Re: Desoldering pump to avoid

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Computer Nerd Kev 9 years ago

>>

>>> Cut tracks with a scalpel held at a sharp angle so the cut edges overlap.
>>> flat it down after with the iron tip - it doesn't take much solder to
>>> secure the join.
>>
>> I've tried a scalpel and often find I accidently jump over a few
>> tracks and leave a big slice over the board. Then I have to check
>> each of the other tracks to make sure I didn't accidently cut
>> through them, but usually I haven't because I usually have to
>> make multiple runs over a track with the scalpel to get all the
>> way through.
>
> Use a Swan & Morton size 10 blade and stab with the point rather than slice
> with the curved part.
>
> If you need to carve - the blade is blunt.

OK, I'll keep that in mind. Given the sort of nonsense I often get up to with scalpels, blunt blades are quite a possibility.

__ __ #_ < |\| |< _#

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~misfit~ 9 years ago

F*ck off with your insults. I read further down the thread and see you've got commercial interests and good reason to insult me for your own profit.

As for reading this post further - no thanks.

Shaun. "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders) > Those old Hitachi MOSFETs, were very tough and ideally > suited to public address systems. For high quality audio, they suck. > Fundamentally, they are quite non-linear at anything under an Amp or > so of bias current. The negative tempco of gm means that any fast > rising transients and/or when using low impedance speakers will cause > a severe curtailing of dynamics. > > I suggest you compare your MOSFET POS to an ancient Phase Linear 400 > (or 700), or almost any other BJT amp. You will be stunned at how much > better the old PLs sound. Reliability, of course, is a different > matter. MOSFET amps tend to be very reliable, when properly designed. > As an example of very poor design, I refer you to the old and now > defunct, NRG (energy) brand of MOSFET amps. Extremely unstable > designs.

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~misfit~ 9 years ago

Yeah I get that. I'm not exactly cloth-eared and my MOSFET amplifiers sound far better than anything else *I can afford*. They were originally made in Auckland by an ex-employee of Perreaux in the 1980s. I have a couple 1970s Perreaux band PA amps too and use the low channel of one for a subwoofer amp. (I used to tour with a band doing stage lightning and soundmixing in the 1970s.)

Yeah, seems a stretch of the imagination.

Indeed. To insult me as a lead-in to his reply to me shows that he's not good with people - unless he's just brave when he's behind a keyboard....

Shaun. "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders)

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Clocky 9 years ago

I think he firmly believes in his own spin.

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~misfit~ 9 years ago

Ok, thanks.

That's the worst kind of religious nutcase. (Think Jonestown...)

Cheers,

Shaun. "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders)

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Phil Allison 9 years ago

** You just reminded me of the Perreaux BJT amplifier I saw and serviced in the early 80s - it was " P2200 " IIRC.

The design was reminiscent of a PL700, but with two large power transformers. The transformers had their 120V primaries and 65V secondaries wired in series. The mid point of the secondaries went to ground and the ends to a bridge rectifier and pair of large filter electros.

Now, there is a *BIG* problem with this idea: in order for the DC voltages on the electros to match, the load current drawn from plus and minus supplies must match exactly - cos nothing forces the two transformers to share the 240 supply evenly.

As it was the DC rails were offset by 11 volts at idle, due to a 10kohm / 10W resistor on the positive side that fed a speaker relay.

On music programme, the rail offset varied about the 11 volt value.

The correct way is to have the secondaries wired in parallel, thereby forcing equal sharing of the AC supply voltage - but that could not be done in this case.

Peter Perreaux made no similar error with his MOSFET models, he got nearly everything near perfect, particularly with the heatsinking and fan cooling set up.

There was one oversight though, that caused a lot of grief for owners about 5 or 10 years later. Anyone here know what it was ?

.... Phil

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Re: Desoldering pump to avoid

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