Astec RBQ202 Power Supply Pinout Needed - Page 1
Forum section: electronics / repair

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 28, 2019, 11:52:14 pm
content: Help!!So I have this Astec RBQ202 open frame power supply that I would like to use around the lab.It has an unlabeled 8-position barrier strip for its outputs. The side label says it has 4 outputs: CH1:+5V 25A, CH2:+12V 5A, CH3:-12V 2A, CH4:-5V 2A, total 200 Watts output power.But I can't remember the output terminal pinout, or how to get the thing started. It needs to have a load, or a terminal shorted to ground, in order to start and stay on, but I don't recall how to do it.I've looked for manual, schematic, pinout, etc and I can't find any useful info. Can anyone give me a hint about this power supply?

author: fzabkar
author_rank: Super Contributor
timestamp: January 29, 2019, 08:53:24 am
content: Look at the capacitor ratings. For example, the 4700uF 10V capacitors would be filtering a 5V rail, probably CH1. The 330uF 16V capacitors would probably be on the 12V rails. If all channels share a common ground, then the polarity of the caps should tell you whether they are on the negative or positive rails.

author: Chris56000
author_rank: Frequent Contributor
timestamp: January 29, 2019, 10:16:36 am
content: Hi!Unfortunately I haven't any official Astec info on this but looking at your picture as posted, I'd venture to suggest the LH-most pair nearest the LH chassis are CH4 (-12V 1A) and the RH-most pair nearest the RH chassis are CH1 (+5V 25A) - this can be deduced from the gauge of the wire on the filter choke, so by using a continuity meter on the remaining terminals you should locate the returns - if the outputs are floating you'll get four different readings across each pair of terminals that correspond to a channel, if CH2/CH3/CH4 are common you'll get continuity between two or three terminals!If there is a separate enable the track to that pin will be much thinner than the other main output tracks and this will help identify it!Astec power supplies normally have a floating enable when used - connecting it to COM/0V shuts them down into standby so your unit should come straight on - if not it is faulty & needs investigation!!

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 29, 2019, 06:54:19 pm
content: Hmmm....OK....I don't have much more info at the moment but here's what I learned fooling around last night.It appears, using DMM, that there is no common ground among the output channels. Also no common ground between input line power ground and output.If I power the unit on with nothing connected to the outputs, the green LED near the rightmost terminal (see photo) comes on, stays on for a second or two then fades out. There is some voltage on the outputs while the green LED is on but I haven't been able to get a consistent voltage reading during this time. Once the LED is out, there is no voltage on the outputs.I connected a brake light bulb to terminals 1 and 2 (leftmost pair) and a 2.2 ohm resistor across the next pair (3 and 4) and this causes the power supply to stay on and it does look like about an amp's worth of brightness in the #1156 brake light bulb. The 2.2 ohm doesn't get warm.That's all the data I have right now and I won't be able to get anything else done until later this evening.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 29, 2019, 07:10:26 pm
content: Quote from: Chris56000 on January 29, 2019, 10:16:36 amThanks... but the channels are:CH1:+5V 25ACH2:+12V 5ACH3:-12V 2ACH4:-5V 2AAccording to the label on the side. Unfortunately I have no idea what terminals correspond to which channels! I would "assume" that the pairs are CH 1 thru 4, left to right... but who knows. I'll test again under your assumption of right-to-left ordering.I don't think my brake light bulb will light up visibly on only 5 volts ... but who knows.Yes it will. I need more coffee!!!

author: fzabkar
author_rank: Super Contributor
timestamp: January 29, 2019, 10:36:15 pm
content: There are 8 capacitors on the DC output side of the PSU. Use your DMM to determine how these caps connect to each of the terminals. Also determine how each inductor connects to these terminals.Edit: Does this help?https://www.ebay.com/itm/ASTEC-RBQ202-Power-Supply-5V-25A-5V-2A-12V-5A-12V-2A-EMI-FILTER-/113395399335How about this?-5V Gnd -12V +12V CH1-sense CH1- CH1+sense CH1+

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 30, 2019, 04:03:56 am
content: Thanks!!Quote from: fzabkar on January 29, 2019, 10:36:15 pmThat's definitely this PSU all right.QuoteNow that helps a lot!By connecting a load to CH1- and CH1+, the thing stays on and supplies a solid 5.04 volts. Connecting the sense leads to their respective terminals works but isn't necessary for it to stay running. Also the second terminal from left is indeed Gnd, I had bad contact when checking this at first. So that takes care of 5 of the 8. But...Numbering the remaining terminals 1 thru 4 from left to right, I get1: +16.9 V2: Gnd, 0V3: -11.7 V4: -5.4VSo I'm still confused, or some of the functions of the psu are broken somehow.Where did you find the pinout? It doesn't come up for me on the ebay listing.

author: fzabkar
author_rank: Super Contributor
timestamp: January 30, 2019, 05:03:44 am
content: Quote from: alsetalokin4017 on January 30, 2019, 04:03:56 amThe pinout was my guess, based on the assumption that the channel numbers were in numerical order. Obviously my guess was wrong. Sorry for the confusion.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 30, 2019, 11:27:06 am
content: Well, I appreciate the guess anyway, and it does appear that we have the rightmost 4 terminals correct (I think.) At least I think can get a good 5V out of it.Later on today I'll take it apart so as to be able to see the bottom of the PCB and follow some traces. It's a little tricky to take apart to that point because of the heatsinked components which is why I haven't done it yet.I am operating on the assumption that the PSU is fully functional and I'm just ignorant of the full pinout.