I have to pull out this circuit board in a 17-year-old Belles 21A preamp for a relay switch repair. Should I consider preventive maintenance by replacing or upgrading any of these four electrolytic capacitors that are near the power supply transformers and heat sinks?
The top blue cap is 1500uF 250V.
The top black cap is 100uF 250V
The bottom blue cap is 220uF 35V
The bottom black cap is 2200uF 35V
The top blue cap is 1500uF 250V.
The top black cap is 100uF 250V
The bottom blue cap is 220uF 35V
The bottom black cap is 2200uF 35V
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Definitely replace all of them, since they could fail at any time now.
Why need to repair it again, and maybe have a cascading failure or a damaged pcb?
Check the DC voltage normally on them, and consider using a higher voltage part.
The AC line voltages have gone up in recent years. Also, 105C rated parts are better.
Why need to repair it again, and maybe have a cascading failure or a damaged pcb?
Check the DC voltage normally on them, and consider using a higher voltage part.
The AC line voltages have gone up in recent years. Also, 105C rated parts are better.
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If its only see light use they are probably OK for another decade, if in constant use they will have been warm/hot for many 1000's of hours and are worth replacing I reckon.
Its a calculated risk really.
I replaced the electrolytics in my homebew MOSFET amp built in 1981 a year ago,
since 40 years or use is definitely long enough, but it wasn't displaying any problems.
Its a calculated risk really.
I replaced the electrolytics in my homebew MOSFET amp built in 1981 a year ago,
since 40 years or use is definitely long enough, but it wasn't displaying any problems.
It depends on how they are used and stressed in the circuit. But only use high quality parts
from known vendors.
from known vendors.
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Reminds me of a large sign I saw whilst servicing Ampex AG-440 tape recorders at the Air Force Academy in their big band room:
IF IT AIN'T BROKE
DON'T FIX IT!!!
IF IT AIN'T BROKE
DON'T FIX IT!!!
I would strongly consider replacing them since you are working on the preamp anyway.
As I mentioned in your other thread, I own a Belles 21A. A recap for it is on my "to do" list, but not it is at the top of my list. The caps that do the most work are all decent: Nichicons and a CDE. The small 220uF cap is a Xicon and it is on the output side of a voltage regulator.
The CDE is a "snap in", the others have standard leads.
The PS on my 21A is slightly different from your's: it has 2 2200uFs and 2 220uFs.
I have repaired several pieces of equipment that had problems because of bad capacitors. Sometimes damage goes beyond the PS. I have not had to fix one newer than 20 years old though.
As I mentioned in your other thread, I own a Belles 21A. A recap for it is on my "to do" list, but not it is at the top of my list. The caps that do the most work are all decent: Nichicons and a CDE. The small 220uF cap is a Xicon and it is on the output side of a voltage regulator.
The CDE is a "snap in", the others have standard leads.
The PS on my 21A is slightly different from your's: it has 2 2200uFs and 2 220uFs.
I have repaired several pieces of equipment that had problems because of bad capacitors. Sometimes damage goes beyond the PS. I have not had to fix one newer than 20 years old though.
So do you think my 1500uF and 100uf values fine, I just got some of those in the mail, or is there some reason to go to 2200uF and 220uF there?
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The 1500uF and 100uF values are fine, just make sure they are rated for 250V or higher and make sure the 1500uF is a "snap in". These two caps are for the tube B+ filtration.
The 2200uF and 220uF are for the solid state portion of the preamp and maybe the tube heater voltage.
The original cap brands CDE and Nichicon are fine. Xicons (for the 220uF) never impressed me... I would use a good standard impedance cap there such as a Nichicon VR or a Panasonic M, otherwise the voltage regulator next to it will probably oscillate.
The 2200uF and 220uF are for the solid state portion of the preamp and maybe the tube heater voltage.
The original cap brands CDE and Nichicon are fine. Xicons (for the 220uF) never impressed me... I would use a good standard impedance cap there such as a Nichicon VR or a Panasonic M, otherwise the voltage regulator next to it will probably oscillate.
I bought everything on Digikey, rifling through the online filters to narrow down the choices. Just all Nichicon to make it simple for me. The 220uF I selected was a Nichicon 50V, UKA1H221MPD. The specs seem similar to the Panasonic, but it costs 54 cents more, or double the price. Did I overpay?
I've never used a KA. I tend to stay away from "audio grade" caps for power supplies. I took a look at its datasheet and there was no indication that it is low impedance, so I would tend to believe that it would be safe to use around the voltage regulator. That cap's purpose is to provide stability to the regulator. Is the KA better than a VR or M at that that spot in the circuit? Beats me.