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N_Cook <diverse@tcp.co.uk>: Jan 17 09:31AM On 16/01/2016 21:03, Gareth Magennis wrote:   > Gareth.   I've yet to come across blind bolts, other than for masonry use. ie one sided application , or you have to take the amp apart to fix the tank, using ordinary nuts and bolts for a Marshall Valvestate 100V. Incidently attrocious main board holding, vaguely held nylon standoffs that allow everything to flap about. Now there one substantial bolt and nut and spacer went in there to hold heatsink, loads of 7W resistors, big caps etc, from bouncing around so much

Adrian Caspersz <email@here.invalid>: Jan 17 01:01PM On 16/01/16 21:03, Gareth Magennis wrote:   > I have a picture of a reverb tank with rivets through grommets on a > steel chassis, but then it goes all wibbly wobbly.   > I would be inclined to use 4 x 3mm or 4mm bolts and locknuts.   I'm assuming they are these   http://www.sdproducts.co.uk/push-rivets-removable   Disadvantage in method is ye get a glob of glue rattling around in the bottom of the case :-p   -- Adrian C

N_Cook <diverse@tcp.co.uk>: Jan 17 01:02PM Incidently I find about 20 percent of the tank failures I come across is failure of the connections to the outside world corrossion or insulated wires breaking or solder failure at the flexing point ,70percent are failure of the <>200R coil at the fine wire soldered terminals and only 10% of the time the 200R coil has a break inside somewhere. So just because they lead out the coil wires too tight to the terminals, so easily sorted out without taking the spring anchors and iron pole-piece segments apart.

N_Cook <diverse@tcp.co.uk>: Jan 17 02:47PM On 17/01/2016 13:01, Adrian Caspersz wrote:   > http://www.sdproducts.co.uk/push-rivets-removable   > Disadvantage in method is ye get a glob of glue rattling around in the > bottom of the case :-p   Those are the bulk standard ones, these are 3/8 inch longer in the stem. The chassis is open on the other side so easy to collect them , assuming they pop off the end of the rivets, otherwise you have to remove the main pcb to get to the blind side of where the tank is fixed.

N_Cook <diverse@tcp.co.uk>: Jan 17 09:36AM On 16/01/2016 19:40, N_Cook wrote: > only a matter of fudging the right size and height of top protrusion to > glue over the stem of the switches,if necessary . > Well thats my halfpennyworth   I read original ref as top manual for top pannel. The above idea was for unobtainium contacts under piano keys, rather than just a controls pannel where any old switches , in place of pcb pad contacts, would do

John Heath <heathjohn2@gmail.com>: Jan 16 11:43PM -0800 On Tuesday, January 12, 2016 at 12:11:53 AM UTC-5, Kaz Kylheku wrote: > That's an RMS (predicated on it being sinusoidal), and it is useful. > If it is true RMS, and accurate, then I know that the peak voltage > is 1.414 times that, or 167.9, and peak-to-peak is twice that.   Yes but in my case I needed to evaluate the power consumption of a 2000 watt LED display board. The current for this puppy is spikes of current off the top of the hydro sine wave from all the DC switching power supplies for the sign. This means a peak detector of the current is the wrong answer. For this reason I bought a true RMS current meter to average out the net current to know what the breaker should be for the sign. You can imagine my disappointment when I read the small print that said true RMS provided it is sine wave current. Root Mean Square has a precise meaning and a cheap peak detector divide by .7 is not it. I am just ventilating but it really ticked me off when I found this out the hard way. Worse the biggest letters on this current meter was TRUE RMS. To give this balance it could have been marketing without the support of the engineering. Just the same when those engineers saw the final product with TRUE RMS bigger than life they knew it was a lie. To give this balance again I still use this little current meter and it has a added benefit of measuring DC current as well being a hall effect type meter. And it only cost 50 bucks so you really can not complain other than the lie about True RMS.       > > the old days they would not lie like this just to make a sale.   > Oh, if we pull out some old Popular Mechanics issues from, say, the > 1940's, we will see all sort sof snake oil.   I see your point. Basic human nature will not change over time.

Phil Allison <pallison49@gmail.com>: Jan 16 10:46PM -0800 John Heath wrote:   > Yes , now I see it. It is marked with a big sign saying FEEDBACK --> , ha. So who cares about matching tubes if it has feedback. The feedback should compensate for that yes / no ?   ** Feedback is used to mainly reduce the 3rd harmonic distortion of a push-pull valve power stage - particularly class AB ones as used in most guitar amps.   What it does not do however, is adjust the bias current balance so there is no net magnetisation in the output transformer. Few amps have an adjustment for this so the valves need to be matched, at least in pairs fitted to each side. Using poorly matched valves often results in a large increase in 2nd harmonic (ie bad waveform symmetry ) at low frequencies, since the iron core of the transformer goes into saturation much earlier in one polarity.     BTW:   With transistor amps, the same idle current always flows in both output devices cos they are connected in series.       .... Phil

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