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  #1  
Old 18-11-14, 01:15
kevin powles's Avatar
kevin powles kevin powles is offline
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Default 19 set PSU capacitor

Gents, A friend wants to change the capacitor in his PSU, I have a 30 micro farad electrolytic one here rated at 150v DC. Would this be suitable?, does anyone know the voltage rating of the original 32 micro farad capacitor.

Thanks Kevin.
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Old 18-11-14, 03:55
universalgrl universalgrl is offline
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Default 19 set psu capacitor

The voltage rating of the 32 mfd. cap is 450 W.V.
Part number is PC-67192C-191
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Old 18-11-14, 09:11
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Default Capacitor.

Thanks for that, does anyone know where we can get one, or a modern day equivalent ?.

Thanks kevin.
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Old 19-11-14, 13:52
Bruce MacMillan Bruce MacMillan is offline
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You can try Maplins or RS Components. RS lists a 33uF @ 450V.

Be prepared, the newer components have shrunk a lot since the war.
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Old 20-11-14, 21:59
Chris Suslowicz Chris Suslowicz is offline
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Quote:
Originally Posted by kevin powles View Post
Thanks for that, does anyone know where we can get one, or a modern day equivalent ?.

Thanks kevin.
Is the old one definitely faulty?

They can usually be re-formed (which will be a pass/fail test that avoids the risk of the thing exploding inside the supply unit).

I think I may have a spare which is externally scruffy but did test OK if you want to try a swap.

Your other problem may be the vertically mounted dual capacitor for the vibrator part of the supply...

Chris.
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Old 20-11-14, 22:08
Chris Suslowicz Chris Suslowicz is offline
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Default Canadian Supply Unit No.2 - a few (!) notes...

Date: Wed, 25 Jan 2012 00:03:13 +0100

Something I concocted a while ago. I never did get around to prettying it up with the warning signs. :-(

To: Wireless-Set-No19@yahoogroups.com
From: Chris Suslowicz <chris@suslowicz.org>
Subject: Some thoughts on the Canadian Supply Unit No.2 (Was: Re: [The WS No.19 Group] very basic operation probing)
Cc:
Bcc:
X-Attachments:

This is a fairly complicated unit, as it contains a vibrator as well as a dynamotor power supply, together with various switches and relays to permit power saving on receive/intercom or operation from a 24 volt supply as used in later AFVs. The options are:

a) 12 volt supply. The vibrator supply is capable of running any two of the WS19 components. This would normally be the 'A' set receiver and the intercom amplifier. (Though A & B receivers are also possible but less likely/useful in practice.) Switching everything on will overload the unit. On transmit, the rotary relay operates and the dynamotor will start. The rotary relay also switches the HT1 (275 volt) supply from the the vibrator to the dynamotor outputs.

b) 3-wire 12/24 volt supply. The vibrator supply is still usable in this situation but the dynamotor input is rearranged to take a 24 volt feed (by selecting the 24V position on the internal switch - this connects the twin LT sections (commutator + field coils) in series across the 24 volt supply.

c) 2-wire 24 volt supply. Only the dynamotor side can be used in this situation, and the 12 volt supply to the set (valve heaters and transmit/receive relays) is tapped off the dynamotor LT feed.

Using the vibrator supply gives a considerable reduction in power input and consequent extension of battery life.

All of these units are over 65 years old and should be treated with respect like the war veterans they are.

Effects of ageing.

Electrolytic capacitors will have degraded over time - the aluminium oxide that forms the insulating dielectric layer will have deteriorated and the capacitor may well act as a resistor instead. Applying power will cause a current to flow between the (uninsulated) plates and may break down the electrolyte into hydrogen and oxygen, raising the internal pressure until the casing bursts. Apart from the obvious damage to the equipment, this can be hazardous to the user.

The vibrator is also likely to be nonfunctional, due to the formation of an insulating layer of dirt (from breakdown of the internal sorbo rubber liner) on the contacts.

The grease on the dynamotor bearings may have dried out, and the commutator brushes may be stuck in their holders (usually caused by dust and damp).

Finally, the 0Z4A cold-cathode rectifier may well have died of old age/leakage.

Testing and repairing the unit.

Equipment required:

A multimeter capable of measuring up to 600 volts DC, up to 1 amp DC current, and a resistance range.

