HPN4007C Output Voltage Adjustment Pot
Posted: Tue Sep 14, 2010 10:54 am
I cracked open one of our Motorola (make that Emerson/Astec) HPN4007C switchers in an attempt to tweak up the output voltage. I have checked 6 of these P/S’s now, and they all seem to be running an output of approximately 14.20 Volts DC at their output terminals, under idle/no load condition. They droop down to about 13.95 volts under full load conditions (54 watts TX). They have all been manufactured at various times during 1H2010, based on the manufacturing time stamps on the PC board. I pulled the cover, and was hoping to find the voltage adjustment pot, so I could tweak her up to 13.80 volts DC at the radio's power input terminals (APX 7500 mid-power desk sets and Mobiles), under full load condition. I could have certainly missed it, but I did NOT find any adj pot anywhere on the board, and I checked both sides. Perhaps the ISO 9001 quality is good enough that they do not need to use such an adj pot? I can understand how not having such a pot could shave some pennies off the production cost, not to mention some labor savings realized by the final assbly tech or robot not having to tweak 'em up.
Has anyone else cracked one of these open and found the magic voltage adj pot?
BTW, I must say that I am quite pleased with the performance and quality of these little gems. Very clean on the scope in terms of ripple and over/undershoot in going from idle to full load, and back to idle, and the regulation isn’t bad, either. The assembly quality appears to be very good, too. No complaints here. They have a nice and very big ferrite bead set molded into the nifty power output cord near the business end of the P/S. This helps to alleviate any harmful RFI, even when I place the power output cable right up against the antenna coax feedline. Pretty cool, even compared to issues that will usually arise if you do this with very expensive switchers. Emerson did their homework in designing these babies to avoid RFI problems. For a cheap little P/S, IMHO these things are just dandy. They are also extremely quiet. I can just barely hear them ever so quietly squealing (more like a fast ticking sound, actually, than a "normal" switcher's squealing sound), even when I place my ear smack against the plastic case under full load condition. Can’t even say that about a Lambda switcher (albeit I’m not suggesting the little Emerson is any Lambda, either - no more than Dan Quayle was like JFK…).
Has anyone else cracked one of these open and found the magic voltage adj pot?
BTW, I must say that I am quite pleased with the performance and quality of these little gems. Very clean on the scope in terms of ripple and over/undershoot in going from idle to full load, and back to idle, and the regulation isn’t bad, either. The assembly quality appears to be very good, too. No complaints here. They have a nice and very big ferrite bead set molded into the nifty power output cord near the business end of the P/S. This helps to alleviate any harmful RFI, even when I place the power output cable right up against the antenna coax feedline. Pretty cool, even compared to issues that will usually arise if you do this with very expensive switchers. Emerson did their homework in designing these babies to avoid RFI problems. For a cheap little P/S, IMHO these things are just dandy. They are also extremely quiet. I can just barely hear them ever so quietly squealing (more like a fast ticking sound, actually, than a "normal" switcher's squealing sound), even when I place my ear smack against the plastic case under full load condition. Can’t even say that about a Lambda switcher (albeit I’m not suggesting the little Emerson is any Lambda, either - no more than Dan Quayle was like JFK…).