Resistors - need help identifying (power supply from DVR) - Page 1
Forum section: electronics / repair

author: pickleit
author_rank: Contributor
timestamp: June 21, 2019, 09:08:42 pm
content: I am trying to identify the values of the resistors in the photos.This is what I think they are:R103 - brown, red/pink, black, black, brown = 120 ohm 1%R104 - orange, white, black, pink/red, brown = 39 K ohm 1%R102 - blue, red/pink, red/pink, gold = 6.2 ohm 5%R101 - brown, black, red/pink, gold = 1 K ohm 5%R105 - orange, red/pink, black, gold = 32 ohm 5%R4 - yellow, violet, black, gold = 47 ohm 5%R2 - yellow, blue, orange, gold/ochre, green = 46.3 ohm 0.5%R5 - yellow, black, silver, gold, black = 40.8 ohm 1%RX1 - red, violet, green, gold, black = 27.5 ohm 1%

author: pickleit
author_rank: Contributor
timestamp: June 21, 2019, 09:25:33 pm
content: Additional photos.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 22, 2019, 06:10:57 am
content: some links and infoshttps://www.ebay.co.uk/itm/Humax-DTR-T1010-PSU-Power-Supply-Board-PW1003-01403-00128/273893320948?https://sparedparts.com/products/humax-pw1003-power-supply-pcbhttps://www.austech.info/showthread.php/2816-Humax-power-supply-fix

author: pickleit
author_rank: Contributor
timestamp: June 22, 2019, 12:26:52 pm
content: Quote from: coromonadalix on June 22, 2019, 06:10:57 amThanks for the info, but I would prefer to fix the existing board. Not so much as to save money, but as a learning experience. I Have tested some of the resistors and the results don't match with what I think the coloured stripes on the resistor equate to.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 22, 2019, 01:25:12 pm
content: You may have bad capacitors too.Normally you may have some parallel parts who may affect the read values, take part location notes, remove the parts and retry to fit the color values on the read value on your dmm / meter

author: mariush
author_rank: Super Contributor
timestamp: June 22, 2019, 01:25:26 pm
content: If you're measuring them in-circuit, the value may be affected by other resistors in parallel, or capacitors or diodes/mosfets.Try desoldering one leg of a resistor, lifting it out the board to be sure it's not connecting to circuit board and measuring again.I would start checking for shorted diodes ... check bridge rectifier (do you have 170v/350v-ish on the big capacitor?) , check what I believe are "two diodes with common anode/cathode" set on the top left in the first picture (yeah, just checked the 2nd set of pictures, mbrf10150ctl , 2 x 5A 150v common cathode diodes)If the psu doesn't start or randomly has issues starting, maybe look for some low value capacitor, the starter capacitor (something like 10uF-47uF 50-100v) ... sometimes the ESR goes high on such capacitor and the switching controller chip doesn't get enough power to start up. If you don't have an esr meter but have such a capacitor in spare parts may be worth replacing and testing to see if that solves anything.I'm not sure but they may be using a resistor as a fuse ... probably that resistor to the right of the bridge rectifier and x2 cap with blue dot on it, above the common mode choke.I don't see an actual fuse... i see movs, ptc/ntc right by the AC input, common mode chokes, filtering on input, proper y class capacitors, even the green thermistor... loads of stuff that's optional on other power suppliesIC1 is some kind of offline switcher IC, look at the part number and find datasheet for it , you may be able to find a "typical application" circuit in the datasheet that would be similar to your board.You even have the role of each pin written on the board, I can see there VCC, GND, FB (feedback) , BA, Drain ... see datasheet. You could check voltage (between VCC and GND to see if this chip gets power, I would guess probably something like 5v..10v)You didn't get the actual text written on the chip in any of the pictures you uploaded ... not surprised