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hot tubes
Silver Member
Canada
162 Posts |
 Posted - 01/28/2010 : 05:05:54
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what resistor controls the LED brightness in a MIJ DS-1 ?
thanks . |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 01/28/2010 : 10:54:18
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Hi hot tubes
It's a combination of R35 = 3.9K (3900) ohms (Orange White Red 5%=Gold).
And D2 which is a 5.1V zener.
One end of R35 goes to PIN 15 of the PCB Front edge/wires.
And then off to the LED assembly PCB.
What where you intending to do?
Make it brighter? Dimmer?
Change LED's?
Good luck.
Regards Dr. Bob 
PS MIJ or MIT it's the same resistor/PCB reference designation.
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Edited by - Dr. Bob on 01/28/2010 10:55:00 |
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hot tubes
Silver Member
Canada
162 Posts |
Posted - 01/28/2010 : 14:34:01
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the LED does not work , there is 1.39vdc at the LED and i was going to install a super bright blue LED , sounds low to me ?
thanks DR BoB ! |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/28/2010 : 16:21:42
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| Are you using a PSA supply? A single old MIJ pedal on a PSA supply often has a dim/unworking LED. Try a battery? Or ACA supply? |
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hot tubes
Silver Member
Canada
162 Posts |
Posted - 01/28/2010 : 19:57:31
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| at this point i have only used a 9volt battery . |
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hot tubes
Silver Member
Canada
162 Posts |
Posted - 01/30/2010 : 18:19:54
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i removed R35 and jumpered it to see the voltage increase , and to my surprise there was no change in voltage . do i also nee to change
out D2 ? |
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hot tubes
Silver Member
Canada
162 Posts |
Posted - 02/01/2010 : 01:47:22
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bump !!
Any help would be great thanks ! |
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bassinyourface
Bronze Member
France
76 Posts |
Posted - 02/19/2010 : 18:14:18
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Funny because the same thing happened to me...
The DS-1 is definitely On when I press the footswitch but the led won't light up.
I changed the led and then measured the voltage there:1,32 Volts with a fresh battery.
Any idea ??
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ranjam
Bronze Member
Canada
82 Posts |
Posted - 02/20/2010 : 16:05:33
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| *WARNING* This is just a wild-ass guess. If you can, I would imagine shorting the collector-emitter junction of Q9 would make the LED go pretty good. If that works, I'd look at Q9, or D9. I can't read my schematic very well, but it doesn't look like R35 is 'that resistor'. But on the board layout it does look right. Hmmm. Or short out R34 and see what happens. Again, these are just guesses, but I believe something will show you where else to look. |
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bassinyourface
Bronze Member
France
76 Posts |
Posted - 02/20/2010 : 16:49:53
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Hi ranjam !
Thanks for your prompt reply !
My DS-1 is a 1983 MIJ that looks like this:
uploaded/bassinyourface/boss_ds-1_platine_MIJ.jpg
No Q9 to be found.
Are you sure about that ? |
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bassinyourface
Bronze Member
France
76 Posts |
Posted - 02/20/2010 : 16:54:08
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OOps !!
Didn't link the image properly,so here it goes:
My DS-1 is a 1983 MIJ that looks like this:
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ranjam
Bronze Member
Canada
82 Posts |
Posted - 02/20/2010 : 21:42:33
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I haven't opened my DS-1 for a while, but isn't there a small board with the potentiometers? On the schematic, it looks like Q9, but it might be Q8 as well. The only schematic I have looks so bad! But there is a clearly marked 1M resistor (R34) driving the base, and the LED is connected to the collector. The emitter is grounded. So, the LED has B+ on its anode, but the cathode gets grounded by virtue of the saturation of Q8. That's why I say short out the transistor or jumper R34 and see if the transistor gets driven harder. Something is making Q8 not saturate, so there is a voltage drop across the collector-emitter junction. This means less B+ on the LED. When you measure the LED voltage, you are probably going from the LED anode to the circuit board ground. You should try from LED anode to Q8 collector.
Yeah, I'll say Q8. But again, I haven't looked, and I am going by a truly wretched photo copy of a photo copy of the schematic. |
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bassinyourface
Bronze Member
France
76 Posts |
Posted - 02/23/2010 : 21:24:22
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Thank you for your concern Ranjam.
You are right,I did check and on the schematic Q9 and D9 are on the path of the led.
The early MIJ versions and later versions are built like that
But it seems that my PCB is a ET5205-510 revision B and Q9 D9 are not implemented(as you can see on the photo),so I guess Q4 or Q5 take care of the led in that case.
I will check that this weekend as this is an insanely hectic week for me.
Do you mind if I get back to you later ?
Again,thanks for your help
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Topic |
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DS-1 MIJ LED ?
