The following modifications affect many Akai VCRs including the VS422, VS467, VSF10, VSF30 and others.
NOTE: This information is intended for use by service personnel with the necessary qualifications and experience. VCRs contain dangerous voltages. Dave Sergeant cannot be held responsible for any damage to equipment or personnel as a result of implementing these modifications.
NOTE: the information here is based on information supplied in Akai technical service sheets. However the implementation detailed uses components different from those specified by Akai. The modifications therefore are not supported or recommended by Akai but are based on experience on many units repaired at the workshops here. Although I have confidence in the information as supplied, it should be noted that other service personnel incorporate them at their own risk.
AKAI VCR DISPLAY MODIFICATION
Replacing the capacitors using the existing values (56uF) provides only a temporary cure and it will return within a few months, even using 105C capacitors. For a lasting cure implement the full modification which increases the capacitors to 120uF 105C and reduces the heater voltage. This is done by modifying the secondary winding of the convertor transformer, together with a change of the diodes to Schottky types (to compensate for a lower drive voltage from the transformer).
A kit for this modification is supplied by Akai and available from Chas Hyde (order code 35003) or your normal suppliers. Another kit is also available which includes a replacement fluorescent for those cases (fairly rare) when the display has suffered damage from excess heater voltage (CHS 35013 or 35035 depending on model).
I implement this modification as follows:
Replace C446 and C447 with 100uF 16V 105C (in lieu of 120uF which is
not generally available)
A variation is provide for models which are fitted with a transformer which doesn't have a centre tap. This uses a 2.2ohm resistor which is connected in series with C447 in lieu of the track cut/link. I have yet to encounter one of these models. Please note that the transformer (L404) can sometimes fail with open circuit primary (as can the mains transformer for that matter!).
Some late VCRs already implement this modification. Check whether
there is a copper track to the transformer centre pin and if so do not
do the track cut and link.
AKAI EJECT MODIFICATION
These machines suffer from various eject problems including jamming
and damage to the carriage. The prime cure for this is to insert a small
U-shaped piece of plastic on the left hand side of the main chassis directly
under a black plastic clip.
U-Shaped spacer Akai code MZ732818J CHS 35024
Also recommended to replace are:
A kit is also available (CHS 35529) which includes in addition a mod to strengthen the support of the full erase head - I have not found this necessary and it is cheaper to fit the individual parts as above.
The cassette housing loading arm (item 43) often breaks and needs replacing.
Note when replacing the pinch roller Akai supply a completely different
type now. Pattern pinchrollers are often incompatible with the old
types and are best avoided.
A training video is available for this range of
videos and is very useful in getting to grips with the mechanics and electronics,
and includes additional tips. Available from Willow
Vale (18200TT) and others.
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