Canadian Mk11 Power Supply Unit

[chris vickery]

Do we have any wireless gurus on board?
I have two PSUs that I am trying to troubleshoot.
One, doesn’t do anything when power is supplied.
The second unit, powers up on dynamo but not on vibrate. Any ideas where to start?
I’d also be in the market for a working and tested PSU.
Chris

[Mike K]

Hi Chris

Are these Canadian 19 set power units ?

This article may be helpful
https://www.cool386.com/vibservice/vibservice.html

With vibrators, the contact points become oxidised after a period of storage. You can try to jump-start the vibrator by briefly applying a higher voltage . The points tend to self clean once the vibration action starts.

Another possibility is that the power supplies may need external switching. Are these power supplies you are testing connected to a radio set ?

[chris vickery]

Hi Mike
Yes, I checked each one against a known operational set.
They are Canadian power supplies, I haven’t dug into them too much as I’m not an electronics guy. They are fresh from storage and dirty, , so it wouldn’t surprise me that they are bodged up at the moment. A local ham
indicated to me that these are usually robust but over time things like the capacitors tend to go bad.
I’m just surprised that I didn’t end up with an electrical fire to be honest…
One nice surprise, I have an American made MkII set that I decided to check and it fired right up. Not a bad purchase on that one afterall

[Bruce MacMillan]

first thing to do is very basic. Do a physical check, look for damaged parts or burnt smell. If you have a multimeter check for continuity on wiring including transformer and switches. Make sure voltage switch is set to correct voltage, 12v or 24v. BUT BE VERY CAREFUL when powering up as that big round capacitor on top can rapidly disassemble

The list here is from the 1st echelon. Keep us informed of progress.

[chris vickery]

Thanks Bruce
I’ll do some investigation. I did ensure that the 12v/24v switch is in the correct position prior to attempting to run.
Lucky, neither unit emits any burning smell, so that’s a bonus.
That large cap scares me.

[David Dunlop]

Hi Chris.

I agree with Bruce in that a very good visual inspection for broken/disconnected wires or missing components is the best starting point. Then check the lamp in the indicator socket to make sure it works. The 12V LT is common to both sides of that supply and the lamp is part of that to let you know the LT is at least present. Also check all three fuses. They do not always blow in spectacular fashion. If in doubt with any of them they are easily tested for open circuit status with a multimeter. Replace any failed ones with correct rated new ones.

The Vibrator side is not fussy about the amount of amperage it gets with its 12 V LT and will generally respond to a reasonable amount of Amperage. If it does not respond at all there is a good possibility one of the electrolytic capacitors in the circuit is no longer functioning. These can be reformed back to good working order if you can identify them and carefully remove them. NOT with wire cutters but by desoldering them.

The Dynamotor needs Amperage to spin and if your 12 Volt source cannot deliver what is needed the Dynamotor will just sit there. If your amperage is sufficient to spin the Dynamotor, but it will not, its prolonged sitting may have produced enough surface oxides for the shaft to be sticking in dried out bearings. If you can access the Commutator with your fingers enough to turn it a bit by hand to break the oxides, then it might start spinning again when powered up, but it will need some TLC to keep it that way.

One caution as it has been a while since I have done this. IIRC, these suckers spin in only one direction which is often indicated on the ends of the Dynamotor with little curves arrows either painted , caste or stamped on the housing. Turn in that direction only.


David