06-12-2016, 12:48 PM
(This post was last modified: 06-12-2016, 12:50 PM by Valvebloke.)
Yes. Occasionally the old Eries can go nonlinear, which shows up in the distortion spectrum, and then they really do have to be replaced. But otherwise padding them is easier than replacing them. The tags to which they're connected can be surprisingly brittle (the recoil from a manual solder-sucker can easily snap them) and the resistor leads are very short, so snipping them can bust the tags too. And, as you say, when it comes to value originality counts for a great deal.
A pro would say that junking the Quad II and buying a modern Class D solid-state amp would be the sensible engineering choice of course !
The choke can be rewound (Mike Barker can do it, for example). It's a tedious and foul job though because the dead choke has to be melted out of the bitumen in which it's canned, the lams and bobbin have to be cleaned and the bobbin unwound (think soaking in paraffin or, if you're braver than I am, in petrol), the bobbin has to be rewound, the gapped lam stack has to be reassembled and secured and the whole lot then has to be re-potted in the can. If you use potting compound then you won't be gassed or burned by the bitumen, but that's the last time you'll be able to do the job without, at the least, destroying the original paintwork. It is possible to cut out the middle steps by using a commercial choke. This one https://www.hammfg.com/part/157G is almost exactly the same as the original and economies of scale mean that Hammond can make it for a price that wouldn't be possible for a one-off rewind (although the recent fall in value of the pound against the Canadian dollar has narrowed the gap). I have a cheap slow-cooker hooked to a Variac which I use for melting out and re-potting (woe betide anyone who does this in his other half's oven !). So I expect to have the thing back together quite quickly.
VB
A pro would say that junking the Quad II and buying a modern Class D solid-state amp would be the sensible engineering choice of course !
The choke can be rewound (Mike Barker can do it, for example). It's a tedious and foul job though because the dead choke has to be melted out of the bitumen in which it's canned, the lams and bobbin have to be cleaned and the bobbin unwound (think soaking in paraffin or, if you're braver than I am, in petrol), the bobbin has to be rewound, the gapped lam stack has to be reassembled and secured and the whole lot then has to be re-potted in the can. If you use potting compound then you won't be gassed or burned by the bitumen, but that's the last time you'll be able to do the job without, at the least, destroying the original paintwork. It is possible to cut out the middle steps by using a commercial choke. This one https://www.hammfg.com/part/157G is almost exactly the same as the original and economies of scale mean that Hammond can make it for a price that wouldn't be possible for a one-off rewind (although the recent fall in value of the pound against the Canadian dollar has narrowed the gap). I have a cheap slow-cooker hooked to a Variac which I use for melting out and re-potting (woe betide anyone who does this in his other half's oven !). So I expect to have the thing back together quite quickly.
VB
Ampregen Ltd http://www.ampregen.com
