Boss Flanger BF-2 gets hot (not working at all)

[geezer15]

Hi, I have bought a Boss BF-2 as faulty. When I switch it on I briefly got a faint 'flanger' sound but then it quickly faded to nothing in 2 secs max.

1) The Led does not light- I have tested it with a battery and protective resistor and it does light if powered directly.

2) the battery gets warm. The terminals are not reading as shorted.

3) I started to read the voltages on the IC pins. I then realised several componants were getting hot also a smell of burning so I disconnected the battery and didn't continue.

The readings I did take are from IC5 pin 1) 1.22v  2) 1.23v 3) 1.00v 4) 0.03v

now Pin 5 is interesting it varied between 0.6 and about 1.12 in a regular cycle. Maybe a capacitor charging/discharging?

There is a schematic here http://www.hobby-hour.com/electronics/s/boss-bf2-flanger.php

I have a photo of the board but not sure how to attach it to the post.

Some of the componants getting hot are Diodes 1+2, R 18 + 14 Q11 Q8 and some capacitors I can't see a label for one is 100uF electrolytic. They are all in the same part of the board (near the orange and green leads that connect to the LED). I don't know if they are all getting hot on their own or if one or more componants are heating others nearby. These componant  numbers relate to the PCB I don't know if they are labelled the same in the schematic.

Any suggestion where to start would be helpful. Thanks in anticipation.

Pete

[geezer15]

Ok I hope this lniks to the photo of the board. The componants getting hot are in the top left corner. Hopefully they are identifiable by my description above but there are 5 resistors 2 transistors 2 diodes the large electrolytic cap and the orange and green caps

http://s1228.photobucket.com/albums/ee448/geezer15/?action=view&current=IMG_8452.jpg

[cjlectronics]

Its possible that the 78L05 (IC6) is bad?  You could also have something on the +5v rail shorted and causing IC6 to exceed its current capabilities which will cause it to heat up. 

If none of the simple stuff above works, I usually have to start cutting power traces to isolate the bad section.  This is not for the novice.  You have to know what you're doing. A schematic is necessary and a layout drawing is helpful.

CJ

[Seven64]

i just had my bf-2 apart yesterday, and that one looks like it has been pretty modded.  the brown caps are not stock, mine had all green ones in it.

[Paul Marossy]

Its possible that the 78L05 (IC6) is bad?  You could also have something on the +5v rail shorted and causing IC6 to exceed its current capabilities which will cause it to heat up. 

Sounds like a possibility to me.

[mr clack]

Hey! I am in the same boat at the moment (fixing a BF-2), it is really odd.

Except the issues I am getting is crazy ground that dosn't stay at 0v but no short is read-able across the circuit and the power supply bends 1v in time with the LFO. Across the 5v rail it is higher but it is not a problem with the 78l05 as I replaced it (if you do replace it make sure you check the pins as they are reversed on different brands)

If I find anything out about it I will let you know, I have replaced everything elec caps, IC's, BJT's etc and I just cant seem to get to the bottom of it! there must be somthing in this circuit that is unusual. I am almost at a state of re-building it!!

[geezer15]

Thanks for your input guys I will look at your suggestions.
I contacted the previous owner It has been modded, previous owner had some caps replaced but it had worked since he says.
Need to order some parts then and I'll see what happens. I was thinking replacing the electrolytic caps dont know if they might contribute to the problem but they are old enough to need replacing and i guess it won't do any harm other than waste my time if I can't get it working after. 

[geezer15]

i've just replaced 78l05, ic6, and the circuit is still getting red hot. nothing looks damaged (melted) but the heat could easily damage a whole load of componants i guess. Nothing looks to be shorted externally. I guess I have 2 options as I don't know much electronics. 1) shelve the project 2) replace everything on the board starting with the, probably, heat damaged componants then the electrolytic caps and then everything else. I am not sure how to 'cut power traces' in a helpful way.

[nial6888]

i'm china boy,my englsh is bad,
the first,you must test the 3207 and 3102 is good, them very fragility.

and
1:important !
clock frequency
connect oscilloscope to TP-1
1.adjust VR7 for T=25us.
2.rotate MANUAL FCW.
T should be 2us+-20%

2:very important!!!!!!!!!!!!!!!!!!!!!!!!!
BBD BIAS
Feed 200HZ, sine wave. 0dbm into input jack.
connect oscilloscope to Q3 emitter.
1.while turning MANUAL across its entire rotaion range . set VR6 for clip-free wave form at the peaks.

3:not important,this is regulate tone
RESONANOE
Plug short circuit into input jack.
connect output jack to an amplifier and speaker.
1.while touching screw driver to TP-2,set VR5 to the point where oscillation beging.



the oscilloscope is software well be OK

you can use software oscilloscope

if you not have software oscilloscope .tell me your emill,
my emill is "nial6888@SOHU.COM"

[geezer15]

Thank you,
Your English is good.
I have e mailed you re the software.
I will try the tests but am concerned about connecting power for long as it may cause more damage.

Pete

[Fender3D]

Reading the entire thread I still don't know whether you have 5,6V on IC6 out pin (5V from IC6 + 0.6V from D9).
D1 is a zener, a very-difficult-to-measure-by-multimeter part.
It could be damaged.
You might as well take apart D1, C39, and IC6, it won't flange, but the signal will flow the same.
Check whether doing so it becomes still hot.

[geezer15]

No I'm not getting 5.6 V from the out of ic6. I have pin out,looking at flat side as input ground output reading left to right. input and ground are reading 0.01v and output reads 0.53. Battery reads 8.15v. The odd thing is nothing is getting hot now. That should be good but why? as i've done nothing since my last entry. I guess somthing else has burnt out. I haven't removed D1 C29 or IC 6 yet I was just trying to get the voltage reading first. D9 is reading as good as zero both sides. Just to confirm I am using a, well almost, 9v battery and a jack plug in the input to make sure its 'on' I have no LED to tell me when its on. I assumed I'd know when it got hot   Just to add I've not recieved the oscilloscope software yet but I suspect that will be a learning curve and I'm not sure how the PC will take the reading ie what cable is needed.

[Govmnt_Lacky]

No I'm not getting 5.6 V from the out of ic6. I have pin out,looking at flat side as input ground output reading left to right. input and ground are reading 0.01v and output reads 0.53. Battery reads 8.15v.

If you are correct with your 5V regulator pinouts, AND you are positive that it is inserted correctly into the circuit, then it is obvious that you NOW do not have the proper voltage getting to your regulator. You need to start there and work your way back to where the 9V enters the circuit.

Take a look at R54 and R63 (The two resistors at the very top left of the board in your picture directly below the orange wire) It looks like they are touching. Good idea to seperate them.

Good Luck