DUAL CS 601 Turntable – Anti-Spark Capacitors

I picked this off ebay in Feb 2014, just ahead of the vinyl resurgence. The DUAL CS 601 Belt Drive Automatic Turntable has been my main player since it replaced a sub-par DENON DP-23F. I was not able to find a reasonably priced Direct Drive CS 701 in similarly good condition hence settled for the Belt Drive CS 601 instead. The 1974-1976 German-made 2-speed belt drive automatic record player quite frankly still looks great in current times. Although not as minimalistic per-se as the REGA P1 or P3 but with a floating sub-chassis in a wooden plinth, it is a beautiful looking piece of vintage gear. Even MUSICAL FIDELITY and PRO-JECT have in recent years released ‘Classic’ models that resembled vintage tables like the DUAL.

1970’s DUAL CS 601 with Original DUAL M20E Cartridge by Ortofon (0.5-1.2 g tracking force). Current day production Shure M97xE (0.75-1.5g tracking force) make for a good alternative cartridge on the ULW DUAL tonearm.

Each year, I go under the hood to either grease or lubricate the moving parts. I did at some point ordered 2x NOS M20E stylii and currently have one installed on the turntable. I had also replaced the neon strobe bulb soon after I acquired this player with a LED bulb in the same ‘deep orange’ color. It was a rather expensive upgrade but the original neon bulb was bad and the LED replacement seems to be holding up really well. There was however an issue I was trying to fix this time round.

Of late, turning on the turntable results in a loud ‘pop’ from my speakers as the CS 601 tonearm sets and lowers to start playing the first track. At the end of play, the automatic tonearm returns with a refresh dimple installed couple of years back. The same loud ‘pop’ however is there as the mechanism resets itself as strobe light goes off. Something was obviously off with the pops getting louder as weeks passed.

I did some searching online and discovered it was likely due to a bad anti-spark capacitor. These are not exactly the latest and most compliant by today’s standards keeping in mind this turntable was put together in the mid 70s. DUAL had installed a notorious RIFA 47nF capacitor that was prone to cracking on its outer shell. Once that happens, humidity finds its way into the capacitor. Leave it long enough and some folks have reported the RIFA capacitor exploding under the hood. Instead of waiting to hear a bang or boom and having the gutted RIFA splattering on everything under the hood in the process, I decided to investigate the capacitor locations, numbers and values with the intent of replacing all of them for good measure.

Below are a list of 3 commonly used capacitor combinations used on a variety of DUAL turntables and no different on the CS 601. I included part numbers of the Class X2 MKP replacements I sourced off sg.element14.com. Just be sure to obtain Class X2 compliant capacitors.

1x BFC233841103 – Vishay, 10nF, X2, MKP, 300v, 20%, RM15, 25mm
1x B32922C3473K000 – Epcos, 47nF, X2, MKP, 305v, 10%, RM15, 5mm
1x B32922C3683K000 – Epcos, 68nF, X2, MKP, 305v, 10%, RM15, 5mm

Low cost replacement capacitors from sg.element14.com; the 630v Vishay was of wrong dimensions. I had that cancelled and placed an order for correct dimension capacitor in a separate order.

MKP capacitors are Metalized Polypropylene Film (PP) and preferred by audiophiles especially in signal paths. MKT capacitors are Metalized Polystyrene Film (aka Mylar) are not preferred but are sometimes used in power stages. Given the install locations on the DUAL turntables, MKP/MKT should work just as well. I would avoid Paper Oil Film capacitors regardless of what some audiophiles say about sound quality. While I saw some exotic NOS Siemens floating around on ebay, these are usually vintage capacitors and likely ‘leaky’ given the age of these things.

The 10nF capacitor is located under the power supply plastic cover. While the existing cylindrical shape capacitor looked to be in good shape, I replaced that with a Vishay. Due to the install position, the ideal capacitor should be at least RM15-22.5 pitch (width) and have longer leads of 25mm. Anything less will present a challenge.

10nF 250v capacitor at power supply looks to be in good order and holding charge but was replaced too for good measure with a Vishay 10nF 305v X2 MKP.

The 47nF and 68nF capacitors are located next to each other on the PCB together with the strobe light. The bad RIFA capacitor is the 47nF while the one (yellow capacitor) next to it does look to be a working 68nF. One thing to note however is the service manual and the physical capacitor suggest a 68nF 400v replacement. I did not have a 400v so went ahead to replace with a 305v Epcos instead. Both capacitors should be ideally 15mm pitch (width) and with shorter leads of 5mm.

RIFA 47nF 250v capacitor with crack outer shell, 68nF 400v capacitor behind that. Both were replaced with Epcos (TDK) 305v X2 MKP capacitors. LED Strobe bulb can be seen further in the background on the same PCB.

Tools required for this fix include a soldering iron, copper solder wick, rosin flux and 60/40 soldering wire. If you have a set of helping hands, these will definitely come in handy. Depending on how good you are with an iron, it might help to have some spare capacitors lying around. I botched my working replacement of the ‘replacement’ 47nF by unwittingly applying too much prolong heat resulting in a leaky capacitor. Thankfully, I did order 2 of each from element14 so it did not present too much of an issue. At under $2.00 SGD for 2x each capacitor type, this fix was well under $10.00 SGD with the exception of some time required to remove and install the capacitors.

With the capacitors replaced, the turntable appears to be functioning as it was when I first acquired it. There is a slight ‘thud’ each time the play starts and after the tonearm returns to the resting position at the end of play. This has always been present from memory. I do not know if using a higher value capacitor in place of the 10nF value at the power supply will reduce or eliminate that entirely but perhaps an experiment for another time.

PermaPlug UK 3-pin Wall Plug replaces the original EU 2-pin wall plug.

This time round, I actually replaced the original EU 2-pin wall plug with a PermaPlug UK 3-pin wall plug. I did come very close to replacing the DUAL CS 601 for a newer in production DUAL CS 465 player in cherry wood veneer plinth last Christmas. The Technics SL-1500C on the other hand appears to be a modern day replacement to the Technics SL-1500MK2 without the row of LED buttons and actually looks similar to a Technics SL-1200.

It will be interesting to see a modern day incarnation of the SL-1600/1700/1800MK2 at some point. The Technics SL-1800 was my first turntable but utterly disliked having to leap off my chair each time the tonearm reaches end of play (manual turntable). I might have kept to a SL-1600 (full automatic) if I had that. For now, I am happy with the cheap fix and not having to worry about the loud ‘pop’ that might damage my speaker drivers in the long run. The DUAL CS 601 still looks and plays great after the fix. For the money, I find it hard to single out a new replacement turntable with all the functionality packed into this Panzer tank.

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