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Mesjoggah
Gold Member
Netherlands
595 Posts |
 Posted - 08/11/2009 : 18:42:32
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quote:
Originally posted by Laurie
G'day! Any progress on this one? Enquiring minds want to know....
Unfortunately i must say no, no progress. I need to improve my skills to read and understand schematics and stuff, apparantly i am not a good thinker and if i measure a certain part and it doesn't give the right values i want to replace that part while in nine out of ten the problem lies somewhere else. I guess i should learn the basics first, although i got lucky a few times with this method..
With this DS-1 i really don't know what it could be, it works but it lacks volume and 'balls' in switched on mode, i have signal on pin 2 and 6 of the op-amp so i guess the op-amp is allright?
My thinking leads me to an amplification failure, now amplification comes from a transistor (does it?) so i measured them and replaced two that i thought were suspicious, still no luck though.
I searched for a ground leak but couldn't find one. To go short: i don't know.
I am waiting for a bunch of parts that i ordered from Banzai to arrive. |
Edited by - Mesjoggah on 08/11/2009 18:43:26 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/12/2009 : 00:46:39
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quote:
Originally posted by Mesjoggah
quote:
Originally posted by Laurie
G'day! Any progress on this one? Enquiring minds want to know....
Unfortunately i must say no, no progress. I need to improve my skills to read and understand schematics and stuff, apparantly i am not a good thinker and if i measure a certain part and it doesn't give the right values i want to replace that part while in nine out of ten the problem lies somewhere else. I guess i should learn the basics first, although i got lucky a few times with this method..
With this DS-1 i really don't know what it could be, it works but it lacks volume and 'balls' in switched on mode, i have signal on pin 2 and 6 of the op-amp so i guess the op-amp is allright?
My thinking leads me to an amplification failure, now amplification comes from a transistor (does it?) so i measured them and replaced two that i thought were suspicious, still no luck though.
I searched for a ground leak but couldn't find one. To go short: i don't know.
I am waiting for a bunch of parts that i ordered from Banzai to arrive.
The only amplifying element in this version DS-1 is the 7136 chip. The transistors are buffers and the FETs are switches. If you have signal on pin #6 of the opamp, then it is probably (but not certainly) OK.
Check the continuity of the circuit
- check that pin 6 has zero resistance to one side of the DIST pot.
- Check that the wiper of the DIST pot has zero resistance to one side of R11
- Check the last pin of the DIST pot has zero resistance to one side of R13
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 08/12/2009 : 01:31:39
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Failure of Q2 can cause the behavior you described. Q2 forms a transistor CE-stage amplifier with a gain of ~ 36 dB.
Even if you have changed the feedback capacitor to a value in the nano range the gain decreases significantly.
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/12/2009 : 05:27:50
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quote:
Originally posted by cctsim
Failure of Q2 can cause the behavior you described. Q2 forms a transistor CE-stage amplifier with a gain of ~ 36 dB.
Even if you have changed the feedback capacitor to a value in the nano range the gain decreases significantly.
Oh crap... cctsim's right! Missed that  |
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Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 08/12/2009 : 17:19:48
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[/quote]
The only amplifying element in this version DS-1 is the 7136 chip. The transistors are buffers and the FETs are switches. If you have signal on pin #6 of the opamp, then it is probably (but not certainly) OK.
Check the continuity of the circuit
- check that pin 6 has zero resistance to one side of the DIST pot. zero
- Check that the wiper of the DIST pot has zero resistance to one side of R11 zero
- Check the last pin of the DIST pot has zero resistance to one side of R13 zero
Q2 is ok too..
[/quote] |
Edited by - Mesjoggah on 08/12/2009 17:47:16 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/13/2009 : 06:09:54
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Just curious - how did you confirm Q2 was OK?
Bunch of audio probing to do...
1) Probe the input socket so you get an idea of what the incoming ignal sounds like.
2) With the LED on, probe the base of Q2 (the pin connected to C3). Is it different to the signal in #1?
3) With the LED on, probe pin 2 of the opamp. What, exactly, are the difference between the sound here and the sound in #1?
4) With the LED on and "DIST" set to minimum, probe pin 6 of the opamp. What, exactly, are the difference between the sound here and the sound in #1?
5) With the LED on and "DIST" set to maximum, probe pin 6 of the opamp. What, exactly, are the difference between the sound here and the sound in #1?
6) With the LED on and the DIST set to maximum, probe "connection 8" on the circuit board. What, exactly, are the difference between the sound here and the sound you heard in #5?
7) With the LED on and the DIST set to maximum, probe the base of Q3 (the pin connected to C13). What, exactly, are the difference between the sound here and the sound you heard in #6?
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Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 08/13/2009 : 19:39:32
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quote:
Originally posted by Laurie
Just curious - how did you confirm Q2 was OK? i found an article on a dutch site on measuring a (NPN) transistor
Bunch of audio probing to do...
1) Probe the input socket so you get an idea of what the incoming ignal sounds like.
2) With the LED on, probe the base of Q2 (the pin connected to C3). Is it different to the signal in #1? it has less dynamics
3) With the LED on, probe pin 2 of the opamp. What, exactly, are the difference between the sound here and the sound in #1? much louder and harsher sounding
4) With the LED on and "DIST" set to minimum, probe pin 6 of the opamp. What, exactly, are the difference between the sound here and the sound in #1?much louder and harsher sounding
5) With the LED on and "DIST" set to maximum, probe pin 6 of the opamp. What, exactly, are the difference between the sound here and the sound in #1? it's still loud and harsh
6) With the LED on and the DIST set to maximum, probe "connection 8" on the circuit board. What, exactly, are the difference between the sound here and the sound you heard in #5? it is not so loud anymore and much 'darker' sounding
7) With the LED on and the DIST set to maximum, probe the base of Q3 (the pin connected to C13). What, exactly, are the difference between the sound here and the sound you heard in #6? lower volume and no dynamics compared to point 6
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Edited by - Mesjoggah on 08/13/2009 19:41:36 |
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Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 08/14/2009 : 18:30:58
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Nailed it!
Q8 was faulty!
I placed a spare one and now it works as it should. A big thanks to Laurie and cctsim for their input on this problem!
Q8 is a sk30A, what is a good substitute for that? also is there a good list of substitute transistors available or do you need to check a lot of datasheets first? i do have a lot of new transistors but don't know to what transistors they substitute.
Anyway i am happy i solved it! |
Edited by - Mesjoggah on 08/14/2009 18:32:13 |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 08/14/2009 : 18:38:06
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Hi Mesjoggah
That's good news. 
Regards Dr. Bob  |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/14/2009 : 19:18:37
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quote:
Originally posted by Mesjoggah
Q8 is a sk30A, what is a good substitute for that? also is there a good list of substitute transistors available or do you need to check a lot of datasheets first?
Good news! Congrats!
You can buy 2SK30A FETS on eBay. I bought a pack of 20 from Thailand for spares for about $15.
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 08/14/2009 : 23:21:16
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| The 2N5457 could be used for this but you need to swap the electrodes if I remember correctly. They cost ~ �0.15 in UK. |
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DS-1 no signal - PROBLEM SOLVED!!!!!!
