Tektronix TDS340, hard to turn on?

Question

Hi, I just bought this tek and while it passes all the selftests, it's really flaky at startup. When you press the on/stby button the lights blink once , you can hear some relays switching and it goes dead. Then I keep pushing the button and eventually it "catches on" from then on it operates flawlesly. Sometimes it takes 3 tries sometimes ~30. Has anybody seen the simmilar problem (solution would be nice)? Thanks.

Jim Yanik · Accepted Answer

"janek77"  wrote innews:mH8Jf.42164$ It's old enough for the electrolytic caps ESR to be rising.Time to re-cap the power  105DegF low-ESR caps.-- Jim Yanikjyanikat

Asimov · Answer

"Jim Yanik" bravely wrote to "All" (17 Feb 06  02:45:02) --- on the heady topic of "Re: Tektronix TDS340, hard to turn on?" JY> From: Jim Yanik  JY> Xref: core-easynews  JY> "janek77"  wrote in JY> news:mH8Jf.42164$ > Hi, I just bought this tek and while it passes all the selftests, > it's really flaky at startup. > When you press the on/stby button the lights blink once , you can hear > some relays switching and it goes dead. > Then I keep pushing the button and eventually it "catches on" > from then on it operates flawlesly. > Sometimes it takes 3 tries sometimes ~30. > Has anybody seen the simmilar problem (solution would be nice)? > Thanks. > JY> It's old enough for the electrolytic caps ESR to be rising. JY> Time to re-cap the power  105DegF low-ESR caps.Would it be too obvious if it might be an intermittant power switch. A*s*i*m*o*v

Charles Schuler · Answer

I'd certainly check into that before replacing capacitors.

janek77 · Answer

I'm almost certain it's not a switch, to me it definitely looks likeps is trying to start , but it shuts down almost immediately on overcurrent of some sort.For now its merely annoing, if it gets any worse I'll try the caps.Thanks.

Jim Yanik · Answer

"janek77"  wrote innews:fTvJf.47294$ It could just be a single electrolytic,perhaps the housekeeping cap that supplies the switching control IC.I've seen PS's do just like you described and it was that one cap with a high ESR. -- Jim Yanikjyanikat

janek77 · Answer

For now it seems to be getting better, as I had it plugged in for last couple of days.I,m not rulling a "noisy pushbutton" completely out (yet),but to me it seems like that whatever cap is responsible it seems to be "forming" again.There two distinct possibilities:1: "noisy" switch, which is getting better with useor2: a cap thats getting "formed" after long discharge.Whats your pick?

Matt J. McCullar · Answer

I'd suggest replacing the electrolytic caps in the power supply.  I had todo that with my Tek 2225 before it would start behaving itself.

Tektronix TDS340, hard to turn on?

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