|
Pub mains supply problem?
I can understand lager chillers or lighting triacs causing clicks and bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same time and no other pub mains problem showing itself. The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the initial failure. Not doing so now its in front of me, not fully checked out yet. Mains fuse always ok , just the HT one repeatedly failing after 4 seconds or so. At the same time as this HT one failed the mains fuse failed on another Marshall connected to the same supply - that one just required a change of mains fuse and is still ok. Could a fault causing failure of HT fuse on one amp cause the failure of mains fuse on another amp , with no pub wiring problem at all, even problem local to the power ring/spur to the stage. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
Pub mains supply problem?
"N Cook" wrote in message ... I can understand lager chillers or lighting triacs causing clicks and bangs and noises off but blowing fuses on 2 Marshall valve amps at the same time and no other pub mains problem showing itself. The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the initial failure. Not doing so now its in front of me, not fully checked out yet. Mains fuse always ok , just the HT one repeatedly failing after 4 seconds or so. At the same time as this HT one failed the mains fuse failed on another Marshall connected to the same supply - that one just required a change of mains fuse and is still ok. Could a fault causing failure of HT fuse on one amp cause the failure of mains fuse on another amp , with no pub wiring problem at all, even problem local to the power ring/spur to the stage. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Absolutely certain that the supply is not losing the neutral outside anywhere - particularly if an overhead supply to a country pub ? A friend of mine had a similar problem at a remote monitoring station for water treatment that he had to look after, and the mains kept randomly shooting up to 440v. That would certainly cause the secondary voltage of the mains tranny in the amp, to go up hugely, which would likely blow the HT fuse and / or the mains fuse. Might account for why a similar problem is happening to two unrelated items of equipment, simultaneously ? Have they had any problems with light bulbs failing, particularly any of those new-fangled eco things ? Otherwise, I can't think of anything that takes out the HT fuse on one amp, doing the same to the mains fuse on another. Arfa |
Pub mains supply problem?
Arfa Daily wrote in message
... "N Cook" wrote in message ... I can understand lager chillers or lighting triacs causing clicks and bangs and noises off but blowing fuses on 2 Marshall valve amps at the same time and no other pub mains problem showing itself. The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the initial failure. Not doing so now its in front of me, not fully checked out yet. Mains fuse always ok , just the HT one repeatedly failing after 4 seconds or so. At the same time as this HT one failed the mains fuse failed on another Marshall connected to the same supply - that one just required a change of mains fuse and is still ok. Could a fault causing failure of HT fuse on one amp cause the failure of mains fuse on another amp , with no pub wiring problem at all, even problem local to the power ring/spur to the stage. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Absolutely certain that the supply is not losing the neutral outside anywhere - particularly if an overhead supply to a country pub ? A friend of mine had a similar problem at a remote monitoring station for water treatment that he had to look after, and the mains kept randomly shooting up to 440v. That would certainly cause the secondary voltage of the mains tranny in the amp, to go up hugely, which would likely blow the HT fuse and / or the mains fuse. Might account for why a similar problem is happening to two unrelated items of equipment, simultaneously ? Have they had any problems with light bulbs failing, particularly any of those new-fangled eco things ? Otherwise, I can't think of anything that takes out the HT fuse on one amp, doing the same to the mains fuse on another. Arfa City pub in Pompey Owner didn't notice anything else wrong in the room at the gig and confronting the landlord he said he'd had no problems. I asked the owner if he used a nasty plastic extension lead and he did not really reply but even a problem there could not put a surge on to the kit. Checked the valves and transformers , caps etc and everything seems hunky dory , no wavering of HT of about 440V on dummy load. I looks as though it will have to be replacement 500V, twin 50uF electrolytics although no suspicious heating or bulges /weeping, unless an indisputable reason can be found. Fuses blew to black interior, ie not soft blown. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
Pub mains supply problem?
