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Post by juke46 on May 26, 2017 9:47:38 GMT
Got the keyboard contacts all cleaned nicely. Perhaps some improvement in making selections but still not working (selecting) properly. Some selections are made and some are not until a second or third try. The rotating wipers seem to be having a difficult time finding the "hot spot" activated by the keyboard.
Not as difficult as I had expected to get access to the keyboard contacts. Removed the "clip on" incandescent keyboard lights and the top plate (remove 2 small hex headed screws per switch group) to allow good access to the contacts. It takes a bit of effort to get things lined back up after the contacts were cleaned but not too bad. I made a couple of guide pins from longer screws, by removing the heads, to help me get the "top Plates" back on each switch bank.
The capacitors in the Search Unit are the original factory caps. I am unsure what their job is (perhaps timing?) but I plan to replace them since they are so old (like me). The manual does not have a description of their purpose. I'll check the wiper positions per the manual as well. The circuit board tracks have been carefully cleaned.
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Post by robnyc on May 26, 2017 10:41:01 GMT
Several things to check:
-Do the wipers on the search unit make adequate contact with the traces? Worn "elbows" are a common problem. Note that Rowe inverted & slightly lengthened them beginning with the 1100 (JAL).
-Do the blades on the relays in the search unit have slight overtravel? AMI-Rowe used telephone-type relays which have good wiping action, but fairly weak blades. Be very careful in doing any resetting of overtravel so as not to fracture them. I've seen the results of ham-handed work by idiots on these machines. Pitting is not normally a problem in this unit -but check for it anyway.
-Are the pins in the memory wheel reasonably free? There is a happy medium between too free -where they might just shift if the machine is bumped vigorously and too stiff. That wheel is often oiled and the oil turns to gum after decades. It must be clean and dry.
-One of the capacitors in the search unit sets the duration of the pin-punch. IIRC it is around 100MFD which I increased slightly to around 120MFD. The other fractional value caps are for noise spike suppression. All should be replaced.
-Have the filter and rectifier in the power supply been replaced? Going to a silicon rect and slightly higher filter will "stiffen" the power output.
- Check that the fingers in the edge connector are making firm contact with the traces on the search unit. This is tedious and can wait pending the results of the other measures I've suggested.
RobNYC
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Post by juke46 on Jun 2, 2017 11:53:44 GMT
Checked/carefully cleaned wipers and traces. Wipers appear to have lots of life left. I do have a new spare set.
Carefully cleaned the contacts of the search unit blades - small amount of over-travel
The memory pins are all clean and dry and freely push in with minimal effort but not so easily they cam move by jarring machine.
We do not seem to be having a memory pin push problem since we have already done the power supply filter and rectifier as well as the timing capacitor.
I also just replaced all the capacitors in the search unit since they were all originals.
We have a much better operating machine now but still some minor selection problems. Perhaps one of 20 selections fail.
The selection button end switches and each individual button's contact have been cleaned. I have found that if I make a selection and continue to push (hold down) the selection button the machine always makes the selection. Based on this I took a look at the end switches on each selection button bank. I found that pressing and holding the button down does provide additional over travel of the contact blades. I cleaned each contact again but the problem still exists. I am hesitant to reduce the air gap between the contacts (I am a klutz at reshaping blades despites Ron's best efforts to educate me) but perhaps it is necessary. I think they already have adequate over-travel. Maybe just a bit with the ole burnishing tool?
The few selections it misses have the wipers stopping at the correct "hot spot" on both letter and number traces. A selection fails when the sprag does not engage. I'll study the manual for what sends a pulse to the sprag coil. Has to be the end switches (I think).
The other problem that we can live with is the Scan Control Switch. Regardless of how closely I tilt the micro switch for additional record basket rotation it fall about 5 records short of a full revolution. We are looking for a full revolution plus a 3-4 record slot overlap. I removed it, cleaned it up and operated it by hand. I can't remember if it had 5 or 6 steps to wind up to open the micro switch but all seemed well. I don't consider this too big a problem since we might make 20 selections and if it misses one we never even notice until we make additional selections and that missed record plays.
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Post by Ron Rich on Jun 2, 2017 22:19:06 GMT
Hi Jake,
It would be my bet, that the keyboard switches are OK ! If the search unit stops on the correct wipers, it would seem to me the keyboard has done it's job. I would GUESS the sprague relay contacts on thru the pin pusher plunger(s?) are intermittent--Are the relay contacts clean-dry/free of pits ? Ron Rich
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Post by juke46 on Jun 4, 2017 11:47:47 GMT
I went through and cleaned all the relay contacts once more. Hey, It's working and not missing any selections! I have played a lot of music and no misses! Before I put all of those covers back on we'll continue to play it for a while. The worst one is wiggling that "turntable surround cover" into place.
We are very fortunate to have this site and the assistance it offers! Thank You All!
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