DAC 90A smoothing caps - UK Vintage Radio Repair and Restoration Discussion Forum

M0TAW Tony · 13th Apr 2007, 2:05 pm

Can someone advise whether I can replace the 16uF + 32uF can with a 32uF + 32uF can in a DAC90A. (It would be taller but the right diameter) I have searched for a replacement of the same values but nothing found. I thought there was an old thread on the forum but can't find it.
Thanks
Tony

Hunts smoothing bomb · 13th Apr 2007, 2:15 pm

Hello Tony,

I think I have this right..... Your rectifier is a UY41?
According to TDSL max capacitance for this valve is 50uf so I would say that it's ok to do.
Others here though may correct me if I have missed something.

Cheers
Lee

M0TAW Tony · 13th Apr 2007, 6:23 pm

Hi Lee
Thank you for the reply - yes the rectifier is a UY41.
I've found a reference to these caps in the Recent Repair section on this site where Paul repaired a DAC90A. But he used a triple 32uF in a single can and he connected the 3rd cap in parallel with the second. This would give a 64uF (and a 32uF being the first of the three in the can)? Surely the two would have to be in series to give the required 16uF or am I missing something. (Wouldn't be the first time!)
Tony

Nickthedentist · 13th Apr 2007, 6:29 pm

Quote:

Originally Posted by M0TAW Tony

... he used a triple 32uF in a single can and he connected the 3rd cap in parallel with the second. This would give a 64uF (and a 32uF being the first of the three in the can)? Surely the two would have to be in series to give the required 16uF...

You're right, Paul's radio effectively had 32uF and 64uF caps in place of the 16uF and 32uF originally fitted.

But as Lee said above, 32uF immediately after the rectifier should be just about OK, and a larger capacitance value (e.g. 64uF) after the decoupling resistor isn't a problem, so the end result should be OK

paulsherwin · 13th Apr 2007, 8:37 pm

I would encourage you to think carefully before replacing an electrolytic with another of a similar age. It may look OK, but the reliability is a different matter. I would replace with new electrolytics fitted under the chassis, though if you're really keen on originality you could hollow out the old cap and fit the new ones inside the can.

I agree with the comments made by others regarding values.

Paul

M0TAW Tony · 16th Apr 2007, 7:51 pm

Hi Paul
Sorry - I missed your post. No I wasnt going to use an old can cap. I was just worried that the 32uF +32uF might not be good for the rectifier.
Tony

13th Apr 2007, 2:05 pm	#1
M0TAW Tony Pentode Join Date: Feb 2007 Location: Telford Posts: 104	DAC 90A smoothing caps Can someone advise whether I can replace the 16uF + 32uF can with a 32uF + 32uF can in a DAC90A. (It would be taller but the right diameter) I have searched for a replacement of the same values but nothing found. I thought there was an old thread on the forum but can't find it. Thanks Tony

13th Apr 2007, 2:15 pm	#2
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: DAC 90A smoothing caps Hello Tony, I think I have this right..... Your rectifier is a UY41? According to TDSL max capacitance for this valve is 50uf so I would say that it's ok to do. Others here though may correct me if I have missed something. Cheers Lee __________________ Lee

13th Apr 2007, 6:23 pm	#3
M0TAW Tony Pentode Join Date: Feb 2007 Location: Telford Posts: 104	Re: DAC 90A smoothing caps Hi Lee Thank you for the reply - yes the rectifier is a UY41. I've found a reference to these caps in the Recent Repair section on this site where Paul repaired a DAC90A. But he used a triple 32uF in a single can and he connected the 3rd cap in parallel with the second. This would give a 64uF (and a 32uF being the first of the three in the can)? Surely the two would have to be in series to give the required 16uF or am I missing something. (Wouldn't be the first time!) Tony

13th Apr 2007, 8:37 pm	#5
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: DAC 90A smoothing caps I would encourage you to think carefully before replacing an electrolytic with another of a similar age. It may look OK, but the reliability is a different matter. I would replace with new electrolytics fitted under the chassis, though if you're really keen on originality you could hollow out the old cap and fit the new ones inside the can. I agree with the comments made by others regarding values. Paul

16th Apr 2007, 7:51 pm	#6
M0TAW Tony Pentode Join Date: Feb 2007 Location: Telford Posts: 104	Re: DAC 90A smoothing caps Hi Paul Sorry - I missed your post. No I wasnt going to use an old can cap. I was just worried that the 32uF +32uF might not be good for the rectifier. Tony