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Forum Index : Microcontroller and PC projects : Capacitor Help Please
| Author | Message | ||||
Rickard5 Guru  Joined: 31/03/2022 Location: United StatesPosts: 463 |
I have been having a problem with all 3 Picomite VGA design #1 SD Cards, and tried changing the SD card socket 2 times and I'm out of Sockets , I've even tried A bunch of SD Card and Micro SD cards, and swapping picos. so the last link in the chain is the 100nF Ceramic or MKT Capacitor. I'm trying to order the 100nf cap but I can Find them on Mouser, Digi-Key or Newark, My such Fu is Week could anyone help me find it on one of those sites here is the Caps I used, I might have mis-labeled the bag they were in, I can't read these  I may be Vulgar, but , while I'm poor, I'm Industrious, Honest, and trustworthy! I Know my Place |
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SimpleSafeName Guru Joined: 28/07/2019 Location: United StatesPosts: 319 |
This should get you started: https://www.digikey.com/en/products/filter/ceramic-capacitors/60?s=N4IgjCBcoGwJxVAYygMwIYBsDOBTANCAPZQDaIALGGABxwDsIAuoQA4AuUIAyuwE4BLAHYBzEAF9CAJgAMFBNBAcuAVSED2AeVQBZXOmwBXPrhCFDXIQDEzIALbCuYGTInjxQA |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
104 = 10 x 10^4 pF = 100nF. Same system as resistor colour codes without the colours. |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 857 |
No matter what, I always verify with a meter. |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
Hi Rickard, I know I am located in Netherlands, and shipping can be expensive, but if you send me one of those (or all 3) I will do my best to make them work. If you send 1, and I find the culprit, it could be explanatory for the remaining 3. I think it is very strange that you cannot get either of the boards to work. There must be a common denominator. Volhout P.S. the capacitor may not be the problem. Rather look at the resistor (2.2 ohm), you may have placed a 2.2k ohm resistor, not 2.2 ohm). If you do not have a 2.2 ohm resistor, replace it with a wire link (0 ohm) to test. Edited 2024-07-03 17:08 by Volhout PicomiteVGA PETSCII ROBOTS |
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CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 2075 |
. Edited 2024-07-03 18:26 by CaptainBoing |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
I'll be very surprised if the caps are faulty. That sort rarely fail. In most cases you'd even get an SD card to work without a cap, it just depends on the card. If the caps had failed open circuit the boards might have still worked. If they had failed short circuit there might have been a bang or the cap would be hot. There is no 2R2 resistor on this board. Go back to basics. You need to dig out the multimeter. If you haven't got one then get one and don't go any further until it arrives. :) You don't need a posh one for these jobs. Have you got a proper voltage onto the board? Have you got 3V3 measured at the SD card socket with a card plugged in? Did you check the signal connections from the Pico to the SD card socket (without a card in)? Swapping stuff around without the basic tests is unlikely to get you anywhere - and it won't if the problem is a bad etch or a cracked PCB track that you can't see under the solder resist. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9110 |
The design 1 board does not have a 2R2 resistor and my one works fine with just the 104 capacitor |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
Rickard, Then you can only suspect the soldering of the Pico itself. Did you surface mount the pico as below  Or did you use a header and pins (as below)  Regards, Volhout PicomiteVGA PETSCII ROBOTS |
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stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2123 |
component testers are £5. very useful. got ocillator, pwm, cap esr, inductance, frequency, transistor, resistance  |
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| Rickard5 Guru Joined: 31/03/2022 Location: United StatesPosts: 463 |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
Search for "component tester" on Ali Express, there are more than you can poke a stick at. Eg Component tester Edited 2024-07-05 17:59 by phil99 |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
If you haven't got a multimeter, Rick, get one. It's the most important bit of testgear you can have. Many of the cheap ones can measure capacitors and they can all measure resistance. Some (even cheap ones) can do basic transistor tests too. AliExpress This One includes Frequency, Continuity, Capacitance, Diode and Transistor testing for £5.46 before tax. It even has no-contact voltage checking, comes with reasonable probes and uses 2x AAA batteries rather than an expensive 9V one. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2123 |
even my old maplin meter measures capacitance but few cheap meters measure electrical series capacitance-ESR. An electrolytic can measure what's printed on the can but the cap could be faulty and bulge. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
Simple capacitance meters don't measure ESR anyway. If you are lucky you might find one that measures the leakage, but that's meaningless unless you have the manufacturer's spec to compare it to. If you want to measure ESR you need either a scope (which gets complicateed) or a proper ESR meter. There's no guarantee that a good ESR and accurate value is still a good cap though. It might be today but not by next week! If it's bulging then change it, particularly if it's the sort that doesn't have an X on the can so that it can die less explosively. Even poor and leaky electrolyticas can be re-formed to become good capacitors again. All you need is a controllable constant current source and time. There has been a lot of unnecessary work done, swapping out capacitors that are only 40 or 50 years old. Just because they are old doesn't mean that they are automatically bad or won't last at least another 20 years! If the circuit has been designed correctly and they have been stored at reasonable temperatures they can last for many, many years. OTOH a brand new surface-mounted multilayer ceramic might explode within a couple of months. It will test perfectly and operate perfectly up until that point. Edited 2024-07-06 02:48 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2123 |
I had a quad 202 that was old as me in my 20's and caps etc., all ok when I sold it for transistor amp. it was only 15 Watt flat out switch mode supplies used to jigger electrolytes but don't bother fixing stuff much cos can't be bothered so don't know if still a prob. they put scopes on cheap meters now. ok, not brill but cheap. it's how often you use it https://www.ebay.co.uk/itm/305651686292?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338749386&toolid=20006&_trkparms=ispr%3D1&amdata=enc%3A1GLKmAtxtRI6AZ2JnJtRoxw6&_ul=GB&customid=GB_12576_305651686292.143192034695~1871563806880-g_Cj0KCQjws560BhCuARIsAHMqE0H5YRzsOhtbqv4bQ92eb-K-0vJIWay1qsxtdLPb-OBAPTKZWWb8NP8aAtXVEALw_wcB Edited 2024-07-06 06:13 by stanleyella |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
Cheap scopes give cheap results. :) Digital scopes don't degrade nicely like analogue ones do. You have to be aware of what a DSO is showing you, realizing that it doesn't have to be the truth, depending on signal frequency, timebase, sample rate etc. They are a bit like slide rules - very useful if you already know roughly what to expect. The Quad 202 was lovely. In fact, I like most valve amps. It's a pity the output transformers have become so expensive if you want decent performance. You can now get a SMPS that will provide the HT and heater voltages for a lot less than the cost of a mains transformer! Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2123 |
personally, I thought the valve sound overrated but I remember live music before silicon power transistors. I built a "Texan 20+20" with "epicuticular SILICONE" transistors that blew me away. Henry's Radio, anyone remember them? |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
I remember seeing the Texan 20-20 design. :) There was no way I could afford to build it at that time though. I still like the sound of a decent valve amp. I know it's distorted, but I no longer listen to the hi-fi, I listen to the music. If the distortion helps with that, and it can do in some cases, then I've no complaint. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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