As long as somebody is receptive I'm happy to go on 'splainin' 'til the cow come home.

Quote from: js1970After reading your last post, I diode tested the transistors and they seemed up to snuff. So I cleaned off the cooling fan, fastened everything down tight, and ran it. I had to keep the amp at sensible volumes, but nevertheless, I ran it for about an hour. I must say that thing is a beast. Punchy, defined, with gobs of power. At times, it seemed almost too punchy, too powerful ( if indeed, there is such a thing).

That's "fixed", yup.   :dbtu:

Quote from: js1970Satisfied, I took the lid off and checked the resistor with the back of my finger. Barely warm! Maybe my original observation was a bit askew, or maybe the thermal management of the fan and heatsink made it a non issue. I'm going to take it  to a jam and see how she does.

A bit of (forced) air movement over a component can make a very large difference to its temperature, but it's this final good result that is the key point.

Quote from: js1970fear I have set on a new hobby to which my lovely ,understanding ,bride will be thrilled.

Ahhhh.  Now, a couple of tips.

The first is that electronics, building or faultfinding, is actually quite addictive.  My wife (my third ) is a puzzle buff, crosswords, Suduku's, and the like.  I get a similar charge from solving faults on the bench, and this "charge", endorphins or whatever, is quite addictive.


Secondly, electronics generally isn't horribly messy like working on car engines or building surfboards, but it can be a bit ... untidy.

{My wife's ex worked on big engines and had one in bits in every room of the house except the bedroom, where he had been clearly warned, so when she came home and found another one pulled down in the bedroom and grease on the bedsheets that was it.  Finish.}

For a time we lived in a small flat and there was nowhere that could be set aside for working on electronics projects, so I had a large cardboard box I could put on the dining table and work on stuff without any danger of damaging the surface or leaving solder splashes everywhere, and which could be packed up and hidden away to restore what girls like to think of as domestic normality.

Some flat dwellers have even built specific boxes that open into a mini-workshop or Ham station where it can all be hidden away.

So my hints are;
1. look after her in bed.
2. promptly fix everything that isn't working properly, blinds, heaters, door catches, etc, and she'll be a lot more tolerant of your electronic man-interests.
3. Chocolate.  It's like beer to us or catnip to cats, but only in small quantities of the highest quality you can find.  Here we have "Tim-Tams" which are not particularly up-market, but the dark chocolate ones are very effective at calming upset partners;



And if she ever starts complaining about "all these wires everywhere" gently remind her that you don't work on cars (and make certain that nothing electronic ever turns up in your bed - they really don't like that).

It helps a lot if she's into something creative herself such as music, photography, painting, dressmaking, pottery, writing that killer novel, radiation polymer chemistry, &c&c.

4. don't take my advice on relationships.

ATB to you both.

https://www.youtube.com/watch?v=m2ou-WIxfLY

Quote from: ilyaa on April 09, 2015, 01:42:52 PM
replaced the PNPs

have about ~160V now on each driver collector

getting ~110Vp-p on the tube grids -

next step, see if these tubes are any good!

Okay, that looks really good.  :dbtu:  Did you check the transistors that came out for wrong insertion/faults (It's always good to confirm your surmise just to be certain, defensive of your rep)?

Quote from: ilyaai live East of San Francisco

Ah, I've been reading about your drought situation and you have my heartfelt sympathy.

While homesick in London, Australian poet Dorothea Mackellar penned the rather cheesy patriotic poem "My Country", the second verse (which is the only bit most people can remember) starts...

Quote from: Dorothea Mackellar
I love a sunburnt country,
A land of sweeping plains,
Of ragged mountain ranges,
Of droughts and flooding rains.

They remember it because it's truistic (well, except the bit about the mountain ranges, "ragged" yes, however not very tall by world standards).  But the "droughts and flooding rains" really resonate because it also seems to be a land of extremes, baked hard dry and burning for years, then suddenly - underwater as far as the eye can see; "Sydney or the Bush" as we say.

{I felt the same way myself when I was working there as a tech in a cellar, only seeing the sun as a low foggy orb at lunchtime, a deep longing for a real beach, but I managed to avoid writing any twee poetry about it - I just came home.}

So even our self-absorbed "cellphone generation" are conditioned to droughts.  The last drought in the south-east lasted seven or eleven years (depending on how you define "drought") and Melbourne water storage's were down to similar single percentage digit territory so we had a very long period of water restrictions; car washing forbidden (except for food transport vehicles and commercial car washes recycling all their water), gardens limited to hand watering for half an hour in the evening twice a week (later totally forbidden except with bore or recycled grey water), everybody encourage to take a three-minute egg timer into the shower, a steady rush on dual-flush toilets and domestic "grey" (e.g. laundry) water recovery systems, and so on.

