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Old 8th Dec 2021, 4:58 pm   #1
Goldie99
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Default Dual CS505-2 - Tonearm/wiring change ?

I purchased a cheap, but good looking, Dual CS505-2 a while back, and have just got around to working on it:

Mechanically - it all seems to be working well. Speed checks out ok, speed changes ok, pitch control works, cueing all working fine, all seems good.

Electrically - a couple of RIFA caps on the PS board that'll need changing (one's cracked), a couple of poorly soldered replacement RCAs, and one channel that's dropping / dropped out...

The dodgy RCAs have already been cut off and replaced, and the RCA wiring continuity checked back to the internal connection pcb (all good). As far as I can tell - the channel drop out problem seems to be in the internal tonearm wiring, and specifically, I've now traced it back to the very thin, dark green, tonearm wire, which is the ground connection for one channel. The cartidge itself measures fine, with ca. 700R on each channel, so I'm fairly sure the issue is in the internal tonearm wiring.

It may be coincidental, but the connection pcb 'cover', shown in the service manual and various online videos, is missing entirely, and a couple of the solder joints on that pcb look a little 'suspect', so I do wonder if the previous owner traced the same issue... and decided a cheap sale was preferable ?!

Q. Has anyone changed a tonearm tube (and wiring) on a CS505-2 ? and if so, how ? From various forum threads on the net, it would appear to be possible, but probably not something you'd want to do for the fun of it... ? The part that I think needs replacing is available quite cheaply at Dualfred.de https://www.dualfred.de/Tonearm/Tone...277958-en.html, but I'm reluctant to order until I have a better idea of what I'd be getting into... the rest of the deck looks to be in good shape, so it would be a shame to part it out if I can avoid it.

Any thoughts / advice welcome. Thanks.
Alan
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Old 8th Dec 2021, 9:12 pm   #2
Electronpusher0
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

I have a quantity of spares from a 505-2 I scrapped, I may have the arm with wiring, I will take a look.

Peter
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Old 9th Dec 2021, 10:24 am   #3
Goldie99
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

Hi Peter - many thanks, that could indeed be a better / simpler option. Please let me know what you find, I'd obviously be happy to reimburse the cost + P&P etc.

In case anyone needs it, I did find a very detailed tear-down / assembly thread for the CS505-2 on one of the German forums, with a multitude of highly detailed photos. Beyond that, I've yet to find any instuctions for arm removal / replacement etc.; the SM shows expanded parts drawings, but no instructions as such.

https://www.dual-board.de/index.php?...vielen-teilen/

Alan
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Old 9th Dec 2021, 12:41 pm   #4
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

Before condemning the tonearm wiring (and to save the hassle) you should check the wiring interface plates between the cartridge and arm for tarnish and poor connections etc.The bottom one on the cartridge is easy to replace if necessary, but cleaning the contact points on the top tonearm one and the one on the cartridge may be all that is needed.
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Old 9th Dec 2021, 2:18 pm   #5
Goldie99
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

Quote:
Originally Posted by cheerfulcharlie View Post
Before condemning the tonearm wiring (and to save the hassle) you should check the wiring interface plates between the cartridge and arm for tarnish and poor connections etc.The bottom one on the cartridge is easy to replace if necessary, but cleaning the contact points on the top tonearm one and the one on the cartridge may be all that is needed.
I'd hoped it might be that simple as well, but unfortunately I don't think so. Mine has the 'screw-on' type headshell - so I've checked the cartridge channels with the headshell + cartridge removed from the arm, and with DMM mini-grabber leads on the cartridge terminals. Both channels are measuring just under 700R, so I'm comfortable the cartridge isn't the issue.

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For the arm wiring, I've been using a DMM between each of the 4 terminals at the end of the tonearm, and the corresponding terminal on the RCA connection pcb where the other ends of the tonearm wires are soldered. 3 of them all 'buzz' on a continuity test, while the 4th. gives anything from ca. 10R up to 4M+ (it's not completely 'open' ?), but gives no continuity buzz at all. The headshell and cartridge are obviously removed for those checks, and as I've already trimmed & resoldered the pcb end of the suspect wire, I'm fairly sure now that the wire is damaged somewhere along it's length.

