This is the head disk assembly for an SLO-1700.
It consists of 4 head tips mounted on an assembly (2 video and 2 Hi-Fi).
N.B. NTSC systems combine the Hi-Fi and video onto the same head pair.
The heads are extremely delicate and comprise of two small coils with a very small gap between them. These two small coils can be seen above in the bottom left of the picture.
There are a number of different symptoms associated with heads.
One head clogged
If one head is clogged or damaged, it can sometimes give a similar effect to that seen when the tracking is not correctly set. e.g. A large amount of snow/lines on the picture but usually the bottom of the picture remains perfect.
All heads clogged
If both of the heads become clogged, then the whole picture becomes severely degraded. Although this looks like the worst case, it is the one which is most likely to be solved by cleaning the heads.
If the Hi-Fi head(s) are clogged or damaged, then Hi-Fi sound is either completely lost (linear audio only can be heard and the Hi-Fi light is no longer lit) or a 'clicking' type sound can be heard. If all the heads are worn then white lines are seen on the picture and areas of the picture containing sharp contrast often bleed with black. e.g. If a dark object is placed in front of a white background, the right hand side of the dark object 'bleeds' into the white.
All heads worn
See also the Head Cleaning Guide.
The first step in fixing the heads is to give them a clean. Follow the detailed
instructions in the Head Cleaning Guide. If this
fails to improve matters then they might need replacement.
An easy test to see if the heads are beginning to wear out is to test a pre-recorded tape in the machine. If this plays well in the machine but a recent test recording made on the same machine has white lines on it, then the heads could be worn.
The Maintenance Guide states that the heads and upper drum should be replaced after every 2000 hours of use.
Accessories: adjusting jig, feeler gauge 1, feeler guage 2.
Note: Keep them after replacing the rotary head disk, since they will be needed when replacing the guide arm assembly and the rotary coupler assembly. (They are not delivered with the guide arm assembly or the rotary coupler assembly).
How to refit rotary head disk (1)
How to refit rotary head disk (2)
How to refit rotary head disk (3)
Thanks to Mark Perry for supplying this information