OT tinkering ideas wanted!

Found a typical cct:-

't look too useful - hasn't even got a 'proper' mains transformer (thought it was a bit light!)

Nick H.

It's a switch-mode power supply, very specifically engineered and priced for the PC market, and not much good for anything else unfortunately.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

In message , Nick H writes

Aye; they're RF interference-generators - AKA switch-mode PSUs. If I break one up, I recover the rectifiers, and the high-voltage capacitors large and small (typically 200 to 400 volts working) for use in various valve radio projects, but little else is useful to me, apart perhaps from the mains filter inductors (T1 and T5 in the circuit).

They are supposed to be good as general-purpose power supplies (giving better performance than traditional transformer units) subject to the output wires being connected in the right way. Your example source didn't make a great deal of sense to me - too much bare detail, not enough principle. There are other sites that specifically deal with the practicalities but I don't have any references to hand. Peter

I've fitted an old PSU to our event sound system. The mixer deck and radio mic need a smoothed input (we run it off a 500 watt Chinese generator!) and I've fitted a 12 volt cigar lighter type output to the case for general use - a Godsend to those with flat mobile phones!

Regards,

J. Kim Siddorn, Regia Anglorum

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Oh well, looks like computer power supplies are best recycled as .................... a power supply! I already have a couple of decent bench supplies so I guess it's bin time.

Nick H (G6AUV - inactive!)

In message , Nick H writes

Ah well; then I won't suggest taking the 100uF 400v capacitor out of it, building a Top Band AM all-valve rig (with a very good noise limiter!) around it as the smoothing capacitor, then using the rig at rallies as the load for an engine and alternator...

"Andrew Marshall" wrote

Brings back memories of the Tx I built at school - somewhat above top band if you know what I mean - all valve with lots of exposed bitey bits, yet unaccountably I survived with no more than a few RF burns! If the teachers knew what we were up to they certainly never said anything. Do you think you'd get away with that today when it is apparently the headmaster's fault if a kid hurls himself down some steps in an attempt to emulate spiderman?

BTW, I recognise the G8, but what is an M0 callsign?

Nick H.

Not electrical at all, but a schoolfriend - back in the late

60s - built an airgun during the woodwork and metalwork classes. The teachers had no doubt what he was doing, but it was seen as worthwhile project. (A different world, eh?) The metalwork teacher made a point of teaching him how to case harden the sear and trigger parts (for safety). It used two Morris Minor valve springs and had a smooth bore as they couldn't figure out how to cut rifling grooves with any of the equipment available at school.

Not a great success as a weapon, but we learned some useful skills from it.

Gyppo

In message , Nick H writes

That, I do...

Good for them. Those were the days of common sense, not blame culture (which is starting to infect rallies too, as posts passim in this group have commented on).

I very much doubt it; unless it said 'CE' in that odd font on the back of the kit, they'd not allow it into the school.

It's the Class A call I took out in March 2002, after doing the Morse, a year or so before it was dropped as a requirement; I now have both calls as 'lifetime licences'. I use the M call mostly below 30MHz, and the G call mostly above that frequency.

ObSE:- I'll be going to the Thurlow (Haverhill) rally on Saturday - there's usually a good engine line there, and an amateur station too. Likewise at Henham, though due to unemployment I doubt I'll get there this year.

"Andrew Marshall" wrote (snip):-

Ah, shows how far behind the times I am, it was G4 last time I looked!

I was vaguely aware that the morse requirement for HF operation had been dropped - does that mean I could resurrect my licence and build that top band rig after all? Now where did I put that 813 ;-)

Nick H.

When 14 or so, we made guns, too. Bits of cold water pipe - conduit splits! - and a penny banger. Cap the screwed end with a cap from the plumbers shop. Drill a small hole in the side into which the fuse could be screwed. tip the contents down the pipe, drop in an appropriate sized ball bearing & Robert is your mother's brother.

We learned about wadding and stuff & got the things pretty reliable - once got a ball right through the side of a fifty gallon oildrum, an allotment hut and embedded it immovably in the blade of a spade! How we ever didn't kill ourselves or each other the Good Lord alone Knows ............

Regards,

J. Kim Siddorn,

In message , Nick H writes

Yes, it does indeed. Provided you've got your pass slip, or other evidence of having passed the RAE (I believe even a call book entry may be enough), you can apply for your licence again, and use all amateur bands, not just VHF and above.

Plus another two to modulate it, and an 1845KHz crystal to put it in the middle of the 10KHz-wide part of Top Band where you can run 100W of AM (400W PEP)...

Plus, of course, a small diesel, hot-bulb or hot-tube-ignition engine, and an alternator, to run the rig. Best to try for a position at the end of the engine line, to get away from at least some of the ignition pulses (some of which are strong enough to be picked up by the microphone lead of the portable cassette recorder on which I used to record engine sounds at rallies).

"Andrew Marshall" wrote

Not a problem; I'd use my B40 Rx which has an RIS input - just got to sync it with the worst offenders ;-)

Nick H

In message , Nick H writes

I have a B40(D) also, but it needs a fair bit of TLC before I can use it to any great extent. The RA17L works fine, though - and is only two-thirds of the weight.

I'll have to look up the RIS function on the B40D circuit diagram (if I can find one online). Collecting the antiphase signals from the offending engines could be interesting, though...

"Andrew Marshall" wrote

Good Lord, I didn't expect to find a fellow sufferer in these parts!

From memory it connects to g3 on the first RF - I presume the ships RIS set produced appropriately timed -ve pulses to cut that valve off during the radar transmission period.

Nick H

In message , Nick H writes

(taken to email)

"Andrew Marshall" wrote

Good plan (and apologies to all for increasingly OT thread) but nothing Rcvd.

nunderscorehighfieldathotmaildotcom

Nick H

In message , Nick H writes

The Demon email server seems to be borked ATM - it's doing its occasional time-out/refusal trick...