Thread: HMV 905 Project
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Old 3rd Sep 2015, 1:16 am   #17
beery
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Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 988
Default Re: HMV 905 Project

Hi all,

Thanks David for your help.

Thanks also to Leon for your suggestion about what to do about the rust, I have just bought some scotchbrite pads...

When I restored my Cossor 54 it was just that little bit more rusty and I took the decision to paint it. To give an idea of the condition, the valve sockets were still good, indeed the EHT transformer was ok, but the chassis rust was furry and pitted.
The 905 is not nearly as bad as that thankfully.

I've opened up one of the IF "cans" to have a look at what I need to do to replace the missing final vision IF coil, L28. I have a replacement "can" and trimmer cap, but I can't find a coil former like this. The coil former is made of bakelite, it mounts with a large slotted round brass nut and has an adjustable brass core. Does anyone have one? I might have to use something else...

I've moved one of the smoothing inductors (CK2) back to its correct position and where there is another missing inductor to the right of it I found some extra holes. They happened to fit a monster inductor (CK1, clearly not original) that was also found in the wrong place. However since this inductor measures 500 ohms instead of the 160 ohms of the correct one, I can only think that the set can't have performed too well with it in place (it feeds the timebases).

The original style tag board is almost impossible to find and most newer stuff has completely the wrong pitch. I've some tag strip from Germany that has almost exactly the right pitch if I remove every other tag. The tags are much smaller, but they seem to be the best idea at present. I've attached a photo comparing the old style tags with the new.

That's all for now.

Regards
Andy
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