Problem with SL-1700MK2's patchcords...

jt1stcav

Up and Coming Bottlehead
Not quite sure where the problem lies...

I was playing my Technics SL-1700MK2 yesterday when I noticed my left channel suddenly lost volume, not totally, but greatly reduced from the right channel.

I flipped tubes on my amp and preamp from left to right; that didn't do anything (my pre is a linestage with no balance control). I removed the headshell from the tonearm to look at the leads and they're all making contact. I wiggled the 'table's hardwired patchcords connected to my Music Hall mmf-phono pack MM/MC phono preamp, and suddenly the left channel's volume came back and equally matched the right...for about a minute, then the left channel faded out again. I wiggled the patchcords again...this time a 60 cycle hum was heard (the ground remained connected)...I'd wiggle them some more and the 60Hz hum disappeared and the left channel regained its volume with the right, but only temporarily.

I'm not sure where the problem lies...with the Music Hall's internals or its RCA jacks the turntable's connected to, or the cheap Technics patchcords that are hardwired to the 'table itself. Any ideas?

The SL-1700MK2 is my dad's he bought new in '79. It sat dormant for several years and then my kid bro resurrected it for a year. After buying a Music Hall mmf-5 for himself, I latched onto the Technics (to replace a Denon DP-62L I was forced to sell :tears: ), and it's been working flawlessly for a year now, up until yesterday.

I tend to think the original patchcords are at fault here...can they be replaced with high-end interconnects? Is it even possible to do? I'm no solder slinger, so DIY for me is out of the question. Has anyone else ever replaced the Technics patchcords with a PCB with gold plated RCA jacks so user-changable interconnects (and a ground wire) can be used instead?

Any thoughts by the knowledgeable members here would be greatly appreciated...Thanks in advance! :thmbsp:
 
The cables are a very common failure item, the skinny CD4 lo cap wire didn't hold up. Changing it can be a DIY, but you might wear out your screwdriver taking the bottom off. You will need to solder in the replacements.
 
Hmm, funny somone should start a thread like this now...

I just bought a Technics SL-1411 (grey 1401) with a non working left channel. Been fiddling around with it today and using the multimeter. Now I've narrowed the problem down to what seems to be a shorted interconnect for the left channel.

The cabling from the tonearm comes to a small "pcb" where there's a 5-pole connector (L, LE, R, RE and ground) which is then connected to the cords going out of the table. The cabling in the arm itself seems to be fine but the cabling going out of the table seems to have shorted and therefore the channel is almost completely dead.

I have some more investigating to do but this is as far as I've gotten right now.
 
Wow, I'm glad I'm not losing my mind, that this is a problem with older Technics turntables that others have also experienced.

Thanks everyone for your responses thus far.

I suppose maybe a pair of decent interconnects could have one end stripped off to be soldered to the existing PCB. Can the existing ground still be retained, or would that have to be replaced as well?
 
Just a note...I've been PM'd by forum member jblmar of Brooklyn that the Technics' patchcords could very well be the problem (as also noted by Nakdoc and ztenlund), and that he's done repairs like this for other forum members as well.

Once a diagnostics has been determined, he can recommend adding a PCB to the back of the chassis with RCA connectors/ground terminal soldered to the tonearm's wiring, and I can then use the interconnects of my choice between the 'table and my phono pre (plug 'n' play like a CD player, tuner, et al).

My only concern is shipping my vintage 'table via UPS/FedEx/USPS...we've all either read or experienced the horror stories on how our precious components have been handled through their journey... :eek:
 
I have replaced the cables on both my DP-62L and my Pioneer PL-1000 with higher quality cables. It's a simple operation but you will need to solder them. I consider changing the cheap RCA cables on turntables mandatory.
 
I was thinking of having my DP-62L's patchcords replaced until misfortune forced me to sell my beloved Denon. I can't recall who I contacted (it's been several years now), but this person also did the same thing to his DP-72L and sent me a few pics. I still have a few pairs of unused Cardas CrossLink interconnects that would do nicely for my current Technics. :yes:
 

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Jim,
I was thinking of mounting the RCA jack board on the inside. Would look alot better.

Ron
 
I agree, Ron...I wasn't sure whether it could be done, and if not I'd also settle on the PCB being on the outside. But if it can be concealed on the inside with just the RCA jacks exposed (along with the ground), then all the better!
 
I just soldered the cables directly to the pcb inside the TT, just like the original design.
On the other hand there wasn't much space for me to put in jacks, I actually had a problem at first with the cables (thicker than the originals) where they obstructed the suspension. After some persuasion it's now fine though.
 
I considered that option also, but I kinda like the idea of interconnect interchangability, especially if a pair of ICs crap out like the original patchcords...just toss 'em and connect another pair.

If by chance I had a soldered pair installed and they also bought the farm, then I'd have to replace those and solder on another pair. For a non-DIYer like me, the RCA connectors just make more sense is all. But I'm glad your new ICs work for you, and finally fit around the suspension.
 
It's better to have the option to replace cables by manualy rather than taking the table apart and soldering them in place. I'm a bit surprised that Technics would choose to do it that way on the 1700. That's a very good table.
If I owned the 1700, those cables would have been gone and replaced with the RCA jacks.
I did just that to a Pioneer PL12D II I have sitting in the closet. Makes for a much better and easier setup.

Ron
 
I can understand if there's little available space inside the chassis to mount the RCA jacks to the existing internal PCB (or for DIYers to snip off one end of a pair of interconnects and solder them like Technics has chosen to do), which is why I'd also consider the PCB/RCA jacks on the outside screwed to the back if this was the only option to have IC interchangability. At this point in the game, anything's better than the worthless patchcords I have now.

As soon as I can find a sturdy carton to ship my SL-1700MK2, this problem will be rectified...I miss not being able to listen to my LPs. :sigh:
 
I would surely swap the cables where they plug into the phono preamp to see if the "channel out" or "weak channel" problem follows a particular cable. The key word is "follows."

* * * * *

Technics cables indeed do have a high failure rate.

When checking with an ohmmeter, take special care NOT to run your ohmmeter current through the either coil inside the cartridge. This current can damage the cartridge.

* * * * *

You normally will need to buy a quality cable, cut off one pair of plugs, strip the coax, tin the shield and signal wires, and then solder the four connections to where the original cable attached. There really is no way around this step.

The most important factors are usually the possession of a decent soldering iron and a good pair of wire strippers.

Fred Longworth
StereoTech Classic Audio Repair
http://www.repairaudio.com
 
Stupid me; I failed to mention this on my first post (thanks Fred for reminding me). I have also tried reversing the left and right patchcords on the phono pre, and the weak channel "does" follow that particular cable...this time the right channel was nearly inaudible after about a minute or two of play.
 
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