Technics SL-1300 Power Supply Failure?

[brio50]

Hey guys,

I picked up a shot Technics SL-1300 turntable a couple months for a great price and hoped that it was fixable. It turns out, per the local stereo repair shop's investigation, that the power supply is dead (weird now that I think about it since when I plugged it in the light that's used to monitor RPM was on... I'll have to follow up with the repair store on that one).

Does anyone know where I can get a power supply for this little guy? Are there substitutes, either in the Technics line or different manufacture? Anyone have a friend with a broken one? Is it repairable??


Thanks for your help!

[brio50]

Please help!

[JaS]

The SL-1300 doesn't have a separate power supply, it has a switch, fuse, transformer, transistors, diodes etc that form the power section of the circuitry. If you know which component(s) have gone the part numbers are in the service manual.

http://www.vinylengine.com/library/tech ... 1300.shtml

Regards,
JaS

[brio50]

Jas,

I went through all of the manuals. First let me clarify a few things. I do not have an MK-II, the tag on the bottom of my units says "SL-1300M."

The service manual for my model is: http://www.vinylengine.com/ve_downloads ... 407418.pdf and especially important is this service supplement: http://www.vinylengine.com/ve_downloads ... ce_sup.pdf, which includes troubleshooting steps and component specific replacement suggestions for the symptom I'm experiencing, "Not Rotate (33,45 rpm)."

The people at the stereo shop said it's a power supply issue, couldn't get the part, and that is probably not worth fixing; they weren't very friendly at all. I disagree after reviewing this page of the aforementioned service supplement:



If I believe their assessment, then it appears I have a clear path as to which integrated components may be at fault for a power supply issue: TR1,TR2,ZD1,D1.2, or D3.4.

However, how should I go about doing this and what should I expect? I'm assuming the first, safest, and easiest thing to do is check continuity among components as the following picture shows I'm ready to do.



The thing I don't know is which components I should expect continuity and which I should not. For instance, when probing TR2 (transistor 2) at the bottom left of the circuit board in the above figure with my multimeter's "beep we have continuity function" only the bottom two of the three solder joints "beep." 1) How can I tell which components are good or bad!?



Also, if I have to check voltages, then that means I have to plug the unit in correct? 2) Could I ruin the TT if I had to plug it in the check a voltage with it disassembled? Any recommendations with troubleshooting are much appreciated!

Thanks

[blueworm]

Can you ruin the TT by measuring while it is disassembled. Yes. The worst you can do is to spin up the direct drive motor with the platter removed. The rest generally falls into standard electrical safety.

I would suggest measuring either side of C1 you should have ~ 40Vdc.
If that's good measure either side of C2 you should have ~17.5Vdc.

[brio50]

Can you ruin the TT by measuring while it is disassembled. Yes. The worst you can do is to spin up the direct drive motor with the platter removed. The rest generally falls into standard electrical safety.

I would suggest measuring either side of C1 you should have ~ 40Vdc.
If that's good measure either side of C2 you should have ~17.5Vdc.

Let me make sure I understand, I can do this while the table is plugged in, upside down with the platter removed... if I'm careful and don't spin the direct drive motor? Thanks, I just want to make sure I'm not doing anything wrong as I don't want to ruin anything else.

[blueworm]

Can you ruin the TT by measuring while it is disassembled. Yes. The worst you can do is to spin up the direct drive motor with the platter removed. The rest generally falls into standard electrical safety.

I would suggest measuring either side of C1 you should have ~ 40Vdc.
If that's good measure either side of C2 you should have ~17.5Vdc.

Let me make sure I understand, I can do this while the table is plugged in, upside down with the platter removed... if I'm careful and don't spin the direct drive motor? Thanks, I just want to make sure I'm not doing anything wrong as I don't want to ruin anything else.

If you are careful and dont press start.

[brio50]

First of all thanks for all of your help and for putting up with all these questions!!

Before I took it apart I plugged it in to test her out. The RPM light was off (is this called a cueing light?) then I switched it to start and the light came on, but of course no movement of the platter. Moving the switch back to stop did not turn the light off. Is there some sort of reset in the controls to ensure it won't spin up on me? I'm afraid that it's still set to start.

[brio50]

Anyone!?

[JaS]

It's pointless probing around checking for continuity in an electronic circuit. As the 1300 is relatively simple and there's a list of check points I would arrange the turntable in such a way that it doesn't matter if the motor spins, then go through and check each point. I'd also look for dry solder joints, bulging/venting capacitors or burnt resistors etc.

If the test shows that certain diodes and transistors may be at fault then personally I would take them out of the circuit and test/replace as necessary. If your meter has a transistor tester it helps. Diodes can be checked for continuity or with the diode setting on the meter, but you need to lift one leg from the board first. To be honest they are so cheap I'd replace them anyway as repeated heatings with an iron isn't good for them and it's easier to solder a new component than one with cut leads.

Regards,
JaS

[brio50]

Ok, per usual thanks again for your help. By the way, when you flip the switch to start it increments memo-repeat to 1. In order to turn the RPM light off memo needs to be on 0, then I think its essentially "off."

JaS, thanks for the suggestions... before I start taking components off I ran blueworm's test. I checked voltages with the platter on the turntable, upside down since I knew it wouldn't spin on me , in the STOP position and the START position for C1 and C2:

STOP VOLTAGES:
C1 @ 6.8V, C2@ 6.1V

START VOLTAGES:
C1 @ 32V, C2@ 17.5V

It appears that C1 isn't getting up to 40V, should this be the first thing replaced? Capacitor C1? When I order C1 i should also order all of the diodes and transistors too I guess? Mouser, Digikey? Any referrals?

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?

Thanks soooo much!

[brio50]

I removed the circuit board to see if there was any burnt ICs or broken leads, looks good, in case you guys want to take a look:





The guys that built this board are pretty smart, there's a special pin spacing on the plug for the speed selector that will only let you put it in one way; smart!

[blueworm]

Ok, per usual thanks again for your help. By the way, when you flip the switch to start it increments memo-repeat to 1. In order to turn the RPM light off memo needs to be on 0, then I think its essentially "off."

JaS, thanks for the suggestions... before I start taking components off I ran blueworm's test. I checked voltages with the platter on the turntable, upside down since I knew it wouldn't spin on me , in the STOP position and the START position for C1 and C2:

STOP VOLTAGES:
C1 @ 6.8V, C2@ 6.1V

START VOLTAGES:
C1 @ 32V, C2@ 17.5V

It appears that C1 isn't getting up to 40V, should this be the first thing replaced? Capacitor C1? When I order C1 i should also order all of the diodes and transistors too I guess? Mouser, Digikey? Any referrals?

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?

Thanks soooo much!

Dont know what to make of the value across C1 the schematic makes me beleive that there should be 40V dc. I would switch the Multimeter to V AC and check the AC component it should be very close to zero if a diode was bad you would have an AC value.

The value at c2 seems correct which is good but confusing since c1 is off.

I would'nt bother changing any caps just yet, but as Jas mentioned check all solder joints. The photographs seem to show that the PCB has had work on it before with some pretty shoddy solder joints in a few places.
Try reflowing the solder joints, to do this paint them all first with a q-tip dipped rosin flux then apply heat NO solder.

[blueworm]

I'm sorry I just realised you posted the service manuals troubleshooting guide for this gripe.
Please it would be more sensible to follow it.
BTW you already done the first step and the power supply is OK.
Move on to SW2 test either for resistance or short the contact with some wire and test.