Wireless of the Week - week 45

[Bruce Parker (RIP)]

Radio sets that operated on batteries or vehicle electrical systems often were difficult to supply when used in more static situation such as indoors for training. The need for more reliable and less maintenance intensive power supplies for these applications was met with purpose built rectifiers that were able to supply wireless sets with their required voltages from units that plugged into regular wall sockets. Two such units are presented this week.

The Supply Unit Rectifier No.1 Canadian (photo 4) was designed for use with the Wireless set No.19. It was exactly the same size and mounted in the same way as a regular No.19 set supply unit, but differed in that it rectified an input of 50 to 60 cycle 110 volts to LT (12V), HT1 (265V) and HT2 (540V). The Rectifier No.1 sat in the 19 set carrier frame replacing the 12V/24V unit and operated in the same way other than it plugged into a wall socket instead using a 12 or 24V DC battery. The set could now be operated without the distraction of running a generator to constantly charge batteries. Designed in 1944, most Rectifiers No.1 found today were made by RCA in the 1950s and can be distinguished from battery powered No.1 and No.2 Power supplies by their round vent holes and plug in cord.

The Power Supply, Metallic, CPP-2 and its larger cousin the CPP-5 used a different tactic. The CPP-2 was a metallic rectifier that stepped down 110V AC to either 12V or 24VDC approximating the usual battery supply for wireless sets like the No.19. The wireless set’s power cord would be attached to the rectifier instead of to batteries, and the rectifier would then power the set’s regular supply unit which would provide LT and HT voltages to the radio in the usual way.

The CPP-2 shown here was made by Standard Radio Products in 1952. It is 11-3/8” tall by 18-3/4” wide by 10-1/4” deep and weighs 95 lbs. It comes in a vented metal case with its controls, terminal posts and fuse on the lower front accessed by a hinged metal cover. The 12V to 24V knife switch was internal and a later modification (as on this one) included installing another hinged door on the face to access it. Two lifting handles are inlet on the sides toward the bottom which require some care when using; the unit is top heavy and when lifting with these handles it wants to tip over and drop on your foot.

Most wireless collectors in Canada have owned one or both of these units at least once. If their experience was like mine, the No.1 Rectifier won’t work no matter what and you can’t kill a CPP-2.

[Patrick Johnson]

Hi Bruce,
Thanks for posting this information, it's great news to me since I recently bought a CPP-2 to power my 19 set. Any chance you could post the pages of the manual for all to enjoy?
Regards, Patrick

[Bruce Parker (RIP)]

Originally Posted by Patrick Johnson

Hi Bruce,
Thanks for posting this information, it's great news to me since I recently bought a CPP-2 to power my 19 set. Any chance you could post the pages of the manual for all to enjoy?
Regards, Patrick

Happy to. First batch:

[Bruce Parker (RIP)]

Second batch:

[Bob Carriere]

....for the important information that I can keep on my files.

Bob C

[David Dunlop]

Oh boy! Just before Christmas and now I have two more manuals to look for to compliment the equipment I have on hand.

A number of the 19-Set items have shown up out here over the years. All but one worked when found. Two others quit within a year or so never to be resurrected. They both developed a progressively louder hum before passing on. Three others are still alive and well, but see minimal use. Without detailed schematics or design info, the root cause of the failures is tricky to pin down but the 'failure' seems to result in the main transformer unit becoming electrically inert permanently. A recurring suspicion is they were very finely designed for the 110V AC world with minor cycle fluctuations. In the postwar upgrade to 120V, they were not happy and slowly packed it in. Who knows.

My CPP-2 is my main wireless set supply, covering 2 19-sets, C-42 and vehicular PRC 77 setup. I will post more on that later. It is Serial No. 1319, also dated 1952.

Thanks again for the heads up on these manuals, Bruce. If you ever run across any spares, keep me in mind.

David

[Bob Carriere]

....according to my PS computer power supply my input varies from 112v in the day time and up to 123v right now.....

I use a variac and can dial in my input at exactly 110 or 112v..... when using the CPP 2

We also have a lot of 2 or 3 second blips on our power almost weekly.

cheers

[Bruce MacMillan]

The rectifier #1 uses several 6X5 tubes which are notorious for developing heater to cathode shorts. This grounds the B+ lead and burns out a winding. The power transformer & chokes are all encapsulated in one unit. If one winding goes open then it becomes a small boatanchor.

