First Switch On for the 870

Yesterday, after I had replaced the Electrolytic and what is often referred to "That Capacitor" (the paper capacitor of the mains filter), I switched it on for the first time.

No smoke, bad smells or exploding capacitors, always a good start, the panel lamps seemed a bit dim but otherwise OK. Waiting a minute or so, for the heaters to warm up and get those electrons moving, then crackles were heard a bit of switch cleaner on the volume pot fixed that. I tried an aerial and get a slight increase in noise but nothing seemed to tune on any band.

Testing with a screwdriver on the slider of the volume pot produced a reasonable hum so the amp seems good, just waiting for a cheap analogue meter to come in the post so I can do a few measurement. I did look at old Avo's on EBay but they go for silly money.


 
Changing the caps was an interesting exercise especially the 32 + 32 mFd smoothing cap, the only ones I could find were of a bolt through type that would have needed a slightly larger hole and cost around £20. I decide to try taking apart the old one and found a couple of 32 mfd caps that would fit in side the tube when I got it apart it was fairly well dried up, obviously the right thing to do. Soldering the new caps to the original connectors proved a problem as the internal wires were crimped to the solder tags and the wires would not solder; in the end i had to make small holes in the end plate to feed the new wires through and wrap them round the tags. To get the innards out I had to lever back the flange using a pair of fine cutters so when I reassemble it the flange looked a bit rough   (see picture)
























Following on from that Smoothing Capacitor rebuild I had to decide whether I was going to treat the other the same way, as in a restoration or a repair, so I compromised and replaced the rest with modern ones and saved the parts so I could perhaps restore it later (as if that will ever happen..!!) Just for completeness here is a before and after pic

Next step do some measurements of voltage etc when the analogue multimeter turns up, I do have and all singing and dance digital one but its a bit confusing so as its an old set back to old technology.