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2017-12-15 Olympic 860 Radio Capacitor Replacement 

I was the only bidder on a lot of three radios, one of them is an Olympic model 860 AM transistor radio.  This radio uses four AA cells for a total of 6 volts DC.

Overall the radio is in good condition – no chips or cracks.  I powered it up and if I turned the volume to maximum and listened very close, I could barely hear a station when I tuned it.  It was working, but the electrolytic capacitors were dead, letting almost no audio signal through.

I counted eight electrolytic capacitors, so I got them, they were common values, two 80 uF (used 100 uF), several 30 uF (used 33 uF) and a 3 uF (used 3.3 uF).

I got through replacing several capacitors; there were still a few left, but their leads were covered by the tuning dial.  The screw that held the dial to the capacitor was covered by the plate that had the 5.5 to 16 kHz frequencies on it, so I didn’t want to damage it because it would be easily seen.  It was glued down with tough contact cement so I had to spend a lot of time gently prying it up with a knife blade.  The plate survived with minor bending, which I straightened out.

I got the rest of the capacitors replaced, and applied power to see if it worked.  Success!  But there were damaged wires and loose connections on the battery springs, which I had to resolder.  I glued the dial plate and left it to dry for several hours.  Later I reassembled the rest of the radio and tried it again to make sure it worked.

There are only three deficits, one from wear.  The back snaps into place, and opens with a coin in a slot.  The tabs that hold it in place are worn and the back comes off too easily.  But this isn’t much of a problem because the radio comes withva leather case which holds the radio together.  However the case was poorly designed and the radio is very difficult to remove or insert into the case.  The strain on the case has caused the stitches to tear loose on the case.  If the stitches are repaired, they will probably be torn open again because of the case design.

The other minor deficiency is the earphone jack.  It’s a 2.5 mm jack, which is an odd size.  Also there is an external power jack and it’s the same 2.5 mm jack as the earphone jack.  Putting the plugs into the wrong jacks could damage the radio.  The best solution would be to change the earphone jack to a 3.5 mm jack, which would solve both problems.

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2017-12-15  Royal 500 Capacitors Replaced

From FB group Electronics Hobbyists, regarding the Zenith Royal 500 radios.

Clyde Hendrickson 

There are two 50 uF, 10V electrolytic capacitors under the battery holder.  Replace them with 47 uF, 10 or 16 volts. There is also a smaller capacitor next to the other, it might be a 3 uF, or a 16 uF, 10V.  Use a 3.3 uF or 22 uF.  All three of the replacement capacitors can be soldered to the copper side of the PC board.

The fourth capacitor, 3 uF,  goes from the center pin of the volume pot to the PC board.  This is the one that causes the volume to be very low or zero.  There is enough room to solder the replacement capacitor (3.3 uF) between the center pin and one resistor.

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2017-12-10 Power Outage And Cell Sites

From FB group Bell Telephone…

Paul Triplett

If the power where I live went out a lot, I would be looking into why so many outages.  I have had good luck, just a few times in several years.  One time we could hear the boom caused by arc-over.  I went down a few blocks and saw the 12kV lines lying on the roof of the house.  Some others were sagging a lot, they got hot enough to almost melt.  Obviously a very high current fault.  It affected a half dozen square blocks.

I see the big socket on the side of cellular cabinets.  If there is an extended power outage, there won’t be enough portable generators to keep more than a few cell sites running.  This seems to me to be the biggest gotcha.

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2017-12-09 Datacomm Cabinet Falls Off The Wall

From FB Group Bell Telephone…

Just like the ones we had, but complete.  Ours had areas where the contractors removed the mushroom panels to make room for the digital cabinets or open racks.

We had a contractor install a cabinet with molly bolts into drywall.  It was like that for years with at least a half dozen Cisco switches in it.  The small room was also used to store audio/visual equipment, and because the a/v equipment kept getting stolen, they put a special lock in the door.

One day I got an order to fix one PC that couldn’t connect to the network.  I had to request the special key.  Another guy and I opened the door and were utterly shocked.  The whole cabinet fell off the wall and was lying on the stuff!  Only a single PC lost connectivity because the cabinet was still knee high, off the floor.  We just closed the door and went to get our stupidvisor.  If it had dropped to the floor we would’ve had more than a hundred PCs dead.  😣  😱

Sometimes you just outMurphy Murphy!

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2017-12-04 Converting Tube Set to Transistors 

From FB group Vintage Transistor Radios 

I’ve considered converting a tube set to transistors.  The problem is getting tube bases that aren’t sharp and breakable glass.  Some old electronics used tube base type plugs for relays and plug-in modules.

Then there is the problem of dealing with the higher voltage.  Transistors can handle 300V, but low power JFETs aren’t that high, maybe 60 volts.  But a JFET and transistor could be combined.  The JFET acts like a high input impedance tube, and the transistor handles the high voltage.

Since all solid-state ‘tubes’ would be socketed, the set could be easily converted back to hollow-state firebottles.

