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zerksies
Double Platinum Member
USA
3406 Posts |
 Posted - 03/21/2010 : 15:03:35
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| My TR-2,BD-2,DS-1,CS-3 all light up when i power on my board.I know there is a way to have that not happen buy reversing a resistor or something could someone tell me what to flop around |
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ranjam
Bronze Member
Canada
82 Posts |
Posted - 03/21/2010 : 16:16:35
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| I'm guessing that it would be a board mod. If the pedal lights up as soon as you apply power from an AC source (and a lot of mine do that as well), I'm guessing the flip-flop is wired so the one transistor that is 'on' also controls the switching. The footswitch applies the voltage to cut off that transistor and saturate the other for bypass. You'd have to physically move that voltage 'over'. On a DS-1, the signal goes from Q1 through Q8 over to the flip-flop through R32. My first guess is that by physically swapping the one end of either R31 and R32, or R32 and R33; it might just work. But then, I make a lot of mistakes along my journey to enlightenment, so proceed with caution. |
Edited by - ranjam on 03/24/2010 02:52:49 |
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nosi0
Gold Member
Netherlands
511 Posts |
Posted - 03/21/2010 : 17:43:26
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If you search the forum you will find the answer. I cannot atm because im using my mobile phone. Search something along the lines of change pedal on status, the topic title was something along those lines. How does turning around a resistor change anything? It has the same resistance either way.
Nosi |
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nosi0
Gold Member
Netherlands
511 Posts |
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 03/21/2010 : 18:04:50
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| I have seen this topic a few times, and have heard that it works |
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nosi0
Gold Member
Netherlands
511 Posts |
Posted - 03/21/2010 : 18:27:36
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| Does that not answer your question then? Swap r30 and r31, if that doesnt work then swap q4 and q5. Some pedals have different names for the components you want to swap but for most of then its the ones mentioned above. I believe in the cs-3 they have different numbers |
Edited by - nosi0 on 03/21/2010 18:29:16 |
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zerksies
Double Platinum Member
USA
3406 Posts |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 03/21/2010 : 22:15:55
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| I would start by swapping Q5 and Q7. If that doesn't work continue with R23 and R25, etc. |
Edited by - cctsim on 03/21/2010 22:16:15 |
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nosi0
Gold Member
Netherlands
511 Posts |
Posted - 03/22/2010 : 11:34:53
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Yes one of the two or a combination of the two should do the trick.
On a side note i'm wondering if somebody can explain why swapping the transistors works as they should be identical. Considering the fact that all the same type of pedals either turn on on or turn on off. that would mean that BOSS checks the resistance of all those resistors to make sure the pedal turns on in the correct setting? Or don't all of the same pedal turn on in the same setting? |
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 03/22/2010 : 12:46:58
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| I'll give it a shot on my junky pedals first the one i have modded a dozen times |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 03/22/2010 : 14:06:58
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quote:
Originally posted by nosi0
Yes one of the two or a combination of the two should do the trick.
On a side note i'm wondering if somebody can explain why swapping the transistors works as they should be identical. Considering the fact that all the same type of pedals either turn on on or turn on off. that would mean that BOSS checks the resistance of all those resistors to make sure the pedal turns on in the correct setting? Or don't all of the same pedal turn on in the same setting?
I am not so sure all transistors are identical. There are huge tolerances in all sort of parameters ranging from current gain to min/max currents and capacitances.
The same goes for the resistors and capacitors involved in the flip-flop. Boss typically uses 10% tolerances, so you can imagine there are a lot of combinations.
Ibanez uses a trick that biases on of the resistors differently thus guarantying the flip-flop will swing to off-state at the start. This trick always work and I've used it mostly rather than swapping components.
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 03/23/2010 : 14:02:47
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| Ok i swapped everything, but now the funny stuff i use a bcb-60. when i have the adapter plugged into the board then the wall the ds-1 @bd-2 light up. but when i plug the unit in then plug the power cord into the bcb-60 the lights do not light up |
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ranjam
Bronze Member
Canada
82 Posts |
Posted - 03/24/2010 : 03:21:37
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quote:
Originally posted by cctsim
I am not so sure all transistors are identical.
The schematic says they are the same. And the biasing arangement is such that probably any transistor would work.
quote:
Originally posted by cctsim
There are huge tolerances in all sort of parameters ranging from current gain to min/max currents and capacitances.
I would imagine that's why the universal biasing arangement is used.
quote:
Originally posted by cctsim
The same goes for the resistors and capacitors involved in the flip-flop. Boss typically uses 10% tolerances, so you can imagine there are a lot of combinations.
I don't know my arse from my elbow somethines, but I think a flip-flop is just a basic on/off switch, so as long as the transistor is beyond cut-off and then more than saturated, it's working as intended here. Well, super exceed Vce and the thing will blow, but you get the point. No exact science, but if the transistor Q4 is saturated, the base is at 0.7VDC, and the collector is at 0.3VDC or so. Q5 is at cut-off through R26 and R29...... Geez, I don't know for sure looking at the schematic, but the point was the values are also chosen that if the battery voltage drops off the thing still works. It's biased somewhere along the load line that 1) any transistor will work, and tolerances aren't important. 2) There is ample room for any tolerance in component values, battery voltage, or transistor parameter(s).
I think I have it. I may be wrong, but you have the answer from someone else anyway, so I just babbled on for nothing.
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 03/24/2010 : 04:54:54
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quote:
Originally posted by ranjam
The schematic says they are the same. And the biasing arangement is such that probably any transistor would work.
The name of the transistors might be the same but their characteristics are not identical. To convince yourself take a look at the datasheet of the transistor 2SC2458GR used by Boss in the flip-flop or any other transistor. You will find min/max ranges for most of parameters. The current gain for example could be anything from 70 to 700.
Therefore, although the flip-flop will work properly with room for tolerances, there is no guarantee which transistor will switch on faster. This is why 50% of the boss pedals will start on and another 50% will start off. This doesn't mean the flip-flop is not working properly.
From the datasheet you can also see that hFE is also dependent on Ic. This means that if your battery or power supply drops the biasing is not identical anymore and although the flip-flop will still work the starting state maybe different.
This is what Zerksies observed using two different power supplies. I have observed similar behaviour even by changing the order of a pedal in the signal chain.
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Edited by - cctsim on 03/24/2010 05:13:43 |
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LIghts up
