So, I've got some older HP/Agilent and a Keithley 2001,
That has an assortment of caps.
HP/Agilent had the ChemiCom SME at 85C used throughout.
One piece of gear has the three SME 470uf, 25V,
plastic case cover balooned out.
The other piece has an assortment of SMEs through out.
Circa 1995.
The SME are no longer made, their replacement is the SMG.
Nichicon now make the UHW, a mini-sized, High-Ripple Current,
High-Reliability, long life capacitor-- up to 10,000 hours life.
The specs are good looking compared to the SME/SMG line
and many other caps too.
Question does the lower impedance at high frequency ranges
lead to issues with Volt Meters, Signal Generators etc?
Keithley used the Nichicon VZ, 105C and one KL 85C cap.
Circa 1995.
None of the caps have not physically leaked yet, that I know of.
I was going to replace all the keithley with the same Nicicon VZs.
But the Nichicon UHWs sure look good.
Another question?
Taking one value for leakage current:
470uf 25V = 470^-6 * 25 = 11.750mA * the CV muliplier listed etc.
CV = 11.750mA
SMG: 11.750mA, multiplier is 1.0 at 120Hz
UVZ: 0.118mA, multiplier is 11.75mA * 0.01
UHW: 0.118mA, multiplier is 11.750mA * 0.01
Ripple Current Values:
SMG: 545mArms
UVZ: 380mArms @ 120Hz
UHW: 850mArms (1700 @100kHz) Freq Coefficient adjustment .5 *1700
Links:
SMG - http://www.chemi-con.com/upload/files/6/3/873997624d9b1bc8060f8.pdf
UVZ - NICHICON CORPORATION | Product & Technology
UHW - http://www.nichicon.co.jp/english/products/pdfs/20171003_UHW_e.pdf
My thoughts:
For the price, performance, and life I'd replace everything with the
Nichicon UHWs. That is the SME/G caps and the UVZ caps with
the UHWs. They are all general purpose caps with the UHWs having
much better specs and life.
Your thoughts?
That has an assortment of caps.
HP/Agilent had the ChemiCom SME at 85C used throughout.
One piece of gear has the three SME 470uf, 25V,
plastic case cover balooned out.
The other piece has an assortment of SMEs through out.
Circa 1995.
The SME are no longer made, their replacement is the SMG.
Nichicon now make the UHW, a mini-sized, High-Ripple Current,
High-Reliability, long life capacitor-- up to 10,000 hours life.
The specs are good looking compared to the SME/SMG line
and many other caps too.
Question does the lower impedance at high frequency ranges
lead to issues with Volt Meters, Signal Generators etc?
Keithley used the Nichicon VZ, 105C and one KL 85C cap.
Circa 1995.
None of the caps have not physically leaked yet, that I know of.
I was going to replace all the keithley with the same Nicicon VZs.
But the Nichicon UHWs sure look good.
Another question?
Taking one value for leakage current:
470uf 25V = 470^-6 * 25 = 11.750mA * the CV muliplier listed etc.
CV = 11.750mA
SMG: 11.750mA, multiplier is 1.0 at 120Hz
UVZ: 0.118mA, multiplier is 11.75mA * 0.01
UHW: 0.118mA, multiplier is 11.750mA * 0.01
Ripple Current Values:
SMG: 545mArms
UVZ: 380mArms @ 120Hz
UHW: 850mArms (1700 @100kHz) Freq Coefficient adjustment .5 *1700
Links:
SMG - http://www.chemi-con.com/upload/files/6/3/873997624d9b1bc8060f8.pdf
UVZ - NICHICON CORPORATION | Product & Technology
UHW - http://www.nichicon.co.jp/english/products/pdfs/20171003_UHW_e.pdf
My thoughts:
For the price, performance, and life I'd replace everything with the
Nichicon UHWs. That is the SME/G caps and the UVZ caps with
the UHWs. They are all general purpose caps with the UHWs having
much better specs and life.
Your thoughts?
In general, most wet Al capacitors in test equipment like this get used as power supply rail filters and bypasses. So, leakage is not a big issue, and a modern low impedance conventional wet Al cap replacement will also have sufficiently low leakage, probably lower leakage.
