Unused capacitor section - UK Vintage Radio Repair and Restoration Discussion Forum

Paul Stenning · 10th Aug 2004, 8:30 pm

In the Bush DAC90A I am working on, I have fitted a replacement 32+32+32uF capacitor in place of the original 32+32uF one. At the moment I have left the third section disconnected.

From the point of view of capacitor life, do you think it would be worth paralleling it with the second section (after the decoupling resistor) instead?

Since the decoupling resistor is 10K, the extra capacitance won't make any difference to the hum level. But it seems a shame to have it doing nothing!

Before someone suggests that I fit a 32+32uF instead (which would be the correct thing to do) - I don't have any, but I do have quite a few 32+32+32uF ones.

Sideband · 10th Aug 2004, 8:52 pm

Hi Paul.

Yes seems a shame to waste it. At least if you parallel it after the 10k it will keep it formed in case you need to replace one of the pair again at any time.

Rich.

jim_beacon · 11th Aug 2004, 12:02 am

So long as it is after the resistor, it should be OK, but if you connect it in parrallel with the first section, you run the risk of rectifier damage at switch on (I know, my favourite topic again.....

)

Jim.

Norm_Leal · 11th Aug 2004, 1:10 am

Hi Paul

Any other place you could use an electrolytic? How about cathode bypass of R14?

Norm

Paul Stenning · 11th Aug 2004, 6:46 pm

This set doesn't need a cathode resistor bypass cap. I did this in another set using one of these caps - it worked fine even though it was only running at a few volts.

10th Aug 2004, 8:30 pm	#1
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,071	Unused capacitor section In the Bush DAC90A I am working on, I have fitted a replacement 32+32+32uF capacitor in place of the original 32+32uF one. At the moment I have left the third section disconnected. From the point of view of capacitor life, do you think it would be worth paralleling it with the second section (after the decoupling resistor) instead? Since the decoupling resistor is 10K, the extra capacitance won't make any difference to the hum level. But it seems a shame to have it doing nothing! Before someone suggests that I fit a 32+32uF instead (which would be the correct thing to do) - I don't have any, but I do have quite a few 32+32+32uF ones. __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster

10th Aug 2004, 8:52 pm	#2
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,566	Re: Unused capacitor section Hi Paul. Yes seems a shame to waste it. At least if you parallel it after the 10k it will keep it formed in case you need to replace one of the pair again at any time. Rich. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

11th Aug 2004, 12:02 am	#3
jim_beacon Retired Dormant Member Join Date: Mar 2003 Location: Bishop's Waltham, Hants, UK. Posts: 939	Re: Unused capacitor section So long as it is after the resistor, it should be OK, but if you connect it in parrallel with the first section, you run the risk of rectifier damage at switch on (I know, my favourite topic again..... ) Jim.

11th Aug 2004, 1:10 am	#4
Norm_Leal Retired Dormant Member Join Date: Jan 2003 Location: Livermore, California, USA. Posts: 139	Re: Unused capacitor section Hi Paul Any other place you could use an electrolytic? How about cathode bypass of R14? Norm

11th Aug 2004, 6:46 pm	#5
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,071	Re: Unused capacitor section This set doesn't need a cathode resistor bypass cap. I did this in another set using one of these caps - it worked fine even though it was only running at a few volts. __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster