[KCMike]

 Great to hear you got it playing again.   If you have time when you do the dial pointer light can you post some pictures of how you did it? I couldn't figure out how to get at that light on mine.

[Ron Ramirez]

Yes, I will. I'll also add the procedure to my SX-1500TD bulb replacement thread on AudioKarma.

I know it will probably involve pulling the entire front from the receiver to get to it...should be fun...NOT.

I think I will rebuild the power supply first. Yes, the set is up and running again but how much longer will 46 year old power supply electrolytics last?

[KCMike]

Thanks. I rebuilt the power supply also and some boards that probably did not need it. I do remember the PS board was easy to work on.

[Ron Ramirez]

Well,

Parts have been ordered to rebuild this Pioneer's power supply.

I also ordered some 2mm LEDs, one of which I will attempt to use to replace the lamp that illuminates the dial pointer.

We shall see...

[Ron Ramirez]

The parts arrived a couple days ago. Tomorrow, I shall begin to rebuild the Pioneer's power supply...and then proceed to replace the dial pointer bulb with an LED.

Those 2mm LEDs are really tiny! But not knowing how much space I will have in the pointer, I didn't want to get an LED that wouldn't fit.

[Ron Ramirez]

Wow! A busy day with the SX-1500TD.

First, I tackled the power supply board:

[Image: http://www.philcoradio.com/images/phorum..._00007.jpg]

Here's how it looked after removal from the receiver:

[Image: http://www.philcoradio.com/images/phorum..._00009.jpg]

and after all electrolytic capacitors, transistors, and diodes had been replaced:

[Image: http://www.philcoradio.com/images/phorum..._00011.jpg]

There is also a small board which controls the FM Stereo lamp that contains an electrolytic cap, a diode, and a transistor. This, too, was completely rebuilt.

[Ron Ramirez]

My next step was to restuff the large electrolytic capacitor can in the power supply circuit.

First, the original can, with the replacement Nichicon snap-in cap which will be installed inside the can:

[Image: http://www.philcoradio.com/images/phorum..._00013.jpg]

I cut the can open near the bottom, in a manner that the bottom flange will fit inside the remainder of the can once the "guts" have been removed:

[Image: http://www.philcoradio.com/images/phorum..._00014.jpg]

The new Nichicon is prepared for installation inside the old can:

[Image: http://www.philcoradio.com/images/phorum..._00015.jpg]

Holes were drilled in the base near the positive and negative terminals so the wire leads would fit through. Finally, the new Nichicon is put in place, the leads soldered to the original terminals, the top of the can attached to the bottom with J-B Kwik, and the clamp reattached.

[Image: http://www.philcoradio.com/images/phorum..._00016.jpg]

Following this, the unit was reattached to the chassis and the wires soldered back to the original positive and negative terminals.

[morzh]

Ron

Any reason to change ceramic caps? And small transistors and diodes are usually just fine too.
These are 70s, parts were much better. Electrolytics are the only ones I think that should go. Even resistors are usually fine.
Unless it is a piece of mind thing.....


I would recommend against restuffing large electrolytics.
First I don't think they present antique value and with essential parts explicitly replaced with modern the look is gone, nor it is that important. Why restuff Nichicon when it is a Japanese mfr available today with the same name and making better caps?
However the main reason is: this is solid state. They work with MUCH larger currents compared to tube-based.
This is where thermal becomes important.
By restuffing you thermally insulate the cap that might sore!y need that extra cooling by the ambient.

[Ron Ramirez]

Yup, Mike, piece of mind thing.

This afternoon and evening, I performed the hardest part of this job - replacement of the lamp which illuminates the dial pointer.

To do this, you have to remove the front panel, and then remove the plastic dial following the procedure shown here at AudioKarma.

And then the metal part which is behind the front panel needs to come off.

You have to be careful after removing this, as the dial string can easily come loose now since the tuning shaft is now floating unattached.