A 12 volt DC supply, capable of delivering up to 12 amps continuous and probably about 50 amps peak for short periods (while the dynamotor is spinning up). The latter requirement can be satisfied by connecting an old automotive battery in parallel with the supply - it doesn't have to be a good battery as long as it can hold up the supply voltage when called upon by the dynamotor.
(Note: a 20 Amp bench supply will cheerfully run the vibrator but will not cope with the dynamotor startup current. It _will_ run the dynamotor in the 24 volt configuration, but you cannot test the vibrator section of the supply unit on 24 volts.)

A 110 or 230 volt (to suit your domestic electricity supply) 25 watt lightbulb in holder, some insulated test clips and leads, and an isolating transformer (for safety).

The usual hand tools: screwdrivers (preferably hollow ground) and spanners that fit the nuts, etc.

A capacitor reformer or a variable voltage DC supply capable of 300 volts or thereabouts at low current with both output voltage and current metering (100 to 150 mA should be adequate).

Equipment that is "nice to have":

An insulation tester (500 volt Megger).

High-current DC ammeter. (30 amp capacity.)

--------------------------------------------------------

Important warnings (brought to you by the elves who drink Safe Tea):

(Skull & Crossbones) Some of the metal fittings, nuts, bolts, etc. will have been cadmium plated. This corrodes over time, and the dust is toxic. Also, the tropical varnish/treatment to inhibit mould growth in damp conditions may also contain toxic heavy metal compounds. Do not inhale (etc.) and wash hands after handling. Do not eat or drink while working on this equipment.

WARNING. CADMIUM.

This equipment contains a significant number of components that have been cadmium plated, typically connectors, fixings and brackets. Due to the age of the equipment there may be a possibility of cadmium corrosion in the form of cadmium salts (a white, corrosive powder as cadmium oxide). Care should be taken when opening any equipment for repair or adjustments. The handling, cleaning and disposal of contaminated equipment should be dealt with in accordance with AESP 02000-A-013 Chap 10.




(Radiation trefoil) The power switch has a luminous tip which is radioactive. It is protected by a glass bead - do not damage the bead. Both Uranium and Radium luminous paints were used during WW2.

RADIOACTIVE HAZARD
This equipment uses a component which may contain uranium or radium salts. In certain circumstances this can constitute a hazard to health. Before working on the equipment consult JSP 392 instructions for radiological protection, which gives general information, handling and disposal instructions.

(Lightning flash) High voltages at lethal currents exist inside the equipment when it is running, especially the dynamotor side of the supply. HT1 and HT2 are rated at around 31 watts but are fully capable of delivering much more than that for short periods - the output fuses are 250mA but they are fitted to protect the dynamotor windings - 500 volts at anything up to half an amp _will_ kill you if you get it across your chest.

A certain amount of respect (and due care) is required when dealing with this equipment.

-----------------------------------------------------------

Where to start? The obvious beginning is the electrolytic capacitors, followed by the vibrator portion of the supply unit, so....

1) remove the three fuses on the front panel. CAUTION: the fuseholders are very brittle and may already have cracked inside the panel. Be very gentle as replacing a fuseholder involves the complete dismantling of the supply unit - _everything_ has to come out as the front panel is assembled first then fitted to the chassis and all the other components added.

Note: the three fuses are used to protect the dynamotor secondary windings against short circuit damage (faulty wiring, defective capacitors, etc.) and the vibrator step-up transformer against overload damage from a "stuck" vibrator. HT1 and HT2 fuses are 250 mA (1/4 A) and the VIB fuse is 10A (and marked with a blue spot if you have an original). All are 1.1/4" (32mm) glass cartridge types. Do NOT fit fuses of a heavier current rating - if the correctly rated fuses blow there is a problem which _will_ damage the equipment if it continues to run. The dynamotor output windings are nominally rated at 31 watts, or about 125 mA for HT1, 60 mA for HT2.

2) remove the vibrator and the 0Z4A rectifier.

3) set the power switch to VIBR

4) Connect your capacitor reformer to pin 6 of the 12-way connector (+ve) and pin1 of either connector (or the chassis). If you don't have a spare 12-pt socket for this, you can remove the unit from its case and use insulated crocodile clip leads on the appropriate capacitors. Re-form the vibrator capacitor network (effectively 40 microfarad at 450 volt working) and ensure it can put up with 300 to 350 volts. If you don't have a reformer, use a variable voltage DC supply and a multimeter - start at around 30 volts and observe the current being drawn by the capacitor(s) - don't exceed around 20 mA (reduce the applied voltage if it approaches this) when it falls to a low value (say, around 7 to 10 mA), increase the voltage in about 20 volt steps until it is either happy with 300 volts applied (and low leakage current), or you can't get the leakage current to fall to a sensible value even after several hours - in which case you need to replace the capacitor. CARE! Allow the capacitor to discharge before altering any connections or touching anything - charged to 300 volts it packs quite a wallop and you do not want an electric shock off it.

