Turned on my SL-1100 yesterday and it would only go about 100rpm - Paul Simon interesting in falsetto ...

Cleaned pots etc but no change.

Opening it up to get to the board and two diodes are shorted (showing flow in both directions) - others seem ok.

I am prepared to have a go at soldering new ones in but how do you read the value of diodes for ordering purposes? They are D9 (which seems to have a "5" on it) and D5 (which seems to have a "1" on it) - I will do the big cap 50V 470uF at the same time.

Here's a photo if that helps.

Also any other suggestions about what might need fixing welcome. Thank you.

Jan 17, 2023 15:12:13 GMT 12 paulsaints said:

Opening it up to get to the board and two diodes are shorted (showing flow in both directions) - others seem ok.

I am prepared to have a go at soldering new ones in but how do you read the value of diodes for ordering purposes?

You look at the service manual ...

www.vinylengine.com/library/technics/sl-1100.shtml  (free registration needed to download.)

They are 1S1555 diodes. A search on them shows that 1N4148 might be a reasonable substitute. (Audiokarma thread in results).

www.startpage.com/sp/search?query=diode+1S1555

Jaycar have packs of 5 1N4148 for $1.10.

www.jaycar.co.nz/1n4148-1n914-signal-diode-pk-5/p/ZR1100

Or, from Ebay, a pack of 10 1S1555 for ~ NZD 22.50 - www.ebay.com/itm/162367997929

Did you check D10, D11, D12 for shorts?

(You should be able to right click(Win) or Ctrl-click (mac) on the schematic and open it in a new browser tab, then click on it for a full size version you can download.)

[Edit: (Or just go straight to imgbox.com/OacW34D3 and click on that image to embiggen ;-)]

Cheers!

PS: Actually I know I have a stash of little glass pink diodes like them somewhere, left to me years ago by a friend going overseas... not sure which box they are in, or what they are.

I'll have a look, but hope the above helps! I suppose you could try the Jaycar ones for a quick fix, see if that works, and order the Ebay ones as well if you want to keep it original.

Hi RdM - Thanks, that's very helpful - I have that schematic, but can't see where you saw that D9 and D5 were 1S1555 - how did you find that info? D10, D11, D12 all fine.

Jan 17, 2023 17:16:39 GMT 12 paulsaints said:

Hi RdM - Thanks, that's very helpful - I have that schematic, but can't see where you saw that D9 and D5 were 1S1555 - how did you find that info? D10, D11, D12 all fine.

It's OK - found it at the top - too used to reading resistors right at the marked component. Thanks. Happy to receive any you find

Not sure if this is helpful...

A few months back I had a similar issue with my SL-1210 MK2, it would sometimes spin up to maximum RPM!

Seems like a fairly common problem, I can't remember the exact details but a few of the ICs or Transistors are known to go bad. I got lucky and fixed it by following some advice online, I reflowed the solder (and added a little bit) on a bunch of the components in the speed control circuitry. Might be worth giving this a go...

www.jeremyyoungdesign.com

Thanks, Jerm - my "100rpm" was just a guess - probably was simply max rpm.

I feel competent to solder this board - traces are nicely spaced and components are accessible - but its the "diagnosis" that's problematic.

The motor is supposedly the same as the original SP-10 Mk1, so some things may be in common with later SL versions.

In the end I got a full set of replacement components from eBay. They have kits for various Technics TT's so I'll post the link here in case others have a similar problem (although freight is slow with tracking saying delivery 8 March!).

www.ebay.com/itm/125469141415

He did say that if its going flat out it may be the chip, but I'll do the component kit first and then see.

But I wasn't sure where the chip was because I'll certainly try re-flowing that if you can help me find it on the board - what am I looking for??

I think this was it...



Watch to the end where he shows the transistor reflow.

I think for mine the transistor didn't actually fix the issue but when I went back and reflowed the big IC it worked.

Basically it sounds like these TTs are getting to the age where the solder joints are starting to fail. If you go through and reflow everything you might get lucky.

www.jeremyyoungdesign.com

Thanks, Jerm - good YouTube link.

Interestingly the SL-1100 doesn't have any big ic's at all - see photo - but plenty of transistors. I'll certainly check through those while I wait for the kit to arrive. The guy in the video certainly had soldering skills - looks like he uses a heated solder sucker!

Not long after I got my secondhand SP10 it also spun up at max. speed.

In my case it was a failed field generator coil.

The repair is documented here

www.gennlab.com/technics_sp10mk2.html

Love the Sl-1100 but the PCB issues and difficulty diagnosing makes the old Lenco L75 look very simple and easy ... and, wow, there's lots more electronics in those  SP-10MK2's.

Yes, good thing there are people around who can still fix them.

Just something to note. Have you tested the diodes out of circuit. Also, Matsushita caps are notorious for leaking and being overall unreliable. Not a bad idea to change them, while you're inside it.