N Cook wrote:
Arfa Daily wrote in message ... "N Cook" wrote in message ... I can understand lager chillers or lighting triacs causing clicks and bangs and noises off but blowing fuses on 2 Marshall valve amps at the same time and no other pub mains problem showing itself. The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the initial failure. Not doing so now its in front of me, not fully checked out yet. Mains fuse always ok , just the HT one repeatedly failing after 4 seconds or so. At the same time as this HT one failed the mains fuse failed on another Marshall connected to the same supply - that one just required a change of mains fuse and is still ok. Could a fault causing failure of HT fuse on one amp cause the failure of mains fuse on another amp , with no pub wiring problem at all, even problem local to the power ring/spur to the stage. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Absolutely certain that the supply is not losing the neutral outside anywhere - particularly if an overhead supply to a country pub ? A friend of mine had a similar problem at a remote monitoring station for water treatment that he had to look after, and the mains kept randomly shooting up to 440v. That would certainly cause the secondary voltage of the mains tranny in the amp, to go up hugely, which would likely blow the HT fuse and / or the mains fuse. Might account for why a similar problem is happening to two unrelated items of equipment, simultaneously ? Have they had any problems with light bulbs failing, particularly any of those new-fangled eco things ? Otherwise, I can't think of anything that takes out the HT fuse on one amp, doing the same to the mains fuse on another. Arfa City pub in Pompey Owner didn't notice anything else wrong in the room at the gig and confronting the landlord he said he'd had no problems. I asked the owner if he used a nasty plastic extension lead and he did not really reply but even a problem there could not put a surge on to the kit. Checked the valves and transformers , caps etc and everything seems hunky dory , no wavering of HT of about 440V on dummy load. I looks as though it will have to be replacement 500V, twin 50uF electrolytics although no suspicious heating or bulges /weeping, unless an indisputable reason can be found. Fuses blew to black interior, ie not soft blown. Does these amps have valve rectifiers? GZ34 usually. The cheap Sovtec ones have a habit of flashing over internally and that sees the mains fuse off big time. If the fault is repeatable, you might be able to sort of prove it by temporarily fitting the amps with diode rectifiers for a couple of gigs. 2x 1n4007 in an old valve base (you can parallel up three a side if you are worried) I always have one on my bench for testing, I see a lot of duff valves these days. Ron(UK) |
Pub mains supply problem?
"Ron(UK)" wrote in message ... Does these amps have valve rectifiers? GZ34 usually. The cheap Sovtec ones have a habit of flashing over internally and that sees the mains fuse off big time. If the fault is repeatable, you might be able to sort of prove it by temporarily fitting the amps with diode rectifiers for a couple of gigs. 2x 1n4007 in an old valve base (you can parallel up three a side if you are worried) I always have one on my bench for testing, I see a lot of duff valves these days. Ron(UK) SS diodes in a tube rectifier receptable require a dropper resistor in series as the tube rectifier drops ~50V whereas the diodes drop ~0.7V. Otherwise your plate voltages will be too high. Dave |
Pub mains supply problem?
Ron(UK) wrote in message
... N Cook wrote: Arfa Daily wrote in message ... "N Cook" wrote in message ... I can understand lager chillers or lighting triacs causing clicks and bangs and noises off but blowing fuses on 2 Marshall valve amps at the same time and no other pub mains problem showing itself. The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the initial failure. Not doing so now its in front of me, not fully checked out yet. Mains fuse always ok , just the HT one repeatedly failing after 4 seconds or so. At the same time as this HT one failed the mains fuse failed on another Marshall connected to the same supply - that one just required a change of mains fuse and is still ok. Could a fault causing failure of HT fuse on one amp cause the failure of mains fuse on another amp , with no pub wiring problem at all, even problem local to the power ring/spur to the stage. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Absolutely certain that the supply is not losing the neutral outside anywhere - particularly if an overhead supply to a country pub ? A friend of mine had a similar problem at a remote monitoring station for water treatment that he had to look after, and the mains kept randomly shooting up to 440v. That would certainly cause the secondary voltage of the mains tranny in the amp, to go up hugely, which would likely blow the HT fuse and / or the mains fuse. Might account for why a similar problem is happening to two unrelated items of equipment, simultaneously ? Have they had any problems with light bulbs failing, particularly any of those new-fangled eco things ? Otherwise, I can't think of anything that takes out the HT fuse on one amp, doing the same to the mains fuse on another. Arfa City pub in Pompey Owner didn't notice anything else wrong in the room at the gig and confronting the landlord he said he'd had no problems. I asked the owner if he used a nasty plastic extension lead and he did not really reply but even a problem there could not put a surge on to the kit. Checked the valves and transformers , caps etc and everything seems hunky dory , no wavering of HT of about 440V on dummy load. I looks as though it will have to be replacement 500V, twin 50uF electrolytics although no suspicious heating or bulges /weeping, unless an indisputable reason can be found. Fuses blew to black interior, ie not soft blown. Does these amps have valve rectifiers? GZ34 usually. The cheap Sovtec ones have a habit of flashing over internally and that sees the mains fuse off big time. If the fault is repeatable, you might be able to sort of prove it by temporarily fitting the amps with diode rectifiers for a couple of gigs. 2x 1n4007 in an old valve base (you can parallel up three a side if you are worried) I always have one on my bench for testing, I see a lot of duff valves these days. Ron(UK) SS diodes in this one. Amp is in pristine condition and owner never goes above 3 . 5 off 500mA (T) fuses blew black before but no problem while here. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
Pub mains supply problem?
