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Author Topic: Is a variac needed to start newer radios that have been stored long time  (Read 2763 times)
KD0TLI
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Posts: 42




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« on: October 14, 2012, 08:17:05 AM »

Kenwood TS-430S has bee stored for 15 or 20 yrs.
Is a variac needed to bring it back to life so I dont pop anything. ?
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AC5UP
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« Reply #1 on: October 14, 2012, 08:26:32 AM »

It's a 13.8 volt radio.
I don't see any advantage in trying to start it at 10 volts or less since the radio won't function at that level even if it's working properly.

As for the AC power supply, some will argue the Variac is a good but if it were mine I'd probably fire it up with no load and watch for smoke. If OK, check the output for ~13.8 volts with a low-cost load like an automotive brake lamp. If still OK, turn it off, connect the radio, then bring both up to see how they play.
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K8AXW
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« Reply #2 on: October 14, 2012, 11:50:20 AM »

Concur with 5UP.  Since it isn't HV powered..... no point in bringing it up slow.....  However, I would definitely check the P.S. output first and leave it cook for a few hours before connecting it to the radio.
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W9GB
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« Reply #3 on: October 14, 2012, 01:28:03 PM »

Quote
Kenwood TS-430S has bee stored for 15 or 20 yrs.
Is a variac needed to bring it back to life so I dont pop anything. ?
I would be more concerned with a dead or leaking lithium coin cell.

OBTAIN Service Manuals before EVER opening up an unfamiliar radio.  
Just because it is the not the price of a vintage BMW, does not mean short-cuts with radios work.
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STAYVERTICAL
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« Reply #4 on: October 14, 2012, 01:47:28 PM »

The variac method sounds like it is mainly for use with old analog technology radio's.
Modern digital radio's work with defined voltages on their bus's, and you would risk damage by not giving them their required voltages.
For a general familiarization with the TS430S, and how to open it, pcb layout, changing button battery etc - try this youtube link:
http://www.youtube.com/watch?v=U56M9Bm-QL0

It is a great little radio by the way - I use one just about every day.
It holds up very well with modern radios, particularly if you put in the optional 500hz I.F. filter.

73 - Rob
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W4VR
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« Reply #5 on: October 14, 2012, 05:18:46 PM »

try it with the power supply and if the radio blows up simply toss it in the garbage can.  in all honesty it will probably work ok.  if it were a tube radio you would not be so lucky.
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K4RVN
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« Reply #6 on: October 14, 2012, 09:20:50 PM »

If a HV. power supply using an A.C. primary has electrolytic caps in it, then bringing the primary voltage up slowly can reconstitute the electrolyics. Putting full voltage on a power supply like that which has been idle for some time can cause the electrolytics to short and burn out due to arching of the HV in the caps. At least that is my understanding. I do own a variac and have used it with success recently on a HV power supply for an old transmitter.
I took about three days to slowly bring it up to 120 volts on the primary.

Frank
« Last Edit: October 14, 2012, 09:25:44 PM by K4RVN » Logged
KA4POL
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Posts: 1902




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« Reply #7 on: October 14, 2012, 09:46:32 PM »

This radio requires a 12 to 16 V supply. A variac does not help you there.
In your case I'd first visually inspect components for obvious damage, i.e. leaking electrolytic capacitors.
If this seems to be ok you could use a current limiting supply. Set it to the 2 A which the receiver requires and power it up. Similar for the transmitter.
Depending upon how the radio was stored it may still be fine. In my IC-1271 the memory battery was still ok after over 30 years.
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K4RVN
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« Reply #8 on: October 15, 2012, 06:42:48 AM »

The 430 has been idle for quite a few years, but your power supply probably has not,
don't know that just a guess. I connected my 440 Kenwood after about 10 years of no use and let it sit day and night for a couple of days before using the transmit function. It did fine
after that. I would suggest using it on receive only for a day or so just to cook out any moisture and get it good and warm before throwing the amps to it. I have no experience using a variac on a 12 volt supply so don't know if it would be beneficial or not.

Frank
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W8JI
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« Reply #9 on: October 15, 2012, 07:12:46 AM »

I have never used a variac ever to bring up any old radio, tube or transistor.

I check the tubes, pull the rectifier out, and run them for a few hours with a very small fuse to bake any moisture out. Then I power them up and look for abnormal current or smoke.

I'd bet money my success rate is just as good or better than people who use a variac. If we really look at the practice of reforming capacitors, we'll find the alleged variac method doesn't actually do anything worthwhile.

Reforming requires operation at or above rated voltage with a large series current limiting resistance, generally for a 15 minutes to an hour maximum. If the cap does not come to normal allowed leakage in that time, it is defective and needs replaced.   Anyone who thinks a cap reforms from  walking it up with a variac from a modest voltage to a voltage some amount less than rated without a current limiting resistor and adequate source voltage is fooling himself.

I think the variac idea is one of those old wive's tales that just get passed along. If a cap is so bad it fails from normal voltage application, it should just be changed anyway. If someone wants to reform it, then they should at least do it the correct way.

73, Tom 
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WA3SKN
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« Reply #10 on: October 15, 2012, 08:00:02 AM »

No.
The concept of using a variac is for "re-forming" the electrolytic capacitors in the high voltage supply used in tube rigs.  This is really not an issue with 13.8 volt supplies or the transistor radios they power.
73s.

-Mike.
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AC5UP
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« Reply #11 on: October 15, 2012, 05:33:43 PM »

On a vaguely related note........

In the case of TUBE radios that have been stored for an indefinite period, I do have a wake-up procedure that does not involve a Variac. Remove the 5Y3 or 5U4 rectifier tube. Apply power. Listen for arcing. Make note of any burned out pilot light(s). Check each tube for a lighted filament. Apply a thumb to the metal tubes as a Q&D check for filament heat (do not do this with a 6F6 that has been on for a while if you value your thumb!) etc, etc. Let the chassis cook long enough to chase out some of the residual moisture in the carbon comp resistors. If convenient, poke a pair of AC voltmeter probes into pins 4 and 6 of the rectifier tube socket to see if the B+ winding of the power transformer is alive.

The B+ secondary winding test should be carried out with caution as the transformer could have more spunk than you suspect.

If all went well, power off, put the rectifier tube back where it belongs, then power on to see if the radio plays. If there is a hummmmm, plan on replacing the filter cap(s) and don't be unhappy about that. I'd much rather see the weak parts fail before I start a rebuild. That way the radio should see more play time than bench time in the future, and isn't that supposed to be the goal of this exercise.........?   Wink
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K4DPK
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« Reply #12 on: October 16, 2012, 03:22:57 PM »

Variac?  No,

But I betcha you will need to clean the relays on the low pass filter board.

This is done with a 47 ohm resistor in the antenna connector in series with the 13.8 DC supply.  Just cycle through the bands a couple hundred times.

Phil C. Sr.
k4dpk
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