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eHam Forums => Boat Anchors => Topic started by: WA3JJT on August 10, 2012, 03:15:30 AM



Title: WRL CW-7 Novice transmitter
Post by: WA3JJT on August 10, 2012, 03:15:30 AM
Does anyone have a manual with schematic for a World Radio Labs CW-7 Novice Transmitter from the early 1950's? I have been able to find magazine ads, but no schematic. CQ Magazine had a review in October 1952, but no schematic!!
This was a little 2 tube transformerless number using a 70L7 and 50L6. I'm sure as the Heath AT-1 and others with full power supplies and cabinets started coming out, this little guy had a short life span.


Title: RE: WRL CW-7 Novice transmitter
Post by: KB1WSY on August 10, 2012, 04:47:09 AM
Hi,

Here it is: http://www.tinylist.org/CW7.html (http://www.tinylist.org/CW7.html).

Note that this is not the "original" factory-provided circuit diagram. It is a "reverse engineered" circuit diagram by someone who recently tried to find the original diagram, but failed.

73 de Martin, KB1WSY




Title: RE: WRL CW-7 Novice transmitter
Post by: KA5N on August 10, 2012, 08:14:09 AM
WOW!  A veritable DEATH TRAP!!   While many ALL  American Five radios had the chassis tied to one side of the AC line, but their plastic cases and knobs insulated the chassis from the user.  Other various bits of equipment used a clip-on connector to connect to an actual
ground.  If you manage to plug  the CW-7 in with the wrong polarity and touch  the chassis and some other grounded cevice at the same time.  Zap!! You get a shock that could be fatal.
If you simply must duplicate this rig, then use an isolation transformer.  Better yet set it on
a shelf and use for display only. 
Allen KA5N


Title: RE: WRL CW-7 Novice transmitter
Post by: AC5UP on August 10, 2012, 08:27:38 AM




......better yet, give it to N4NYY




 ::)   (I'm so ashamed of myself for saying that!)


Title: RE: WRL CW-7 Novice transmitter
Post by: G3RZP on August 10, 2012, 08:41:41 AM
A number of circuits I remember from those days sort of got around the death trap by only connecting to the live side of the mains and relying on the ground lead from the rig for the return current. Of course, if the ground got disconnected.......

These days, you'd immediately trip the GFCI with that trick.


Title: RE: WRL CW-7 Novice transmitter
Post by: WA3JJT on August 12, 2012, 04:23:11 AM
Oh yea, I know of the dangers! I'm sure we've all been ?bit" a few times over the years. That's probably why it didn't sell too well! The isolation transformer is definitely a good idea.  I've seen the "clone" effort, and that is probably very close to the original diagram. It's just curious that after being licensed since 1968 I haven't run into one of these rigs.
Thanks for all the input!
73!


Title: RE: WRL CW-7 Novice transmitter
Post by: N4NYY on August 12, 2012, 06:14:32 AM




......better yet, give it to N4NYY




 ::)   (I'm so ashamed of myself for saying that!)

No no no. I have an iso tranformer now. Medical grade!