"N Cook" wrote in message ... Ron(UK) wrote in message ... N Cook wrote: Arfa Daily wrote in message ... "N Cook" wrote in message ... I can understand lager chillers or lighting triacs causing clicks and bangs and noises off but blowing fuses on 2 Marshall valve amps at the same time and no other pub mains problem showing itself. The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the initial failure. Not doing so now its in front of me, not fully checked out yet. Mains fuse always ok , just the HT one repeatedly failing after 4 seconds or so. At the same time as this HT one failed the mains fuse failed on another Marshall connected to the same supply - that one just required a change of mains fuse and is still ok. Could a fault causing failure of HT fuse on one amp cause the failure of mains fuse on another amp , with no pub wiring problem at all, even problem local to the power ring/spur to the stage. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Absolutely certain that the supply is not losing the neutral outside anywhere - particularly if an overhead supply to a country pub ? A friend of mine had a similar problem at a remote monitoring station for water treatment that he had to look after, and the mains kept randomly shooting up to 440v. That would certainly cause the secondary voltage of the mains tranny in the amp, to go up hugely, which would likely blow the HT fuse and / or the mains fuse. Might account for why a similar problem is happening to two unrelated items of equipment, simultaneously ? Have they had any problems with light bulbs failing, particularly any of those new-fangled eco things ? Otherwise, I can't think of anything that takes out the HT fuse on one amp, doing the same to the mains fuse on another. Arfa City pub in Pompey Owner didn't notice anything else wrong in the room at the gig and confronting the landlord he said he'd had no problems. I asked the owner if he used a nasty plastic extension lead and he did not really reply but even a problem there could not put a surge on to the kit. Checked the valves and transformers , caps etc and everything seems hunky dory , no wavering of HT of about 440V on dummy load. I looks as though it will have to be replacement 500V, twin 50uF electrolytics although no suspicious heating or bulges /weeping, unless an indisputable reason can be found. Fuses blew to black interior, ie not soft blown. Does these amps have valve rectifiers? GZ34 usually. The cheap Sovtec ones have a habit of flashing over internally and that sees the mains fuse off big time. If the fault is repeatable, you might be able to sort of prove it by temporarily fitting the amps with diode rectifiers for a couple of gigs. 2x 1n4007 in an old valve base (you can parallel up three a side if you are worried) I always have one on my bench for testing, I see a lot of duff valves these days. Ron(UK) SS diodes in this one. Amp is in pristine condition and owner never goes above 3 . 5 off 500mA (T) fuses blew black before but no problem while here. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Well according to this chap http://www.russandrews.com/article-4...gfrequency.htm the following is true: The effect of incorrect mains voltages The mains voltage has a surprising effect on the performance of a CD player. The motor speed is voltage controlled not frequency controlled with a crystal reference as most people would expect. Even though the motor supply voltage is regulated, the mains voltage does affect it, making it play slightly faster or slower. The effect on the music is quite large, making it sound either fast and exciting or slow and relaxed. I discovered this whilst experimenting to find out why a 'Pandora' isolating transformer, that was claimed to improve CD sound quality, did affect the sound. I discovered that the 'Pandora' was simply increasing the mains voltage by 24 volts, hence increasing the play speed and making the sound appear more 'exciting' I would put the amp on a variac up to about 250v, to see if anything is breaking down at a higher, yet still legal voltage than presently coming out of your bench. I would also be careful not to assume too much. The 2 faults may actually be unrelated, or the amp you have may now have burnt something out that was blowing the fuses. Your customer may also not be telling you what really happened. Did he really use 5 slow blow fuses? Did the two amps really blow at the same time? In a panic (gig) situation people tend to relate all sorts of things that are just not true. Strip the amp down and look for burnt components, arcing on PCB's etc. I've found faults by sticking my nose in there and having a good sniff. With the HT discharged of course! Perhaps a foreign body is floating around. These days I tend to trust my own instincts, not the customers', who can waste hours of your time if you let them. Gareth. |
Pub mains supply problem?
