Sl-7 Disassembly Problem

[Shoji]

Hello xactifan. With model SL-7 this problem may be come from ground line fault. Is not likely switch problem as early in model fabrication series change made to switch assembly to make switch very reliable. START plus the STOP share common ground line so make the check here first before all else. Make also the check of diode D314 plus diode D315 for the correct function. Also look to correct function of the transistor Q307 plus Q308.

[xactifan]

Hello Shoji, I'm afraid it's Game Over...SL-7 doesn't start anymore
No Power! too many disassembly? I don't know. I 've tested continuity
Q307 Q308 D314 et 315 : all OK. The ground wire looked well connected
to mainboard,but was cut to 8"(20 cm) about.
the running SL-7 to my sister is not connected with ground.
do you recognize the different series of SL-7? old or new?
mine:SL-7-EF No DAOJ06G333
other:SL-7-EF No DAOJ06G333 on the bottom board,
and No DA1J14k005 on the side!
they belonged to my father great fan of HiFi materials.
I've checked everything, I don't see,I was careful, but !
Thank you all!

[ATHERMOS]

Hi xactifan,


If everything is alright, then the game is positively not over, check the fuses on line, check the power supply output for proper values. Most discrete components can be sourced from electronics parts shop in case of defects. Starting from the power supply try to find out what is preventing the power up, if in these few days you have undone anything redo it, check again. Think and check logically,it is a good mental exercise and you would be rewarded.


Cheer up.

[xactifan]

hello Athermos,
I really appreciate your encouragement to continue,I was a little discouraged I must confess,but it is difficult to let go...SL-7 is bewitching!
As I said I know nothing about electronic,I must learn about testing this components so more detailled guidance would be welcome for what I do.
Is there a danger of manipulation?
Hopefully

Cheer up again

[ATHERMOS]

Hi there,

Step1. Put back everything into your SL7 , as far as practicable put it back to as it was.
2.The turntable should be unplugged from the mains while conducting the initial tests.
3. Check the power transformer primary side (the side connected to the mains supply via a fuse, power switch etc.) for continuity with a multimeter or a DIY continuity tester , hint, look for values similar to the running SL7 you have.
4.In a similar way test the secondary section of the power transformer.
5. Power up the turntable and check for the rectified and filtered DC output, compare it with the reference values obtained from the good SL7 in the idling condition.

Go on checking logically and compare the results with the other SL7 under similar conditions.

Cheer up, don't lose hope yet.

[xactifan]

Hello,
I used your precious procedure. I 've tested the two sides of power transformer:
one with two yellow wires:continuity ok
other with four wires: blu blk wht brn, I found continuity only between
blk and wht. Is it normal? Where do I mesure the values , at the same place?

hunter on the way...

[ATHERMOS]

Hi there,

You will have to compare the values you get from the other SL7 in this regard.

Go on to the next step, power it up and check for the rectified DC value and the value of the supply that is being fed to the motor PCB.

Check in particular for blown fuses and/or transistors in the power supply.Compare the voltages at various parts of the power supply and elsewhere with the values obtained from your other SL7 under similar conditions.

Above all, proceed logically and try to pinpoint the cause of its recent behaviour.


Cheers,

[Shoji]

Hello. Is sad to hear you are having this problem. Is necessary to make the check of power supply for correct level at the regulator IC1 plus also regulator IC2. Only make check if have competance for check or else ask technician to make such check. Regulator IC1 input to pin 1 18 Vdc with the output to pin 2 12Vdc. Regulator IC2 input to pin 1 12Vdc with the output to pin 2 5Vdc. Make also the double check for all correct with ground line in this circuit. Take much care when make this checks as easy for test probe to make slip for short circuit of component plus also take much care as live AC power in circuit.

[xactifan]

Hello,
I could not find anyone to do the thing ,so finally I have tested IC1 and IC2

IC1 pin 1 input: value fluctuates around 2-3V with peaks at 12,14,17V(rarely) who fall immediately
pin2 output: around 2V

IC2 pin 1 input and pin2 output around 2V

For IC1 and IC2 pin 3 and ground gives 0

I have not used the Multimeter so I verified by testing a battery that I got a fixed value
Was does that mean this is the fault , or may be an index ?

Cheers

attached photo which shows the condition of welds
[album]12186[/album]
[album]12187[/album]

[Shoji]

Hello xactifan. With low value and fluctuate on IC1 pin 1 is require to make the check of circuit before this. Make temporary remove from circuit of the capacitor C3 and make check of figure again. If still make problem make good for C3 connection and make temporary remove of C6 and make check of figure again. If still make problem look to correct function of recitifier D1 plus also the input from CN1. Again please to remember to take much care with such check. From photgraph you show is look like IC1 plus IC2 have been make with solder before. Is idea to clean residue of flux and make good this solder connection. Please only make this attempt if have the experience for makeing good solder connection. Is very quick to make plenty of damage to circuit board if not have solder experience

[xactifan]

Hello shoji, Testing again IC1 and IC2 I found lower values, I had to set the multimeter in the lowest range position 200m. I noticed about IC2 that pin1 was broken and replaced by a soldered wire. The mainboard seems to have been removed in the past,it is fixed with only one screw and the cover on the cushion of the tonearm's motor is missing.

Now I'm faced with my soldering inexperience and after your warning caution it would be wise not to remove the capacitor. I should learn and try before first, I think. Although I suppose there is a hierarchy in testing the components is it possible to test rectifier and the input from CN1 and how to measure values?

[ATHERMOS]

Hello xactifan,


Nice to to hear from you again. Your diagnosis clearly indicates that the rectified and filtered voltage going to the 3 terminal regulator ICs (78xx, or higher current variants)is below the value expected. There is a provision for running the turntable off 12 Volts DC. Please try it to confirm that the fault is in the power supply only.The IC with the broken pin can be easily procured from a nearby electronics parts stockist if the jointed pin (soldered) is problematic. But before soldering on the turntable PCB you must properly ground the iron, connect a length of insulated copper wire from the iron (nearer to its bakelite handle where it is least hot ) and ground the same physically (the actual grounding area must be wet to ensure good electrical conductivity). This is of utmost importance so as to prevent new damages (inadvertent) because the PCB has CMOS devices.

Check the rectifier diodes , the incoming low voltage AC.


Cheers and keep up your spirit.

[ATHERMOS]

IC1 pin 1 input: value fluctuates around 2-3V with peaks at 12,14,17V(rarely) who fall immediately
pin2 output: around 2V

Yes, there is a broken soldering joint waiting to be spotted. It is very difficult but try tapping every possible place on the PCB to see if the voltage rises to say 17 volts.

Cheers!

[xactifan]

Hello Athermos

I think you're right because the problem happened just after disassembly/reassembly the turntable,it was running just 10 mn before. . I've then noticed that spacer IC1 IC2 was hanging ,this has been a little twisted the pins. The soldered wire does not seem broken.Continuity of the rectifier is good,is it the right test?
Now I'll strum gently on the PCB hoping soon listen to music!
Always grateful for your insight to resolve the investigation