Repairing Quad 306 and not cleaning solder flux

[steevo]

Hi I have just requilt a Quad 306 channel and the amp seems to work but there is low level buzz coming from both the speaker HF and LF drivers Its only low level but compared to the other channels its noisy.
I replaced all the resisors on the board and some of the non critical capacitors, along with some of the transisors, I sued the c service manual to get the component valuse. When I built up the PCB I did not clean of the solder flux from the PCB and I was wondering if this could be slightly conductive creating a capacitive coupling between some of the low level stages. The buzz is destroying the signal to noise ratio of the amplfier.

Can anyone help and give some guidance on the source of this noise.

Thanks
Steevo

[Mooly]

I would recheck all your work. Flux isn't the problem.

What's fitted in a production amp and what appears in a service manual may not always agree... changes are made in production runs etc.

Sometimes the final grounding (as intended by the manufacturer) is only achieved when the PCB's are screwed back into place. Couldn't say whether that applies here.

Check the amp in isolation with inputs shorted and no other components except a speaker connected.

[DF96]

Flux can be a problem. Many years ago I built the Nelson-Jones tuner from a kit. It seemed noisy, even on strong signals. Not white noise, but rougher than that. I noticed that it was worse in damp weather. To cut a long story short, I eventually found that there was some flux left on the PCB around the bias for g2 on the input RF dual-gate MOSFET. Scraping this away cleared the fault. The problem was not the flux itself, but the moisture it absorbed to become a noisy resistor in parallel with the bias arrangements.