HP-65 more on the card reader

[Geoff Quickfall]

Heat or cold treatment, may cause a temporary connection on a cold solder joint or within an IC between a broken contact as you know.

I would remelt each solder joint in the amp circuit and check all other connections including the card reader PCA to Main PCA gold post connections.

The only fix for an intermittent connection on the IC is a replacement from a junked donor.

The dampening couple may be the source of the read write problem also. It is obviously failing as evidenced by the screeching noise. There should be no slippage here and the replacement material (see above links) should not slip but should absorb motor vibrations.

Resistors seldom fail so I don’t think it was that but introducing the pot resistor will aid in setting the card reader pass through speed. This speed is also controlled by the pressure exerted by the pinch roller which is adjusted by the eccentric cam.

Get a hold of the HP 97 tech manual (HPMuseum thumb drive) which gives the descri on how to adjust the eccentric cam plus the optic current draw as the cam is adjusted.

Manually adjust the cam once the entire assembly has been repaired and reassembled:

1. remelt the solder joints on the card reader PCA.

2. Replace the dampening couple material by reusing the aluminum sheath and inserting wire insulation of two different sizes. (See above YouTube links).

3. Clean card reader head (isopropyl alcohol).

4. I assume the ball bearing still resides in the card reader frame.

5. I assume the card reader sense fingers were not bent or accident readjusted under the card reader assembly and the balls, roller and spring guides are all there.

6. To manually check the eccentric cam: Once assembled run a known good preprogrammed card. If it doesn’t read adjust the cam by turning it five degrees. Continue to read and adjust until you hit the sweet spot.

Of course if it is the sense amp or the controller IC then a replacement will be needed.

Geoff

Pm sent.