I always use a variac to bring the power up to 110V and no more. This ensures I don't exceed the input voltage but also allows the filaments to completely warm up. A line voltage of 120+ volts is a 10% increase in output voltage. The 540V B+ to the xmtr is now close to 600V and may stress the rectifiers resulting in a failure.

My unit has been in use for about 10 years with no problem and it's much quieter that using a CPP2 to power the dynamotor. (also much lighter )

[Bob Carriere]

My unit has been in use for about 10 years with no problem and it's much quieter that(n) using a CPP2 to power the dynamotor. (also much lighter )

....that you have a one of a kind power supply that feeds directly the HT and LT to the rec/transmitter without using the dynamotor???

Cool....... was it homebuilt?

cheers

PS..... Duh ...read your email again..... you are using the rectifier #1 which is supplied by your variac...... never actually ever seen one.....

....so, I assume, the regular power supply unit fed by the CPP 2 has the same 6x5 (3) tubes and susceptible to also being fried if the tubes go wrong........ will need to test my tubes and spares to make sure they do not have a grid short .......

[Bruce MacMillan]

The power supply I'm using is the one (photo #4) that Bruce posted. It is a psu that supplies the necessary HT & LT to the set. It was made for the military, mine is dated from the 1950s.

The CPP2 only provides 12V or 24V to power the normal vibrator/dynamotor psu for the 19 set. You don't have to worry about the tubes/valves. The normal psu uses a 0Z4 rectifier.

The specs of the Rectifier#1 states that it works from 90V to 135V using inductors to regulate voltage but I'm not sure how well it works, as stated there are a lot of dead ones out there.

The photo shows the rectifier #1 in use here.

[David Dunlop]

After my initial reply to your post, I started wondering how on Earth I had ever rebuilt my CPP-2 after finding it in a completely disassembled state without references.

Did some digging in the basement Man Cave which eventually led me to a little used filing cabinet drawer. Some patient sifting through a number of ACCO Binders eventually revealed copies of both manuals. Happy Dance followed.

With regards to the issue of failed Rectifier Supply Units, a local amateur friend of mine, Don Trueman, has had first hand experience with this problem. Following are his observations and solution:

"Here's the poop on 6X5's...this is a rectifier tube with an indirectly heated cathode. Indirect cathodes have a breakdown voltage between the heater and the cathode, and can withstand the voltages differences on the negative half going cycle. The problem with the app in the 19 set supply is the bridge circuit used for the 540 volt side. The reverse voltages are very high and the cathode of V1c is well above ground potential, so super-imposing the plate voltage reversed (see PRV or PIV) on the tube floating already puts a huge stress on the heater cathode break-down voltage. V1c shorts and takes out V1d, the two that fail. Answer is to solid state the two tubes, ie. 1N4009 diodes in salvaged octal bases...you do get high voltage showing before the rest of the power supply warms up and the voltage is somewhat higher than 540 but seems to work ok...I made these changes a long time ago (2004!) to both my ac supplies and they've been fine.
The power supply is a regulated unit (noisy mechanically) and when keying up to transmit, it may throw a ripple in to the regulating circuit (windings) that kicks off a voltage spike that tips the cart…"

Hope this helps.

Cheers,


David

[Bruce MacMillan]

Originally Posted by David Dunlop

Answer is to solid state the two tubes, ie. 1N4009 diodes in salvaged octal bases...you do get high voltage showing before the rest of the power supply warms up and the voltage is somewhat higher than 540 but seems to work ok...I made these changes a long time ago (2004!) to both my ac supplies and they've been fine.
David

This is a good solution and many people add a dropping resistor in series with the diode to bring the voltage down to what it should be. This mod can also be done to equipment that uses selenium rectifiers. You'll need a gasmask when one of them fails.

I was surprised to find the problem with the 6X5 was known before the war. Zenith used them a lot and was well aware of the high failure rate. The same issue happened with it's little brother, the 6X4. It was used in the RS6 spy set.

The important thing is these mods are reversable with no changes to the original equipment.

[benamucke]

Had this No. 1 Rectifier 35 plus years (used 1or2 times a week) and never a problem. Also the 19 MKIII on eBay is my old set, and the HP Canadian on Kijiji I'm part owner.
Ben in Toronto

[benamucke]

Forgot the picture