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Old 5th Oct 2018, 11:26 am   #1
m3vuv51
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Default Clansman PRC 320 DCCU

hi all,a few weeks ago my 14volt charger blew up while my 320 was on charge,i pulled it apart and there was a cap gone bang and blew a fuse,the cap looked like an aluminium electrolytic,it had spewed its guts all over,the strange thing was tho what was left of the can contained what looked like a slug of ferrite rod!,strange,i replaced the fuse took what was left of the device out and it seems to work ok now,anyone have a schematic for one of these,or know what it was blew up?,cheers paul m3vuv.
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Old 5th Oct 2018, 11:40 am   #2
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Default Re: prc 320 dccu

You might find a circuit on VMARS website.
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Old 5th Oct 2018, 11:48 am   #3
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Default Re: prc 320 dccu

no luck already looked there,may email collin guy g4ddi,he is quite an expert on the 320,should of asked him at the horncastle radio rally but forgot!
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Old 5th Oct 2018, 9:02 pm   #4
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Default Re: Clansman PRC 320 DCCU

I have a 14V DCCU on the bench at the moment Paul which didn't enjoy 28V at its input and now only has 15V at its output. If you need any photos let me know... I have been searching for a cct as well without any luck, so if you do manage to locate one I would certainly appreciate a copy.
Thanks.
Martin
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Old 6th Oct 2018, 4:45 am   #5
m3vuv51
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Default Re: Clansman PRC 320 DCCU

hi martin,i could do with a pic of the bottom board,also the value of the silver looking cap near the fuse on the bottom board if possible,if i do manage to find a schematic ill give you a toot,regards Paul m3vuv.
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Old 6th Oct 2018, 9:12 am   #6
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Default Re: Clansman PRC 320 DCCU

The silver caps by the fuse are marked as 80uF at 125V/85C. Probably tantalums so very expensive to replace like-for-like. If one has blown I would replace both C2 and C3 with a standard electrolytic. 125V may be a tad over-rated if the DCCU isn't being subject to potentially harsh power sources any more as it looks like they are part of the filtering on the 14V input, so you could drop the voltage rating a bit, and perhaps increase the capacitance in the electrolytic if necessary. Tants tend to have a 'real' capacitance close to that marked, electrolytics maybe not so...

Board 2 photo attached. Also board 4. Hope this helps.


My DCCU has an additional smaller board with some ICs on it. The board is a different colour material and the wire numbering is higher than the rest, so I'm presuming this is a later mod?


Cheers

Martin
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Old 6th Oct 2018, 7:07 pm   #7
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Default Re: Clansman PRC 320 DCCU

hi martin,your board is different to mine,on yours on the top of the board where the fuse is( next to the diode) thats where the exploded cap is on mine,ive chatted with colin guy from vmars(g4ddi) he hasnt a schematic for the 14volt one but sure he has one for the 24 volt version,ill let you know when i get one,regards Paul m3vuv 73.
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Old 6th Oct 2018, 7:23 pm   #8
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Default Re: Clansman PRC 320 DCCU

While rebuilding a dead DCCU is interesting as an exercise, I really wouldn't recommend using one to charge Clansman battery-packs these days.

The DCCU stuffs charge into the battery until the thermal-sensing-diodes in the battery detect a temperature-rise.

Basically, it waits until the battery's cooked, then turns-down the charge.

While this might have been 'OK' in the 1970s/1980s when a repeatedly-cooked battery [they'd generally survive 100 or so cycles of such abuse] could be replaced at Taxpayer-expense simply by quoting the relevant NSN to the quartermaster-sergeant, that's not the case these days. I'd be minded to gut the DCCU and replace the innards with a modern 'intelligent' charger that includes discharge/recharge-cycling and doesn't depend on cooking the battery to know when to turn-off.

[here, for my PRC320 I've re-equipped a 4AH battery-pack with 15AH of Li-ION goodness... which is lighter than the 4AH NiCd legacy cells...]
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Old 6th Oct 2018, 7:53 pm   #9
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Default Re: prc 320 dccu

Quote:
Originally Posted by HamishBoxer View Post
You might find a circuit on VMARS website.
Unlikely. If a schematic is available for the DCCU (and Clansman schematics are rare), then another problem prevents just shoving them out on some website - and that's copyright. I was the first person to officially obtain declassified copies (incidentally free of charge) of Clansman EMERs from the UK government, and while further copying and sharing wasn't prohibited for the usual "study purposes", random distribution or wholesale copying (e.g. via a website) was clearly prohibited, because of Crown copyright. As far as I recall that won't expire until 2040.