Most of Victoria was facing a similar unthinkable situation to that California is now facing - actually running right out of reticulated water.  Some country towns depended on tanker trains.

This led to some permanent changes such as the widespread switch from water-hungry European gardens to dry land gardens using drought tolerant native species, and in my region permanent restrictions on what reticulated water could be used for.

The last year we were given a target of 90 litres per person per day, but SWMBO and I have lived on tank water where an empty tank is a very rude and expensive wake up call, and managed to get our use down to 40 litres per day for the both of us.  You have to get creative and perform triage, buckets in the shower with you to recycle on the garden, the veggie patch first priority, then established plants and trees that seem to be suffering, and to hell with the lawn (it just turns into dust bowl).  Fill your swimming pool or spa?  That's a joke, right? (but the rich can buy a truckload recovered/cleaned non-drinking water at between $0.25 and $1 a litre if they really must - a similar price to petrol).

It also caused a lot of agriculture to get serious about water conservation, and the first thing to go was highly wasteful flood irrigation of fruit trees replaced with specific drip-feed systems, many millions of dollars on irrigation canals to reduce leakage and covers for evaporation (and a vast reduction in the 90% of the gigalitres being wasted).

So I have to wonder how Californians are going to respond to this fairly new situation; are people pulling together, accepting of restrictions in a dire situation, or is it more a matter of "it's my Constitutional Right to use as much water as I can pay for"?  Certainly we have selfish "water cheats" and a system of Water Inspectors who can turn up and give you a stern lecture, but very few of the bone headed actually have to be dragged into Court.  The vast majority of coffee shop and dinner party conversations tend to include a friendly competition for a low use score, and exchanging saving and reuse tips and tricks.

Not only did the tank business boom, a whole new range of tanks suitable for suburban and tight inner city house blocks appeared, slimline to fit;



...and innovative water-fences;



If everybody co-operates for the common good {aaarrgh..."socialism"} then you can get through it, but if f!!*-You-Jack-I-M-Alright dominates then you are all going to be "up *s!!t* Creek in a barbed-wire canoe without a paddle" (not that it will matter much since even that creek will be dry) as taps stop flowing altogether and you have to get by on bottled water

It's an uncomfortable truth that a city of several million people becomes effectively uninhabitable only about 24 hours after you cut the water off, so I hope you have your zombie-bunker ready if the thirsty hoards come pouring out of SF.


(Stan Cross, 1933)

Certainly by all means check the PNP's.  In this case it's a sort of super-LTP with two devices on each side.  The PNP emitter-followers ('coz that's all they are) act like buffers on the bases of the NPN LTP and allow a much higher input impedance.

There is no DC NFB around this loop so there could well be a largish offset betwteen the LTP collectors.  As long as you still have enough voltage swing to drive each of the grids to zero volts from Vbias (i.e. 55Vpk) then you should be right.  Some voltage imbalance is common with valve LTP PI's.



(ed: typo)

I'm sorry but I'm confused.

I don't see how we made the leap from high voltage supply transformer to supply safety grounding, some assumption in there that I'm missing.  Also given that almost every amplifier I deal with has a solid safety ground and no problems with mains-borne noise I'm wondering what is happening with the mains supply at your place.

"Ground lifting" with a resistor or anti-parallel diodes can certainly cure or reduce noise from some sources such as earth loops (grounded stomp supply?), but the problem is that you cure your sound problem at the increased risk of winding up dead if the ground lift fails, and I don't think that is a good trade off.

The normal (and highly effective) cure for mains-borne fridge pops and drill whine is a solid safety earth and a line filter (say recovered from a dead computer power supply).

Quote from: JLTIt's funny how these projects seem to get just a little more complicated (and expensive) with each plot twist.

Yeah, it can be a bit like stepping onto a running exercise treadmill - but you really can't complain about a mystery speaker for $2.50.

You have plunged off the beaten track here a bit, so there will be some experimenting, you'll have try what seems a good idea and see if it really is.

Planning is good - "long think, short do".   :dbtu:

 :dbtu:


Hi lucid77, welcome.

Quote from: lucid77-15db jack plays fine on the same settings and then will cut volume every couple seconds. Doesn't loose volume all together, but definitely cuts quite a bit. Is this normal?

"Normal" in the sense that this is typical of how plastic sockets fail, particularly PCB mounting ones (which they mostly are these days).

Unlike the older metal chassis mount type, somebody trips over a guitar lead (seems to happen at least once every practice I've attended) and the sudden wrench is transmitted by the socket to the solder connections where it is mounted on the board, and they crack.  You may find that if you push the plug from side to side or up and down that you can turn your signal on and off at will.

This will almost certainly be a cracked solder joint under the socket.  If you get the board out and look at the solder side while moving the socket it is very likely you will see some movement in the joints (bright light, lens).  Sometimes the copper tracks break and he entire joint moves, but if you can see the socket tag(s) moving inside the solder joint then a touch with the iron and some fresh solder normally does the job (until the next time).