"Gareth Magennis" wrote in message om... Well according to this chap http://www.russandrews.com/article-4...gfrequency.htm the following is true: The effect of incorrect mains voltages The mains voltage has a surprising effect on the performance of a CD player. The motor speed is voltage controlled not frequency controlled with a crystal reference as most people would expect. Even though the motor supply voltage is regulated, the mains voltage does affect it, making it play slightly faster or slower. The effect on the music is quite large, making it sound either fast and exciting or slow and relaxed. I discovered this whilst experimenting to find out why a 'Pandora' isolating transformer, that was claimed to improve CD sound quality, did affect the sound. I discovered that the 'Pandora' was simply increasing the mains voltage by 24 volts, hence increasing the play speed and making the sound appear more 'exciting' Gareth. I'm surprised that Russ Andrews would make such an incorrect statement; true, the spindle motor is DC driven but it's controlled by A PLL reading the RF frequency from the pick up, the motor speed is varied to maintain the correct frequency and that will be locked to a master oscillator. The oscillator frequency would have to vary with supply voltage for Russ's statement to be true. Martin -- martindot herewhybrowat herentlworlddot herecom |
Pub mains supply problem?
"Martin Whybrow" wrote in message ... "Gareth Magennis" wrote in message om... Well according to this chap http://www.russandrews.com/article-4...gfrequency.htm the following is true: The effect of incorrect mains voltages The mains voltage has a surprising effect on the performance of a CD player. The motor speed is voltage controlled not frequency controlled with a crystal reference as most people would expect. Even though the motor supply voltage is regulated, the mains voltage does affect it, making it play slightly faster or slower. The effect on the music is quite large, making it sound either fast and exciting or slow and relaxed. I discovered this whilst experimenting to find out why a 'Pandora' isolating transformer, that was claimed to improve CD sound quality, did affect the sound. I discovered that the 'Pandora' was simply increasing the mains voltage by 24 volts, hence increasing the play speed and making the sound appear more 'exciting' Gareth. I'm surprised that Russ Andrews would make such an incorrect statement; true, the spindle motor is DC driven but it's controlled by A PLL reading the RF frequency from the pick up, the motor speed is varied to maintain the correct frequency and that will be locked to a master oscillator. The oscillator frequency would have to vary with supply voltage for Russ's statement to be true. Martin -- martindot herewhybrowat herentlworlddot herecom Well apart from any motor schenanigans, the data is simply clocked out at a fixed 44.1KHz. I have no idea what this guy is thinking about. Most bizarre. Gareth. |
Pub mains supply problem?
Martin Whybrow wrote:
I'm surprised that Russ Andrews would make such an incorrect statement; true, the spindle motor is DC driven but it's controlled by A PLL reading the RF frequency from the pick up, the motor speed is varied to maintain the correct frequency and that will be locked to a master oscillator. The oscillator frequency would have to vary with supply voltage for Russ's statement to be true. I do know that if you use a modern DVD player as a CD player, line voltage will have no effect at all on how it sounds. They all use switching power supplies, most of them 100-240 volt autosensing. No matter what you put into it, inside everything is run off of 5 and 12 volts DC. What's silly about the faster running theory is that it's digital and the frequency of the sound is based upon the sample rate clock, and not the speed of the disk. Some CD players, usually portable ones read ahead anyway and buffer the data, the ones that don't have to keep the speed the data comes off the disk the same as the sample rate and as you say have PLL locking circuitry to do it. It's been a long time since I cared, but I think that audio CD's are written (punched?) at different speeds to keep the data rate constant as the disk becomes wider. They read from the center out, so the disk spins slower at the center and faster at the edges. I think that's called CAV (constant angular velocity), but I may be wrong. The onlygimick I know of to improve audio CD quality that works is to use a specific car polish on the disks, which makes them sound "brighter". That's due to the way players use to handle read errors, they just repeated the missing sample. However that worked over 20 years ago, I seriously doubt that it is needed now. But buying a tranformer to up the power line voltage if it is normal is IMHO just a gimick sold to the ignorant. BTW, if you are in the EU, it really does not make sense because while all players sold in the EU are designed for the 230 volt standard, no one changed from 220 or 240 to 230, and so they really are designed to work properly with a range of at least 220-240 and probably a lot more. The last time I saw anything current production with a 220/240 volt selector switch on it was around 1983. By 1985 all of the equipment I saw was autoswitching between 220 and 240, and much of it between 120 to 240. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM |
Pub mains supply problem?
"Martin Whybrow" wrote in message ... "Gareth Magennis" wrote in message om... Well according to this chap http://www.russandrews.com/article-4...gfrequency.htm the following is true: The effect of incorrect mains voltages The mains voltage has a surprising effect on the performance of a CD player. The motor speed is voltage controlled not frequency controlled with a crystal reference as most people would expect. Even though the motor supply voltage is regulated, the mains voltage does affect it, making it play slightly faster or slower. The effect on the music is quite large, making it sound either fast and exciting or slow and relaxed. I discovered this whilst experimenting to find out why a 'Pandora' isolating transformer, that was claimed to improve CD sound quality, did affect the sound. I discovered that the 'Pandora' was simply increasing the mains voltage by 24 volts, hence increasing the play speed and making the sound appear more 'exciting' Gareth. I'm surprised that Russ Andrews would make such an incorrect statement; Actually after a virtually insignificant bit of further reading I realised what this Russ Andrews is all about. http://www.russandrews.com/lookup/0/...Cable-3400.htm I don't think any further comment is necessary, this kind of crap has been done to death. Gareth. |
Pub mains supply problem?
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
Pub mains supply problem?
N Cook wrote:
According to Regulation 27 of ESQC Regs 2002, UK mains should be 230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? Why? Ron(UK) |
Pub mains supply problem?
"N Cook" wrote in message ... According to Regulation 27 of ESQC Regs 2002, UK mains should be 230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I'm not sure it is the job of a repair tech to "Mod" customers' equipment unsolicited for whatever reason takes your fancy. Adding fuses may simply be adding in unreliability. Gareth. |
Pub mains supply problem?
Ron(UK) wrote in message
... N Cook wrote: According to Regulation 27 of ESQC Regs 2002, UK mains should be 230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? Why? Ron(UK) On the assumption that the one of the 2x 22nF, 400V DC decouplers to the o/p valves could have failed and self-healed, I replaced those. And with all lead-free boards I now routinely put a 2Kg pull at each end, via thin-nose pliers, of all 1 or more watt resistors, any resistors mounted off board or any that look a bit discoloured. All passed - what should I call this test ? I'll add fuses if it bounces back, with still nothing suspect anywhere. As for power surges , the owner was thinking of a protector - anyone any suggestions ? can they protect from a surge to say only 255 volts ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
Pub mains supply problem?
"N Cook" wrote in message ... According to Regulation 27 of ESQC Regs 2002, UK mains should be 230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Oddly enough, I had an amp in a few weeks back (can't remember what it was now - oh to be young again ...) which had a pair of rear panel fuseholders. This amp used 4 x EL34 I seem to recall, and each fuseholder was located in the anode feed of each valve pair. They were actually labelled "output valve fuses". In all the years I have been mending these things, I can't ever before remember seeing fuses in this position. Interestingly, I have an old AC30 in at the moment which has shorted turns on one half of the output transformer. This has completely thrutched the output valve on that half - the anode was glowing orange and the inside of the glass is badly flowered. Had the unit have had anode fuses, I guess the appropriate one would have opened and saved the valve. But in general, I am not in favour of altering a design, if only for that fact that it may compromise any electrical safety approvals that the equipment has. Arfa |
Pub mains supply problem?
Arfa Daily wrote in message
... "N Cook" wrote in message ... According to Regulation 27 of ESQC Regs 2002, UK mains should be 230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Oddly enough, I had an amp in a few weeks back (can't remember what it was now - oh to be young again ...) which had a pair of rear panel fuseholders. This amp used 4 x EL34 I seem to recall, and each fuseholder was located in the anode feed of each valve pair. They were actually labelled "output valve fuses". In all the years I have been mending these things, I can't ever before remember seeing fuses in this position. Interestingly, I have an old AC30 in at the moment which has shorted turns on one half of the output transformer. This has completely thrutched the output valve on that half - the anode was glowing orange and the inside of the glass is badly flowered. Had the unit have had anode fuses, I guess the appropriate one would have opened and saved the valve. But in general, I am not in favour of altering a design, if only for that fact that it may compromise any electrical safety approvals that the equipment has. Arfa No thermal fuses in those sort of transformers I suppose, asuming it started with a few shorted turns and progressively worsened. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
Pub mains supply problem?
"Arfa Daily" wrote in message ... "N Cook" wrote in message ... According to Regulation 27 of ESQC Regs 2002, UK mains should be 230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Oddly enough, I had an amp in a few weeks back (can't remember what it was now - oh to be young again ...) which had a pair of rear panel fuseholders. This amp used 4 x EL34 I seem to recall, and each fuseholder was located in the anode feed of each valve pair. They were actually labelled "output valve fuses". In all the years I have been mending these things, I can't ever before remember seeing fuses in this position. Interestingly, I have an old AC30 in at the moment which has shorted turns on one half of the output transformer. This has completely thrutched the output valve on that half - the anode was glowing orange and the inside of the glass is badly flowered. Had the unit have had anode fuses, I guess the appropriate one would have opened and saved the valve. But in general, I am not in favour of altering a design, if only for that fact that it may compromise any electrical safety approvals that the equipment has. Arfa Marshall commonly do that on their more current models, but the fuses are on the cathode. Here's an example: http://www.schematicheaven.com/marsh..._100w_2100.pdf Gareth. |
Pub mains supply problem?
"Gareth Magennis" wrote in message om... "Arfa Daily" wrote in message ... "N Cook" wrote in message ... According to Regulation 27 of ESQC Regs 2002, UK mains should be 230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Oddly enough, I had an amp in a few weeks back (can't remember what it was now - oh to be young again ...) which had a pair of rear panel fuseholders. This amp used 4 x EL34 I seem to recall, and each fuseholder was located in the anode feed of each valve pair. They were actually labelled "output valve fuses". In all the years I have been mending these things, I can't ever before remember seeing fuses in this position. Interestingly, I have an old AC30 in at the moment which has shorted turns on one half of the output transformer. This has completely thrutched the output valve on that half - the anode was glowing orange and the inside of the glass is badly flowered. Had the unit have had anode fuses, I guess the appropriate one would have opened and saved the valve. But in general, I am not in favour of altering a design, if only for that fact that it may compromise any electrical safety approvals that the equipment has. Arfa Marshall commonly do that on their more current models, but the fuses are on the cathode. Here's an example: http://www.schematicheaven.com/marsh..._100w_2100.pdf Gareth. Oh Christ. What is happening to my head ???? You are quite right Gareth. It *was* a Marshall, and I remember now, the fuses *were* in the cathodes. Was there a LED across them too to indicate if they had failed ? Boy, my memory is going. Must be mercury poisoning from my fillings, or lead poisoning from the solder ;-) Anyway, I guess the same still applies as cathode current very nearly equals anode current ... Arfa |
Pub mains supply problem?
N Cook wrote: I can understand lager chillers or lighting triacs causing clicks and bangs and noises off but blowing fuses on 2 Marshall valve amps at the same time and no other pub mains problem showing itself. The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the initial failure. Not doing so now its in front of me, not fully checked out yet. Mains fuse always ok , just the HT one repeatedly failing after 4 seconds or so. At the same time as this HT one failed the mains fuse failed on another Marshall connected to the same supply - that one just required a change of mains fuse and is still ok. Could a fault causing failure of HT fuse on one amp cause the failure of mains fuse on another amp , with no pub wiring problem at all, even problem local to the power ring/spur to the stage. Brief surges ? I had a JVC TV blow its internal mains fuse every 2 years or so even when not active (but in standby). Eventually a plug-in surge suppressor stopped it. Graham |
Pub mains supply problem?
Eeyore wrote in message
... N Cook wrote: I can understand lager chillers or lighting triacs causing clicks and bangs and noises off but blowing fuses on 2 Marshall valve amps at the same time and no other pub mains problem showing itself. The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the initial failure. Not doing so now its in front of me, not fully checked out yet. Mains fuse always ok , just the HT one repeatedly failing after 4 seconds or so. At the same time as this HT one failed the mains fuse failed on another Marshall connected to the same supply - that one just required a change of mains fuse and is still ok. Could a fault causing failure of HT fuse on one amp cause the failure of mains fuse on another amp , with no pub wiring problem at all, even problem local to the power ring/spur to the stage. Brief surges ? I had a JVC TV blow its internal mains fuse every 2 years or so even when not active (but in standby). Eventually a plug-in surge suppressor stopped it. Graham Bet it occured at night. Very few power stations/generator sets are needed to power the grid in the middle of the night. At some point it becomes necessary to start up another one and what happens to the grid at that time ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
Pub mains supply problem?
N Cook wrote: Eeyore wrote in message Brief surges ? I had a JVC TV blow its internal mains fuse every 2 years or so even when not active (but in standby). Eventually a plug-in surge suppressor stopped it. Bet it occured at night. I don't recall any particular pattern to it. It may even have had a transorb itself - and it was over sensitive. Putting another effectively in parallel took the load off it. Graham |
Pub mains supply problem?
