| Electronics > Repair |
| Tektronix TDS754D - acquisition board test fail |
| << < (3/8) > >> |
| Rax:
I did exactly what my last statement above indicates and here's a pic of my actual PS board. |
| Rax:
On further work on this, I seem to have a PS board (nearly?-)identical with the TDS520B. Yes, that one - the closest scope to this still supported with component-level SM. So, if I were to believe that, the 25V may - possibly - be a 1V lifted version of the 24V rail on the 520B? The current rating seems to match. I'll examine the corresponding parts. |
| Rax:
Further report - replacing C21 (for which I used a UC KYB 1000uF/50V) and C102 (Nichi HE) - the two electrolytics on that rail - hasn't improved anything. The ripple on the +25V is still about 160mV, and the acquisition tests still fail. I think I'll call it a day and think further where I am with this in the morning. |
| Rax:
I finally got to get back to this. Some pieces needed to fall in place: * Get the right Pace tips for SOJ packages * Get chips from Terra Operative (Thanks a bunch!! :-+) * Read a lot and watch a ton of Pace vintage videos! A feast in their own right, to be fair. So I'm half way through the job (though something tells me I may have at best done a third?...) and have removed the suspect chips (207, 208, 214, 216). I welcome any good tips on soldering the replacement SOJ chips. I do have some low-temp Chipquick paste, plenty of syringe-disposing flux, thin regular solder, etc. I do have a hot air tool (cheapo thingie I am not in love with but works OK). I am thinking of cleaning the pads very well (Pace SX-90), be generous with flux on the clean pads, then try to use a chisel tip with careful application of thin solder and run through the pins at deliberate speed. The alternative is to use the Chipquick and the hot air tool, but I have far less confidence I'm not going to end up with bridges and maybe even loose stuff going stray in there. There's some chips in there that get very hot and low-temp solder may get a bit too excited with that in time. |
| TERRA Operative:
Looks like you got the old chips extracted pretty well. I used my Hakko hot air gun to remove the chips, then solder sucker to clean the pads. To install the replacement chips, I used 0.3mm solder and a conical tip on my iron to solder the legs one by one. I position the chip, solder one corner, adjust then solder the opposite corner, then finish the rest once the chip is perfectly positioned. Lots of flux to make soldering easy, followed by lots of isopropyl alcohol to clean it all up at the end. |
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