Electronics Technician - Pitch & Pixel

I haven't tested the diodes out of circuit but I presumed that if they are passing current both ways while in situ they are shorted - could that change back to "one-way" if taken out of circuit?? Just learning as I go ... Certainly all caps going to be changed. What I find difficult is the diagnosing. If a component is "wrong" then you have to ask why? - did something else fail and cause it to fail, and, going the other way, if a component fails, what other damage does that cause to downstream components. So I figure I'll end up replacing most components including some transistors. If anyone has experience on "diagnosing" feel free to enter coaching mode ...

Best to remove one end of the diodes to test them. The circuit can still partly function in both DC directions with a current of 1mA from the diode check function of a multimeter, making in-circuit testing of diodes and other parts, such as transistors, erroneous.
Components fail for a variety of reasons. Resistors absorb moisture over time and can change the resistance, even resulting in outright failure from localised heating of an eroded resistance element. The circuit board itself also absorbs moisture. Capacitors, especially electrolytics, dry out over time and lose capacitance. Plastic film caps are usually very reliable but can crack with temperature. Oil-filled caps suffer from increased leakage over time. If they’re in a critical part of circuit, it can cause it to malfunction and make other parts fail as a consequence.
But these are all gradual processes. Sudden failures are usually the result of power spikes, or if a component finally wears enough that it either short-circuits or goes open circuit, with consequences for the rest of the circuit. Transistors and ICs have tiny wires connecting the external pins to the silicon chip. They can be oxidised over time and eventually lose contact, causing intermittent operation. Gold plated lead-out wires usually fare the best over time. Freeze-spray can help to isolate which part is having a problem by rapidly changing the temperature of the part in operation, causing it to change dimension slightly and exaggerate the misconnection.
Yamaha transistors were notorious for this. One of their preamps I worked on started with intermittent noise and eventually, over years, failed in one channel. I ended up replacing all the transistors in both channels (for consistent sonics).
Also solder joints can crack over time from heating and cooling of components, usually power transistors or resistors that are normally relatively warm in operation. This process can also occur inside the component. The internal connection breaks from metal fatigue from being heated and cooled so many times.

AMR-iFi R&D

Thanks, Colin - lots of experience there! So it looks like I'll end up doing a replacement of most of the components when they arrive, but is there any "hierarchy" of re-soldering joints that you would suggest I get onto while I wait for the "kit" to arrive, or is it really just a guess.

ok - bought full recap / new transistor set from eBay - very good guy to work with. Did as suggested and went bit by bit - but after a single replacement of the big 470μF 50v capacitor all was back to normal. So, good news, SL-1100 all back to stable speed - bad news is I now have an $80 repair kit I no longer need (sans 1 470μF cap). Maybe I'll get brave and swap out the rest some day down the track. My soldering skills very modest. I should have guessed the main cap because, for a while, it was slow to move from switch-on to ready light. Here is a pic of the old cap as measured - not much there, but tell me if I am measuring it correctly - seems totally dead. And a pic of Paul Simon having re-covered his voice ...

Good you found it. 
Looks like you’re on resistance measurement, which would show open circuit with a cap. Press the mode button to make the display show uF. Some meters can’t measure large capacitances over 200uF. You might also want to check the maximum capacitance the meter can measure. Also, the ESR (equivalent series resistance) should be measured when suspecting an electrolytic cap. But you need a meter that measures ESR for that. Failing that, just replace the cap, as you’ve done.
I’d replace the other parts too if you can! If the cap above measures fine, and that’s all you replaced, the intermittent issue may still be there and resurface later.

AMR-iFi R&D

For checking capacitance, ESR, as well as inductance, resistance, diode, FET & transistor parameters, this kind of meter is worth having.
They used to be on TM, a friend bought me one a few years ago.

It's a bare board;- there are 3D print plans for top & bottom - I just printed the bottom at the library MakerSpace - also other enclosures.

They're all over Ebay - some almost seem too cheap! In no particular order, a few random links:

www.ebay.com/itm/404074701873
www.ebay.com/itm/385270793548
www.ebay.com/itm/394360911210
Similar, unbelievably cheap, the description tells what it can measure, the same as above.
www.ebay.com/itm/174447249780

A very handy meter.

Feb 15, 2023 20:11:15 GMT 12 colinf said:

Good you found it. 
Looks like you’re on resistance measurement, which would show open circuit with a cap. Press the mode button to make the display show uF. ... Also, the ESR (equivalent series resistance) should be measured when suspecting an electrolytic cap. But you need a meter that measures ESR for that. 

Thanks for that - measuring nF the meter is all over the place so not the right meter for this cap. The instructions don't give a capacitance list, but they have a range which show Resolution of .1uF at 100uF as the highest in the chart, so maybe 470uF is out of range for this tester.

nF is nanofarads, or 10 e-9 Farads. uF is 10 e-6 F. (e is exponent)
470uF is 470,000nF. The meter won’t read this on nF scale. Also the measurement of nF-size caps (small ones!) can be affected by touching the probes, as the skin is both resistive and capacitive.
The meter will be out of range for the 470uF cap if the most it can measure is 100uF. But if it does measure something and has auto-ranged itself to nF scale, you can be pretty sure the cap has failed, and the replacement was necessary.
If that’s the case, the other caps may have aged as well.

AMR-iFi R&D