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- Peavey PV14 mixer, 2012 - 1 Update
- Fender G-DEC 15 watt "memory locked" - 3 Updates
| N_Cook <diverse@tcp.co.uk>: Nov 10 03:56PM Had some TOP249YN around so tried one in there and went in to .8 sec clicking protect mode. Thinking it was a mismatch in sense Rs I sent of for some TOP244YN. Replaced and still went into protect mode even with a load on the nominal/actual ? +15V line as that line is current monitored by a dropper to feed the opto-isolator. Double DVM-D test on the opto in circuit showed no response. Removed the CNY17 and replaced with a 4N31 which passes the double DVM-D test in circuit, will mains power up again tomorrow . So some overvoltage/overcurrent to the C-E of the opto when the ps failed. |
| "Arfa Daily" <arfa.daily@ntlworld.com>: Nov 10 02:12AM "N_Cook" <diverse@tcp.co.uk> wrote in message news:m3nrdt$ctq$1@dont-email.me... > button > Press that button again > then rotary selector knob to change display to read "off" I hate these micro-controlled bollox amplifiers with a passion. DSP 'modelling' I can just about live with, but rotary encoders for controls ? But even worse, normal pots, connected to A-D inputs on a micro ?Virtually every one I see has a problem that's down to finger trouble ... Just a couple of weeks ago, I had a Vox Valvetronix combo in that said "comes on very quiet". Well that's because it's the way you set it before saving and switching off, you moron. RTFM, or better yet, buy an amp with just a volume and three tone controls on it. I currently have a 4 x 6L6 Fender in for repair that has uP controlled bias, FFS !! What a load of utter nonsense. What on earth was the designer thinking of, or his supervisor when he approved it ? The micro is currently doing absolutely nothing - not even any clock present, although the 3.3 volts is present on the chip. The bias is supposed to be controlled by four PWM signals driving transistors, but of course, as there is no clock, these drives are missing with the result that the output grids are all at -89 volts ... The board that this lot is all on is utterly unrepairable, with SM components the size of gnat's cocks. We're currently trying to persuade Fender to tell us if this board is available even, let alone its price ... >:-( Arfa |
| Phil Allison <pallison49@gmail.com>: Nov 09 08:24PM -0800 Arfa Daily wrote: > components the size of gnat's cocks. We're currently trying to persuade > Fender to tell us if this board is available even, let alone its price ... > >:-( ** Hughes and Kettner make similar amps: http://ru.hughes-and-kettner.com/products.php5?id=111&prod=Switchblade%2050%20Combo All the pots are just encoders for the DSP system, so every tiny movement makes an annoying click. The blurb says " ..an built-in tube technician..... " Yep, a tiny SMD board adjusts the idle current and, if out of range, even biases off the particular valve. The trick circuit allows allows H&K to use a small toroidal output tranny - cos it keeps bias balance spot on. Had one of the little horrors on the bench back in July, dead because the heater fuse had blown. Bastard to get open and put back together too. When running, I found it was riddled with HF oscillations under all load conditions - open, resistive and speaker load. The output stage is a Marshall clone, but there was no cap across the 12AX7 phase splitter anodes - I found fitting 100pF fixed the oscillations. Beware. ... Phil |
| N_Cook <diverse@tcp.co.uk>: Nov 10 08:27AM Owner just needed a simple practise amp, but ended up with this thing that is way over the top and needs driving lessons before you can use it. Reminded of the acoustic bass player and his Roland Cube that kept returning to me as it distorted, but absolutely no problem that I could find. Eventually it emerged he just wanted a simple but small amp and speaker for his bass and ended up with all this DSP stuff. His opinion was that as he didn't want any of the features other than volume , he turned all the controls anti-clockwise. That put the "type" feature into octave bass under-imposing an octive under his acoustic bass, hence the observed "distortion" |
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