GB for DC coupled B1 buffer with shunt PSUs - Page 99

Salas · 27th September 2009, 06:59 PM

No, not on 7812, just across the collector to base pins on its pads underneath the PCB, of the relay driving NPN BJT (the lower one near the 300//300 or 600//600R positions). The 2 mysterious relay chatter incidents occured due to oscillation of that transistor. The reason is still obscure. Several NPN types were checked to no avail. So it can still be a 546 or 550. Both types giving no problem at all with 3 relay types on the mega majority of builds. Unfortunate individual relay or 7812 are two scenarios to scrutinise further. But the remedy is a 150nF mylar film or ceramic cap, tried and tested on those two incidents with complete and measured success on Kannan's hand held Fluke with miniscope display.

kannan_s · 27th September 2009, 07:04 PM

Quote:

Originally Posted by Salas

No, not on 7812, just across the collector to base pins on its pads underneath the PCB, of the relay driving NPN BJT (the lower one near the 300//300 or 600//600R positions). The 2 mysterious relay chatter incidents occured due to oscillation of that transistor. The reason is still obscure. Several NPN types were checked to no avail. So it can still be a 546 or 550. Both types giving no problem at all with 3 relay types on the mega majority of builds. Unfortunate individual relay or 7812 are two scenarios to scrutinise further. But the remedy is a 150nF mylar film or ceramic cap, tried and tested on those two incidents with complete and measured success on Kannan's hand held Fluke with miniscope display.

Picture shows the Film cap - ceramic cap wprks as well - solder it only if needed
kannan

jean-paul · 07:12 PM

Haven't soldered anything yet but could it be that decoupling the 7812 cures the problem too ? The relay coil could let the 7812 oscillate.

Salas · 27th September 2009, 07:14 PM

Yes, first thing I mentioned back then, next thing that Kannan will look in to. If it happens again to any new proto build, do cross investigate. Its not a repeating enough theme untill now so we could not get more statistical study.

kannan_s · 27th September 2009, 08:39 PM

Quote:

Originally Posted by Salas

Yes, first thing I mentioned back then, next thing that Kannan will look in to. If it happens again to any new proto build, do cross investigate. Its not a repeating enough theme untill now so we could not get more statistical study.

Onething strange about this problem that I noticed was that it did not oscillate but the transistor was repeatedly switching low and high with unequal period - something looked like unable to drive the inductive load rather than 7812 oscillating. I will test this with decoupling cap on 7812 - say 100nF and report. Right now I am working on something else - kept this aside, probably try this test in couple of days
Kannan

Tea-Bag · 27th September 2009, 09:02 PM

Quote:

Originally Posted by jean-paul

Haven't soldered anything yet but could it be that decoupling the 7812 cures the problem too ? The relay coil could let the 7812 oscillate.

JP,
Did you get your boards?

F1 FAN · 27th September 2009, 11:44 PM

What might be the dimensions of each board ? I back tracked 20 or so pages but did'nt see them mentioned.

Quote:

Originally Posted by Salas

Is there any el cheapo stepped 20-25k on epay with fake Dale pre assembled for you to try?

These look interesting.Any thoughts on them?.http://cgi.ebay.ca/VALAB-Audio-23-St...d=p3911.c0.m14

Thanks salas,crt and others for your efforts in getting this wonderful project up and running.

grufti · 27th September 2009, 11:48 PM

Quote:

Originally Posted by F1 FAN

What might be the dimensions of each board ? I back tracked 20 or so pages but did'nt see them mentioned.

These look interesting.Any thoughts on them?.http://cgi.ebay.ca/VALAB-Audio-23-St...d=p3911.c0.m14

Thanks salas,crt and others for your efforts in getting this wonderful project up and running.

I bought one of his. Smooth transaction. Like it.

Tea-Bag · 28th September 2009, 12:13 AM

Quote:

Originally Posted by F1 FAN

What might be the dimensions of each board ? I back tracked 20 or so pages but did'nt see them mentioned.

Hypnotize basic board is 127X68.58mm
Mezmerize is 197.49X68.58mm

Salas · 28th September 2009, 12:26 AM

Quote:

Originally Posted by F1 FAN

Thanks salas,crt and others for your efforts in getting this wonderful project up and running.

You are welcome.

27th September 2009, 07:05 PM	#983
jean-paul diyAudio Moderator Emeritus Join Date: Sep 2002 Location: The Netherlands	Haven't soldered anything yet but could it be that decoupling the 7812 cures the problem too ? The relay coil could let the 7812 oscillate. __________________ It's only audio Last edited by jean-paul; 27th September 2009 at 07:12 PM.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

27th September 2009, 06:59 PM	#981
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	No, not on 7812, just across the collector to base pins on its pads underneath the PCB, of the relay driving NPN BJT (the lower one near the 300//300 or 600//600R positions). The 2 mysterious relay chatter incidents occured due to oscillation of that transistor. The reason is still obscure. Several NPN types were checked to no avail. So it can still be a 546 or 550. Both types giving no problem at all with 3 relay types on the mega majority of builds. Unfortunate individual relay or 7812 are two scenarios to scrutinise further. But the remedy is a 150nF mylar film or ceramic cap, tried and tested on those two incidents with complete and measured success on Kannan's hand held Fluke with miniscope display.

27th September 2009, 07:14 PM	#984
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Yes, first thing I mentioned back then, next thing that Kannan will look in to. If it happens again to any new proto build, do cross investigate. Its not a repeating enough theme untill now so we could not get more statistical study.

Currently Active Users Viewing This Thread: 3 (1 members and 2 guests)
dungdochi1978