Confirming This is a Capacitor - Page 1
Forum section: electronics / beginners

author: bostonman
author_rank: Super Contributor
timestamp: December 12, 2021, 03:15:59 pm
content: I don't believe I've seen a capacitor that looks like a resistor (see C86 in the attached) and want to confirm it is one.This is from my C64, and, from looking at the schematic, this should be either 68pF or 82pF. For my board I think it should be 68pF, and, assuming it's a capacitor, I looked online for five-band capacitors. The colors seem to match for a 68pF, and the circuit works, so I assume it's a capacitor, but wanted a second opinion.According to the schematic, the capacitor should be across pins 4 and 5 of an 74LS629N which are C ext pins. Pin 4 connects to a 22k resistor, and the other side is fed with 5V.This looks correct, does anyone have any input?

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 12, 2021, 06:08:55 pm
content: Check the pin 4 and pin 6 continuity to the "capacitor". The color code reads 68. Check the resistance across the "cap" if it is very high it is a cap. Otherwise it "looks like" a 68 ohm resistor

author: Benta
author_rank: Super Contributor
timestamp: December 12, 2021, 06:13:52 pm
content: Yep, capacitor.Tubular caps were not unusual back then and were preferred for automatic insertion machines like for the resistors.

author: MK14
author_rank: Super Contributor
timestamp: December 12, 2021, 06:19:33 pm
content: Quote from: Benta on December 12, 2021, 06:13:52 pmIn NO way am I trying to disagree with you. But for my (and maybe others) future reference. What signs are there to look out for, for noticing that it is a capacitor, rather than a resistor ?(Other than the obvious component C-number designation) ?

author: bob91343
author_rank: Super Contributor
timestamp: December 12, 2021, 06:20:44 pm
content: You will notice it has five color bands, while the resistors have four. Yes it's a capacitor, ceramic, 68 pF.

author: wraper
author_rank: Unknown
timestamp: December 12, 2021, 06:21:23 pm
content: Quote from: MK14 on December 12, 2021, 06:19:33 pmIts green-ish color.Quote from: bob91343 on December 12, 2021, 06:20:44 pmResistors often have 5 bands too.

author: gamalot
author_rank: Super Contributor
timestamp: December 12, 2021, 06:38:36 pm
content: Quote from: wraper on December 12, 2021, 06:21:23 pmThe 5-ring resistor usually does not appear on this kind of old equipment, and the last ring is white, which is not what you can see on ordinary color-ring resistors. If it is a capacitor, it is easy to explain. The 4th ring is gold indicating that the error is 5%, and the last ring is the withstand voltage, which may be 900V for color white. Actually I have seen similar capacitors, similar body color and similar 5th ring color.---I just noticed that the term you guys used is "color band", oh my poor English!

author: CaptDon
author_rank: Super Contributor
timestamp: December 12, 2021, 06:44:04 pm
content: What a kludge design. Where is the designator for that 22k hanging there in outerspace and sharing a pad? And yes, I have tons of 5 band resistors that look identical to that (capacitor?). I am holding a 51 ohm 1/8 watt in my hand right now. Green, Brown, Black, Gold, Yellow. Beige body just like the one in the picture. I would assume nothing and measure it.

author: james_s
author_rank: Super Contributor
timestamp: December 12, 2021, 06:49:49 pm
content: Quote from: CaptDon on December 12, 2021, 06:44:04 pmIt's a C64, it was one of the cheapest microcomputers on the market at the time, far cheaper than anything else with similar capabilities so yes, it's a bit of a kludge design. The low price and high performance (for the era) made it enormously popular though and it sold in huge numbers.

author: MK14
author_rank: Super Contributor
timestamp: December 12, 2021, 06:50:30 pm
content: Quote from: CaptDon on December 12, 2021, 06:44:04 pmI'm guessing, but given that the IC number, is a VCO. Maybe, the original design and its prototype(s), worked perfectly. But, with production component variations, temperature changes, etc. The VCO fails to work as intended, so they needed to correct the initial (possibly rushed) design.

author: Gyro
author_rank: Super Contributor
timestamp: December 12, 2021, 07:00:51 pm
content: What are the odds? ....https://www.eevblog.com/forum/beginners/capacitor-looks-like-a-resistor/Actually, probably higher than I thought. There must still be a lot of C64s around!

author: BrokenYugo
author_rank: Super Contributor
timestamp: December 12, 2021, 07:12:36 pm
content: Quote from: MK14 on December 12, 2021, 06:19:33 pmI've never seen one that wasn't a different body color from the resistors around it, as you can see in the provided pictures, same goes for the axial inductors. These are a sort of greenish yellow, I've also seen them with a pink body. Use in circuit is also often a giveaway, e.g. bypass caps.

author: Benta
author_rank: Super Contributor
timestamp: December 12, 2021, 07:24:25 pm
content: The body colour is not really relevant.But notice that it's shorter and fatter and differently shaped than the resistors.

author: DavidAlfa
author_rank: Super Contributor
timestamp: December 12, 2021, 09:21:50 pm
content: Never seen this. However, thee last band is white, which isn't a standard tolerance color.Such weird electronics they made back in the day...

author: bostonman
author_rank: Super Contributor
timestamp: December 13, 2021, 12:21:00 am
content: The first indication this is a capacitor: the C64 is working.Otherwise, every point mentioned in this thread has many valid points if not for having a schematic and a designation number.I almost forgot about inductors with color bands and how similar they look to resistors.Since it was mentioned, why are some resistors different colors?On a side note, if forced to pick a poison, I'd rather have resistor looking capacitors than these new surface mount component markings. I recently fixed an Agilent scope, and, thanks to the help of this forum, was able to figure out (I should say narrow down) the type of component I needed to replace. At least a resistor looking capacitor can be narrowed down easier.

author: DavidAlfa
author_rank: Super Contributor
timestamp: December 13, 2021, 07:23:50 pm
content: SMD parts start to get weird around 0603 sizes, below that, most parts don't have markings.Oh, then you realise there's nothing in the silkscreen, you're f*** even having the schematic.Following traces for a week... Another chapter of a sucessfull "repairing nightmares" series...