freestompboxes.org

Hey Guys
I stupidly wasn't paying attention and used the wrong polarity adapter on My ibanez ge 300 EQ which takes 18 volts.
so I think i've fried something. it turns off the LED for that socket on my power supply when inserted and wont power up.
the socket on the power supply is still working with other pedals and it won't work with batteries
I could not find a Schematic for this but i've attached some pics
could someone suggest what to check to see if i can fix it. I've lifted up the pcb and there is a diode and a resistor connected to the power LED.
this was originally battery only but i wired up a battery clip adapter and connected it to the power jack.
Thanks in advance !

i forgot to mention that the led still works when power is connected
and a signal is heard though the amp when bypassed

saw something online about checking the IC's with a multimeter 1st time i've done this . Im getting a Vcc+ reading of around 18 volts on
both IC's as this is an 18v pedal does this mean the IC's are fried and everything else is ok?

If you are getting 18v on the IC Vcc pins that shows that the power input circuitry is ok, it tells you nothing about the state of the ICs.

Looking at the photo of the board it appears that the things most likely to be damaged be reverse polarity are the 2 regular ICs LM1458C (I think), one transistor (type unknown), and a custom hybrid board (the beige potted multi-pinned thing in the bottom right corner). It could be any or all of these that are faulty.

You reallyl need a schematic, detective skills and signal tracing gear to pinpoint what is faulty, or just change all the active components. The problem is the potted hybrid is probably not readily available.

Dirk_Hendrik probably knows way more about this pedal than I do so if he doesn't respond you could try and PM him.

hey thanks man
the Ic's are texas instruments mc1458p
the transistor says C1815BL 8F
can I test the transistor in circuit with a multimeter ?
What does the large potted beige thing do is it a capacitor? can this be tested?

HoggYBhoY wrote: .....
I could not find a Schematic for this but i've attached some pics
.....
I've lifted up the pcb ......

So you know already how to lift the pcb and you are not scared to do it.

Hows about lifting the pcb again and take one (or more) picture(s) of the solder/trackside ?
I think this could increase your chance for a schematic and to repair it.... just saying....

ok thanks man heres the pic

HoggYBhoY wrote:hey thanks man
the Ic's are texas instruments mc1458p
the transistor says C1815BL 8F
can I test the transistor in circuit with a multimeter ?
What does the large potted beige thing do is it a capacitor? can this be tested?

Testing a transistor in circuit can be done but is not always reliable. The C1815 is a common transistor, NPN silicon, general purpose audio, the full number is 2SC1815...., the 2S is implied. A lot of transistors that start with a single character are the same (but not all).

No idea what the potted beige block does so no way of testing it yet, it looks a bit like a thick film hybrid of 80s/90s era. Maybe the mojo that makes this pedal what it is.

So is it a good idea to test the transistor in circuit and how is this done?

HoggYBhoY wrote:So is it a good idea to test the transistor in circuit and how is this done?

With an "in circuit transistor tester".

We had one at work but it was so unreliable it was always best to take the suspect transistor out and test it properly. (IMO, YMMV of course.)

ok ill look up transistor testing.
In regards to the IC chips i've tested they have a voltage but can i test if they are actually faulty or will i need to
remove also ?

Without a schematic the easiest way to test the ICs is to carefully unsolder them and build up a simple circuit on vero or perf board using an IC socket.

When replacing them fit sockets in the board so they can be easily swapped if necessary in the future.

If you know for sure that a chip is faulty then it is safest to snip it out with a pair of fine nosed cutters and remove the legs individually. This way there is much less risk of damaging the PCB with heat.

You will have the schematic tomorrow

I'm on it

sinner wrote:You will have the schematic tomorrow

I'm on it

What the....!??

OK you beat me to it.

Or ask Mictester. He probably designed it. He designed all Boss and Ibanez pedals, as well as most 70's and 80's Japanese HiFi Systems.

moving to Modern Stompboxes

@HoggYBhoY

Can you make a list with caps values [better codes on them]. Keep the naming true to the board's silkscreen [C807 - value, and so on...]

Thanks

heres the pics guys

Alright. Got everything I need apart of slider pots value

You can take the board dimensions for me as well

the restor next to the LED and a diode is a 4.3k ohms 5%

the board has a 104 mm width and 82 mm length