* Dual Power Supply Recommendations * - Page 1
Forum section: electronics / general

author: BeatleFred
author_rank: Newbie
timestamp: September 09, 2012, 05:14:11 am
content: I am looking to set-up an electronic workbench with test equipment, mostly to test/repair vintage audio amplifiers form the 1970's (Sansui),and open reel Teac/Tascam recorders (Teac A-3440), and I'm looking to obtain a dual power supply that puts out about 40 volts at 1 or 2 amps or more.Are the old-school models going back to the 80's, 70's, or even 60's a good choice? I know theyre built like a tank, but because of their age, they may have issues that need attention before they can be used properly to make accurate measurments, some models I had in mind: HP-6255a, Lamda LQD-422, and Harrison Labs 802B (and do these older units have limiting protection?)New model I was considering: Mastech HY-3005F-Y. Any helpful comments/advice appreciated.

author: saturation
author_rank: Super Contributor
timestamp: September 09, 2012, 12:53:17 pm
content: I think old linear supplies from those eras were better made all around, and I prefer them for fast response time, stability, low noise aka PARD, and durability. Assuming its not abused, age could kill its electrolytic caps, but if the units were not stored but used for most of its life until its recent sale, chances are even the old caps are working due to reforming effects. The trick is finding a good used supply, and knowing how to test them: see Agilent's document AN 372-1.See the thread on Power Designs supplies, these are perfect for audio work, the precision models specs have few equals today as general bench supplies, its more a cross between a precision reference and a standard supply.Most lab grade supplies have levels of protection, at least short circuit and current limiting. Others have over voltage protection crowbars. It should be described in the manual for the model you intend to buy.The Mastech unit you list is a good and popular supply, just make sure its a real Mastech, I got mine from mastechpowersupply.com, as there seems to be clones or counterfeit of it too; the real ones have consistent quality and are well made, just email Sean and see if that's his store too, say on Amazon or eBay.The Mastech I have injects more noise made worse by the digital panel meters and the fan, the analog gauged oldies are far quieter electrically, and are also quiet operationally: they are all ambient cooling alone, no fans. I can easily dial a voltage precise to uV on old supplies whereas the Mastech mV at best.I bought 3 Power Design precision supplies and a Kikusui dual supplyall4 in specification at ~ $150 total, delivered, from eBay. If you're not in a rush, wait for the best deals as they appear.

author: BeatleFred
author_rank: Newbie
timestamp: September 09, 2012, 08:30:09 pm
content: Thanks for the reply. This is the one I was looking at on Ebay:http://www.ebay.com/itm/Regulated-DC-Power-Supply-Mastech-HY3005F-3-Variable-Triple-Output-2-Variable?item=110944788612&cmd=ViewItem&_trksid=p5197.m7&_trkparms=algo%3DLVI%26itu%3DUCI%26otn%3D3%26po%3DLVI%26ps%3D63%26clkid%3D1930718603002094830After some haggling the seller was willing to come down to $180 for it, which seems like a reasonable price. The counterfeit isssue is a concern, of course. seems like the seller has a good + fdbk record, but I will contact Mastech directly as you suggest.On the other hand, there are some HP 6255a's on Ebay, which goes to 40 volts (compared to 30V on the Mastech), however, most are being as-is/untested, so its tough to say whether they have issues or can be put to use on the workbench right away. Some may be calibrated and checked out to be good, but they are usually more expensive and I'm on a tight $ budget, so its hard to make a decision between a new or older one.

author: saturation
author_rank: Super Contributor
timestamp: September 09, 2012, 10:24:56 pm
content: Its safer to buy from folks who specialize in test equipment, which suggests they know something about how the supplies work and what can go wrong. The seller you linked stocks toys and charm bracelets along with power supplies. The link I left sells only MTE, so Sean is a better risk.

author: BeatleFred
author_rank: Newbie
timestamp: September 10, 2012, 04:39:54 am
content: I emailed Sean and he replied. The one I mentioned is out of stock, but he said there is a new model available, basically the same, only slightly different display, and has a 10 turn pot:http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/volteq-variable-power-supply-hy3005d-3-triple-outputs-30-v-5a-new-model/prod_81.htmlIs 30 Volt sufficient for most applications, or would a 40 or 50 Volt model offer significantly more capabilty?Then again, there is an "old-timer" like this one:http://www.ebay.com/itm/HP-Agilent-6255A-Power-Supply-0-40V-0-1-5A-Calibrated-/220571615418?pt=LH_DefaultDomain_0&hash=item335b17c0ba

author: saturation
author_rank: Super Contributor
timestamp: September 10, 2012, 12:09:48 pm
content: Those are good supplies. But as a rule used supplies I wouldn't pay more than $50, shipping tends to be costly as they tend to be heavy. I target $20 for supplies and $20 for shipping UPS ground. I've seen that HP go for as little as $20, its usually ~$50.http://www.ebay.com/itm/HEWLETT-PACKARD-6255A-DUAL-DC-POWER-SUPPLY-0-40V-1-5AV-MANUAL-GOOD-CONDITION-/290754943938?pt=LH_DefaultDomain_0&hash=item43b2585bc2The above looks like its from someone who took care of it, albeit the seller is a merchandiser. You can obviously parallel linear supplies for double the current or series to double to voltage.Your questions suggest you maybe very new to electronics, so its safe to buy a Mastech to avoid a bad used purchase. Good luck and enjoy your new lab!