"Arfa Daily" wrote in message ... "Gareth Magennis" wrote in message om... "Arfa Daily" wrote in message ... "N Cook" wrote in message ... According to Regulation 27 of ESQC Regs 2002, UK mains should be 230V +10% - 6%, which gives a range of 216V to 253V. I variaced up to 250V , switching on and off a few times, giving HT1 of 464 , nicely stable with amp under load. A thorough inspection of all components only revealed slightly loose nuts holding the iron laminations on the filter choke, which I cannot see as a problem. Otherwise inside and out it looks brand new, only some of the large binding post (lead-free of course everywhere ) solder joints looked grey but otherwise sound. Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each of the two EL34 anode supplies as well as the 500mA (T) regular fuse ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Oddly enough, I had an amp in a few weeks back (can't remember what it was now - oh to be young again ...) which had a pair of rear panel fuseholders. This amp used 4 x EL34 I seem to recall, and each fuseholder was located in the anode feed of each valve pair. They were actually labelled "output valve fuses". In all the years I have been mending these things, I can't ever before remember seeing fuses in this position. Interestingly, I have an old AC30 in at the moment which has shorted turns on one half of the output transformer. This has completely thrutched the output valve on that half - the anode was glowing orange and the inside of the glass is badly flowered. Had the unit have had anode fuses, I guess the appropriate one would have opened and saved the valve. But in general, I am not in favour of altering a design, if only for that fact that it may compromise any electrical safety approvals that the equipment has. Arfa Marshall commonly do that on their more current models, but the fuses are on the cathode. Here's an example: http://www.schematicheaven.com/marsh..._100w_2100.pdf Gareth. Oh Christ. What is happening to my head ???? You are quite right Gareth. It *was* a Marshall, and I remember now, the fuses *were* in the cathodes. Was there a LED across them too to indicate if they had failed ? Boy, my memory is going. Must be mercury poisoning from my fillings, or lead poisoning from the solder ;-) Each push/pull pair have their cathodes connected together and are grounded via a fuse. There is a LED and resistor across the fuse so if it blows the LED lights. It should be noted that if a faulty output valve blows a fuse, the valve is toast and you would not normally change just that one faulty valve, or at least I wouldn't. So these fuses are not really there to protect the valves. Quite possibly why they are not universally used? Anyway, I guess the same still applies as cathode current very nearly equals anode current ... Arfa There is also the Screen Grid G2, used as a second anode to consider, which is not normally directly connected to the Anode. Here's another Marshall schematic showing switchable Triode/Pentode type operation and a cathode fuse. http://www.schematicheaven.com/marsh...x_45xx_50w.pdf Gareth. |
Pub mains supply problem?
N Cook wrote:
Very few power stations/generator sets are needed to power the grid in the middle of the night. At some point it becomes necessary to start up another one and what happens to the grid at that time ? Generating systems don't just get "slapped on line" at startup, at least here in the USA. I don't believe you'd find that in any but third-world countries. The generator is brought up to speed/frquency and voltage (and stabilized) to match that of the grid before it's brought on line. Only then does the plant operator raise output in conjunction with the rest of the grid providers. It's a constant job to maintain the grid at nominal levels and requires constant voice and data transfers amongst the providers. I'm not going to say that surges don't happen when abrupt loads are dumped on or dropped, but that's another subject too long to explain in one post. |
Pub mains supply problem?
