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jefrs

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About jefrs

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    Somewhere in England
  1. jefrs

    iPad

    As comfortable as lying in bed with an ipad? Seriously though the ipad is far more of a media player toy than a computer. What it does it is good at. Wireless. To Apple Airport for sounds, bluetooth cans! Camera. Portable. Garageband or Amplitube? Garageband is easy but Amplitube better bells and whistles. Neither anywhere near as good as a DAW on a laptop/pc.But Line6 Sonic Port (lightning) is better than Amplitube iRigHD interface
  2. It may take a moment to get the head around it but that 5V(?) high-current heater is also firing hot electrons onto the rectifier anode. They are supposed to do that and why a valve rectifier cannot be run off an ordinary heater circuit. SS diodes are more efficient. Increasing B+ will alter the bias requirement. Cathode bias can cope with a lot of variation but the one in there is intended for 5881, Rk (and load/OT) on EL34 is different. Keep an eye on the EL34, see how they glow. Can you safely measure B+ and bias volts? I don't think valve amps are designed as energy efficient applia
  3. Yes it has its own heater but it also forms part of the power supply, it is not wasted. That current drawn from the heater goes into the HT. It is supposed to do that. That heater is also acting as a cathode. It is not just heating the cathode but supplying power too. That is why it has its own high current supply from the PT.
  4. By drain on the heater, do you mean the valve rectifier heater? - that is supposed to be supplying power, and quite a lot of it, to the amp. It is a feature, not a fault. If you mean the other valves' heaters then that is taken off a separate winding on the P/T, it is unaffected by the rectifier whether valve or solid state. Now the pre-amp bottles run their heaters in series from a supply of +13.5VDC on mine (due to my high mains volts again) but the output valves have 6.3VAC supplied heaters.
  5. Yes, it has been running a long time ;) - but it ain't dead yet! One of the first things I had to do when I got mine, many moons ago now, was connect the fan because there was a wire off at the PCB. Then I observed it made the amp hum and had to re-route the fan wires as twisted-pair. The fan supply should not be taken from the middle of the PCB near a valve base. Part of the heat 'problem' is lack of sufficient vents and running the bottles 'upside-down'. The fan is a "computer" fan, my PC has additional fans (controlled by temperature) due to old house dusty environment and cats. The
  6. You can get a plug in solid state rectifier that directly replaces the 5AR4/etc bottle. example http://www.watfordvalves.com/product_detail.asp?id=3071 Expect to get more volts with solid state diode rectifier.
  7. My standby switch actually exploded out of its back. It is an AC mains switch being asked to perform at >400VDC, no wonder it arcs. Completely the wrong tool for the job. It is also an odd size. I used some big "repair washers" to fit my MV there. You do not need a standby switch, you /can/ bypass it, spade connectors are easy to do this to. Just use the on/off switch and silence the amp with the input socket (it shorts = silence) like you are supposed to do. The standby switch is a fashion accessory. The Chinese rectifier in mine also made pop-corn noises, that was arcing over too
  8. Do please note that my main "tone opening up" mod was to put 820k shunts around both R5 and R6 (both 1Meg), reducing it to 450k. The logical reason for using a 1W resistor here is that they are longer and can thus "stand off" a higher voltage, not that they pass much current, even if they had the entire HT across them, they would only see 0.18W P=E^2/R. My C4 "bright cap" is now on a bright switch. However the CH2 "bright cap" C6 is disconnected. Do check component values here, I found some on the PCB that did not match the circuit diagram. Also, for interest, my B+ appears to be 420V
  9. I have used JJ-6V6GTS aka JJ-6V6S in there with no problem at all but have not / would not crank it right up. No red plate there. Note our mains is almost 250VAC so the 240Veuro PT will be running HT B+ a wee bit higher than spec hence 34.3V seen. Usual and current op valves are =C=6L6GC it's not just loud, it's bloody loud! I have taken chassis pics but cannot remember if I ever posted them on here. It will be the same as yours with a bit of tidy-up plus some damage from dropping. Let me know if you really, really need them?
  10. This is a pretty old thread now but I have just been notified of a reply. Any questions re BC30 mods? 1) I changed my ISP and hence email addresses, thus notifications got lost in the aether. 2) What was the Epiphone forum is now a Gibson forum. I lost the linky. Re - Greenbacks. They do not break in but just keep sounding better and better as they age. Re - speaker cable. I tend to use mains twin-flex. Mains twin-flex is often better than fancy hi-fi speaker cable, both electrically and more robust. Do solder the connections on because they need to be low resistance, crimp connec
  11. I was suggesting the schematic does not always show the correct component values fitted to the PCB. Can you read my diagram? PM me if you need a more legible one.
  12. The reverb is quite wet. You can get an acoustic feedback howl through the tank so make sure it is bagged and secured down. The amp runs in triode or tetrode* mode, both are Class AB. Only a single-ended amp can be guaranteed to be Class A, you can build a Class A push-pull but they are low-output, little more than the SE job, and they require a /very/ large OP transformer. Depending on choice of output valve the tetrode may give 26-30+ watts at full chat. In triode mode it is likely to be over 15 watts. For some reason this is a very loud amp. This could be down to a good efficient output
  13. You are probably running a line level signal (2V) into a low level input (millivolts). This can work but you should not run the piggy-back amp to max volume: even so you may overload the circuit between its input and its first volume control. Better, place an attenuator between first and second amp: do you have something like a Graphic EQ pedal that can reduce the signal?
  14. Problem with any cathode/self biased amp is that you are limited to the nearest "preferred" value resistor. But near-enough is good-enough, it's called self-bias because it is self limiting. You may find it is hot now but the next value may be too cold: Murphy's Law. Another thought, if the cathode voltage is too high, do check the solder connections and redo with pukka tin/lead fluxed. These lead-free PCB are terrible for cold joints (high resistance).
  15. Tone suckers! Add your pedal FX one-at-a-time until you find the thieves, then bin them. Keep your pedal board down to the essential minimum. Ditch the ones you don't use every day.
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