Hello!
I am new here, but have always liked this forum and found it useful, so thought I should join and contribute.
This week I'll have
three IBM 5150's (two Rev B, one Rev A), and an
IBM 5153 CGA monitor. The 5153 appears fine from a no-signal power-on test. The 5150's don't work.
I know I'll be able to get them all working. I've restored dozens of vintage machines over the past few years with complete success. My lab of test gear grows ever larger...
The latest achievement is fully restoring a Compaq Portable II, including making a new power supply module from a modern TFX-size ATX power supply board.
I plan on functionally and cosmetically restoring them all, keeping the 5150 Rev A and 5153 for my collection, and selling the two 5150 Rev B's.
The three 5150 power supplies will be converted from their 110V to 240V as per the guide by Paul Axford, which the link has just died for. The 5153 monitor is a 240V one already.
I have a few questions that I can never seem to get straight answers for (maybe there are no straight answers for them; I understand some may depend on the circumstances).
1.
Is there any harm in replacing the dozens of 10uF tantalum capacitors with 10uF 50V leaded multilayer ceramic caps? It seems silly to replace tantalums with tantalums in vintage gear, unless you enjoy electronics popcorn. So far I've used 10uF MLCCs with great success.
2. This relates mainly to the IBM 5153 CGA monitor I'll be re-capping. Of course the infamous RIFA PME271M Y2 film caps will be replaced, along with all the electrolytics. I have a list of caps from someone else, so have begun sourcing them. But the list doesn't have dimensions or pitch, so I won't be ordering until I amend the list with those details (and probably publish in this thread). The list noted two caps as low ESR from his measurements. Of course, more caps may have been low ESR, but are now high ESR from age, so the list may not be accurate.
My question is,
can you usually replace most general purpose electrolytics with low impedance types? I imagine most of the electrolytics are general purpose in the 5153 monitor. And most caps I can source that are rated for
long life (is this what I want for vintage gear that will sit unused often?), are low impedance types, such as NCC KY and Panasonic F*.
I know I can match most of the caps with general purpose or low impedance if I go to Digikey. It'd be a good $120+ for all the caps for the three 5150 PSUs and the 5153.
I will be making a JLC+LCSC order soon. They have a coupon available right now which will get me
all the Lelon caps I could need , for $0, since I'll be ordering a bunch of other stuff.
I was thinking of putting Lelons in the 5150 and 5153 that will be going in my own collection. As an experiment; what could go wrong? If they fail early after spending most of their years on the shelf, I can report back.
From my hours of googling, Lelon seems to be in the range of Teapo, and regarded to be "okay". Of course, I've read the thread about these caps on this forum, and how hard it is to qualify caps, and how much anecdotal evidence and "opinions" float about, so I'm not too sure what I'll do.
Most of the values of caps I need, are only available from LCSC of the low-impedance type. usually 4000-8000hr 105°C rated.
Think I could fill the 5153 with new low-impedance caps? Or should I stick to finding general purpose caps except for the two mentioned in this list? (
https://www.dropbox.com/s/olxmp5huf8bbe37/5153.pdf?dl=0) (source:
http://www.vcfed.org/forum/showthread.php?59266-List-of-Capacitors-in-IBM-5151-5153-and-8513-Monitors)
I'll go through the monitor when I'm taking down all the capacitor dimensions and lead spacings, and see if I can find datasheets of the models of cap. The monitor could have caps from late 70's to early 80's, as it was in production from 1981 onwards, and I'm unsure of the year of my particular one until I receive it.
Some of the caps are next to very hot power resistors, and often fail. Should I maybe find some 125°C rated caps for these places? Part of these are three 4.7uF 250V.
The others are in the power supply section of the monitor. This is a very inefficient switching power supply, producing a single 115VDC output. Would be nice to replace with a modern unit, but that voltage seems hard to find.
I have no qualms about replacing things like power supplies with superior modern designs, as long as it looks mostly the same externally.
3. When you can't find datasheets for an old electrolytic, so all you know is the marked capacitance and voltage, and the ESR measurement is likely unreliable,
is it good practice to replace with a general purpose cap of simply similar physical size? Choosing low impedance if it's in a SMPS (or only certain parts of a SMPS)?
Sorry if I've rambled and asked some tough questions. Wondering if there's anyone watching this space with some experience or opinions.
Thanks!