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Author Topic: Burn in  (Read 17510 times)
K2OWK
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Posts: 1279




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« on: July 28, 2010, 09:35:42 PM »

I have been using boat anchor radios for a while. I started ham radio in the mid 1950s, so those boat anchors do not appear so old to me. Now for the question. I am to understand that when powering up an old radio it should be done in steps, starting with a low voltage and then bringing it up slowly to full power. I have not done this before. I just plug it in and turn it on. I have not had a problem doing this before and have not had any exploding caps as I am told can happen. Now that the old equipment is becoming more expensive and the parts harder to obtain, I would like to start using my VARIAC to bring the voltage up to full power in small steps. I assume this is to reform the caps. What should be the starting voltage? What duration and what power steps should be applied? For example should I start at 1/4 voltage and leave that on for say a day? Then step it up to 1/2 voltage for a day and so forth, or would the recommendation be different? I am sure there are hams out there who have used a burn in method that has worked. Please give me your methods so I do not distroy any expensive boat anchors I might buy in the future.

Thanks,
73s
K2OWK   
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G3RZP
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« Reply #1 on: July 29, 2010, 01:19:01 AM »

Depends a bit on the rectifier. If it's a 5Y3 or similar (but NOT an 83), I pull all the ubes except the rectifier and put a voltmeter on the B+ line after the filter choke, then gradually wind up the input until the correct B+ is obtained, keeping a look out of smoke etc. Take about 20 minutes to wind it up to give electrolytics time to reform. If all seems well, replace tubes and carry on.

If the rectifier is a 5Z4 type (including 5V4 i.e. indirectly heated) it's probably better to substitute a 5Y3 temporarily, since the cathode will take a lot longer to start doing anything. Even better in both cases is a 'solid state' rectifier i.e. some diodes mounted in an old tube base. But don't exceed the rated B+ - it will be higher since there's no load - and I would generally go back to the tube rectifier once I had established the electrolytics etc were OK. One or two of my power supplies were inherited from my father: they're still going strong with WW2 era electrlytics in them!
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N8CMQ
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« Reply #2 on: August 05, 2010, 05:17:27 PM »

I don't do much on the old boat anchors, plug em in and fire em up! Monitor the B+ as the rectifier warms up, and pull the plug if there is sparks or smoke...
I just recapped an SX101, and I didn't have problems till after! The flux bridged the terminals of the B+ and ground, scraped off the flux and the problem was gone.
Now, if I can find out about the 12BY7 first oscillator...
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N8CMQ   Jeff Retired...
KE3WD
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« Reply #3 on: August 05, 2010, 07:58:39 PM »

If the set hasn't been powered for a long length of time, reforming the caps can indeed help out in their longevity. 

This is one of those things that doesn't always need to be done, but once you encounter the one that needed it, well, it will cost you more time and money to correct. 

The AC variac is one method. 

Another method, just put a 100W lightbulb in series with the AC and let it sit there for 24 to 48 hours like that.  Maybe not as great as the variac method, but the old hands knew about it and it does work. 

Besides that, every test bench should have a lightbulb that can be switched in series with the UUT, a great fuse saver - short finder method, and paired with the Variac plus a bit of experience using, it can be a formidable tool in the troubleshooter's arsenal. 
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G3RZP
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« Reply #4 on: August 06, 2010, 04:30:19 AM »

I don't know if you US guys have had the green environmentalists changing the law, but over here, you would be very lucky to find a conventional 100 watt light bulb. They are now banned from sale, and most places have sold all their stock. Needless to say, the series light bulb trick works with a filament type light bulb, not one of these fancy low energy, low light, lots of mercury types that are the only sort we can get.
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N3QE
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« Reply #5 on: August 06, 2010, 07:02:45 AM »

You know, there's different goals people have with respect to boatanchor radios.

Some don't really care if the radio works at all, it just has to be all original.

Some really want the radio to work with all original parts. For them, using a variac to slowly reform the electrolytics makes perfect sense. I think this is the approach you were discussing.

