UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Heathkit IM-28 VTVM

WaveyDipole · 11th Oct 2019, 3:45 pm

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.

11th Oct 2019, 3:45 pm	#5
WaveyDipole Nonode Join Date: Mar 2013 Location: Leicester, UK Posts: 2,535	Re: Heathkit IM-28 VTVM 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. Last edited by WaveyDipole; 11th Oct 2019 at 4:14 pm.