5) Re-set the reformer/DC supply to a low value and set the power switch to the DYN position.

6) Repeat step (4), you are now reforming C32A, the Dynamotor HT1 smoothing capacitor.

7) Take your isolating transformer and connect a test lead to one output, and a second test lead in series with the 25 watt light bulb to the other output. With the vibrator upside down (pins uppermost) and the thick pair of pins furthest away from you, connect the right hand pair of pins (one thick, one thin) to your test leads. Apply power. The 25 watt lamp should light and may flicker continuously if the vibrator is running - a steady glow means the contacts are probably stuck closed (you can feel if it's running by touching the vibrator canister with an insulated screwdriver or wooden stick - NOT a lead pencil in case you contact a live pin or there's a leak to the case), if it is stuck try disconnecting the power, tapping the vibrator a few times, then reconnecting. Leave it running for a few minutes to clean the contacts up.

8) If you've got a current-limited variable low voltage supply, connect the vibrator (using the same pins as in (7)) to that and apply about 6 volts - if the vibrator hums and draws a couple of amps, it's probably good to use. (Don't use a vehicle battery, if it's truly stuck you may melt the vibrator coil or permanently weld the contacts closed - the coil is rated at 6 volts or less for a 12V series vibrator.)

9) Reinsert the vibrator and the 0Z4 rectifier into the supply unit, insert the 10 amp (blue spot or band) fuse into the VIBR fuseholder. Connect your multimeter between pin 6 (+ve lead) of the 12 way connector and chassis (-ve lead) and set it to the 300 volt DC range. Set the front panel power switch to the VIBR position. Connect your 12V supply to the 6-pin connector.
Switch on the 12V supply and hopefully you should get 250V to 300V output on your multimeter.
(It may take a few minutes to build up to full voltage as the 0Z4 warms up and the capacitor continues to re-form.)
Let it run for a few minutes to stabilise. If there's no output and the vibrator is running, suspect a dead 0Z4A - switch off and remove that, then connect a voltmeter between pin 3 or pin 5 of the valveholder and chassis - with the vibrator running you should have around 300 volts AC on pins 3 and 5 (or 600-ish between 3 and 5), mind your fingers! Also check that the resistor between the capacitor and the 0Z4 cathode has not failed (open circuit - replace and re-test if so) else fit a working valve or a solid state replacement (a pair of 1N4007 diodes on an octal plug should do it).

10) Dynamotor time! Switch everything off and make sure the HT1 has gone away. Working on one brush holder at a time, remove the cap (carefully), and check that the brush is free to move in the holder. Replace the cap carefully, do not damage the spring. Check that the armature is free to rotate under finger pressure - otherwise you may need to clean out and re-pack the bearings. (If this in necessary, do NOT mix Lithium based grease with the existing grease in the bearing, as the two will react to form a compound with minimal lubricating and possibly abrasive properties - if you can only get lithium grease, you will need to wash all the old grease out before re-packing the bearings.)

11) Connect your heavy-duty 12 volt supply to the input, switch on and put the front panel switch to the DYN position. The dynamotor should start and run smoothly.
(If it runs slowly, gets hot, or continues to draw a heavy current after startup, it probably has a short circuited armature and will have to be replaced - they're probably beyond the skills of an amateur repairer, and would cost a small fortune to have repaired professionally.)

Off load current consumption for the dynamotor is approximately 4 amps, if it's drawing 15 to 20 amps then the DC windings have probably failed and the unit may be beyond repair. The starting current for the dynamotor is in excess of 20 amps on a 12V supply - probably close to 30 amps, which most low voltage power supplies will have extreme difficulty in providing.

12) Switch off and insert a 250mA fuse into the other two fuseholders (HT1 and HT2). Connect your voltmeter (300 volt DC range) between chassis and pin 6 and switch back on - you should have 250 to 275 volts. Switch off again. Set the voltmeter to the 600 volt range and connect it between pins 4 (positive) and 7 (negative). Switch back on and you should see a reading of 490 to 540 volts.

