Many thanks! Very clarify the photos, the component can be see in their real shape. Unfortunately in this case there are differences between pl50 and px50. I can't find in the scheme the component. I don't know wich type of component is it, could be a diod but I'm not sure. I think the only way to get the part is extracting it from an other similar unit. I was located a site with incredible stock of legendary walkmans with a very affordable prices but I think is a fake or fraudulent site, be careful! www.designorigins.co.uk
You could do a diode check between the pins to see if they conduct about 0.6V in one direction and open circuit in the opposite direction. I had a look online for a schematic and couldn't find anything.
Oh and that website is definitely dodgy! Photos and descriptions look like they're taken from an auction site and most seem to be discounted to £33
ok i found this schematic of another aiwa hs-pl55 i think it is the same component .... they are 4 diodes connected on the buttons converge on an output .... our walkman have the mixed circuit between these schemes
Diodes Incorporated MMBD4448HCQW is a 5-pin surface mount quad diode array with common cathode. Not sure if it would be small enough (SOT-353).
Many thanks guys! Now I'm a bit confusing, I don't know if the component has 4 or 5 pins, this is the aspect of the pcb
At Silver965's pictures of the component, I can see two pins at the front side and one more at the back side, but the pic doesn't have the best perspective for what I need to see
It makes sense, base in the schematic, that the component has 5 pins, but now has only 4 pins, it could be the 5th pin dissappears when the heat broke the component
The other possibility is the component has 4 pins and there is a join t between two traces, in this case I think there would be these ones
So let's start again from the diagram .... the output of the broken piece (light blue) goes directly to the transistor (Yellow) .... from the hold button comes a wire (red) that connects to a 220k resistor (224 on the resistor) the output of the resistor goes on the base of the transistor and on another 220 k resistor that goes towards ground .... on my pl 50 and so .... Then a wire starts from the transitor that goes directly to the piece broken and must necessarily be one of the contacts (test if it continues)
Yes, it has continuity with the transistor, then the diode has 5 pins. I'm investing if the part suggested by Mattb1970 matching the available space, however it seems to be out of stock in the main sites. I'll continue searching, meanwhile another options.
I think I know the function of the diodes in this circuit. When the Remote switch [S6] is set to OFF, Q13 is turned on and this pulls the cathodes of the diodes [C] to GND, so the anodes will be at 1 diode voltage drop (typically 0.6V). When each button S7, S8, S9 and S10 are pressed points [D], [E], [F] and [G] will be pulled down to approx 0.6V. I believe each switch will have a different voltage level (set by potential dividers) and is measured by the comparator IC5 to determine the function. The diodes are there to block the signal in case you press more than one button at a time, as this would only confuse the comparator.
I'm not an expert, but it makes sense and explains very well the function of the diode and the insights of this part of the schematic!
Mattb1970, I found that on Ebay: https://www.ebay.com/itm/5PCS-MMBD4...066542?hash=item2ce5914f6e:g:m74AAOSw9Ydcano9 I think is the same diode as you mentioned, I'm going to measure and if it fits I'll make an order. Regards
Hope it fits. Will take some patience and steady hands to fit. I usually use leaded solder and a bit of flux to help the solder flow nicely. Good luck!
That's a good idea Silver965, maybe attach with thin wires or enamelled copper wire to protect the solder pads from lifting.
