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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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27th Jul 2020, 4:59 pm | #21 | |
Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
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Re: TIP30 substitute for regulated -12V
Quote:
Thanks for your note... the regulator tab connected to the aluminium is isolated...and all the other parts are isolated... If i swap this with the 7812 should I change anything at all or just swap exactly how the 7912 is right now? Thanks ! |
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27th Jul 2020, 5:07 pm | #22 |
Nonode
Join Date: Mar 2008
Location: Virginia Water, Surrey, UK.
Posts: 2,872
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Re: TIP30 substitute for regulated -12V
The centre connection and tab on the 7812 must be taken to the -12V line. It is only taken to chassis when used in more conventional +12V form. Your photo seems to show the trace from that pin going nowhere!
I can't really see what that diode and output-side capacitor are doing, not much I suspect. Your choice as to leaving them in place. But I would probably remove them for now.
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Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk |
27th Jul 2020, 5:10 pm | #23 |
Nonode
Join Date: Mar 2008
Location: Virginia Water, Surrey, UK.
Posts: 2,872
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Re: TIP30 substitute for regulated -12V
The pins on the 7812 should go in naturally to the circuit board. Tab on the bottom, insulated.
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Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk |
27th Jul 2020, 5:13 pm | #24 | |
Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
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Re: TIP30 substitute for regulated -12V
Quote:
Thanks a million again for your help, will try and get a 7812 and see what I am getting then... |
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27th Jul 2020, 5:19 pm | #25 |
Nonode
Join Date: Mar 2008
Location: Virginia Water, Surrey, UK.
Posts: 2,872
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Re: TIP30 substitute for regulated -12V
I keep trying to see in the photos what that extra diode and capacitor are doing. I think they are placed right across the output of the regulator. That's quite conventional in symmetrical (+ and - voltage) supplies, using a shunt diode to to protect the regulator. The cathode would go to ground, the anode to the -12V line. The capacitor is just smoothing any noise on the output. So leave them in for now, if they are across the -12V line and ground.
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Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk |
27th Jul 2020, 5:25 pm | #26 |
Nonode
Join Date: Mar 2008
Location: Virginia Water, Surrey, UK.
Posts: 2,872
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Re: TIP30 substitute for regulated -12V
The centre pin of a 7812 definitely needs to go to -12V, not ground, and that should be the anode of the big diode (the end without a band).
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Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk |
27th Jul 2020, 5:28 pm | #27 | |
Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
|
Re: TIP30 substitute for regulated -12V
Quote:
Just looking at the pin out of the 7812...so pin 1 is V+ in, that is connected to (according to my "drawings" ) that diode cathode and digital ground.. is this correct? the pin1 should not be connected to the the point of rectified DC? Or I am way too confused now.. will order anyway the 7812 and test it ...just afraid that i am soldering this pcb too much... might burn the thing... thanks again Jeremy |
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27th Jul 2020, 5:35 pm | #28 |
Nonode
Join Date: Mar 2008
Location: Virginia Water, Surrey, UK.
Posts: 2,872
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Re: TIP30 substitute for regulated -12V
I suggest that if you are worried about damaging the pcb, make up a small pcb for the -12V supply and test that outside the amplifier first so you can check the results.
Or at least disconnect the -12V line from the rest of the amplifier while you are testing. Pin 1 (input) of the 7812 goes just to the +ve of the big 1000uF capacitor (rectified dc from the diodes), nowhere else. Pin 2 ("ground" or common) goes to the -12V line (the other side of the 1000uF capacitor) Pin 3 (output) goes to digital ground and diode cathode (white ring) Just try removing the 7912 (or the transistor) and putting the 7812 exactly in its place. But make sure pin 2 (centre/tab) does somehow end up connected to the -12V line, isolated from chassis.
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Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk |