Electronics Fault Finding - Vellerman RIAA Pre-Amp - Part 1.

Great troubleshooting video, Andy. Break it down into sections. Excellent. As for the "741" I would be really sus on it. That black crud on the pins makes me think it is either a counterfeit or has been exposed to some corrosive chemicals. I think the chap needs an 800 deg F iron tip. Like you said- Get on with a hot tip, solder, I get off quick. Be sure the traces are clean. Now I use isopropal not rubbing alcohol to clean with. Acetone can damage some plastics and can leave an oily residue. Yes, I totally agree on the blobby joints. Too easy to get a rosin joint. I have seen kits put together with the "lytics installed backwards, and same with bridge rectifiers. I also suggest testing every part before installing. I have found more than one part bad out of the new box. (HeathKit had 2 massive screw ups. Resistor bands were painted the wrong colors, and diodes had the cathode band printed on the anode end. Never trust new parts! Always verify. Many kit builders here were really pixxed off over those errors. It actually made articles in the magazines here.) At least it appears he uses rosin core solder and as shiny as the connections are, like not that useless "lead free" crap solder. I have also seen entire boards eaten up by the builder not following instructions and using acid core solder. 🙄 Next "Care" pkg I will send you something that would make troubleshooting on IC's easier for you. Of note: I have seen IC socket pins break off in the plastic causing a hard to find intermittent problem (Same on tube sockets). Also have seen socket pins lose tension, and the IC leg doubled over under the IC, with the IC soldered to the board. Boy that was really a nasty one to find!! Having a good schematic really helps. Glad you got the assy. manual to help out with. Marking each part on the pictorial to verify it is in the correct location is a good idea.

Hi Andy, I’m going to change my name to Mr Blobby : )) Having now obtained some more Weller soldering tips I need to practice soldering and more importantly checking circuits! Thank you for filming it, hopefully other subscribers can gain some useful tips and tricks, looking forward to the next part. 👍

The 741 was never going to work in a stereo circuit as it is a single and not a dual amplifier. You had a better chance with the TL027 because at least it has two amplifiers in the package. Almost all of these opamp based RIAA circuits use a NE5532 though. From the look and markings of the original 741, it is ancient, I would guess at mid 70s manufacture. It is branded "RS" for Radiospares as they were then or RS components as they are now. The black stuff on the legs is pretty common on components that have been stored for that long. I wonder what opamp was specified on the component list.

i built a valve phono preamp its magic no hummmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm good old days of kits

*Velleman is with an r ...