Electrolytic cap markings  - Page 1
Forum section: electronics / beginners

author: soldar
author_rank: Super Contributor
timestamp: May 17, 2023, 07:46:52 am
content: This post is about markings on electrolytic caps and not really about the mobo on which they are mounted.HP computer mobo, from about 2010 I guess, started freezing more and more often.Visual inspection shows electrolytics leaking so I suspect that is the cause.I cannot interpret the markings on the caps. No manufacturer name. All are marked 105º.There are a total of 17 blue caps of three different types.Type A- Qty 4 - All appear in good state and might not need replacing.Diameter 10 mm, height 20 mm.MarkedO847. Which I would interpret as 840 uF and the initial letter O for some voltage, maybe.Type B- Qty 8 of which 4 are definitely bad.Diameter 8 mm, height 20 mm.MarkedO844. Which I would interpret as 0.84 uF but I begin to have serious doubts about the meaning of these codes.Type C- Qty 5 - All need to be replaced.Diameter 8 mm, height 12 mm.MarkedO847, same as A. Maybe same capacitance but lower voltage.Searching the Internet for those codes, for the mobo, etc has not produced anything useful so I might have to just guess.Types B and C are located between the RAM slots so I would deduce 6.3 volt would be enough. Maybe they are paired so the big one provides the bulk of the capacitance while the small one has extremely low ESR for transient response?Initially and absent any further info I would be inclined to leave A's alone and replace all B's and C's with a single value of, say, 1000 uF, 6.3 V, low ESR, 105º, if I can find them in 8 mm diameter. Diameter is critical while height does not matter.Can anyone provide info on similar caps from other motherboards?What would you recommend?

author: Gyro
author_rank: Super Contributor
timestamp: May 17, 2023, 08:28:57 am
content: Unfortunately those numbers probably won't help you. They look like date codes, eg. 2008 wk47. There's always the possibility that I'm wrong of course. There ought to be markings further down the sleeves.Edit: It's not a good sign, quality wise, that they haven't 'syncronised' the sleeve to produce capacitors with markings in the same place.

author: soldar
author_rank: Super Contributor
timestamp: May 17, 2023, 08:47:10 am
content: Quote from: Gyro on May 17, 2023, 08:28:57 amGood thinking! The year 2008 is very probably when they were produced but the first "O" seems to be in a different font and I took it to be the letter O and not the number 0.No, there are no further markings. Yes, they do look like very low quality caps.The only markings are RLA, O844 and the temperature rating.I am guessing the values are not really critical so I would try any "reasonable" values. Now I am trying to find out what is "reasonable".

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 17, 2023, 10:18:51 am
content: If they are located near the RAM then probably any similar 6.3-10V rated caps should do. You may check if they are not connected with a +12V line too.I haven't seen +12 V rail caps near the RAM, but who knows.I would look with a DMM where else they are connected too.Or, I would put any Low ESR 1000uF 10V caps here, switch it on, and measure a real voltage.

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 17, 2023, 10:27:42 am
content: Quote from: soldar on May 17, 2023, 07:46:52 amI recommend to look more closely to tbose caps with a good light. Take out the RAM. I almost sure there are full markings with a rated capacity and rated voltage.

author: Gyro
author_rank: Super Contributor
timestamp: May 17, 2023, 10:41:43 am
content: A web search for RLA series capacitors yields a couple of options. United Chemi-con do one, but they are black sleeved, larger and snap-in. The more likely is the Vishay RLA series, these are blue and wire ended so probably a sensible match. They are obviously properly marked, so I wonder about the ones on your motherboard - there are plenty of image hits on Ali - never a good sign.The standout feature that you need for this application is Very Low ESR. The attached datasheet starts at 16V rating which sounds a bit high. If you can measure the operating voltage across the caps then you may be able to estimate the capacitance value from the physical size - probably check with other reputable manufacturers of very low esr capacitors (Epcos, Panasonic, Nichicon, Rubycon) as a cross-check.https://www.vishay.com/docs/28448/260rla-v.pdf

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: May 17, 2023, 10:43:42 am
content: I have a Peak Instruments ESR meter, most old caps will show a high ESR, but whether that improves the old motherboard is debatable as it’s guesswork as to what the problem is.https://www.peakelec.co.uk/acatalog/esr70-capacitor-esr-meter.htmlSJ

author: gnif
author_rank: Unknown
timestamp: May 17, 2023, 10:56:05 am
content: Quote from: Gyro on May 17, 2023, 10:41:43 amSorry but this is usually not the case for motherboards of this vintage. Often the replacement caps are larger as this motherboard is from the era of the capacitor plague where they were overrated based on their flawed design.https://en.wikipedia.org/wiki/Capacitor_plague

author: soldar
author_rank: Super Contributor
timestamp: May 17, 2023, 01:06:38 pm
content: Quote from: Gyro on May 17, 2023, 10:41:43 amBy golly you are right my good sir! They are positioned in such a way that they only show one side and I could not see the other side but looking more carefully I see.Type A- Qty 4 - All appear in good state and might not need replacing.Diameter 10 mm, height 20 mm.1500 uF, 16 VType B- Qty 8 of which 4 are definitely bad.Diameter 8 mm, height 20 mm.1800 uF 6.3VType C- Qty 5 - All need to be replaced.Diameter 8 mm, height 12 mm.820 uF 6.3 V.So, any recommendations as to low esr replacements?Good place to buy by mail in EU?

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 17, 2023, 01:24:13 pm
content: This is not a very rigorous science. Any actual Low-ESR type caps should do. The only strict parameter for me is diameter - it has to be the same to fit well.If your power supply was good then +12V caps don't die and live a very long happy life, so Type A really may not need replacement.Type B - 1500, 1800, 2200 uF 6.3-10 V d8 caps should do.Type C - 820, 1000 uF 6.3 or 10 V d8 should do.Of cause, Japanese electrolytes like Nippon or Panasonic are the best but they are the most expensive too and may be overkill. Actual middle-class Low-ESR caps will work fine and long too.As for me, I have a lot of different polymer caps so I would put polymer type 1000-1500 uF 10 V d8 into a CPU Vcore.And, it is good to check caps in the power supply with a ESR meter too.Can't say anything about shops because I typically do shopping in local shops in Kyiv (it's the capital so we still have real electronic shops here but not only internet shops). Also, pre-war I bought a lot of Chinese polymer caps from LCSC, and they are good (Now it stopped posting to Ukraine).

author: beatman
author_rank: Regular Contributor
timestamp: May 17, 2023, 01:39:10 pm
content: low esr 105c quality caps from panasonic nippon vishay rubycon or nichicon do the job fine.just by the equal mf capacitance and same or slight bigger voltage.i do this lot of times successfully.the capacitors values must be printed on the other side mf-volt.

author: soldar
author_rank: Super Contributor
timestamp: May 17, 2023, 04:14:59 pm
content: I need to find out about shipping costs but I will probably order 10 of each:https://www.mouser.es/ProductDetail/Panasonic/EEU-FR0J821Aluminium Electrolytic Capacitors -Radial Leaded 6.3VDC 820uF 8x11mm LS3.5mm0,439 €https://www.mouser.es/ProductDetail/Panasonic/EEU-FS0J182LAluminium Electrolytic Capacitors -Radial Leaded 6.3VDC 1800uF 9000H 8x20mm0,603 €

author: TimNJ
author_rank: Super Contributor
timestamp: May 18, 2023, 12:12:35 pm
content: I think the original caps were OST brand. Funny they don’t have OST printed on them, but that “0” which is before the three numbers might actually be an “O”? Looks a little more bold than the others.Anyway, doesn’t really matter. You’re replacement choices will be fine.Example:https://m.aliexpress.us/item/2251832075194639.html?gatewayAdapt=gloPc2usaMsite4itemAdapt

author: wraper
author_rank: Unknown
timestamp: May 18, 2023, 12:45:12 pm
content: Quote from: TimNJ on May 18, 2023, 12:12:35 pmBranding should be on opposite side which is not shown on the photos. I think these are OST RLA too.

author: soldar
author_rank: Super Contributor
timestamp: May 18, 2023, 01:26:43 pm
content: Quote from: TimNJ on May 18, 2023, 12:12:35 pmI feel sheepish that I looked and looked and did not see the markings until I was told to LOOK! and then I saw them.My excuse is that my eyesight is not what it used to be (actually it never was) and also that the plastic film is very reflective and very low contrast.Yes, they are marked OST, 6.3 V and capacity value.I have ordered the replacements and should have them by next week.Then the ordeal of replacing them on the motherboard will begin.

author: adonios77
author_rank: Newbie
timestamp: December 04, 2023, 11:15:25 am
content: If you look carefully those capacitors, there are 2 sides.(2 photos attached bellow)The original markingvalueson those specific capacitors are:Type A(x4)(side+):RLAO847105º(Coulombs degree)(side-):OST16v 1500µFDimensions:Φ10mm H19mmType B(x8)(side+): RLAO847105ºC(side-): OST6.3v 1800µFDimensions: Φ8mm H19mmType C(x5)(side+): RLAO844105ºC(side-): OST6.3v 820μFDimensions: Φ8mm H12mm/!\Warning:Note that the capacitors with the same code mark "O847" (TypesA&B) have totally different values and dimensions!(i) Replacement:These 'Electrolytic Capacitors' can be found easily but possibly need to go down town to a 'central' shop. (are cheap, about 0,5€)Not need to be same brand, find 'compatible' but just be ware to meet original properties/values (marking,dimensions) .Themarkingcould include information on nominalcapacitance, the degree ofdeviationfrom the nominal value, and ratedvoltage. (note alsodimensions)Capacitance:μƒ(uF|μF)(micro Farads)1Farad = 1.000.000μƒ | 1μƒ = (10-6) = 0,000.001 FaradsDeviation:ºC(Coulomb's degree)Rated Voltage:V(Volt)Dimensions:Diameter & Height(eg. because needs to fit on motherboard between memory slots)eg.Diameter8 milimeters = Φ8mm = Φ0,8cmHeight19mm = 1,9cm(i) C = Q/∆φHere Q is electric charge, which is measured in coulombs (C), and ∆φ is the potential difference, which is measured in volts (V).(i) "Electrolytic capacitors: these capacitors have large volumetric efficiency. This means that they have a large capacitance for a given unit of the capacitor’s weight. One of the plates of such a capacitor is usually an aluminum ribbon, covered with a thin layer of aluminum oxide. The electrolytic fluid acts as the second plate. This fluid has electrical polarity, therefore it is paramount to ensure that such a capacitor is added to the circuit correctly, according to its polarity."/!\Warning:Damaged Capacitors like in photo below: swollen, that has 'throw up' part of electrolytic fluid dried, can cause random BSODs more and more often, with increasing frequent if/as the time you keep using the PC is passing.