Marantz PMD430 portable cassette recorder - No Audio

[Bargainhunter]

Thank you for your reply.
My schematic clearly shows pin 5 connected to the emitter of QU01.  It's the symbol with the arrow pointing away (NPN). Please double check and let me know if I'm wrong.
Also pin 5 is connected to ground.  It does not show that on the schematic but I have attached a photo of the pc board.  I drew a red line indicating a jumper wire from pin 5 to the case leg of switch S702.  One of the four mounting legs goes to ground.  Should this jumper be attached here?

[Bargainhunter]

Thank you for your help.
My schematic clearly shows the emitter of QU01 going to pin 5.  The symbol shows the arrow pointing away as in a NPN transistor and is going to pin 5.  Could you double check your schematic and let me know if I'm wrong.  Also I traced pin 5 on the circuit board and it is connected to ground by way of a jumper going to one of the mounting legs of switch S702.  I've attached a photo with a red line showing where the jumper is attached.  Wouldn't this cause the 3.3 volt rail to be 0 volts on all connections to QU01's emitter? 

[Bargainhunter]

Sorry, I forgot to attach the photo.

[wasedadoc]

I'm using the schematic posted by Smoky.  Se my trace in red.

I still think you problem is around QU01.  What is your response to my "MUST" statement above?

[wasedadoc]

On the board photo, JK03 contacts are numbered 1 to 7 from left to right.  Your red line is from pin 3, not 5.

[Bargainhunter]

Thank you, thank you thank you. wasedadoc.  I did not see that!  On the my schematic (attached) the pins are left to right 7 to 1 and on the photo of the pc board, the pins are left to right 1 to 7.  That totally confused me.  So the jumper wire is correct.  I agree with your "MUST" statement.  Take a look at the schematic I attached.  QU01's collector and emitter is reversed from smokey's schematic.  Is my service manual wrong?  Where can I download the full service manual like Smokey's?

I agree with you that the problem is with QU01.  I have no 3.3 volts going to the IC's  I wonder if QU01 was installed backward.  That would mean the Base on Emitter were reversed.  The two schematics have the Emitter and Collector reversed. [ Attachment Invalid Or Does Not Exist ]

[wasedadoc]

You have not attached your schematic.  If yours has emitter and collector swapped compared to Smoky's then yours is wrong.  That voltage circuit could not work if different from Smoky's schematic.

[Bargainhunter]

Attached is the my schematic. [ Attachment Invalid Or Does Not Exist ]

[wasedadoc]

Attached is the my schematic. (Attachment Link)

Nothing attached.

[Bargainhunter]

I don't know why my attachments are not working.
I will try again

[Bargainhunter]

Here is the full schematic.

[wasedadoc]

Not a case of collector and emitter swapped.  Slightly different design.  Your schematic has the 3.3 Volt point going to pin 5 and Smoky's has the 4.5 Volt supply going there.  You need to do a continuity check on your board to see which of these is the case.

1.  There was a design revision.  Your board corresponds to your schematic.

2.  There was a design revision.  Your board corresponds to Smoky's schematic.

3.  There was only one design. Your schematic is correct.

4.  There was only one design.  Smoky's schematic is correct.

[wasedadoc]

Long, long past my bedtime here.

[Bargainhunter]

Thank you for all your help.
I will check out the circuits to see which is correct.
 
I have to find out why the 3.3 volts is missing. 
I'll let you know what I find out in the next few days.

[Smoky]

Bargainhunter, If you open the battery compartment to your tape deck, the serial number should be printed on a piece of tape. Let us know what it is.

[wasedadoc]

A difference between the two schematics is that on Smoky's the four LEDs DX01, DX02, DX11, DX12 are powered by the 4.5 Volt side (collector) of QU01.  On the other schematic all those points are fed from the 3.3 Volt side (emitter) of QU01.  If that was a deliberate design change I would have expected the resistors in series with the LEDs to have been changed to maintain their brightness levels but they are not.

Another difference is RX01.  In Smoky's schematic that 220 ohm resistor is on pin 4 of WX01.  In the other schematic it is on pin 5 and in series with all the LEDs.  That would mean that the brightness of each LED would depend on what other LEDs are on.  That doesn't look right.

I think Smoky's schematic is correct and the other one is not a different design version but just has drawing errors.

But whichever that doesn't address the issue of QU01 emitter not being anywhere near 3.3 Volts.

[Bargainhunter]

Thank you for all your help.  I ordered some 2SD1020 transistors.  When I receive them I will set up a breadboard and duplicate the circuit with QU01, DU01 zener, CU01 1000uf 6.3v and RU01 100 ohm resistor.  If I apply 4.5 volts to the collector, should I get 3.3 volts on the emitter or would I have to apply a load from the emitter to ground to turn on the transistor?

Smokey:  The serial number is 69U270242.  I hope this helps. 
Thank you.

[wasedadoc]

The transistor is not used as a switch.  It is used as an emitter follower, essentially providing the same voltage (less the 0.6 Volts Vbe drop) as the zener but with greater current capability.

There is no need to duplicate on a breadboard.  That circuit is absolutely standard and well understood.  Duplicating it will merely confirm that it works.  Instead do this.

