AKAI VCRs VS422 series


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.

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Very common is an Akai VCR with no display, although it works in all other aspects.  Frequently a machine comes in with another fault and the customer doesn't even mention the lack of display! The root cause is failure of electrolytic capacitors C446 and C447 in the dc-dc convertor which provides the supplies for the high voltage and heaters for the digitron.  However the original circuit also overdrives the heaters and after prolonged usage causes damage to the digitron.

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)
Replace diodes D416 and D417 with BYV10-40 Schottky diodes (in lieu of RB100AT)
Cut track between C447 and L404
Add link C447 NEG side and centre tap of L404

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.


This modification affects the same range of models as the display modification above.

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. 
To locate where this goes look along the inside bottom left side of the unit and you will see the plastic clip which holds a sliding plate down, about 2 inches from the front of the chassis.  Insert the new part underneath this clip between it and the metal bottom of the chassis such that it 'firms up' the clip. After you are happy with where it goes apply superglue to the top and bottom faces of the part and stick it in place.

U-Shaped spacer     Akai code MZ732818J    CHS 35024

Also recommended to replace are:
Gear Eject (40)           CHS 35005
Arm Shutter (56)         CHS 35008  (upgraded part)

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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