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Originally Posted by WaveyDipole
The meter is marked "BENTON HARBOR MICH." and there is no "U", just "Heathkit IM-28", so it would seem to be the US model. I have already PM'ed the member regarding the USA plug. I also noticed that the schematic shows a mains selector and fuse, but this example does not seem to have either. The mains cable is soldered directly on to a tagboard which connects the transformer and elsewhere. The black connector that joins the two windings in series is evidently not original so its seems to have been adapted at some point.
Thanks for the heads up on the 6AL5 and you mention of the EB91 as an alternative. Both the 6AL5 and the 12AU7A are genuine Mullard and look in pristine condition. The only thing I have been able to determine for now is that the heaters look OK. In any case, I will be very careful, although it is good to have a backup option of the EB91 just in case!
BTW, the seller was aware of the US heritage of the instrument because of the Nema5 plug, but was also unsure as to whether it would run on 240v.
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When I first saw the transformer primary connection. I knew that it was connected for 240 volts.
The later Heath offerings were all designed for export using dual primary transformers. I think their reasoning was to ship everything out of the US instead of locations out of the country. Around the same time, they opened retail establishments in the larger US cities. Before that, everything was mail-order.
Dave, USradcoll1, trying to remember!