1.  Put the QU01 that you have back in the board except its emitter leg.  Emitter not connected to anything.

2.  Power up.

3.  Measure and note down the voltage at its collector.

4.  Measure and note down the voltage at its base.

5.  Measure and note down the voltage at its emitter.

6.  If the emitter voltage is zero or lower than (base voltage - 0.6) then QU01 is faulty.  Replace with another NPN or SD1020 if available.  Go back to step 1.

7.  If you are at this step the emitter is somewhere between 2 and 4 Volts.

8.  Power down.

9.  Leave the emitter connected to only the positive lead of the meter.

10.  Switch the multimeter to measure current.  If not an autoranging meter select 200 mA range.

11.  Connect the negative lead of the meter to the board where the emitter would normally be connected.

12.  Power up and operate playback.

13.  Measure and note down the current.

14.  Power off.

15. Disconnect meter and switch it back to measuring voltage.  Switch it off. 

16.  Post back here with all the noted down measurements and whether you had to replace the transistor to get to step 7 and whether audio was heard at step 12.

[Bargainhunter]

Thank you wasedadoc.  I really appreciate your help.

I did try lifting the emitter of QU01 and got 0 volts.  I removed the 2SD1020 and tacked a NTE293 in its place with the emitter lifted and also got 0 volts. Since the NTE 293 is not an exact replacement, I ordered some 2SD1020's off ebay.  I should have them in a few days.

I will try your recommendations and get back to you.

[wasedadoc]

Thank you wasedadoc.  I really appreciate your help.

I did try lifting the emitter of QU01 and got 0 volts.  I removed the 2SD1020 and tacked a NTE293 in its place with the emitter lifted and also got 0 volts. Since the NTE 293 is not an exact replacement, I ordered some 2SD1020's off ebay.  I should have them in a few days.

I will try your recommendations and get back to you.

For the emitter lifted voltage test you don't need an exact replacement.  Any NPN transistor in that test with a few volts on its base should give much more than 0 Volts.  Either your NTE293 is also faulty or you are doing something wrong with the way you are connecting/measuring.

[floobydust]

I agree, you're missing something and should not get 0V on the emitter, especially with a new transistor which indicates the transistor is not the problem.
You can measure the voltage across the zener/cap as around 3.9V for the base. If it's 0.7V with the emitter at 0V, then it will be getting hot...

[floobydust]

Now I'm getting somewhere.  I wired up the 2sd1020 transistor, the zener the 1000uf electrolytic and the 100 ohm resistor as in the diagram and BINGO,  I got 3.5 volts on the emitter.  I tried the NTE293 and also got 3.5 volts on the emitter.  So now I'm getting someplace.  I couldn't solder the 2sd1020 or the NTE293 on the circuit board with the emitter lifted because I had a couple traces starting to lift because of the soldering and de-soldering.  I also have the 1000uf electrolytic off the board because I didn't have a 6.3v electrolytic to solder on the board.  The original cap was bulging.  I used a 10v 1000uf to do the testing but it is too large to fit on the board.  I have some 6.3v caps on order and they should arrive tomorrow or Monday.  I will then test the transistors on the board with the emitter lifted and measure the voltage.  If I don't get 3.3 volts, then I know there is a problem with a connection on the circuit board or a component on the board.

Uh your post ended up in the wrong thread https://www.eevblog.com/forum/repair/need-help-sourcing-stainless-steel-crimp-on-ring-or-lug-terminals/msg4368601/#msg4368601

[Bargainhunter]

Now I'm getting somewhere.  I wired up the 2sd1020 transistor, the zener the 1000uf electrolytic and the 100 ohm resistor as in the diagram and BINGO,  I got 3.5 volts on the emitter.  I tried the NTE293 and also got 3.5 volts on the emitter.  So now I'm getting someplace.  I couldn't solder the 2sd1020 or the NTE293 on the circuit board with the emitter lifted because I had a couple traces starting to lift because of the soldering and de-soldering.  I also have the 1000uf electrolytic off the board because I didn't have a 6.3v electrolytic to solder on the board.  The original cap was bulging.  I used a 10v 1000uf to do the testing but it is too large to fit on the board.  I have some 6.3v caps on order and they should arrive tomorrow or Monday.  I will then test the transistors on the board with the emitter lifted and measure the voltage.  If I don't get 3.3 volts, then I know there is a problem with a connection on the circuit board or a component on the board.

[wasedadoc]

1. That bit of circuitry is not sensitive to component layout. To make troubleshooting and measuring easier you can solder some wires to the solder side of the board and have the transistor at the other ends. Even wires a few feet long would be OK.

2. The capacitor is not essential for circuit operation. Zeners are noisy devices and it is standard practice to put a capacitor across them. Yes you should have a capacitor there for the final repair but you can troubleshoot and get audio working without any capacitor there.

[Smoky]

Since I have two of these tape decks, I thought I would de-solder one or two of the 96 electrolytics buried in each of these things. So the very first one I checked was on the Meter/LED board (PX01).

Would you believe, it appears to have been installed backwards What are the odds of that!

Sure enough, the (-) side of the 10uf/16v capacitor (CX01) goes straight to pin 10 of the LC4011B (QX01).

All I can say is, thank goodness I have ten other projects I haven't finished from last year

Back in the box these go!