MXR M117 repair

[AnalogPackrat]

Also, you mentioned that you changed out the transistors. What types did you use? Have you verified they are compatible with the originals and that their pinouts match the layout (or that you mounted them accounting for different pinout)?

 

[ubxf]

Thank you guys i'm definitely over my head on this one. I'll follow your advice and try to learn.
I changed the transistors and got NTE equivalent NTE159 for 2N4126 and NTE199 for ZTX109c
I didn't realized they could have different pin out so i mounted them like the originals

 

[CJ]

I bought the mxr micro flanger, 99 bucks, sounds as good as the vintage a/da flanger I use to own, and it takes up 1/4 the space. You can harvest those Reticon chips from cheap stomp boxes but I forget which ones,

 

[AnalogPackrat]

Thank you guys i'm definitely over my head on this one. I'll follow your advice and try to learn.
I changed the transistors and got NTE equivalent NTE159 for 2N4126 and NTE199 for ZTX109c
I didn't realized they could have different pin out so i mounted them like the originals

You don't learn to swim by walking on the bottom. Just keep at it.

NTE199 is ECB vs ZTX109 is EBC with pins down and flat face toward you.

https://www.el-component.com/bipolar-transistors/nte199
https://alltransistors.com/transistor.php?transistor=48518

 

[ubxf]

Thank you, so that was a big f up on my part. I will correct the mistake, do you think i might have fried some components because of the miswiring?

 

[JohnRoberts]

Rather than speculate the best approach IMO is to empirically measure how parts are behaving.

Just like op amps have finite rules of behavior, transistors are just a combination of NP and PN junctions. in fact NPN stand for 3 layer negative, positive, negative. PNP stands for positive, negative, positive. Using a VOM with diode scale can measure the transistor junctions. When out of the circuit you can see diode junctions. For NPN diode current flows from base to emitter and from base to collector when measured out of circuit. Flow direction is opposite for PNP devices.

In circuit, best practice is to measure DC voltages. An active base emitter junction will generally show a half volt drop (in opposite directions for PNP from NPN.

JR

 

[ubxf]

Ok thanks John

 

[JohnRoberts]

Generally if you mark up the schematic with measured DC voltages, experienced technicians can predict which components are misbehaving from those voltage readings.

JR

 

[AnalogPackrat]

Thank you, so that was a big f up on my part. I will correct the mistake, do you think i might have fried some components because of the miswiring?

Looking at the schematic I'd say it is unlikely, but repeated solder/desolder cycles might. Try to be quick with the iron and solder wick/sucker. A short piece of small heatshrink or a piece of insulation from stripped wire can be used to prevent shorts on transistors where you have to cross adjacent leads to match the PCB.

And along the lines of what John mentioned, try to verify the transistor pinout once you've removed it. From the base (B pin) to collector and to emitter should read as a diode with the same orientation. PNP will have both one way and NPN both opposite of the PNP.

 

[AnalogPackrat]

I bought the mxr micro flanger, 99 bucks, sounds as good as the vintage a/da flanger I use to own, and it takes up 1/4 the space. You can harvest those Reticon chips from cheap stomp boxes but I forget which ones,

What's inside the new ones? BBD or digital simulation?

 

[CJ]

i'm sorry, it is an Ibanez mini flanger, been buying pedals like crazy lately, i do not know what is inside,

but wait, there's more:

"The 100% analog circuitry offers amazingly natural-sounding tones and affords players a classic, warm, and full-sounding flanger that won't take up excess space on your pedalboard!"

seems less noisy than the a/da also.

prices seem to be dropping on the a/da, more like 500 instead of 1000, maybe because of the ibanez?

 

[AnalogPackrat]

There's a clone of the MN3005 out now. Not cheap ($15+).

 

[grid_stopper]

I believe both xvive and cool audio offer clones. both expensive!

 

[DanMcCullough]

If you are interested, I can fix it for you, if this is beyond your ability. I have original parts for these. I am in Northern Indiana.

 

[ubxf]

Hey Dan, i appreciate the offer and it is probably beyond my abilities at the moment but i'm using this project to learn. With the good and kind advice from this forum members i'm making good progress. Using NTE replacements parts blindly was definitely not good.

 

[DanMcCullough]

No worries. I hope you get it working.

 

[AnalogPackrat]

I hope you haven't given up on the repair.

 

[ubxf]

No, thanks for checking in. I'm just waiting for some parts to arrive and methodically going with the schematic and tracing the circuit . That's what i should have done first

 

[JohnRoberts]

If you have a VOM maybe check DC voltages and mark up a schematic.

JR

 

[ubxf]

Both my VOM and my scope are not working so it made it a little harder, but the pedal is working. Thank you all, your advice was greatly appreciated. Do you guys know what the value of R43 variable 500k trim clock is supposed to be ? I had to replace it and ended up setting it randomly at 320K because i don't have a way to measure the frequency of the clock at the SAD