Technics SL-1300 Power Supply Failure?

[JaS]

By the way, I'm still not clear on how to test diodes / transistors... I should check for continuity with the TT in the start position with the diodes, and I need a transistor tester function on my multimeter or else I'm SOL?

From a quick Google search it seems that basic electronic testing procedures are pretty well covered so I'll throw you a few random links - I haven't read through them so caveat actor!

http://www.kpsec.freeuk.com/components/tran.htm

http://www.kpsec.freeuk.com/components/diode.htm

http://www.kpsec.freeuk.com/components/capac.htm

Regards,
JaS

[brio50]

JaS,

Thank you for the links, I finally found some time to work on the TT. I performed tests on suspect transistors (TR) and diodes (D) with respect to the service manual guidelines. I found some interesting results, and some suspect parts seemed to have been worked on before or at least has a burnt sort of extra rosin (not factory) look on solder joints.

Here's how I tested the transistors: http://www.kpsec.freeuk.com/components/tran.htm, and I used the multimeter (MM) setting "2k with the diode symbol under it" with the assumption it's the diode tester.



The diodes D1/2 and D3/4 along with the zener diode ZD1 checkout.

Questions:
0) Do I have NPN or PNP transistors, as the link suggests most are NPN, but was that true for the SL-1300 back in the 70s?
1) What's the deal with TR10/11 and TR 12/13? They seem to have shared emitters (E) and their results look weird (see yellow highlighted boxes above).
2) Course of action? Purchase transistors and replace them? I definitely want to replace TR1 and TR2 because they look like they've been fooled with. Maybe I should just buy a bunch and start with those two, incrementally testing.
3) What's the best way to remove these components, solder sucker? OHHH and also, I did all of the testing with the components on the board (never de-soldered). Maybe this is why some of the tables above look weird?

Thanks so much!

-Brian

[brio50]

Any input guys?

Also, I can't find a place that carries TR1 (Panasonic 2SD389A-Q - http://doc.chipfind.ru/pdf/panasonic/2sd601.pdf ) or TR2 (Panasonic 2SA720-R - http://doc.chipfind.ru/pdf/panasonic/2sa07202sa720.pdf)... does anyone know where I can pick up these or something similar to these transistors?

Also interesting is that TR2 is PNP, not NPN. Maybe this is why I got "weird" results in the test above?

Thanks

[brio50]

So I think I just found the mfg. website which shows alternatives.

TR1: 2SD389A-Q Not on Panasonic Website Any ideas?

EDIT: Maybe this guy http://search.digikey.com/us/en/product ... -ND/603616 ?

TR2: 2SA720-R http://industrial.panasonic.com/www-cgi ... A0720+8+WW = DSA4002 http://www.semicon.panasonic.co.jp/ds4/DSA4002_AED.pdf

[brio50]

any links for suppliers guys? Thanks!

[markyk]

I replaced the 2SD389A-Q in my SL-1800 with NTE196 (there may have been a post somewhere here or in another turntable site). It worked fine. It didn't fix my issue and sure enough, the old transistor seemed to be OK after testing it out of the board. My local electronics store had it, as does Mouser. These folks: http://www.expediters.com/ seem to have the 2SA720-R but that's just by a look on their website - I have no experience with them.

[brio50]

Thanks for the input markyk... I'm not sure if it's worth my time to hunt down each component. I might be better off hunting down an SL-1300 that has a good circuit board.

[markyk]

Even if you find a replacement board, there's a good chance that the electrolytic capacitors have degraded and that could result in speed wobble. Just a warning. The SL-1300 service manual, unlike the other Technics service manuals I've seen, doesn't have a separate electronic component (transistors, diodes, resistors, capacitors) listing, making it more difficult to figure out what's in there. I took a quick look and it seems that the transistors are available if you're willing to do some hunting. If you wait for a replacement board, you may find one soon, or ... who know's when. If you go that route, you need to do some research because it's very likely that the same board was used in various models. In this case, you should start looking at the service manuals for the SL-1400 and SL-1500.

[markyk]

Previously, I had done just a quick skim over the previous responses since like a lot of the folks here, I just have experience with the model I have (SL-1800). I've spent more time reading it and before replacing the transistors or board, here's a few things you may want to try:

Have you cleaned the speed selector switch? If it's badly oxidized or dirty, that could explain your problem. Use deoxit or similar non-conductive, fast-drying product meant for electronics. If it's not easy to switch between 33, stop (if there is a stop position) and 45 and you use deoxit and there's no change in how easily it moves, you're not doing it correctly.

The 1300 is an automatic turntable and if there's something wrong in how it senses the record or tonearm position, that could explain the problem. There is a way to do manual playing by moving the tonearm over the record and lowering the tonearm (you need a record) - you might want to try that out.

