Hi Paul! Thank you very much for this and your previous VC15-videos, very informative 👍 I have the second version of the VC15, still made in the UK. A question about discharging the filter caps. How to you discharge the caps when the leads are on the underside of the board and also the traces to the caps? I read on some Marshall forums that you can connect an insulated alligator clip on a wire from pin 1 on preamp valve V1 to another clip to ground and that will discharge the caps after a while. Is that how you do it or do you have another preferable method on the VC15? Thank you :-)
To be honest, I've never in the years I've worked on valve amps had to ever discharge any caps! Of course I do check for residual voltage before I delve into an amplifier, but I've no 'go to' method of discharge as I've never once needed to do so. Basically when looking a something I'm unfamiliar with, I'll first check the there is continuity between the chassis, negative side of the amp and the earth pin of the mains plug, then usually plug the amp into a mains socket, but switched off. Most reasonable well designed amplifiers 'should' self discharge when switched off with a route to earth via resistors. I would then check the HT side for residual voltage - in the case of the VC15, using the solder pads on the top of the board, though the leads from the 450v smoothing caps are also visible on the top of the board, so wouldn't be an issue to rig-up a discharge resistor. But modern standards require capacitors to be able to self discharge and the VC15 takes about 30 seconds to get down to a few volts after switch off. The issue is of course very different with some vintage amps and self builds. As always, check before you delve inside, but it's never been an issue for me so far.
Ive recently bought this amp and got it serviced. Not a tech myself but the clean channel sounds very stiff and cold to me - no compression or warmth. Would altering the bias help with this?
@jamesbowskill2067 Yes, I feel setting the bias hotter would give it more aggression. But I feel that the drive channel can be set to give a clean but aggressive sound with no change in bias.
Hi Paul! Thank you very much for this and your previous VC15-videos, very informative 👍 I have the second version of the VC15, still made in the UK. A question about discharging the filter caps. How to you discharge the caps when the leads are on the underside of the board and also the traces to the caps? I read on some Marshall forums that you can connect an insulated alligator clip on a wire from pin 1 on preamp valve V1 to another clip to ground and that will discharge the caps after a while. Is that how you do it or do you have another preferable method on the VC15? Thank you :-)
To be honest, I've never in the years I've worked on valve amps had to ever discharge any caps! Of course I do check for residual voltage before I delve into an amplifier, but I've no 'go to' method of discharge as I've never once needed to do so. Basically when looking a something I'm unfamiliar with, I'll first check the there is continuity between the chassis, negative side of the amp and the earth pin of the mains plug, then usually plug the amp into a mains socket, but switched off. Most reasonable well designed amplifiers 'should' self discharge when switched off with a route to earth via resistors. I would then check the HT side for residual voltage - in the case of the VC15, using the solder pads on the top of the board, though the leads from the 450v smoothing caps are also visible on the top of the board, so wouldn't be an issue to rig-up a discharge resistor. But modern standards require capacitors to be able to self discharge and the VC15 takes about 30 seconds to get down to a few volts after switch off. The issue is of course very different with some vintage amps and self builds. As always, check before you delve inside, but it's never been an issue for me so far.
@@paulwilliams4984 Thank you Paul! I see 👍Excellent explanation of the situation and what to check for/do in this case. Much appreciated 🙏
Ive recently bought this amp and got it serviced. Not a tech myself but the clean channel sounds very stiff and cold to me - no compression or warmth. Would altering the bias help with this?
@jamesbowskill2067 Yes, I feel setting the bias hotter would give it more aggression. But I feel that the drive channel can be set to give a clean but aggressive sound with no change in bias.