EEVblog #281 – BK Precision 8500 Electronic Load TeardownPosted on May 23rd, 2012 33 comments
What’s inside BK Precision’s 8500 300W 120V/30A DC Electronic Load?
It is also known as the Itech 8512.
could the transformer have been placed in the front in order to have a more even weight distribution for the unit?
That could be it. With the transformer at the back, it likely tombstones… or acts like those Weebles from the 70′s
Haha, love the sped-up whistling.
thank u so much David for that great jop …
please one episode on how to design an inverter
because it is too hard to fresh eng. th do that ….
thank u agaen
I have the same unit and while it’s built well, some of the components inside are very crappy. Funny how you omitted that being all “independent”. Also the “RS232″ on the back is TTL and plugging in a serial cable will damage the unit. They could have built in an optoisolated USB interface for extra $20 or just made an IR window with and IR USB cable attachment. That’s tightassery right there for which you chastise other brands. That cable you have doesn’t come with the unit normally, you have to buy it separately as well and it’s a bitch to find in stock.
Feels like you are becoming a marketing machine for Agilent and whomever else sends free test gear.
That agilent scope you got screams product placement all day long. What’s next, Coca-Cola with bottle labels facing the camera at all times? Not impressed.
I have two of these loads and both included both RS232 and USB interface in the box.
I have used them a lot (at a low power level) and there have not been any problems, except a few caveats in the user interface.
Lelon caps have a bad rep
Like I said – don’t expect any serious bashing. Now that expensive gear started rolling in for free, all of it will be visible at all times in all videos and none of it will have any major flaws in reviews.
Dave, I wanted to applaud you for mentioning the source of the BK Precision electronic load.
Then when I logged on I read Wartex’ comments and your response. I see he shares my concern (unease?) about the “possibility” of a slide down the slippery slope. I (like Wartex I think) don’t think you are on it and I don’t even think you will go down it. However, reviewing free stuff means you have to be super careful. It leaves you open to critisism from uncharitable persons, however unjustified you may feel it to be.
Liked the review Dave, Its an interesting product.
Regarding any such ‘Slippery Slope’,
The beauty of the internet, If you don’t like it, dont view it.
Anyways; A leopard does’t change its spots and (like my Ozzy Engieers Mates over here in the UK) I fully expect you to keep saying it how you see it for a long time yet. John.
Lelon are so-so. I haven’t seen any failed ones myself, but there are reports of them going bad in LCD monitors. But, compared to where they would normally live in a monitor, they are not in a high heat position in this unit. I would have liked to see Japanese caps for that price, but oh well.
Delta Electronics uses cheap caps (Ltec) in a lot of their power supplies. Yet there are very few complaints – they know what they are doing.
In most cases it’s not the poor quality of the caps alone that kills them, but shit thermal design as well. Some designers expect a cheap capacitor of unknown origin to perform as good as a brand name capacitor, they push too much ripple current thru the caps AND stick them right next to the heatsink of the power diodes (which is always too small and runs crazy hot), and that’s when things start going south. Or it’s all just planned obsolescence, who knows. All i know is that it gives me work.
What happened to commenting on the actual topic? This topic is about an electronic load teardown. The comments have morphed into a discussion about Dave’s objectivity and subjective comments about some potential yet-to-be substantiated, could be true capacitor quality.
Dave: the reviews are excellent and hit the key points for design information. I believe this is your only intention. I don’t know if you have been secretly bought out by “The Man”, but that doesn’t seem to get in the way of producing a good review – albeit cursory of this particular topic at this point.
What I hope is that you take this topic further. For example, it is relatively easy to build a static load (as you have done in an earlier episode). However, turning that into a fast, stable dynamic load is another story. Perhaps take the tear-down a bit further and walk through the schematic to illustrate some of the design choices. Cheers.
I would have commented on topic if i could actually afford one of those load testers.
Agreed on commenting on the schematic, but chances are, with the part number on the MCU erased, there is no schematic to speak of.
Looks similar built like my BK 1785B PSU where I tried to silence the fan:
With it came an IT-E131 TTL/RS232 cable that IS isolated.
I’ve got one of the ITECH IT8511′s which I got about a year ago on ebay for a bit over $500.
It is only rated at 150W, but I opened it up and followed along during the tear down video and it looks identical to yours in terms of all the resistors and MOSFETs. I wonder if the wattage is purely a configuration parameter so they can charge more.
Anyway, I am glad I opened it up as the transformer had obviously taken some force during shipping and was bent over against some of those unsecured TO-220′s MOSFET’s. One of the feet is also broken – unfortunately ITECH skimped a bit on the feet and handle in comparison to the BK version.
The part number on the main chip is also ground off on mine. Stupid practice!
I’ve used it for testing a few PSU designs, but also for battery testing. The controls are a bit weird in places, especially the battery mode with no response unless you press the exact combination of buttons.
I’ve also got the BK 9130 triple output PSU which is fantastic, but a bit pricey. I could justify buying that as I use it almost every day, unlike the DC load.
Keep up the great work.
Thanks you… Cok guzel bir yazi olmus tebrikler…
Man I hate your reviews. Every time you review something cool I always find myself running out to find and purchase one.
Half of the stuff on my desk is now there because of you and I am running out of space.
I actually purchased the BK 8500 from a guy on eBay used for 400.00. Pretty darn good price I think anyway. Already got it and put it to the test and well it performs just as I expected from your review. I just so happened to have a great use for it and thought of plenty more uses for it already that I had never even thought of. Kudos for the excellent review.
Haters will be haters so don’t ever let them get to you as I can already see they wont. I too have watched all of your videos although I did not find you until about a year ago, I have since watched every video you have produced and seeing as I have watched them one after another I can tell you I have not seen any of this so called slippery slope. Your reviews to me seem just as honest and forthcoming today as they have in the past.
Keep up the good work is all I can say and I look forward to hating you for making me purchase cool things for some time to come.
Hi! I’m designing an electronic load and I wonder what kind of IC is used in BK-P as Current Sense Amplifier on the input shunt resistor? The 120 V (or 300 V in BK-P 8502 model) input voltage is too high for most of IC… I want to also have 120…150 Vin in my dummy load but best IC I’ve found is Linear LTC6101 and it handles only 100 Vcmr
I’m a design engineer and would love to see a detailed review on this hardware given the experience you have accumulated with it since the tear-down, any plans to post such a video? I’m interested because we are looking at equipping our lab with these and I’d like to know what I’m in for.
Looking forward to a review of the BK 8500.
Can you confirm that the 8500 can be _controlled_ over USB from a controlling PC, but that current and voltage readings cannot be _read_ by the PC over USB?
The spec sheet seems to indicate that through what it doesn’t say.
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