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Sending power into rig unused for 30 years : Precautions ?
On Aug 16, 1:04*am, wrote:
Now retired I'm trying to become active again. My TS-520S has not been on for 30 years. I don't have a variactor ( variable transformer ). At the TARC advice was to put a lightbulb in series to take the surge. * Should I use a high resistance ( low wattage ) bulb or vice versa ? Would this be as good as a simple *L-C network ? Somebody said just plug it in. Are there any other ideas ? Thanks for your kind assistance. Dave WB3DWE *Temple, TX A couple of disclaimers first: a) I know diddly/squat about Ham equipment. I am not a Ham. b) I have been noodling about with vintage equipment, tube & solid- state for now over 30 years, so I am familiar with the species. What I write below is a generic approach to (re)starting vintage equipment after some years at idle. So: As I understand, the Kenwood is a tube-based unit, however it has a solid-state rectifier and is mostly solid-state in general. What this means is that there is some validity to bringing up the voltage slowly using a Variac as the caps will see a gradually increasing voltage - unlike what they would see from a tube rectifier which does not pass current until about 70V or so. That it is from the transistor era, at least in part, suggests that the filter caps may be of sufficiently recent manufacture as to be likely to be good - the operative word here is *LIKELY*, not *certainly*. Kenwood was also not know to use cheap-junk caps in their equipment. HOWEVER: A variac is really no better than a dim-bulb tester unless it is equipped with a current meter (amps or watts) that will read the actual current draw of the unit. I have been known to RANT on this subject at length - but I will spare this group and merely state that UNLESS you have the means to measure actual current drawn by the unit and at a sufficiently fine degree as to give you useful data, don't waste your time with a Variac. It gives you a false sense of security. IF you have the means to measure current - either with your VOM in series or with a poor-man's ammeter (measure voltage drop across a 1- ohm resistor, for example), this technique is very useful. Raise the voltage s-l-o-w-l-y, watching the meter all the time. It will jump up (typically) then slide down as the caps charge. Slowly-slowly-nicely- nicely until you reach operating voltage over 4-5 minutes or so. And KEEP WATCHING! If the caps start to fail at full B+, you will see that meter creep up. If they go anything beyond about 80% (SWAG guess - more below) of the nameplate rating of the unit, you have real problems. Now, here is where I cannot comment beyond the generic - I have no idea what the quiescent vs. active current draw is with the Kenwood. THIS IS IMPORTANT. As you will not be transmitting or whatever, you should be operating at/near the quiescent current. This may be a very small percentage of the full nameplate rating - my guess is that this is so. You will need to know what that is. If you are operating even 5% beyond the "proper" quiescent current, that will be expressed as heat somewhere - and eventually *POOF* at some unobtanium or expensive part. You get the point. The idea is to bring power to the beast slowly so that failed caps or similar may be discovered before any actual damage is done. For this to work you need a means to determine whether the unit is taking excess current - and you need to be able to measure this in fine-enough increments to be worthwhile. Otherwise, you are wasting your time as a small problem or series of small problems will be invisible to crude means. I keep this unit for these sorts of tests: http://www.oaktreeent.com/web_photos...P-5220_web.jpg It is an metered Iso-Variac, overkill for once-in-a-while needs, but I use it constantly. Peter Wieck Melrose Park, PA |
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