reissue dod 250 overdrive preamp mod troubles

[YouSirName]

NEED SOME HELP PLEASE! - I just modded my dod 250 reissue to 1979-80 grey specs and I tried it out and there is no sound. I removed C2, replaced C1 with 0.047 uf, replaced R8 with 10k, and replaced V1 with LM1458N, (dual 741 op-amp), using a socket. The signal goes through the pedal fine in bypass, but when engaged the only sound is the occasional faint distorted crackle when I pound the strings hard. The only thing I can guess is that I may have damaged something by overheating with the soldering iron. I even reversed everything back to stock, to see if it would work again and it still didn't work. Can somebody please give me some suggestions!

[tubelectron]

Well...

1 - the 1458 has not the same pinout as the 741, but has the same as the 4558, so interchangeability is direct.
2 - the only thing that can be damaged severely while soldering is the chip (but as you use a socket) and the diodes (usually abuse-resistant)... Unless you are using very badly your soldering iron !
3 - C1 was 56n, I suppose that C2 was 1n, R8 was 100K, and IC was 4558 if it is the yellow RI. The change to grey values wouldn't make the unit faulty.

You've probably :
- burnt diodes and/or IC...
- maybe burnt a cap or a resistor by excess heat or bad soldering technique (dirty joint or iron...)
- put the IC and/or its socket in the wrong position...
- put the 2 diodes in the same direction...
- made some bad joint solder somewhere, maybe hidden (take a magnifier)...
- made a mistake in rewiring...
- made a mistake in component placement or value reading...
- made any other silly bug that you are unable to see... As it often arises to us !

A+!

[Steve Mavronis]

Make sure you didn't do something silly like insert the IC in the wrong way or bend a leg that is used, or maybe you have a bad solder joint somewhere. Try a different 1458.

Here is a photo of my YJM308 board that i modified the same way. Look at the chip orientation. The part labels are the same on the YJM308 and reissue yellow 250 which both use the same exact base PCB:

[YouSirName]

Thanks for your input guys. Greatly appreciated. I just wanted to let you know that I found the problem, (with the help of a friend), and it is something I've never heard mentioned before in any of the online forums about modding a DOD 250. This problem may be obvious to those who are more knowledgeable about electronics than I, but I'll point it out anyway, just in case. The "Grey Spec" mod calls for the removal of C2, and supposedly this is not essential to complete the circuit. However, I found when I inspected the pcb, (yellow reissue), I noticed that the solder point for one of C2's terminals actually bridges the gap between C5 and R2. So in effect, by removing C2 I have now created an open in the circuit. My solution was to clip a piece of a capacitor terminal to use as a conductor, which I then soldered ptp from C5 to R2. I put the pedal back together and it worked perfect!

[Pyr0]

I'm not sure which schematic you are referring to for this, but the capacitor that is normally removed is the small feedback cap that goes from pin 6 to pin 2 of the opamp, there should also be a 1M resistor in parallel with it, so removing this cap should not kill the sound.
Are you sure you removed the right capacitor ?

[YouSirName]

I'm sure I removed the right one, C2. You can actually see just what I'm talking about in the picture Steve Mavronis posted of his YJM308, just above this post. If you look at the pcb, you can see that the only connection one side of R2 has to the circuit is through C2 and directly after this is C5. If you remove C2, one end of R2 is disconnected from the circuit.

[Steve Mavronis]

Here is an illustration I made from my YJM308. C2 connects to both sides of R2 and doesn't break any connection if removed: