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"Gareth Magennis" <sound.service@btconnect.com>: Jun 03 09:22PM +0100 I have a Mesa Boogie Dual Rectifier on my bench which runs 3 sections of ECC83 at over 400v Anode voltage. The spec says these have 300v max Anode voltage.   How can this be?     Here's a link to a different model's schematic to the one I have, that does a similar thing:   http://www.schematicsunlimited.com/m/mesa-boogie/mesa-boogie-dual-rectifier-amplifier-schematic       Gareth.

"Gareth Magennis" <sound.service@btconnect.com>: Jun 03 09:27PM +0100 Oops, I'm an arse,   that would be Anode to Cathode PD, so probably in spec.     But anyway, this does seem rather a curious thing to do, most other guitar amps I've ever seen don't have pre-amp valve Anodes anywhere near this, they are always well downstream of the Power amp HT.       Gareth.                 "Gareth Magennis" wrote in message news:0mJbx.752771$m15.315085@fx45.am4...   I have a Mesa Boogie Dual Rectifier on my bench which runs 3 sections of ECC83 at over 400v Anode voltage. The spec says these have 300v max Anode voltage.   How can this be?     Here's a link to a different model's schematic to the one I have, that does a similar thing:   http://www.schematicsunlimited.com/m/mesa-boogie/mesa-boogie-dual-rectifier-amplifier-schematic       Gareth.

Phil Allison <pallison49@gmail.com>: Jun 03 11:21PM -0700 Gareth Magennis wrote:     > How can this be?   > Here's a link to a different model's schematic to the one I have, that does > a similar thing:   http://www.schematicsunlimited.com/m/mesa-boogie/mesa-boogie-dual-rectifier-amplifier-schematic     ** The problem I see there is the heater to cathode voltage is over the 180V limit for a 12AX7.   http://free-hosting.infodiv.com/audiotube/small_signal_triode/small_signal_triode0034/12AX7_Page_1.jpg   Same goes for all the Fender amps that use 12AT7s for the phase splitter, where the cathode voltage is around 140V when the spec says 90.   http://free-hosting.infodiv.com/audiotube/small_signal_triode/small_signal_triode0002/12AT7_Page_1.jpg   The reverb drive valve in most Fenders is also a 12AT7 where the anode voltage is over 400V ( driving a small tranny) while the spec is 300.   I bought a dozen JAN numbered 12AT7s once ( branded GE ) that lit up purple inside if you used them in the reverb position in Fenders, plus made a lot of noise. They were perfectly OK in the phase splitter position.   Amp makers often say to use only their brand name valves, sometimes for a good reason.     ... Phil                     .... Phil

"Gareth Magennis" <sound.service@btconnect.com>: Jun 04 05:39PM +0100 "Phil Allison" wrote in message news:5d351c76-368f-4d54-b830-2a8ac0e3ee21@googlegroups.com...   Gareth Magennis wrote:     > Here's a link to a different model's schematic to the one I have, that > does > a similar thing:   http://www.schematicsunlimited.com/m/mesa-boogie/mesa-boogie-dual-rectifier-amplifier-schematic     ** The problem I see there is the heater to cathode voltage is over the 180V limit for a 12AX7.   http://free-hosting.infodiv.com/audiotube/small_signal_triode/small_signal_triode0034/12AX7_Page_1.jpg   Same goes for all the Fender amps that use 12AT7s for the phase splitter, where the cathode voltage is around 140V when the spec says 90.   http://free-hosting.infodiv.com/audiotube/small_signal_triode/small_signal_triode0002/12AT7_Page_1.jpg   The reverb drive valve in most Fenders is also a 12AT7 where the anode voltage is over 400V ( driving a small tranny) while the spec is 300.   I bought a dozen JAN numbered 12AT7s once ( branded GE ) that lit up purple inside if you used them in the reverb position in Fenders, plus made a lot of noise. They were perfectly OK in the phase splitter position.   Amp makers often say to use only their brand name valves, sometimes for a good reason.     ... Phil         Right, measured all the voltages today. It has 6 pre-amp valves. One half of V2 runs at 343v Anode/Cathode, the Reverb valve is pretty much as you described Fenders circuit, i.e. a mighty 398v on a ECC83, running through a small tranny. All other valves run below the 300v Anode max.   I also measured the Heater/Cathode voltages. One was 206v, another 205v. All others well below the 180v max.     This made me laugh though - I was measuring the Heater/Cathode voltage using pin 5 as reference, and measuring pins 3 and 8 with a multimeter. I got the various voltages on V3 to V6, but V1 and V2 measured around -10v. That's a NEGATIVE 10v.   I had to have a good look at the schematic to find out how this was possible!       Thanks, this has been educational.       Gareth.

bud-- <null@void.com>: Jun 03 07:12PM -0600 On 6/3/2015 9:40 AM, Cydrome Leader wrote:   > I have to agree with Phil here. The key here is plug-in device. This is > why "surge strips" or any sort of power strip with surge supression are > just pure trash.   Experts at the IEEE and NIST say say they are effective. That is based on research and experience.   Where is a source that agrees with you?   > surge, real or imagined into ground, you elevate the voltage on that > segment of the ground circuit. That destroys or interferes with all the > other equiment connected to that that ground.   The IEEE surge guide clearly explains how plug-in protectors work. It is not primarily by earthing the surge.   And as any competent manufacturer, along with the IEEE and NIST make clear, and as I wrote in my 1st post, "if using a plug-in protector all interconnected equipment needs to be connected to the same protector. External connections, like coax also must go through the protector. As explained in the IEEE surge guide (starting page 30) plug-in protectors work primarily by limiting the voltage from each wire to the ground at the protector. To do that all wires must go through the protector."   As I also pointed out, the amount of energy that has any reasonable probability of being absorbed in a MOV at a plug-in protector is asurprisingly small 35 joules, and in 13 of 15 test cases it was 1 joule or less (US). That is based on research. The largest energy is actually not for the largest surges. One reason the energy is so small is there is arc-over at about 6kV from panel busbars to the enclosure - and the established arc is hundreds of volts. That dumps most of the energy of a large surge to earth, and limits the exposure in a house. The second reason is a surge is a very short event. That means the current components are relatively high frequency. That means the impedance of the branch circuit is more important than the resistance. The result is the amount of surge current is quite limited which means that the energy is limited.   What I have written is based on surge guides from reliable sources which I have linked to, and on published research.   On the other side are opinions by you and Phil.   Maybe if you figured out how they worked....

"Ralph Mowery" <rmowery28146@earthlink.net>: Jun 03 11:19PM -0400 "bud--" <null@void.com> wrote in message news:556f987f$0$29478$c3e8da3$e074e489@news.astraweb.com... >> just pure trash.   > Experts at the IEEE and NIST say say they are effective. That is based on > research and experience.   Personal experiance tells me they work. During a thunderstorm a transformer let go that feed my house and three others. I had surge strips on all the electronics that plug in the wall. Two of the strips and a MOV on the stove were taken out. No other damage. Two of the other houses lost their TV sets and some other things. Did not talk to the third house to see if he lost anything or not.

Phil Allison <pallison49@gmail.com>: Jun 04 01:09AM -0700 Ralph Mowery wrote:   Cydrome Leader wrote:   > > Experts at the IEEE and NIST say say they are effective. That is based on > > research and experience.   > Personal experiance tells me they work.     ** Simply because MOVs work - ie they conduct hard with large voltages applied.   Under lab test conditions, they work as advertised.     However, a NASTY electric shock hazard arises when they become damaged, go leaky and for whatever reason the safety earth at the power outlet is high resistance ( corroded for example ) or has become non existent.   Then, the MOV used on the hot or active line will conduct AC current to all the exposed metal of all the items plugged into the surge protector's outlets - plus all interconnected items in a home computer, audio or video system.         .... Phil

bud-- <null@void.com>: Jun 04 09:13AM -0600 On 6/4/2015 2:09 AM, Phil Allison wrote:   >>> Experts at the IEEE and NIST say say they are effective. That is based on >>> research and experience.   >> Personal experiance tells me they work.   I have seen a number of people say they are effective in high lightning - high surge environment Florida.     > ** Simply because MOVs work - ie they conduct hard with large voltages applied.   > Under lab test conditions, they work as advertised.   > However, a NASTY electric shock hazard arises when they become damaged, go leaky   A strawman, since as I have written that is very unlikely. The surge energy they experience (at least in the US) is tiny even for near worst case surges.   > and for whatever reason the safety earth at the power outlet is high resistance ( corroded for example ) or has become non existent.   Of course that is a problem with, for instance, a refrigerator that develops 'leakage'. I have seen several reports of refrigerators that will trip a GFCI (trips on about 5mA ground fault) but will run on a circuit without a GFCI.   And then there is a H-G fault on 'grounded' metal cased equipment.   Another strawman - where are all the dead bodies from surge protectors?   The IEEE says they are effective.   So does the US-NIST.   Reliable sites that agree with you - zero.

micky <NONONOmisc07@bigfoot.com>: Jun 04 07:43AM -0400 >those software radios, that convert early on to a low frequency and then >do the rest digitally. I have a Sansa Fuze, about the same era, and I am >quite impressed by the FM radio.   Yes, me too. I have another Clip somewhere, that I can't find. It had a microphone and the abilitiy to record voices. Could be very useful some time. but that time hasn't happened yet. I don't think it's legal in Maryland without the other party's consent, where I live, but it woudl be some other places.   The new one has no microphone. The tuner seems about the same. Even a pretty strong station, it made a difference where I was standing, even in my wooden house, but it also worked pretty well in a steel frame store.   Because I already had one, it was very hard to buy another, especially new, so I looked on ebay. Ebay still had two auctions from last fall, and the bidding went up to 37 and 38 dollars. The new one a couple days ago was 35 dollars plus tax at a local store (Best Buy) That's with 4Gigs. One of the auction items was only 2 Gigs. Not that I need more than 2, but it still shows how people can bid more than something is worth. (The new ones have a slot for inserting some sort of memory card, in addition to the 4 or 8 gigs they come with.)   >But there isn't much space in there for >analog components (not when you take away the space for the screen and the >battery), so it likely is something fairly digital.   Does that make a difference in power consumption?   >Apparently most smartphones have the ability to tune the FM broadcast >band, using similar digital circuitry, but in North America that function >is often turned off through software.   Yes, I have a phone like that too, a Huawei. I thought it would be good for walking, but it's too heavy afaic and no one calls me when I'm walking and I usually don't have anyone to call.   But it was good when I had outpatient surgery at the hospital last month, and had to spend about 4 hours in bed there afterwards. Listened to the radio (FM only) and when the phone rang and I answered, the radio stopped automatically. Started up again when I hung up.   >in and the volume high. See how long the battery lasts. Recharge it and >then do it again with the volume at low. I would think the battery lasts >longer with the volume at low.   Well, I'm sure of that but I'll never get around to doing tests. I was interested in people's estimates. If 80 or 90% is too high.

"Mark Zacharias" <mark_zacharias@labolgcbs.net>: Jun 04 05:52AM -0500 "N_Cook" <diverse@tcp.co.uk> wrote in message news:mkn69j$l99$1@dont-email.me...   > Ah the feindish Aiwa AD 6900 lump from 1970s, just. Someone wanted me to > repair one 2 months back , via post, until he found what 2 lots of postage > would be.     Yeah - sometimes I wonder if I'm just too lazy, but on the other hand there was never a reason these things had to be so difficult to service. I think the design engineers went from indifference regarding service issues - straight over to antagonism.   "You want to service this? F--k you."   "Our marketing guys just want to sell more new junk."   Mark Z.

whit3rd <whit3rd@gmail.com>: Jun 03 02:14PM -0700 On Wednesday, June 3, 2015 at 1:13:26 AM UTC-7, Andre Majorel wrote: > Found in a yoghurt maker whose heating element never turns off :   > http://www.teaser.fr/~amajorel/ee/f/ti3070s2.jpg   Probably a thermostat, PEPI and Klixon are manufacturers of this form of thermal switch.   If it must be replaced, you may find that 'authorized' repair of the appliance is required. Stocking and numbering of appliance parts is deliberately made obscure, and covered by layers of (usually feigned) concern using words like "tamper", "unsafe", "unauthorized".

Andre Majorel <cheney@halliburton.com>: Jun 04 09:37AM > appliance is required. Stocking and numbering of appliance parts is > deliberately made obscure, and covered by layers of (usually > feigned) concern using words like "tamper", "unsafe", "unauthorized".   Curious that two of two would say it's a thermostat even though the wires are of different colours. Reportedly, the yoghurt maker never clicked.   DC voltage across the device is a steady 0.0 mV.   The resistance is all over the place. Constantly changing values centred around 1.4 k one moment, then around 105 ohms the next, then 60, then 75... Tried shining a filament lamp on the device to heat it. Turning the light on or off sometimes causes an instant 30% jump in the resistance. Hours of fun.   Whatever this is, it's probably defective.   Thanks.   -- André Majorel http://www.teaser.fr/~amajorel/ It is difficult to get a man to understand something, when his salary depends upon his not understanding it. -- Upton Sinclair

isw <isw@witzend.com>: Jun 03 09:35PM -0700 I have come across a thermocouple that I can't identify. From other factors, I suspect it is a type K, but that's what I want to confirm (because if it's not, the temperatures will be wrong).   All insulation is glass fiber, or something just like it (makes you itch). The sheath is woven but not varnished and appears to be all white. The positive wire is white with a blue (or black??) tracer, and is not magnetic. The negative is white with a red tracer, and is magnetic.   I've looked at a lot of documents on line that list a whole lot of color combinations, but nothing I've found matches what I have.   Any ideas?   Isaac

whit3rd <whit3rd@gmail.com>: Jun 03 11:25PM -0700 On Wednesday, June 3, 2015 at 9:35:43 PM UTC-7, isw wrote: > The positive wire is white with a blue (or black??) tracer, and > is not magnetic. The negative is white with a red tracer, and is > magnetic.   Put one end in icewater, the other in boiling, and expect type J: 5.26 mV type K: 4.09 mV type E: 6.32 mV type T: 4.28 mV   T, at least, is very unlikely; neither wire ought to be magnetic. Type J definitely has one wire magnetic. It's usually red vs white.

Phil Allison <pallison49@gmail.com>: Jun 04 12:52AM -0700 isw wrote:   > I have come across a thermocouple   ** Where you found it is a big clue.     > that I can't identify. From other > factors, I suspect it is a type K, but that's what I want to confirm > (because if it's not, the temperatures will be wrong).     ** You don't have a K-type pre-amp/adaptor or a DMM with one to try it out ?   Then how do you propose to use the thing?   BTW you will need a K-type two pin plug, normally yellow colour.           .... Phil

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