Marshall commonly do that on their more current models, but the fuses are on the cathode. Here's an example: http://www.schematicheaven.com/marsh..._100w_2100.pdf Gareth. Oh Christ. What is happening to my head ???? You are quite right Gareth. It *was* a Marshall, and I remember now, the fuses *were* in the cathodes. Was there a LED across them too to indicate if they had failed ? Boy, my memory is going. Must be mercury poisoning from my fillings, or lead poisoning from the solder ;-) Each push/pull pair have their cathodes connected together and are grounded via a fuse. There is a LED and resistor across the fuse so if it blows the LED lights. It should be noted that if a faulty output valve blows a fuse, the valve is toast and you would not normally change just that one faulty valve, or at least I wouldn't. So these fuses are not really there to protect the valves. Quite possibly why they are not universally used? Hmmm. I certainly wouldn't replace one output valve on its own, but I am not convinced that a period of sufficiently excess current long enough to blow the fuse, is going to result in the valve becoming 'toast', unless you are suggesting that the valve is toast in the first place, and that was what lead to the fuse blowing ? If so, I think it is pretty rare to find any internal faults, apart from the occasional inter-electrode short, which result in valves drawing excess current. Most times when I've seen the condition, it has been due to external failures, such as a fault in the bias supply, or a leaky grid coupling cap from a phase splitter anode. Or a wire off the grid - see my post in Mr Cook's "Marshall" thread :-) It's hard to see what other reason than protecting the valves, Marshall felt that they had for putting fuses in. Anyway, I guess the same still applies as cathode current very nearly equals anode current ... Arfa There is also the Screen Grid G2, used as a second anode to consider, which is not normally directly connected to the Anode. Yes, that is why I said "very nearly equals", the additional g2 current flowing in the cathode, being small at only a few mA, compared to the anode current. Here's another Marshall schematic showing switchable Triode/Pentode type operation and a cathode fuse. http://www.schematicheaven.com/marsh...x_45xx_50w.pdf Gareth. Interestingly, the cathode fuse is about what you would expect at 300 mA (or possibly 500, it's not too clear) but the main HT fuse appears to be rated at a staggering 3 amps ! Only the output valves are fed from the 'raw' HT line, everything else preamp / phase splitter-wise, being fed via a 22k resistor, R30, which is going to limit any downstream current to what ? about 10 mA to keep an HT rail of a coupla hundred volts at all the ECC's ? What on earth were they thinking of, when they put a fuse of that rating in the HT line ? I know it says that it's an 'F' and that it is a picofuse, but even so ... Am I missing something here ? Arfa |
Pub mains supply problem?
"Arfa Daily" wrote in message ... Marshall commonly do that on their more current models, but the fuses are on the cathode. Here's an example: http://www.schematicheaven.com/marsh..._100w_2100.pdf Gareth. Oh Christ. What is happening to my head ???? You are quite right Gareth. It *was* a Marshall, and I remember now, the fuses *were* in the cathodes. Was there a LED across them too to indicate if they had failed ? Boy, my memory is going. Must be mercury poisoning from my fillings, or lead poisoning from the solder ;-) Each push/pull pair have their cathodes connected together and are grounded via a fuse. There is a LED and resistor across the fuse so if it blows the LED lights. It should be noted that if a faulty output valve blows a fuse, the valve is toast and you would not normally change just that one faulty valve, or at least I wouldn't. So these fuses are not really there to protect the valves. Quite possibly why they are not universally used? Hmmm. I certainly wouldn't replace one output valve on its own, but I am not convinced that a period of sufficiently excess current long enough to blow the fuse, is going to result in the valve becoming 'toast', unless you are suggesting that the valve is toast in the first place, and that was what lead to the fuse blowing ? If so, I think it is pretty rare to find any internal faults, apart from the occasional inter-electrode short, which result in valves drawing excess current. Most times when I've seen the condition, it has been due to external failures, such as a fault in the bias supply, or a leaky grid coupling cap from a phase splitter anode. Or a wire off the grid - see my post in Mr Cook's "Marshall" thread :-) It's hard to see what other reason than protecting the valves, Marshall felt that they had for putting fuses in. Anyway, I guess the same still applies as cathode current very nearly equals anode current ... Arfa There is also the Screen Grid G2, used as a second anode to consider, which is not normally directly connected to the Anode. Yes, that is why I said "very nearly equals", the additional g2 current flowing in the cathode, being small at only a few mA, compared to the anode current. Here's another Marshall schematic showing switchable Triode/Pentode type operation and a cathode fuse. http://www.schematicheaven.com/marsh...x_45xx_50w.pdf Gareth. Interestingly, the cathode fuse is about what you would expect at 300 mA (or possibly 500, it's not too clear) but the main HT fuse appears to be rated at a staggering 3 amps ! Only the output valves are fed from the 'raw' HT line, everything else preamp / phase splitter-wise, being fed via a 22k resistor, R30, which is going to limit any downstream current to what ? about 10 mA to keep an HT rail of a coupla hundred volts at all the ECC's ? What on earth were they thinking of, when they put a fuse of that rating in the HT line ? I know it says that it's an 'F' and that it is a picofuse, but even so ... Am I missing something here ? Arfa Kind of puzzled me too - only thing I can see is to protect against a shorted reservoir cap after the 100 ohm resistor, or a faulty Triode/Pentode switch. Maybe these can arc if you switch them at full power or something, or maybe its to protect against running the amp without a speaker connected. Dunno. I'm sure they had their reasons, unless that is a typo. Gareth. |
| All times are GMT +1. The time now is 06:54 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 DIYbanter