audio-talk

Whether AC or DC heaters, you need 10n from each end of the heater transformer secondary directly to chassis. Simply rectifying and smoothing for a DC supply is actually worse than AC, as you've found, because you've converted a nice (ish) sine wave into something with sharp edges and harmonics. You...

I wouldn't touch a DC motor, either, not unless it has a servo wrapped round it. The favoured Mclennan motor is:
https://www.mclennan.co.uk/product/9904 ... ous-motors

Beware that an oscilloscope rarely has more than 9 ENOB (Effective Number Of Bits). So although many scopes now have 12 bit ADCs, they're only accurate to about 8 bits, or 48dB. What that means is that any distortion <0.5% could be the scope. And usually is. Next, to get even that poor performance, ...

Exactly, mislaignment is inevitable. Shame about the scuff marks. Having just taken the motor apart, I can tell you that 3mm is exactly the right size to drill out the rivets on the end of the three mounting pillars. Having done that, standard 15mm M3 threaded pillars will do just fine as replacemen...

Yes, lots of ways to make it. I've just made and used a puller to get the pulley off a TD150 motor. Only it didn't work quite as expected. It pulled the shaft out of the rotor! Still, I can open up the motor and fit it with a new shaft...

My TD150 motor doesn't have an external thrust pad, yet the end of the shaft is a polished dome. Perhaps the pad was lost? That's an expensive eBay part. It has one good feature and one terrible. The good feature is that it allows you to adjust rotor height for minimum vibration. The terrible featur...

Beware that outbuildings get damp, causing machine tools to rust, making a proper dehumidifier essential. Electronics doesn't like damp, either. I passed on an analogue oscilloscope to a friend who kept it in a shed. I'd had it for 30 years without trouble but shed damp killed its EHT within a coupl...

PSUD2 has a column for RMS measurements, so it can determine capacitor ripple current for you. It tends to over-estimate slightly because it doesn't know about transformer saturation limiting ripple current to a practical 4-6 times load current and often assumes 7 times. But that will give you a saf...

I have a subchassis and subplatter should they be useful. I bought a very tatty and incomplete TD150 for £15 because I wanted the Bowden cable cueing device. Its motor had a bent shaft. The steel top plate was recycled into something useful, although I can't remember exactly what.

A whole lot less, I suspect. Looking at the power supply diagram, I think that swapping the position of the 1R resistor and the 10mH choke would put a tamer waveform across the choke (and therefore its leakage field) but make no difference to the filtering or final voltage. PSUD2 could confirm or di...

I can think of a disadvantage to active rectification. I would expect a capacitor input supply using active rectification to impose higher ripple current because the on-resistance of the FETs will be lower than the slope resistance of the equivalent diodes, and higher ripple current means greater se...

I used an angle grinder to cut a bit of 1/2" steel plate for making the spacer/mounting plate for the Dickson tool holder on my Hobbymat. Turned out there was a lot of stress in that steel and I had to machine both sides equally to get it flat. Buzz easily comes out of all drivers, even tweeter...

Ah, I assumed you had a nice traditional analogue scope, not the final generation where they fitted digital control (to make it cheaper). The picture said a thousand words... I figure you won't need more than five leads. I have rather more. You need T pieces so that you can monitor the signal you ar...

That's a tonking great angle grinder! I've only ever used a toy one, but I have used a big circular saw, and at start-up it swung me sideways by a couple of feet, so I assume the same happens with that angle grinder. But someone is going to be very upset when they get back and see what it did to the...

OK, you have an analogue scope with onscreen display. Very posh. But possibly a little beyond you. That last trace looked suspiciously as though it was in mixed time base. A picture of the entire scope would be handy. Buy the scope a present of five 50 ohm 4ft BNC leads, two T pieces, and two 50 ohm...