The Tale of Three Cobras       

They say bad luck comes in threes, how about radios? 

By Spitfire (County-wide 441)  

 

 

It all started innocently enough with our budding classic radio roundup.  A loose, flexible, open forum on channel 21.  No formal schedule or anything.  Just talk about the radios of old.  So with Ebay just a mouse click away, the window-shopping began. I started off with a couple of 23 channel transistor radios that where cheap to be had, and aesthetically appealing to no one but me.  This got me into the club.  A Regency CR-142 and its sister in looks only, the CR-123B.  I also put in a dash of influence from Sandbagger, with his extensive knowledge of radios from the "heyday" of CB radio.  Now, in our loose definition of what qualifies as a classic radio, the one real requirement, as I see it, was having 23 channels.  But also deep inside I felt that only a tube radio would truly be classic.  I have never owned a tube transceiver before, so I was not too sure of what I was getting into.  Sure, I thought, replace a capacitor or two and maybe a weak or bad tube,  a quick realign and get on the air, right?  Well, like many other restoration projects, this one tended to take on a life all its own. The real life version of which I will now relate to you.

I was looking around on Ebay at tube rigs and wanted something affordable, but a known good talker. I settled on the B&K Cobra CAM 88 by Dynascan Corp. USA.

The name says it all.  It seems to be Cobra's first radio.  Looks cool and known to be a "talker".  So the shopping began. I managed to land one for $25 plus (ugh) shipping.  Ok, so the radio was one of those "it lights up,  but untested".  No problem, I figure, Iím in this to resurrect and restore, how bad could it be? The ad says complete with mike, a UG8 un-amplified D-104,  so I figure the mike alone is worth the price.

Well, the reality has been quite an experience.

Meanwhile, while I patiently await on UPS to bring my new classic home, I am having fun with my SBE Trinidad.  A rig suggested by Sandbagger, which I have been very happy with for an everyday radio. That was a $12 special from Ebay.  Nice talker with great audio.  Looks good too with its wood grain cabinet.

Finally, the UPS man brings my new toy.  I open it up to clean things up and look for any obvious problems before plugging it in. Things werenít very good looking from the standpoint of restoration.  First off, the chassis was pretty rusty.  Not just dirty, but pretty "looks like it was stored in a basement" ugly. The front panel had two holes drilled in it for some unknown reason.  Some insulation was melted on the speaker wire and the "S" meter - Groan!  The pictures on Ebay had made this rig look much better than it actually was.  Yes I know, Caveat Emptor.  But sometimes ya gotta take a chance.  On the operational side, things were a bit better.  It transmitted with around 2.5 to 3.5 watts, which made me feel better.  But there was a definite A.C. hum coming through the speaker, and some real "funkiness" (a vague technical term) going on with the "S" meter, and modulation light during receive.  Possibly the melted insulation there?  Well, all-in-all, the radio seemed not too bad a platform, but it was ugly.  So I decided to look for a better looking Cobra CAM 88, but one listed as "needs work".  It turns out the second Ebay 88 I found, was in much better physical shape.  So now I have a better candidate for restoration. The first problem was to replace the electrolytic can. I have a selection of electrolytic can capacitors on hand that I picked up at a flea market cheap for use in the few tube receivers I have. Turns out I got lucky there.  The Cobra called for 30,20,10 MFD @ 400v.  I had, can you believe it, the right size and all!  A 30,30,10 MFD @ 450v.  Man, I thought,  this is starting out ok.  So now, the first radio became a parts donor while I kept a note on what I took for possible restoration later.  Fast forward a moment, and that didn't happen, because in the end, that one radio brought 3 back to life!  But in that process, it has exhausted its own life.  But I donít want to get ahead of myself here.  By now the word is out, on the channel 21 street, that I am bringing a CAM 88 back to life.  "Low Key", one of the channel's regular horse traders, tells me he has a Cam 88 he's willing to let go.  He has it in the original box, with manual, and the A.C. and D.C. power cords.  Wow! I said yea.   The price of admission?  Ten bucks.  I am in.  So now this becomes my third Cam 88, which has since been referred to as, the "Low Key 88".  So by this time I am already deep into the 2nd 88.   The biggest problems were that all the electrolytic caps needed to be replaced.  I gave it an alignment and things were looking pretty good.  It had a couple weak tubes that I swapped out from the parts radio.  But one of the 12AX7ís was bad, and the parts radio tube was questionable at best.  So I go to Zern's , a local farm and flea market, that Friday night to see the electronics guy there in a corner store.  He had all kinds of parts there from stripped equipment,  plus some old radios, tubes etc.  A virtual goldmine for a packrat.  I have also gotten tubes from him before in the past.  He had a NOS 12AX7 in stock for $4.  Cool, this is working out pretty well.  I get home, put it in, and tune things up.  So now, #1 restoration is ready for on air checks.  Receive is good, as it can hear a signal down to .2uV.  Awesome!  Fire it up on air, and gets good reports on audio, receive sounds good and warm, like a big old tube radio sounds.  Nice, even the "S" meter works well.