Some don't mind if some original parts blow up, as long as they can repair them and keep the radio running. When I find a boatanchor and it's obvious that failed electrolytics and wax capacitors and tubes etc. have been replaced over the past half century (easy to spot... electrolytic can styles and brands have slowly changed in the past 50 years in perfectly obvious ways) I know that it's been a workhorse radio, kept running and in good repair.

Some really like ripping out every electrolytic and wax capacitor in the radio and replacing them even before they turn the radio on. They call it "recapping". Astonishing but it's a verb. In some sense it's kinda pretty to see all the orange drops in the chassis, but in reality probably only 10% of them might have had to be changed out to begin with. Not that the old wax capacitors were perfect but they probably were "good enough" at least as cathode and filament bypasses.

Some recap but stuff the replacement electrolytics into cans and even stuff modern caps into the old wax capacitor bodies. It can be very pretty but IMHO doesn't have much to do with the "workhorse radio" mentality I prefer.

Tim.
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KE3WD
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« Reply #6 on: August 06, 2010, 08:15:44 PM »

On this side of the pond, we still can walk into a store and purchase - and use - filament light bulbs. 

At least for now. 

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G3RZP
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« Reply #7 on: August 06, 2010, 11:14:14 PM »

KE3WD,

You're lucky! But I hear that in New Zealand, they've gone back to filament type bulbs because the lower energy efficiency is more than offset by the energy requirements of the disposal problem.

In Europe, the whole thing was pushed through by a politican from Eastern Europe with no engineering or scientific background.
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W8JI
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« Reply #8 on: August 07, 2010, 08:52:34 AM »

I have never in my life brought an old radio up in tiny steps, and I rarely have problems with components.

Here's what really happens......

If you have an electrolytic that has deformed so badly it cannot take rated voltage, it will fail soon anyway. You can bring it up slowly and try to reform it, but it will NEVER really reform fully because to form it fully you have to run it over the rated voltage. Most caps are not even run at the rated voltage.

Turn it on with a very marginal fuse, watch the voltages and color of tube anodes carefully, and you will find any parts that need replaced. If you bring it up slowly you probably only slightly prolong the inevitable.

73 Tom

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W3LK
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« Reply #9 on: August 07, 2010, 05:04:57 PM »


In Europe, the whole thing was pushed through by a politican from Eastern Europe with no engineering or scientific background.

I thought Al Gore was from Tennessee?
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K2OWK
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« Reply #10 on: August 11, 2010, 03:47:45 PM »

Well thanks for all the replies. I am still not sure how to burn in and old boat anchor, or the voltage timing on each setting of my Vaiac (Powerstat). I guess I will have to guess and hope I am right.For information: yes Al Gore does come from Tennessee.Regards,73sBarry K2OWK
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W3LK
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« Reply #11 on: August 12, 2010, 11:39:20 AM »

For information: yes Al Gore does come from Tennessee.Regards,73sBarry K2OWK

I know; It was a joke. sigh .....
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AA9XY
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Posts: 6




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« Reply #12 on: August 12, 2010, 01:01:13 PM »

When I have ran something on a variac to reform the caps, I started at about 35 volts, and raised the voltage up about 10-20 volts an hour.  I did this once with great success on an old PA amp that I used NOS electrolytics on.  No ripple and B+ dead on the mark after about 6 hours of re-forming.  Keep in mind that "reforming" doesn't always work........especially if something is from the 30s or 40s.  Paper caps are almost always bad or going that way.  I usually replace all of them if I'm going to use something heavily.  Sometimes, if a piece of equipment is going to see limited use, then replacement of HV bypass caps and audio coupling caps will fix it "good enough." 

My $.02, and 73,

Alex
AA9XY
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K2OWK
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« Reply #13 on: August 12, 2010, 01:51:17 PM »

Hi Alex and W3LK, Thanks Alex, that is what I needed to know. I buy equipment from The 1950s and 1960s and so. I have a Heathkit SB-401-1 that is in daily use with no problems all original. I was lucky I just plugged this thing in and it worked with no smoke or fireworks.

Yes I know it was a Joke. I am just being a wise guy.

Regards,
73s
Barry K2OWK
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