13) switch back to the vibrator position and short pin 8 to chassis. The rotary relay should operate and the dynamotor will start and run.

You should now nave a fully functional Supply Unit No.2.

(I wrote this lot for the group on the 30/05/2011 and appear to have completely failed to post it!)

Further thoughts:

The Supply unit No.2 will run British or Canadian Mk.3 sets, or any specially modified Mk.II sets. The Mk.II set may have an "M" stencilled on the front panel (built that way at the factory), or the power input plug painted red (converted in the field). If you're not sure, check Pin 1 on the power connector, if it's connected to chassis it's an original set and needs Supply Unit No.1, but if there's an insulated wire leading to the pressel line (Tx relay), it's been converted and can use the No.2 or No.3 supply unit with the 12-pt to 6-pt "dogbone" lead.

I think that's enough to be going on with.

Chris.
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  #7  
Old 20-11-14, 23:03
eddy8men eddy8men is offline
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thanks kev for asking around on my behalf and thanks to all for your ideas especially chris for the very informative reply.
I have a 19 set in the Cromwell and was very keen to get the intercom working as we need comms to safely operate the tank, unfortunately my capacitor failed the first time it was powered up, no explosions but it got hot enough to start leaking brown fluid from the bottom of the case, I could have switched to vibrator but was advised not to by some guys who often use 19 sets as it was prone to failure. I have been trawling the net this evening and cam across the 19 set forum who are offering a solid state vibrator for £15 which I will order. I have also bought a 30uf capacitor from ebay which was rated at 450v A/C but could anyone confirm if this is ok with the dynamometer. ie does it produce AC or DC.
I look forward to hearing the replies as the radio is a really important bit of the tank which is often overlooked during restorations, plus in the short time that the capacitor worked we managed to get the world service on the headsets which was really cool, it sort of made the tank come alive in a strange kind of way.

cheers

rick
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Old 20-11-14, 23:12
eddy8men eddy8men is offline
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pic of the installation
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1945 Mk3 Dingo
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Old 20-11-14, 23:25
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kevin powles kevin powles is offline
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Default Stowage pics.

Rick, have you seen these stowage pics for the centaur before?.
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1941 Standard Mk1 stowage Carrier, Caunter camo.
1941 Standard Mk1 stowage Carrier, light stone.
10 cwt wartime mortar trailer.
1943 Mk2 Daimler Dingo.
1943 Willys MB.
1936 Vickers MG carrier No1 Mk1 CMM 985.
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Old 20-11-14, 23:27
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I can photo stat the book, it's in polish will require translation.
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3" Mortar Universal Carrier 1943 registered 06/06/2009.
1941 Standard Mk1 stowage Carrier, Caunter camo.
1941 Standard Mk1 stowage Carrier, light stone.
10 cwt wartime mortar trailer.
1943 Mk2 Daimler Dingo.
1943 Willys MB.
1936 Vickers MG carrier No1 Mk1 CMM 985.
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Old 21-11-14, 00:03
eddy8men eddy8men is offline
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lol I have spent many hours pouring over the pics and trying to find all the ces. I have the "Cromwell tank vehicle history and specification" book which is the Cromwell bible, if you don't have one then get it

rick
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Old 21-11-14, 00:51
Chris Suslowicz Chris Suslowicz is offline
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Quote:
Originally Posted by eddy8men View Post
...I have also bought a 30uf capacitor from ebay which was rated at 450v A/C but could anyone confirm if this is ok with the dynamometer. ie does it produce AC or DC...

cheers

rick
That will be a phase shift capacitor for an AC induction motor and will be perfectly OK for the job. The only things that matter are the capacitance value (and 30 is easily close enough to 32, especially as the electrolytic capacitor tolerance is something like -10/+50%) and the voltage rating.

The dynamotor produces DC with a certain amount of commutator ripple on top, and the capacitor is there to flatten that out and prevent a whine on the set audio.

Best,
Chris.
p.s: Nice tank! (If I didn't know better I'd have accused you of having pinched it off the production line.)
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Old 22-11-14, 20:51
eddy8men eddy8men is offline
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thanks chris, comms always seem to be a bit of a dark art to me, even when I was in the army I never really knew what I was doing !

the Cromwell is a real beauty to be sure, it's just a shame it nearly bankrupted me doing it
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