So by this time, I have become familiar with the CAM 88 inside and out.  Feeling confident, I start to bring back the Low Key 88 (#3).  During which time I discover a Cobra 98.  This radio looks much like the 88, but to me, it has more sex appeal with its black face, and burnished aluminum trim.  It turns out to be the same inside with the exception of an internal SWR bridge, and some minor production type changes.  As the work is going on with the Low Key 88, I find and buy a good shape 98.  Easily put on the air with only an alignment and the replacement of a couple of the Ďpaperí caps underneath.  It is now in regular use. Has a very good receive, as good as the first 88. Down to about .2uV.

So back to the seemingly easy, but troublesome Low Key 88.  Got it up and running and discovered the receive to be off by 2 channels down.  Noticed that the 2nd I.F. can was replaced with a 455kc part.  Knowing the radio well by now, I knew it should have a 475kc I.F..  So I immediately assume ,ah ha!, here is the problem.  So after much careful surgery to remove the 475kc can from the parts rig, and the same careful removal of the 455kc can. I installed the right can and it tuned up real sensitive but still 2 channels off.  Oh now what? After talking to Sandbagger, and checking the schematic, it turned out that the  receive mixer crystal was bad.  Easy fix, as it turns out that the parts rig still had some more good stuff to offer up.  Now I am past all the receive issues, time for on air testing.  Can I get a radio check? Whatís your í20? Sounds good they say.  Cool smile of accomplishment.  Except this was only its first night on the air. The second night turned out to be that it worked for ten minutes and then the transmit audio fell flat on its face.  Geez, now what? Time to revisit the audio section.  I replaced a shorted cap at the first speech amp, and a 12AX7 tube.  Fortunately I recently did some horse trading and acquired 6 good used 12AX7ís and an assortment of high voltage capacitors.  Replaced the bad cap and put in a good tube and things seem better, but not up to standard yet.  I am awaiting some more tubes from Ebay to put in a new final and a driver, and some brand new 12BA6ís for the two I.F. stages.  I hope it will bring up the receive.  So we will see if I can improve the audio, which I now believe to be related to the neutralizing of the final.  Iíll wait for the new tubes and see. But hey, the radio's back from the dead.  Two down and one to go.  Ah, you say, it's back to the original parts rig now for restoration.  A daunting task at best, especially now after supplying parts for the two other radios.  But instead, along comes yet another CAM 88!   I wasnít even looking for another at this point, but it was a freebee, and I never turn down free radios. This one came from an old time CBíer who was downsizing.  So I acquired it from Firestarter, as part of the trickle down effect after he had picked up a truckload of the old rigs, and passed it onto me.  It is in decent electrical shape, but I havenít quite got passed fixing the physical damage.  Once again, the parts rig comes to the rescue.  This time donating the speaker and grille as well as the "S" meter.  The original rig is looking pretty hollow by now, a shell of its former self.

So this is the point I find myself at now. The first rig is empty, the second is now the best performer, and is now in the hands of a new owner who wants to get into classic radio with a little push by me. The Low Key 88, the third radio, is in operation with good receive, down to about .3uV, not as good audio transmit, but it came back from being way wacked out, and I am not done yet!  The fourth rig, is the newest (by serial number as well as to me) and the cleanest, so I have high expectations for that one.

Amazing how interest in one tube rig, has led to bringing 3 tube rigs from the brink of death and added another just because it looked cool but the same inside.

Thatís my tale of the three (or is it 4?) Cobras.

Ed note: The disease is spreading. The classic radio club is now 4 persons strong and growing.  Restoring old rigs can be rewarding, and it breaks up the usual monotony of the same old inane banter on the channel......

 

Back