I'm recapping the power supply in a Tektronix 2235 late-1986. The scope seems to work but just to ensure no troubles. It's lean for electrolytic capacitors, they seem to be the minimum value that would work.
The primary capacitor is a Sprague can-electrolytic 75uF 450V that tests OK at 90uF and 0.17 ESR for Tek P/N 290-0978-00 (C906). But 31 years old.
I initially selected UCC 82uF 450V but I see Tek upsided the cap for the 2235A model to 270uF ?!
Another problem is modern capacitors are all -20% verses the older -10% spec.
So my new 82uF cap ends up smaller than the original, measuring 72uF... which annoys me.
I can fit a 10mm snap-in which I think I will do, but what value? The PSU is rated 40W, 10R NTC so the on/off switch
The Sangamo 840uF 12V (290-0945-00) did not age well. They have a hard epoxy seal which is cracked on most of them. One took a leak on the PCB and had high ESR. I put in 1,000uF 25V UCC KYB's.
I replaced the Rifa PME271 X, Y caps notorious for burning up. Damn things are still for sale at Digikey.
The primary capacitor is a Sprague can-electrolytic 75uF 450V that tests OK at 90uF and 0.17 ESR for Tek P/N 290-0978-00 (C906). But 31 years old.
I initially selected UCC 82uF 450V but I see Tek upsided the cap for the 2235A model to 270uF ?!
Another problem is modern capacitors are all -20% verses the older -10% spec.
So my new 82uF cap ends up smaller than the original, measuring 72uF... which annoys me.
I can fit a 10mm snap-in which I think I will do, but what value? The PSU is rated 40W, 10R NTC so the on/off switch
The Sangamo 840uF 12V (290-0945-00) did not age well. They have a hard epoxy seal which is cracked on most of them. One took a leak on the PCB and had high ESR. I put in 1,000uF 25V UCC KYB's.
I replaced the Rifa PME271 X, Y caps notorious for burning up. Damn things are still for sale at Digikey.
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