I instituted the free sharing of document soft copies (a policy that vmars still maintains I am pleased to see), but Clansman documents were a special case, all being relatively recent. My own policy is to freely share copies, but only with those individuals who will give me a written statement that they want the material "for personal study purposes". That means if anyone breaks their promises and starts selling copies, and I receive a complaint from the government (probably unlikely - they are all busy doing Brexit!), then I can't point to the steps I took to protect their material.

If a schematic for the DCCU exists, then it will be in one of the EMERs for the radios that used it. Probably the PRC-351 or PRC-320 manpacks.

Richard
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Old 6th Oct 2018, 10:37 pm   #10
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Default Re: Clansman PRC 320 DCCU

Mine has an additional smaller board fitted as well Paul, which looks like it could be a later mod? Tants tend to fail s/c, so if it is it might have taken another component with it? I once watched one go off like a mini-Roman Candle in a Racal receiver I was working on. Very impressive. It filled the room with acrid fumes but there was no doubt what else had now failed in that set!

Thanks Richard. I was thinking it might be amongst the battery charging EMER info so will check in the docs I already have for those sets. Most of which you organised!

G6T - all noted. This box has been under my bench for some time and I would like to find out what failed after its exposure to 28V and fix it back to original if possible. I'm sure your right about long-term use. Are there any particular units you can recommend?

Cheers

Martin
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Old 7th Oct 2018, 1:37 am   #11
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Default Re: Clansman PRC 320 DCCU

Well I've got mine working again, replaced the bulbs in it with LED's while it was apart, put a 100uF tantalum cap in it rated at 100V, so fingers crossed!

Cheers all M3VUV 73.
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Old 7th Oct 2018, 9:23 pm   #12
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Default Re: Clansman PRC 320 DCCU

Great stuff Paul. Suspect the fault on mine is on the reg board as the output volts from board 2 look OK. The reg could be common to the 14 and 28V versions as it’s doing the same job after the inverter section, which is different. So any possible help with ccts would be very gratefully received...
Martin
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Old 9th Oct 2018, 12:31 am   #13
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Default Re: Clansman PRC 320 DCCU

hi g6 tanuki,ive just filled one of my old batter cases with 7s x 5p 18650,11ah total,ive fitted a 7s bms,any idea if the clansman dccu will charge these?,i need 29.4 volts,my dccu outputs 30.1 volts,i thought i could stick a diode in series with the output of the dccu and use the .6v drop to get 29.4,any ideas,how do you charge yours?,regards Paul m3vuv.
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Old 11th Oct 2018, 2:19 pm   #14
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Default Re: Clansman PRC 320 DCCU

The DCCU isn't what you want to charge 18650s; like I mentioned the DCCU is designed to charge NiCd cells and does so by charging until a significant temperature-rise is measured by the sensing-diodes embedded in the battery-pack; the DCCU then shuts off.

This is not a healthy way to charge LiION or NiMH cells.

Have a look here: https://batteryuniversity.com/learn/..._ion_batteries for the right way to do it.

Note the comment that "Venting with flame is connected with elevated temperature"....

I charge mine using a modified ex-power-tool BMS.
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Old 11th Oct 2018, 6:11 pm   #15
m3vuv51
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Default Re: Clansman PRC 320 DCCU

wont the bms take care of it if i feed it with power?
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Old 11th Oct 2018, 6:40 pm   #16
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Default Re: Clansman PRC 320 DCCU

Yes - what voltage does the BMS expect, both as supply and battery-stack?

The BMS needs to be programmed to the number of batteries in the stack, and also may need to be downrated if the input voltage is excessive.
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Old 11th Oct 2018, 7:08 pm   #17
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Default Re: Clansman PRC 320 DCCU

well the bms is for a 7s battery pack,shouled charge to 20.4 volt untill it cuts off,so cant i use the dccu with a diode in series for the .6v drop as my dccu outputs 30 volts.?
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Old 11th Oct 2018, 7:33 pm   #18
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Default Re: Clansman PRC 320 DCCU

The DCCU and the BMS are likely to fight each-other, with less-than-predictable and unlikely-to-be-beneficial results: DCCU is expecting to be provided with the temperature-sensor-diode signal which you won't have.

Better to forget the DCCU and just use a normal regulated supply, then let the BMS do its thing.
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