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2017-12-09 Datacomm Cabinet Falls Off The Wall

Datacomm
on December 9th, 2017 by - No Comments

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 

Radio, Television entertainment Transistors Vacuum tubes
on December 4th, 2017 by - No Comments

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 Instead Of Aux Input

AM Band Radio Frequency Radio, Television entertainment Repair, alignment Transmitter
on December 3rd, 2017 by - No Comments

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

Uncategorized
on November 28th, 2017 by - No Comments

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

Medicine and health Other Off Topic Politics
on November 22nd, 2017 by - No Comments

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 

Digital Telecom Telephone Uncategorized
on November 21st, 2017 by - No Comments

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 

AM Band Radio Frequency Receiver Repair, alignment Toroids and Cores
on November 19th, 2017 by - No Comments

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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2017-11-15 Zenith Royal 755 Vintage Radio Excellent 

AM Band Radio Frequency Receiver Repair, alignment
on November 15th, 2017 by - No Comments

From FB group Vintage Transistor Radios 
I’m flabbergasted.  I received the Zenith Royal 755 I won last week – auction link is below.  the seller said repair/parts, but I’m amazed at how good a shape it’s in!  I suspect that it was in storage for most of its life.  The leather case is nearly new, except for a few bug chew marks on one side.  The battery holder looks like has never had any C cells in it!  I connected it to a 9V power supply and it wouldn’t turn on as the seller said.  The battery holder leans against the power lugs on the back of the volume control so I checked it and the switch doesn’t make contact when it clicks on.  So I bypassed that and the stations come in great.  The volume control seems like it has never been used – smooth as a baby’s butt.  The other minor problem is the dial cord slips around the control shaft toward the ends of the dial.  So for $40 I got a winner.  It’ll be a winner after I fix those two problems.  👍 👍 👍 😁

I was again surprised when I connected a milliammeter in series with the power supply and the Royal 755, which uses 6 C cells.  I turned up the radio to above normal volume and the current drain peaked at a bit over 10 milliamps.  I’ve found that most cheaper pocket radios with the 9V battery draw twice that much at low volume, so I’m pleasantly surprised to find that these Zenith radios are so thrifty with batteries.
 http://www.ebay.com/itm/311997495264

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2017-11-14 Closed Minded People And Politics

Politics
on November 14th, 2017 by - No Comments

From FB group thread discussing C. K. refusal to pledge allegiance to the flag.

Rich Gallego

By your your way of thinking, then almost no one should vote.  Because most of those who think they should vote because they believe they’re informed should also not vote.  They’re just as much MISinformed as they are informed.

You think I don’t know what I’m talking about?  Just go ask the average ‘informed’ person if he or she has been informed about *both* sides of the story.  You’ll seldom if ever find someone who has.  Almost everyone is closed minded.

Ike was right: “Those who are not in the middle of the road are in the gutter.”
Rich Gallego said:  “.. what happens when a large segment of voters know very little about today’s policy debates or even the basic workings of American government?”

You can already see what happens.  The approval ratings of Congress are below 20 percent.  Boss Tweet’s approval ratings are the lowest of any president for this time in office.  It already happened: people who don’t have a clue elected officials who don’t know – or don’t care – about policy, and ignore the basic workings of American government.

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2017-11-10 Built Phase Shift Oscillator From YouTube 

Uncategorized
on November 10th, 2017 by - No Comments

I watched the YouTube video of Radiofun232 testing the PSO that he built according to the schematic he showed.  I modified it somewhat.  My objective was to decrease the frequency down to 400 Hz.

I used three 0.1 uF capacitors and a 0.56 uF instead of the 0.47 uF.  Instead of 1k I used 2.2k.  I replaced the 1.8k collector load resistor with a 2.2k.  I also used 9 volts, but I changed the base bias resistors from 3.9k to 4.7k, and from 12k to a 10k and 25k trimpot in series to allow adjustment.

I used a 2N3904 instead of the BC547.  I adjusted the collector voltage to 4.5 volts.  I could connect the +9V, and sometimes I would see a slight blip on the scope and on the frequency meter, but not a continuous oscillation.  There is not enough gain to sustain oscillation.  The lack of an emitter resistor and bypass capacitor means this circuit will be too sensitive to temperature changes.

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