For these circuits, lower impedance is always better, as it will usually reduce any residual noise on the supply rails compared to stock. The other advantages are longer life, which will allow you to forego the next re-cap for quite some time, possibly a decade or two, or even more.
In general, I select among 105°C caps having the same lead spacing and similar can size, according to highest ripple current spec, then lowest impedance. Sometimes, it's helpful to consider parts with higher voltage ratings, since higher voltage parts can have a longer life and lower impedance / higher ripple. Just make sure that the can size is compatible with the PCB. If in doubt, take out an existing part and measure the lead spacing and can diameter to make sure.
The Nichicon UHW look very good, among the best conventional Al caps. I've also found the UCC KZN series to be very high quality and high performance as well, along with the Panasonic FM and FR. I would stay away from polymer caps, or basically anything but a conventional wet Al cap, as there's no need, and some of these caps can fail catastrophically unless they are voltage derated. It's too complex, and there's no need, given the high quality and performance of the parts mentioned already.
I have also not found any performance or calibration issues from replacing an otherwise good PSU cap with a new higher performance cap. Most test equipment doesn't allow the bulk power supply voltages to control any calibration sensitive parameters. Still, if the device has PSU rail voltage trims, it's always a good idea to re-trim them after you've changed the PSU components. Most 'modern' (late 70s and forward) T&M gear doesn't bother with PSU trims, as their regulators are sufficient.
Even if the installed caps are still basically good, I think it's wise to replace them if it's simple, and if you can do the re-work without damaging the PCB, just to 'reset the clock' and get a decade or two of trouble free performance out of the device. Best of luck!
For these circuits, lower impedance is always better, as it will usually reduce any residual noise on the supply rails compared to stock. The other advantages are longer life, which will allow you to forego the next re-cap for quite some time, possibly a decade or two, or even more.
In general, I select among 105°C caps having the same lead spacing and similar can size, according to highest ripple current spec, then lowest impedance. Sometimes, it's helpful to consider parts with higher voltage ratings, since higher voltage parts can have a longer life and lower impedance / higher ripple. Just make sure that the can size is compatible with the PCB. If in doubt, take out an existing part and measure the lead spacing and can diameter to make sure.
The Nichicon UHW look very good, among the best conventional Al caps. I've also found the UCC KZN series to be very high quality and high performance as well, along with the Panasonic FM and FR. I would stay away from polymer caps, or basically anything but a conventional wet Al cap, as there's no need, and some of these caps can fail catastrophically unless they are voltage derated. It's too complex, and there's no need, given the high quality and performance of the parts mentioned already.
I have also not found any performance or calibration issues from replacing an otherwise good PSU cap with a new higher performance cap. Most test equipment doesn't allow the bulk power supply voltages to control any calibration sensitive parameters. Still, if the device has PSU rail voltage trims, it's always a good idea to re-trim them after you've changed the PSU components. Most 'modern' (late 70s and forward) T&M gear doesn't bother with PSU trims, as their regulators are sufficient.
Even if the installed caps are still basically good, I think it's wise to replace them if it's simple, and if you can do the re-work without damaging the PCB, just to 'reset the clock' and get a decade or two of trouble free performance out of the device. Best of luck!
Thanks Monte, that is what I was thinking...better to ask now then be sorry
later (ala - polymer caps).
My process is the same as yours, that is 105C, lead spacing check, Ripple, then
impedance. As they say they are very low impedance...I wasn't sure if there
might be issues.
So I had one set of caps that I could use in the sig gen
theuy are Nichicon PW: 470uf, 35V, 105C.
1220 * .75 = 915mArms.
Not bad and better then the swollen caps.
UPW - NICHICON CORPORATION | Product & Technology
Thanks for the insight.
later (ala - polymer caps).
My process is the same as yours, that is 105C, lead spacing check, Ripple, then
impedance. As they say they are very low impedance...I wasn't sure if there
might be issues.
So I had one set of caps that I could use in the sig gen
theuy are Nichicon PW: 470uf, 35V, 105C.
1220 * .75 = 915mArms.
Not bad and better then the swollen caps.
UPW - NICHICON CORPORATION | Product & Technology
Thanks for the insight.
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