It is a little concerning that a valve short could do so much damage *before* the HT fuse blew. That's the whole point of properly dual-fusing an amp like that - instead of relying on the single mains fuse as many manufacturers still do. If a 5W resistor blew that sounds like a screen resistor, or t...

That's a great recommendation burnsy - I had vaguely heard of these kits but hadn't seen them before. The SE-5A (great name, although if you're not a vintage aviation buff you may not know why!) looks absolutely perfect. I think I know what I want for Christmas now :-). Even for someone experienced,...

Actually, if you can find the time, doing a little reverse engineering on this amp will probably teach you a lot about how they work - it's a fairly simple circuit. It's maybe not the ideal candidate for experimenting with since it's a PCB amp and these are harder to work on - especially to avoid do...

Yes, if you run a 4-ohm attenuator as a dummy load in parallel with an 8-ohm cab, 2/3 of the power goes to the dummy load and only 1/3 to the cab - but there's then a fairly serious mismatch too, since the total impedance is now only 2.66 ohms. This is probably not a good idea if you're cranking the...

Unplugged (open circuit) is equivalent to 'infinite ohms', not zero. Zero is a short circuit. Actually valve amps are surprisingly more at risk from an open circuit than a short - without a current draw from the output transformer, the voltage can peak high enough to arc in the valves (which can blo...

There's actually no difference in the rectifier arrangement between single-ended and push-pull amps - both normally use single rectifiers. The difference is in the output section which is fed from them. Dual rectifiers are used only where either a single rectifier can't handle the current - which us...

I believe those are the rectifier diodes for the DC filament supply for the preamp valves. The others are the rectifier diodes for the HT. You'll soon find out if you remove them... the amp will stop working! Changing the speaker impedance can't *not* change the reflected primary impedance, no matte...

Or look for a second hand Load Box... which you may be more likely to find than a pair of 65s. I love G12-65s, they're some of my favourite speakers ever, and of the modern high-power Celestions they're certainly the closest to G12M-25s, but they still don't sound the same. In particular, if you lik...

If you love them, love the amp, love the tone, and can't easily trade the amp for a 2266, the solution is simple - get an attenuator. If you knock off 3dB that's equivalent to halving the power of the amp - probably just about enough to get you into the safe range, since the 2466 isn't really a full...

If there's *any* question whatever that the fan isn't working right, stop using the amp and replace it. If it sticks, the amp is toast. Best of all, replace the fan and then sell the amp before anything else bad happens. Apologies if this doesn't go down well with anyone who owns one, or any colleag...

I would still suspect a power valve is the cause - that would explain the rising hum and current draw after 15 minutes. A bad R83 by itself won't do that, if anything it will *reduce* the current draw - and it would have to be vastly too high in value for that, beyond the point where it would just f...

It's looking pretty good now. It took a while to get used to - it's very different from every other forum, but now I really like it and if anything it's the white ones that are harder on the eyes. It actually reminds me of looking into the back of a valve amp in a dark room... that lovely mixture of...

These amps don't have the best reputation for reliability and serviceability - they're extremely complex, quite difficult to work on and contain parts that are not really standard items in a valve amp (especially in the Midi-controlled switching circuit) - and the combo seems to suffer from heat-rel...

I totally agree, and if I was playing at the sort of volume and regular exposure that many professional musicians do, I wouldn't hesitate to spend that sort of money. A lot of us with poor eyesight will drop that much or more on a pair of designer specs without thinking about it (or at least accepti...

I don't usually for my own gigs, because I tend not to play all that loud (and relatively infrequently, damage is related to exposure time as well as volume) - although I've got my first gig with a new band coming up and that may no longer be true! (playing bass, with two guitar players each with Ma...