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2017-12-03 AM Oscillator To Replace Aux Input

From FB group Vintage Transistor Radios 

For the last few months, ever since I started experimenting with oscillators on the AM broadcast band, my attitude towards auxiliary audio inputs has changed.  Earlier I thought  that it would be convenient to have an aux input.  But I was leery of making changes to the collectibles radio circuits that might affect their value. 

Instead I use an AM oscillator next to the radio.  I’ve built a few of the oscillators and they are cheap, easy to make, stable and can be easily modulated.  They can be powered by a few AA or AAA cells or a 9V battery, and use low current so the batteries can last.  The headphone output can be used to modulate (AM is monophonic only), or another transistor can be added to give the higher input impedance that an auxiliary input has.

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2017-11-28 Royal 500 And 3.5mm Phone Jack

I finally got around to spending some time online to search for a replacement jack for the corroded one in the Zenith Royal 500 I’m working on (#473430).  I had to destroy the jack to get the nut off, the whole jack was green.  The hole was so corroded the plug wouldn’t fit.  I ordered jacks from Arrow.  They are Switchcraft 35PM2A and cost about 3 dollars US each.  

I poured straight white vinegar into a squirt bottle and squirted it around the jack and battery terminals.  I didn’t see it bubble or foam.  So I sprayed some cheap imitation CLR on the same places and nothing much seemed to happen after tens of minutes.  I squirted water on it to wash off the chemicals and dried it with a paper towel.  I should remove the whole battery holder and soak it in the vinegar to neutralize the battery juice.  But I’m concerned that the vinegar might dissolve the corrosion on the battery connections and they might crumble, and have to be replaced.  Also the copper wires might be corroded inside or on the ends.

The jack’s ground lug served as a terminal for connecting the leads of two electrolytic capacitors, but I replaced them with tiny ones that fit on the trace side of the PC board.  The jack’s ground lug will be free to be used just for the ground wire and wire from the output transformer.

Bigger problems

I have been handling the chassis a lot while working on it.  I finally got it back together and connected power but I got nothing.  I traced it down to the driver transformer primary which was open.  My expert analysis (heh) found that the transformer’s primary side had two leads coming out.  But one of those was on the top of the transformer.  So they left a length of wire long enough to reach to the hole in the PCB.  The other lead came out the bottom and is the only lead supporting that side of the transformer.  The transformer is close to the edge.  As the chassis is handled, the forces on the transformer push on that single lead, and the lead moves vertically and laterally, and the movement tears the very fine primary wire loose, causing the open.  The transformer is built so that it’s very difficult to repair the break.  The solution is to replace it.

I believe the best way to prevent this is to squirt some hot glue under that side of the driver transformer so that it can’t move.  Also, avoid handling the chassis anywhere near that transformer.

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2017-11-22 Don’t Feed Homeless – Don’t Enable Them

From FB group Orange Talk

Comment on Thanksgiving Day “Don’t feed the homeless, it just enables them.” 

So let me get this straight:

“Don’t enable them (homeless)”

By not feeding them, they are going to go away?  Go away to  someone else’s neighborhood and steal to get something, like the kid’s bike, so they can get enough to get something to eat?

Or you want to cause them to get sick enough to end up in the emergency room, where the taxpayers again have to pay for it?

I realize there are no easy answers, but the “don’t enable them” doesn’t look like a humane or acceptable answer either.  The ball is again in your court, don’t screw it up again.

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2017-11-21 Phones And Line Levels 

From FB group Bell Telephone…

In the days of analog phones like 500s and 2500s, Ma Bell had the phone matched to the line, so whatever the line length was, it compensated and the signal levels were very uniform, it worked great.

Then came along the full duplex digital system, and everything went to hell.  The signals were separated so if the levels were too high, there wasn’t a problem with feedback or howling.  So whatever was too low or too high never got corrected.  The result was there were constant complaints from the users that the volume was too high or low.  And of course there was constant finger pointing because of different vendors and equipment.  So nothing seems to have gotten much better, same with cellphones.  😣

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2017-11-19 Royal 510 PCB hairline crack 

For FB group Vintage Transistor Radios 

Speaking of fuzzy garbled audio…  I won another auction for a Zenith “Royal 510” which I’d never heard of.  It turned out to be a Royal 250.  The seller got no bids at all, so with less than a minute left I bid the minimum ten dollars.

I got it this afternoon.  It needed the usual capacitors, but after I got done doing those, it was microphonic, any vibration from the speaker would set it off into a squawk or buzz.  I started poking around to find a loose solder joint, and I finally found one and fixed it.  But it still squawked.  I had to poke around and flex the PC board quite a bit before I narrowed down the point that was causing the problem.  It was a hairline crack in the PCB trace, least where one would expect, in the middle of a trace thickly covered with heavy coat of solder.  I bridged the crack with two heavy wires imbedded in the thick solder.  I don’t think it will break again.  I guess the PC board was flexing when it was being shipped, and finally the trace cracked.  The board itself looks okay.

I put it back together and Humpty Dumpty is working okay.  In the center of this photo is a ‘dogbone’ shaped piece of solder with the almost invisible hairline crack in the middle.

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