After taking the front of the receiver basically all apart, it looks like this:

[Image: http://www.philcoradio.com/images/phorum..._00017.jpg]

Now, by carefully lifting up the assembly which holds the dial lamps, the dial pointer can be carefully removed from the dial string. Here's how it looks:

[Image: http://www.philcoradio.com/images/phorum..._00018.jpg]

The dial lamp is held inside the assembly. You have to carefully un-bend two tabs and then the lamp itself is revealed.

[Image: http://www.philcoradio.com/images/phorum..._00019.jpg]

[Image: http://www.philcoradio.com/images/phorum..._00020.jpg]

As it turned out, the original incandescent lamp is much larger than a 2mm LED. In fact, a 5mm LED will easily fit here. I just happened to have a couple 5mm white LEDs on hand.

[Image: http://www.philcoradio.com/images/phorum..._00021.jpg]

I carefully went over an LED with sandpaper to make the bulb more opaque so that it would diffuse the light better.

Taking careful measurements with my DMM, I determined which wire connected to ground and which one didn't. The one which did not was connected to the LED's anode; the grounded lead to the LED's cathode.

I then reassembled the dial pointer and reattached it to the dial string.

[Image: http://www.philcoradio.com/images/phorum..._00022.jpg]

The anode lead is not connected directly to the 8 volt AC source - it connects through a silicon diode.

[Image: http://www.philcoradio.com/images/phorum..._00026.jpg]

The cathode lead does not go directly to chassis ground - it is shunted through a 390 ohm resistor.

[Image: http://www.philcoradio.com/images/phorum..._00027.jpg]

[Ron Ramirez]

Voila, it works:

[Image: http://www.philcoradio.com/images/phorum..._00023.jpg]

[Image: http://www.philcoradio.com/images/phorum..._00024.jpg]

[Image: http://www.philcoradio.com/images/phorum..._00025.jpg]

[Image: http://www.philcoradio.com/images/phorum..._00028.jpg]

It doesn't seem to be too bright, though. (And the package calls this a "high" brightness LED.) A quick voltage check indicated the LED was only getting 1.5 volts; it should be getting 3 volts. Guess I messed up on my calculations. Tomorrow, I will remeasure the voltage and if necessary, I will reduce the voltage dropping resistor to 300 or 270 ohms before buttoning this one up.

[Ron Ramirez]

I would recommend against  restuffing large electrolytics.
<snip>
By restuffing you thermally insulate the cap that might sore!y need that extra cooling by the ambient.

Acked, but the new Nichicon is much smaller than the original. I needed some way to hold it in the chassis. I've seen some pictures on AudioKarma where some guys put the newer caps in plastic pipe so the original clamps may still be used, but leaves the top and bottom exposed to the ambient air. Perhaps that will be a consideration for the next time?

[morzh]

In power supply you can simply use higher capacitance or even higher voltage cap, or both ad so find one larger size.

[BrendaAnnD]

This is the point at which I usually find out if I've bollixed things up good and installed the replacement cap with the wrong polarity.

[KCMike]

  Nice work Ron and big thanks for taking time to post the dial light replacement procedure it will really help.

[Ron Ramirez]

Thank you, Mike.

I remeasured the voltage applied to the LED and, yes, it was only 1.5 volts.

Long story short: I did some recalculations and found that I needed a 20 ohm dropping resistor. I didn't have a 20, but I found an old carbon comp 22 ohm that had drifted up to 32 ohms. So I used it in place of the 390.

The LED is now getting 2 volts and I'm satisfied with that.

Photos:

[Image: http://www.philcoradio.com/images/phorum..._00029.jpg]

[Image: http://www.philcoradio.com/images/phorum..._00030.jpg]

[Image: http://www.philcoradio.com/images/phorum..._00031.jpg]

The dial pointer goes out when the receiver is in PHONO 1, PHONO 2 or AUX mode (but the dial remains lit).

I'll post a circuit later showing the entire LED conversion.