MC-505 LED Replace

Forum for TR-606/808/909, TB-303, MC-202 and other boxes from 1970-1980's
Post Reply
lotsanobs
Posts: 2
Joined: 01:08, 2 January 2017

MC-505 LED Replace

Post by lotsanobs »

I will be replacing some dead tactile switches for my MC-505 pads.
On key pad 14, pad works but LED light isn't showing, so definitely a dead LED there.

Anyone know the spec for replacement LED's for the MC-505 pads ?
The Roland LED part # is: slr-56vct32 (for pads 1 - 16 & TAP)

Would like to replace original reds with new BLUE LED's.
Thanks.
User avatar
genesis92
Posts: 22
Joined: 11:01, 9 January 2017
Location: Near Paris
Contact:

Re: MC-505 LED Replace

Post by genesis92 »

they seems to be regular 5mm through hole leds so you can buy 5mm blue leds but the voltage drop of blue leds is higher than red, yellow and old green (570nm) leds.
sometimes that can cause problem to the electronic but if I have free time and find the service manual with schematic I can check this point.
http://www.digikey.com/product-detail/e ... ND/2337245
the specs of the original led is:
Color Red
Lens Color Red
Lens Transparency Clear
Millicandela Rating 25mcd
Lens Style/Size Round with Domed Top, 5.00mm
Voltage - Forward (Vf) (Typ) 2V
Current - Test 10mA
Viewing Angle 40°
Mounting Type Through Hole
Wavelength - Dominant 630nm

I've checked the schematic it's ok but beware the old leds have less light efficiency than the newest ones so I think you will have more ( 100 times! ) light output with new leds.
to give you an idea the original led in the TR-505 is 25mcd @ 40° @10mA. a blue newest one will be more 2000->5000mcd @ 40° @ 20mA!!!
the original led forward voltage is 2v and is drived by high and low side transistors with 47 ohms limiting resistor.
the DC current is near (5-(2.2v+0.6*2))/47 = 34mA but less because it's scanned
with a blue one you will get (5-(3+0.6*2))/47 = 17mA in DC but less by the scanning rate
if you are blinded by the new leds you will have to increase led limiting resistors value.
you must have some skill in electronics and double check anode/cothod orientation on the PCB
ZipSnipe
Posts: 52
Joined: 15:10, 21 January 2014

Re: MC-505 LED Replace

Post by ZipSnipe »

Good find and good info
Peter2020
Posts: 1
Joined: 11:23, 19 November 2020
Location: Bradford
Contact:

Re: MC-505 LED Replace

Post by Peter2020 »

ROHM SLR-56x 585 nm Yellow LED, SLR-56 Dome, Diffused Through Hole package
ROHM's lamp LED lineup covers various types including high-brightness/high-reliability LED lamps suitable outdoor displays.https://www.enrgtech.co.uk/product/leds/ET16782684/SLR-56YY3F
Circular φ5 LED lamp Applications: Coin Processing Machines Portable Data Terminal Digital Multimeter: Handy Type PLC (Programmable Logic Controller) Motor Control: Brushless DC AC Servo Network Attached Storage DVR/DVS Motor Control: Stepper Motor Motor Control: Brushed DC POS (Point Of Sales System) Electric Bike Smart Meter Embedded PC X-ray Inspection Machine for Security Surveillance Camera Intercom / Baby Monitor Surveillance Camera for Network Fingerprint Authentication Device Machine Vision Camera for Industrial GFCI(Ground Fault Circuit Interrupter) Digital Multimeter: Bench Type Display for EMS Solar Power Inverters
Post Reply