Switch Mode Power Supply - Page 1
Forum section: electronics / repair

author: bob225
author_rank: Frequent Contributor
timestamp: April 13, 2018, 05:16:20 pm
content: Hi AllI recently picked up a new Project a Roland RD-150 circa. 2002, The main control board was smashed to bits what i have now rebuilt after many hours and swearing at itNow The SMPS is playing up with a nasty buzz and crackle - initially it was putting out a low voltage (under load) what was cured by a re-capRoland have discontinued support for this model 8-10 years ago so spares are non existent, I do have the service notes but the SMPS is a Daughterboard and is not covered, i cant even get the specsPart numbers on the pcbKPC1694V-0B104F8044PAPart numbers From the service notesSWPS1A1DU2L3B10402127512 (Roland)Input 100-240vOutput +15, -15, A GND, D GND and +5vAs far as i can tell the DC to DC transformer is a - EEL19-H, Dual primary, Dual secondary (5v and a -15, 0v, +15 centre tapped) I can't find a off the shelf replacement from any UK or US supplierAny help appreciated

author: tautech
author_rank: Super Contributor
timestamp: April 13, 2018, 09:28:25 pm
content: Like many SMPS the design most likely closely follows the controller IC's datasheet 'typical application' schematic.Identify the controller IC and get the datasheet is the first step. If more than one datasheet is available get them all and hunt for a schematic that closely resembles the SMPS you have.So what symptoms is the SMPS exhibiting now ?

author: coromonadalix
author_rank: Super Contributor
timestamp: April 14, 2018, 03:32:53 am
content: A1DU2L3B104 seems to give some results, but no schematics found, it seems an self oscillating smps .. sold as an unit only as you said, but findig it seems impossible?you could find some compatible physical size maybe from meanwell NET-35C series ?? avoid cheap china knock off

author: bob225
author_rank: Frequent Contributor
timestamp: April 14, 2018, 10:20:00 am
content: Thanks for the repliesI have been drawing a blank on all the searches, There is no IC on the board just a P4NK60ZFP and feedback on the 5v sideIf it comes to it will design a board but I'm a bit rusty and out of touch with modern dc-dc convertorsEdit. Symptoms - Intermittent buzz Like a bee in a coke can lol and the odd ping emanating from the transformer

author: SeanB
author_rank: Super Contributor
timestamp: April 14, 2018, 01:24:59 pm
content: First, clean off the flux residue from the board, and then resolder all the joints of the capacitors, the switching transistor and the transformer and the secondary side diodes. The main primary side capacitor looks like it is dry jointed, though that could be lead free solder, but resolder it anyway. Resolder Th1 and the 2 jumper wires as well, the ring around the solder joins looks suspicious.the 2 270k SMD resistors are the start up circuit for the self oscillating power supply, check they have not drifted high in value ( you can check in circuit with no power applied using a DMM, they should measure around 270k or slightly lower, more than around 300k they are failing and need replacing) and that all the resistors are not cracked. Clean the board again after the resolder and checking it.

author: KhronX
author_rank: Frequent Contributor
timestamp: April 14, 2018, 01:25:52 pm
content: Might be worth replacing / "refreshing" those two little electrolytics on the primary side (lower-left corner of the top photo).At least in cheapo ATX power supplies, where the 5V stand-by supply is done with these self-oscillating two-transistor circuits, they relatively often use an electrolytic in a position i've seen called as the "critical cap". When that entirely craps out, the output goes high-voltage.Not sure that's the case here, but should be easy enough to try out and see if it helps.

author: SeanB
author_rank: Super Contributor
timestamp: April 14, 2018, 01:55:11 pm
content: Lower left is secondary side, on what looks like 15v rails for opamps. They are not regulated or used for feedback at all, just give a voltagewhich will probably be regulated on the main board to give a regulated rail.

author: bob225
author_rank: Frequent Contributor
timestamp: April 14, 2018, 02:24:07 pm
content: Pic's where before I reworked and recapped the board (using Panasonic and Nichicon caps). I have retested the transformer (out of circuit) and the inductance and resistance has changed a fair bit on the primary of the 15V side since the first test so I think its not got long to liveLooking at this again and the problems I'm having getting parts and specs, I have ordered a MW RPT-60C what is in UK stock, that makes it more time and cost effectiveI will up do a update once I have the parts next weekI have a little Arduino project that I'm playing with in the meantimeQuoteCorrect, There is a 12v reg on the jack board this then feeds the main processor board, the feed back is on the 5v side what feeds the main boardSorry guys and girls, I'm very rusty with all the theory as its been a good 15+ years since I had to use it in any real situations - and those last 15+ years has been board swapping and minor component replacement

author: Arek_R
author_rank: Regular Contributor
timestamp: April 14, 2018, 07:14:40 pm
content: Whoa, I didn't knew that you can get SMPS with these outputs from MW...

author: bob225
author_rank: Frequent Contributor
timestamp: April 15, 2018, 01:23:51 pm
content: I didn't think of actually changing out the psu until it was mentioned above - I have a few MW supplies - the open board type is fine in this application and cheaper than the enclosed version, I will put a mylar type film under it so i don't get any issues

author: bob225
author_rank: Frequent Contributor
timestamp: April 20, 2018, 06:43:39 pm
content: Update. All installed and cabled - Just ordered some new tactile switches as I have 2 slightly iffy ones on the control board

author: matt ristrom
author_rank: Newbie
timestamp: July 07, 2021, 07:27:16 pm
content: I realize this is an older thread but was hoping someone is still around that has a schematic for the RD150 or even just the pin-out showing voltages on the secondary power supply board. I have an RD-150 on my bench with a dead power supply. Super excited to put a replacement power supply back in but have no idea what the pin-out was for the original supply.If anyone has this info, a schematic, or a service manual please let me know.Matt

author: matt ristrom
author_rank: Newbie
timestamp: July 07, 2021, 08:51:53 pm
content: Thanks Bob! I have the pin out I needed now from the service manual and a new power supply ordered from Mouser. Just hope the chips on the other PCB's are still in good shape.

author: Because
author_rank: Newbie
timestamp: November 12, 2021, 05:00:50 pm
content: Hi!I’m new to this forum. I have a faulty psu on my RD-150.Thanx to your previous posts I will change the psu. I haven’t found the service manual. Can anybody mail it to me? Or tell me if the pinout you gave in other posts it’s from top to bottom? Thanx in advance.

author: Because
author_rank: Newbie
timestamp: November 24, 2021, 08:30:53 pm
content: Please, anyone can help me?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 24, 2021, 08:46:16 pm
content: The SMPS circuit is not shown in the Service Manual.

author: Because
author_rank: Newbie
timestamp: November 25, 2021, 04:39:03 am
content: Thanx a lot. The pinout is in the manual.