This is a very common generic problem with a lot of modern amps, stomps, and synths where plastic sockets are used.


Cleaning sockets
One way to clean a socket is to use a (smoking) pipe cleaner (with plastic twill) folded double and dipped in some metho (o.n.o.) and worked in and out while also slowly rotating.  I've made it a habit as part of my gig prep to give my sockets a going over and found it does help to minimise on-stage problems and stuffing about (which is never good look).

...and to illustrate the point, just had a lovely 3 hour Greek lunch for the step-grandson's 21st at an inner-city taverna.  I've loved Greek food ever since I went there, and this was a real treat.    <3)

---

I think that in their hearts people like Exxon and the Koch Bros know that climate change is going to be a kind of end game for them because things are going to change so radically they are effectively being knocked out of the game entirely, so there is a mad scrabble to accumulate the biggest pile of gold before the $&!% hits the fan.

I'm reminded of a Russian saying; "I know there is starvation in the world, but this bread if for my child."

It's a raw survival rather than winning strategy.  There was a time in the 70's when it looked like companies such as BP were reinventing themselves into renewables, solar (and nuclear), but a widespread political polarisation has become a sort of deathlock on looking for new directions - renewables and conservation to the left, and laissez faire oil and coal to the right.

Two tribes with different world views, and different totems.

:duh


A couple of million households, including mine, have voted with their feet/wallets;

Quote from: http://www.energymatters.com.au/renewable-news/em3819/2009, output was just 18 gigawatt-hours.
2011; which was 225 gigawatt-hours
2012 – Solar energy supplied 550 gigawatt-hours to Victoria

:dbtu:

Which makes me optimistic that while the politicians serve their coal fired masters the population is going a different way.  Then we have the current government - a dysfunctional neo-feudal theocracy straight out of 1850, and I despair.   


um ... that's a raw, unpeeled onion Our Glorious Leader is munching into...   
Being somewhat less popular than a dose of the clap, it's apparently some sort of "I'm so tough..." statement.  Nobody doubts he's tough, it's that he is also a totally loose cannon that has done more damage to his own side than anything else.  Think Yes, Minister meets Gilbert & Sullivan.

Service manual from our old friends here;
http://elektrotanya.com/crate_b150_bass_combo_sm.pdf/download.html

{wait 30 secs until "processing" changes to "Get Manual"}

Quote from: ilyaa on April 04, 2015, 07:21:46 PM
on a separate note, i did some snooping around the PI and found that:

its clear from the underside of the board that the driver transistors were replaced - they are MJE 3439 - which seems like a suitable replacement BUT whoever put them in did not orient the b/c/e terminals correctly - i did some tests with the DMM on diode range and they have the base and the collector switched. probably took a guess and guessed wrong!! so no wonder the voltage is bad. im assuming they are probably fried because of that error? i found some replacements at the electronics shop near me so ill get those and put them in and see if the voltages look better -

Well +1 for spotting the previous repair, and another +1 for realising and proving it was botched.   :dbtu:

Safer to assume they are dead, you don't know what else has happened to them (in the light of putting them in the wrong way).

{moral:  Your gear, and you can take a punt and it will be on your own head; client gear, where your client may end up looking like a doofus mid-song with a smoking amp, requires a higher standard (lest your rep end up smoking as well - your rep is your business card, to the individual tech it should be everything.  A good rep will feed you and maybe make you rich, but a bad rep can get you famous in the worst possible way).  They don't know and trust you to do it right, and by doing it right you build trust and good word of mouth, and that's priceless.}


Through a glass darkly, you seem to be gaining ground ilyaa.   :dbtu:

BTW, may I ask where you live?

Ah.  Yes.  Well this was about 1/4-inch diameter and about a foot long, so if it hadn't been choka-blocked full of gunge it would have been a piccolo didge.  It was stalling something like a half-horse lube pump.

{Supposed to drain the initial detergent oil at 300hrs, next fill at 1500hrs, machine had by then done over 2000hrs.  A row of 12 machines, over a million each, and nobody had bothered to change the furshlugger OIL gor blimy.  }

A didge is a bit of a cultural thing.  Apparently you are supposed to go walkabout with your didge master until you find your didge.  May need a bit of finishing, and decoration of course, but it should come off the tree basically whole.  As a result Koories aren't too impressed by random blowing drainage pipe etc.

The trick to didge playing is "circular breathing".  Basically being able to inhale quickly through your nose while puffing out your last from your mouth so the sound is uninterruped.

Now I will be the first to say that didge playing;



... is generally about as exciting as Morris Dancing;



..., perhaps a bit less so, but I have encountered one young didge player who kept a group of us spellbound for more than half an hour with what he could do with it.  Lots of people have a go, young white fellas in particular, but not too many are any good at it - what you might call the doof end of didge playing.  A good didge will support all sorts of resonant modes above the fundamental (say around 50Hz) and dual modes in raspy chirps.