I've since found that the faulty one of the five (4 cartridge + 1 arm ground) is actually routed slightly differently to the other four, between where it exits the tonearm and passes through to the RCA pcb, so it's possibly been 'examined' before (it's the opposite side of a screw).

I'm going to try to strip a little of the insulation from the suspect wire, as close to the tonearm exit as I can realistically get, just to try and localise any wire break or damage - if it's in the arm tube, or the internal terminals at the headshell end of the tube, no chance. If it's between the arm tube and the RCA pcb, and exposed enough, I could envisage possibly splicing a new section in...

Alan
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Old 10th Dec 2021, 11:32 am   #6
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

Hello Alan,
I have found the arm.
It is from 505-2 but has a fixed cartridge holder rather than the type that unscrews, also the actual cartridge holder that clips underneath is missing. See pictures.
You also mention that the cover is missing from your tone arm connection board. I also have that, again see picture.

If you want them how does £10 including postage sound?

Regards
Peter
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Old 10th Dec 2021, 12:10 pm   #7
Goldie99
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

Hi Peter - many thanks for checking - that's indeed quite a different arm & headshell arrangement to mine. I imagine the arms are quite possibly interchangeable, but with the differences, and the missing headshell parts, I'll pass for now if I may.

I did manage to localise the fault in my suspect tonearm wire somewhat more yesterday, and unfortunately it's somewhere in the arm tube or mount area, and completely inaccessible in terms of a repair, and certainly not without removing and dismantling the arm. On the plus side however, I spotted a complete, and identical, 505-2 tonearm on the auction site, which I've just now purchased, and which will hopefully be a 'drop in' replacement (it was eBay item 294615368681). The seller seems reliable, and has plenty of good feedback, so here's hoping...

Alan
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Old 10th Dec 2021, 3:27 pm   #8
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

Could you perhaps convert it to 4-wire working, perhaps with the ground and RH shield connections commoned at the headshell end rather than at the tagstrip under the deck? Not tried it myself, but I can't see why it wouldn't work.

Or would that cause hum issues?
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Old 10th Dec 2021, 5:06 pm   #9
Goldie99
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

Interesting idea, but unfortunately the later headshells only have 4 (accessible) connections on the headshell, and the corresponding 4 pins on the headshell end of the arm.

The 5th ground connection wire must be either connected internally within the tonearm tube, or near the back end of it, as all 5 wires are visible near the pivot point. It's also just grounding the arm to the chassis, there's no connection to the signal grounds anywhere I can see or measure; that wire just goes to the RCA connection tagstrip, where it grounds via the tagstrip mounting screw to the chassis.

Alan
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Old 18th Dec 2021, 5:25 pm   #10
Goldie99
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Default Re: Dual CS505-2 - Tonearm/wiring change ?

Just to put this one to bed - I've now completed the tonearm 'swap' for the used item I found on eBay (it was indeed identical). The swap was largely straightforward, as soon as I'd found the tonearm replacement instructions in the original CS505-1 service manual (courtesy of Alfred @ dualfred.de), and has now completely resolved the missing channel problem. The only minor misadventure was a miniature e-cllip / lock washer, which inevitably decided to 'ping' off, and make the usual bid for freedom... it succeeded, and has since had to be replaced (fortunately, Dual show the exact sizes in the SM).

The original issue was / is due to a break in one of the tonearm wires, probably at the completely inaccessible tonearm mounted terminals, at the headshell end of the arm. The Nylon (?) connection fitting is press fitted into the arm tube and 'crimped' in position, so, short of major surgery, is completely impossible to repair.

Finally, should anyone need any parts for a CS505-2 tonearm - I have the following parts available, free of charge (collection, or + P&P) for any forum member needing them. It's essentially a complete tonearm, but with the faulty tonearm tube/wiring, so the tube with integral wiring would need replacing. Spare tubes/wiring are available at dualfred.de if needed.

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Alan
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