It's possible you could have a problem with the motor. With the platter off, if you look inside from the top where the spindle is, there should be 3 metal sensors on the circular wall surrounding the spindle. Take a magnifying glass and look below these sensors. You should be able to see 4 tiny wires connected to from the (typically) brown base to the area behind the sensor in a diagonal orientation. You won't be able to see the termination point of these wires but if any of them are cut, you have a problem. This is the way it is with the SL-1800, I'm guessing most of the Technics DD turntables with this type of motor has the same elements.

Oh - it looks like you were testing the transistors while the turntable was off. Doing that while the transistor is in circuit is unreliable. I know on the SL-1800, testing a good 2SD389A-Q in circuit - it appears that the transistor is bad.

[brio50]

So the switch seems fine, it moves smoothly. I have yet to check what would happen if I manually moved the tonearm, as I don't want to put it back together yet.

I plugged her in, flipped the switch to the start position (no movement of course) and went through and diode tested the suspect transistors according to the service supplement. The resistances were definitely different, but not for the better. I simply did a C-E and E-C test on TR1, TR2, TR3, and TR14 as these should all be open circuits...

TR1
C to E: 0
E to C:-1

TR2
C to E:-1
E to C: 0

TR3
C to E: 0
E to C:-1

TR14
C to E:-1
E to C: 0

Very confused, these should all be 0! What baffles me is why the stereo shop said the power supply was out in the first place; I don't understand what they could've meant... those unhelpful assholes.

Anyway, so this is where I am:

1) hunt down the resistors and replace them or
2) build a new board from scratch ( i've always wanted to learn how to make PCBs, and i know sparkfun has some free layout software: http://www.sparkfun.com/tutorials/109 ). It doesn't seem like it would be worth trying to find an old SL-1300 and trying to salvage the component, as it would only be a temporary fix until something else burned out again, eg. speed wobble with bad caps...

I should probably to try fix it first, ie. 1), before jumping to 2) as it would be much more expensive, but the circuit doesn't seem too complex... maybe there's an electronics engineer out there who's looking for a fun project!?

[markyk]

If you want experience making a PCB vs. trying to fix your turntable, go and make a PCB. But its pretty much a waste of time and money if you're only trying to fix your turntable. PCB's in these Technics models are single-layer PCB's and unless you can see obvious physical damage, it's unlikely that the PCB board itself is the issue. In looking at your picture of the PCB, that doesn't seem to be the case. One thing I did see (on the picture of the bottom of your PCB) is that one lead of R7 seems not to be soldered. Somebody's selling a SFDP130-01 board from a SL-1500 where the platter spun (but had speed consistency issues) on eBay. Looking at his board, there's solder at one end of R7 where yours doesn't have it.

In the ve_technics_sl-1300_service_sd7407435.pdf file available here, the solution to many of the issues is "Replace printed base assembly". I'm not sure if this is why you think the PCB board itself is the problem or not but at that point, Technics felt that it was just easier to replace the whole board vs. trouble-shooting individual components. They weren't suggesting that the PCB board itself was the issue. Sorry if I'm make a bad assumption here.

As I mentioned earlier, in doing a quick search, it seemed that your transistors are readily available and if they're not that expensive, it wouldn't hurt to replace them. I'm not sure about your testing. Typically for NPN transistors, out of circuit, using the diode test feature, if you put the red on base, black on emitter, the voltage should be between .49v and .9v, reversing the leads would give 0v.

Besides checking the R7 solder, it wouldn't hurt to take a magnifying glass and carefully look over the bottom of the PCB for bad solder joints, given that it seems that the board was worked on before. I've made the same error of not properly soldering a component before. You can also look at the top for obvious damage.

[ginger321]

I read all that you've been going through.
I can't add anything of value to you but I thought I would tell you my brief story.
I have a Pioneer PL55DX 4-Chanell from the same era. Its been sitting all these years and I decided to set up the old gear.
After playing around 12 albums, it stopped turning. The same identical thing happened. The strobe light has a faint value of "on" but the turn table would not turn. Found a fuse blown, replaced it and the fuse blew again when I plugged it in. I didn't even have to push the lever to turn it on. Same thing, faint value of strobe light "on". Took it along with my original electrical schematics to a repair shop and they told me nothing they could do with it. The motor is gone and you can't get a replacement. I would love to know if you find the problem with yours because there's a good chance that the problem you have is the same as mine. I just don't know if the shop really knew what they were doing.

Phil Maier
Ocean City, Md.
240-876-3549

[brio50]

Hey guys. So sorry for the long delayed reply. I found a working SL-1300 in poor cosmetic condition but in pristine working order. Simply swapped the circuit boards and now I'm in business.

Original Unit:


Replacement Unit (Note different 220/110V transistor? and selector, but circuit boards were the same!)


I believe the problem lies in the transistor TR# of my old circuit board, as it looks like someone at the stereo repair shop failed miserably. Does anyone here on the forum want to take a shot at replacing the transistors for me? I'd be happy to pay for the parts! I just don't have a nice soldering setup right now...

Thanks,
Brian