Like mouth harps they are on a single note and its harmonics, so guys like this fella had a clutch of didges so he could work in with guitarists, Blues &c very well.

Certainly if you already have a tranny with a suitable high voltage secondary use that for a simpler rectifier/filter.

A 200VAC tranny will give you a peak DC voltage of;

200 * 1.414 = 282.8V  which will load down a bit - near enough.   :dbtu:

Quote from: CraftyZA on April 04, 2015, 07:49:01 AM
Thanks. Will do that tripler. Just a question. In south africa we have between 240 and 250v mains. Mine is sitting at about 251. So i need to aim for almost 1:1 ratio.

We also have a 240/250V 50Hz system here in Australia.

But the multiplier runs from the nominal 60VAC coming out of your transformer secondary (a transformer you already have?).

If it has a suitable primary for your mains, you have no problem (apart from remembering to connect the safety ground to the transformer, chassis, &c).

Mains trannies are hardly ever specified by turns ratio, but by the RMS voltage on the primary and secondaries at rated load current.

An unregulated supply such as this is perfectly suitable for the application.  Leo didn't use regulators.   

As a design, I can't see how you can go wrong with the Alembic/Fender Dual Showman circuit JMF posted above.   You know this works.  :dbtu:


A note about the power supply.

Your 60V trannny should still be quite usable with this doubler circuit, viz;

60V_RMS

60 * 1.414 = 84.84 volts peak.

A lightly loaded multiplier like this outputs n-times Vpk, so this doubler will be 2 times Vpk.

84.84 * 2 = 169.68 volts

170V is not a lot but is reasonably respectable for this preamp, however to give its best I think it needs a bit more voltage, so I'd consider extending the multiplier by a stage to a tripler and you will get around;

84.84 * 3 = 254.52 volts

Around 250 which would be closer to the original.


HTH

Quote from: guitar.teenI may be a teen but I hate new stuff haha

Built my first radio pre-teen, built a bandload+ of valve amps and a PA in my teens, now retired. (so)


Protip: It's all just gear.  Okay.  Some you like, some you don't, but that depends very much on the designer, not the technology (thermionic/s.s./steam/&c).

Broadly electronic gear can be either;

- designed to be built.  Only.  One-way throwaway.  Hard to get at, no documentation.

- designed to be serviced.  Easy and obvious access to conventional circuits and layout, with due consideration to actual operating conditions (e.g. plastic PCB-mount input sockets, the source of much user pain.)

Whatever technology it is, you thank the second, and curse the first (sometime unto the seventh son of the seventh son  :grr ).



Generalise. (ya gotta)
As an industrial design and service tech I was mainly called in on "electronic" problems but I often found that I had to cross the demarcation boundaries between sensors and the electronic, to the muscle, electrical power control and motors, hydraulic, air, and mechanical.

My favorite is spending a day and evening chasing an intermittent "electronic" fault in a huge textile machine, and working through electrical switchgear to the lube pump, and finally a blocked outlet pipe - and dancing a jig like a couple of mad indians, waving this short length of pipe in the air, whooping and hollerin' much to the puzzlement of the night shift.  Tired and covered in oil, the head of Maintenance and I were ecstatic.

Born in Melbourne, I've lived in London and rural England where I first got interested in critters and what they got up to, but basically an inner-city boy until mid-life, electronics study, career, and bands/theater teching, I also liked to get out in the bush for long walks, but getting ill turned out to be an opportunity to take a more rural direction and actually live in various places in "The Bush".  Visited Lake Eyre several times for long stays - simply mind-blowing wild life and isolation.

The inner city suburbs of Carlton and Fitzroy are where I lived for many years and I think that Porteños would find them quite tolerable with a huge range of eating places, pubs with live music, many small theaters, art galleries and such.  We have people from around 120 different countries and walking down Brunswick St (which I used to live just off) you can sample the cuisine of most of them.

Sydney has the wonderful harbour setting, "the (surprise) view to water" and fantastic surf beaches, but even Sydney-siders agree that Melbourne is great coffee and great food.

It also once had a good manufacturing base until the country put all our chips on "mining boom" which went well for a while, but has now gone bust, meaning that in future we will all be living off servicing each other in service industries - everyone will be waiting on everyone else's table.  Or something.  Never understood the "Science" of Economics - can't predict and can't explain what happened.  The kids that took Eco's as school were all a bit odd.  :duh   Not at all like us fact-based science geeks.  8|


{but somehow we now have a buffoon for a Prime Minister, and a government hijacked by a bunch of Tea Party neo-con ideologues that nobody expected - but mercifully it's "fascism moderated by incompetence"   :grr   I guess we'll get over it - eventually.}