OK I screwed up my DRRI

[Rick1114]

It was just a matter of time. I was experimenting with the tone stack, maybe a bit too much...

Right after swapping some resistors & the bright cap and treble cap I realized the treble control was working funny (it was lowering treble as you turned it up). I tried flipping the bright cap around to check if I just oriented it wrong, and then tried other caps to see if it was defective. By then the problem had gotten worse. Neither the treble or bass controls on the vibrato channel are working at all at this point. They controls work on the normal channel ,but both channels are noisy (I have the normal channel routed to the reverb/vibrato). Something is seriously wrong & I don't know where to start! I've already checked the tubes, solder connections and looked for blown resistors. I have a feeling it may be a shorted resisitor/cap, but I don't know which one!

Is there a way to test the parts while still in the circut?

I am such an idiot!

Rick

[tubeswell]

Sounds like you wired the treble pot the 'wrong' way round. Try swapping the wires to the two 'outside' lugs.

I would not try swapping caps or resistors until you've switched the treble pot around. Are all your solder joints clean, and not shorting on any thing else? Use you meter to check for correct voltages.

[Shea]

If it's not that, then another possibility is a bad connection from the cold lug of the bass pot to the 6.8k resistor, or from the other end of that resistor to ground.

Shea

[Rick1114]

If it's not that, then another possibility is a bad connection from the cold lug of the bass pot to the 6.8k resistor, or from the other end of that resistor to ground.

Shea

That's what I'm thinking I'll try next when I get home tonight. I didn't start having any problems until I put the original 6.8k resistor back in, along with some other caps changes. The connections seem fine, but It may be a little banged up from when I yanked it out. Those little tootsie roll resisitors are fragile and break easy. I just hope I didn't inadvertantly cause any other damage, but upon inspection, nothing "looks" fried. To top it off my multimeter is not working properly so I can't narrow it down.

[52 Bill]

Those boards are not very tolerant to overheating and the traces will start to come un-attached from the board. I'd check to see that all of the solder pads are making continuity to the traces in the sections that you have been working on.

[Rick1114]

I checked all the connections on the tone circut with a multimeter and they are fine. Did not test the pots yet. The vibrato channels volume goes from off, to very little volume & back to off, as you turn the pot. The treble and bass controls have no effect. The reverb is noiser than usual when you turn the pot. The vibrato seems fine.

The normal channel is fine as long as I don't engage the reverb - then you get some pops and crackles (I have the normal channel routed through the reverb/vibrato).

Any ideas of where I look next?

EDIT: I found the bad connection! It was from the treble cap to the clip that goes to the bottom part of the PCB. It seems the solder pad came off underneath, so it looked okay upon inspection. This PCB is a bitch! Now I gotta figure out how to make this connection stick.

[tubeswell]

So you are saying the trace solder pad has come away from the board

Then scrape the trace covering back to the copper further down the trace where it is still attached to the board, and solder a bit of 22ga bus wire to the trace, and to the component in question to get a 'sound' joint (tee hee)

[Liam]

Or just find another point on that trace to connect to.

[Rick1114]

FYI - BillM has a great section on fixing PCB's on his Blues Jr modding site. I was able to repair the connection using his methods.

http://home.comcast.net/~machrone/bjr/mistakes.htm