10:40 am

Back to the PZ6, the subject of the OP's questions. Back in the day I bought one of these to power the Sinclair power amps.

Blew it up, twice. Sinclair were pretty good with the guarantee and replaced it twice, with ones they had that had previously been repaired. Basically fried series pass transistor.

So anyway be careful not to short it or take too much current, because there is no overload protection.

Craig

17th Feb 2020, 5:35 pm	#1
ajs37 Heptode Join Date: Jun 2003 Location: Bristol, UK. Posts: 900	Sinclair PZ6 PSU I am trying to sort this PSU out as it is not working - I saw that the bridge rectifier (BR1 on the circuit diagram) had been replaced, according to the polarity on the diagram. Now it is possible to insert the rectifier the wrong way round, so this may be the problem. Looking at the printed circuit diagram (see photo) I am beginning to think I am going doolally. I think BR1 is shown incorrectly in the photo - am I correct, or am I really going soft in the head? Thanks - all help received gratefully! Cheers Andy Attached Thumbnails

17th Feb 2020, 5:47 pm	#2
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Sinclair PZ6 PSU The circuit diagram looks ok to me but it might be me who's losing the plot. Alan

17th Feb 2020, 5:47 pm	#3
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Sinclair PZ6 PSU The diagram looks OK to me.

17th Feb 2020, 6:10 pm	#4
ajs37 Heptode Join Date: Jun 2003 Location: Bristol, UK. Posts: 900	Re: Sinclair PZ6 PSU ok - it's just me then! I always had problems with diode polarity going back to school physics lessons! Thanks very much! Andy

17th Feb 2020, 6:22 pm	#5
llama Octode Join Date: Jun 2006 Location: St Osyth, Nr Clacton, Essex, UK. Posts: 1,482	Re: Sinclair PZ6 PSU I feel your pain! It's always seemed a bit odd that the positive supply comes out of a cathode - valve or semiconductor. But I rationalise it in my head by thinking of the direction the current flows. It has to be more positive at the diode anode in order to flow as a positive supply into the load. Makes it make sense to me, anyway! Graham __________________ Half my stuff is junk - trouble is, I don't know which half!

17th Feb 2020, 6:55 pm	#6
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Sinclair PZ6 PSU If it's any consolation Andy I think we all have brain cell failure over things like this from time to time. When it happens to me I usually resort to 'googling' in an attempt to prove my sanity. Alan

17th Feb 2020, 11:00 pm	#7
ajs37 Heptode Join Date: Jun 2003 Location: Bristol, UK. Posts: 900	Re: Sinclair PZ6 PSU thanks for the supportive comments chaps!

18th Feb 2020, 8:06 am	#8
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Sinclair PZ6 PSU The way I look at a bridge rectifier schematic is; the arrow of each diode points in the way that the current flows, so the 2 diodes in the upper half of the bridge with the arrow pointing up are pointing to the +. In the traditional sense the current flows from the + to the -, so the 2 diodes in the bottom of the bridge are also pointing up to allow the current back to the transformer after it has flowed around the circuit.. Mike

18th Feb 2020, 8:38 am	#9
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,982	Re: Sinclair PZ6 PSU One of the nonsenses with electronics in general is that "conventional" current flow is from + to -. However the actual electrons flow from - to +. The best example is with a valve, where conventional current flows from anode to cathode, but of course the electrons move from cathode to anode. Craig

18th Feb 2020, 9:59 am	#10
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Sinclair PZ6 PSU Craig, I remember being taught the 'fiction' about 'conventional current' back in 1971, so some things don't change with the passing years!

18th Feb 2020, 10:33 am	#11
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,982	Re: Sinclair PZ6 PSU The clue alas is in the word "conventional". Dates back to Benjamin Franklin in the early 1700s, way before anyone knew about the electron and its charge. Franklin arbitrarily came up with the idea that electricity flowed as a result of excess electrical fluid (+) and a deficit (-). And that is where we get the idea of conventional current. And because it was a convention that everyone used, it was not redefined once Millikan and JJ Thompson determined that negative charge on the electron. Craig

18th Feb 2020, 10:40 am	#12
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,982	Re: Sinclair PZ6 PSU Back to the PZ6, the subject of the OP's questions. Back in the day I bought one of these to power the Sinclair power amps. Blew it up, twice. Sinclair were pretty good with the guarantee and replaced it twice, with ones they had that had previously been repaired. Basically fried series pass transistor. So anyway be careful not to short it or take too much current, because there is no overload protection. Craig