News from Ferrograph World:
The heads are not designed to be relapped, so Mr Martini-Yates is not convinced there would be any improvement. It looks like it's a new(er) head that's needed, which he can supply. I'll endeavour to straighten up the tape path when I get it back together so the new one doesn't have the same 'keystone' wear.
However, as I'm impecunious at present, and not back to the head-reinstallation stage, I'll leave that for now. I would like to try straightening up the old one as an exercise as well, so I'll see how that goes.
For now, I have been going through the PSU checking values after the transformer calculations. There are a number of 'Visconol-X' capacitors, some of which test open-circuit so I am replacing them with some film types I have already.
Questions:
- I have seen reference on here to testing capacitors with a 'Megger' type machine for breakdown resistance. I might be able to stretch to one of these as the older ones are cheap. Is this worth it? At the moment all I can do is test for continuity and/or turn on the machine with the capacitor I want to test and see if the smoke comes out.
- I like dual cans, but the right values are not available. My calculations suggest replacing the (for example) 8mFd + 16mFd PSU filter/reservoir capacitor (C24 & C26) with a 16+16mFd would not adversely affect the filtering. There are a couple more of these. Could I use 16+16mFd in all these locations? (C9/C13 & C11/C12)
- There is a 0.1mFd, 350V 'MICAMOLD' capacitor between the AC contacts of SW3, the motor switch. Is this purely to prevent arcing? As it is on a mains AC line, though the capacitor is not between LN or L/N and Earth, should this be an X/Y type?
- C3 is marked as 0.02mFd 360V, but in the unit it is bypassed by a resistor and a 3100pF(? - value half illegible) 'Suflex' (picture attached). What is the reason for this not being on the circuit diagram? Is it a pre-calculated snubber circuit for the speed control switch?