Pin outs of RAMAC Connectors
Back to Home Page
Apparently this RAMAC unit was lent without schematics or cables. Some of the "exercises" for the students were:
- find plugs for the now unusual 4 row plugs on the RAMAC
- try to identify the usage of each wire in each of the 4 unusual plugs
- wire up required interface cables (now about 8 feet long)
- interface to the RAMAC using now commonly available plugs.
The following is the result:
Two connectors of disk select servo input One connector of high current, noise solenoid, clutch, switch wires One connector of low current & noise potentiometer excitation & wipers
UPDATE: Oct. 24, 2006 - correction to Track Potentiomenter connections!
See Track Pot Corrections
Two connectors of disk select servo input
Connectors to MARKITE (vertical resistive) Strip - 26 K ohms - 52 taps
Connectors A1 and A2 Connectors A1 and A2 again
On the student board end, these are called D1 and D2, on the board, D1 is female, D2 is male
TOP A1-A Disk 26 A2-A Disk 1 B " - 27 B " - 2 C " - 28 C " - 3 D " - 29 D " - 4 E " - 30 E " - 5 F " - 31 F " - 6 H " - 32 H " - 7 J " - 33 J " - 8 K " - 34 K " - 9 L " - 35 L " - 10 M " - 36 M " - 11 N " - 37 N " - 12 P " - 38 P " - 13 R " - 39 R " - 14 S " - 40 S " - 15 T " - 41 T " - 16 U " - 42 U " - 17 V " - 43 V " - 18 W " - 44 W " - 19 X " - 45 X " - 20 Y " - 46 Y " - 21 Z " - 47 Z " - 22 AA " - 48 AA " - 23 BB " - 49 BB " - 24 CC " - 50 CC " - 25 DD BOTTOM DD
Notes: as of August 2006
- "TOP" is the positive end of the resistor
- IBM (227-3534-0) calls top data disk # 00, the bottom # 49
- - This chart seems to call it Disk 1 through 50
- - The actual top an bottom disks are wind shields
One connector of high current & noise solenoid, clutch, switch wires
Connectors B and E (socket E document used the numbers listed)
pin B-AA does not show which polarity of Tachometer, where is return?
Connectors B and E
Note - on the student end, this male plug is labled "E"
Comments Chassis Gnd. B-A Chassis Gnd. E-A - 1 not used B Chassis Gnd. B - 2 " C " C - 3 " D " D - 4 " E " E - 5 " F " F - 6 " H " H - 7 " J " J - 8 " K " K - 9 " L " L - 10 " M " M - 11 " N " N - 12 " P " P - 13 Upper & lower Crash smps ?? R No Conn. R - 20 Solenoid (2) C Disk In S Disk In Ctrl S - 21 Solenoid (1) H Track Odd T Track Odd Ctrl T - 22 Upper ?? Crash S ?? U No Conn. U - 23 Solenoid (3) H Common V + 40 V V - 24 Solenoid (1) A Head W Head Ctrl W - 25 Solenoid (2) F Disk Out X Disk Out Ctrl X - 26 Solenoid (1) D Even Trk Y Even Trk Crtl Y - 27 Solenoid (3) F Common Z + 40 V Z - 28 Tachometer AA No Conn. AA - 29 There is a rumor that the tachometer shared a return with the solenoids - V-24 - was ground? - this may have to be changed? Solenoid (5) B Clutch Com BB + 125 V BB - 30 Solenoid (5) H Outer Clutch CC Clutch Out/Down Ctrl CC - 31 (Out/Up, as per 227-353-1 page 54) Solenoid (5) D Inner Clutch DD Clutch In/Up Ctrl DD - 32 (In-Down, as per 227-353-1 page 54)
One connector of low current/noise potentiometer excitation & wipers
See Track Pot Corrections
Connectors C and F (socket F document used the numbers listed)
Some items unreadable - Marked with * or ?
Connectors C and F
Note - on the RAMAC, this is labeled "B2", student end, this male plug is labled "F"
Trk Pot A C-A ** ?? F-A - 1 Trk Pot B B Not used B - 2 Trk Pot C C " C - 3 Trk Pot D D " D - 4 Trk Pot E E " E - 5 Trk Pot F F " F - 6 Trk Pot H H " H - 7 Trk Pot J J + 5 volts J - 8 Trk Pot K K Trk Pot Wiper K - 9 Track Detent 1 * L . L - 10 Track Detent 2 * M . M - 11 Disk Det Sw (3) Lock N . N - 12 Track Detent 3 (Com) * P . P - 13 Disk Det Sw (1) VNLK ??* R . R - 14 Disk pot Wiper S Disk Pot Wiper S - 15 . T . T - 16 Head Cable A U . U - 17 . V . V - 18 Head Cable C W . W - 19 . X . X - 20 Head Cable D Y . Y - 21 . Z . Z - 22 Head Cable E AA . AA - 23 Head Cable B BB . BB - 24 Head Cable H CC . CC - 25 Head Cable F DD . DD - 26 TRK Pot A,B,C,D,E,F,H,K - missing G - ?related to Pot Pins of fig 3.1-4? which is which?
Text and images from
RAMAC RESTORATION PROJECT by Cris Hong, Hagop Kozanian and Neal Rambhia Senior Design Project June 9,2004
On Page 22
"Upon taking a closer look at the data, we were able to make several obervations.
- "We found that pins one, three, and eight were not conduction. They are the points corresponding to the positive node, track 80, and track 100.
- "We found that the gear that moved the wiper on the potentiometer has been offset by several teeth. This offset a track pin be approximately 2 tracks. For example, pin 4 originally had its origin at track 20 but today, because of the offset, pin 4 resided at approximately track 22.
- "The constant resistance step betweenn pin 5 and pin 11 shows that the potentiomenter is farily linear. Moving from pin 5 to pin 11, we found that we had a resistance step of 3.8 KOhm between each tap."
The implications of the above are:
- The students must have connected the plus connection to pin 11, HOME
- and used zero volts for HOME
- There is no way to seek to tracks 60 through 100
- using the original nulling system
with out repairing the potentiomenter?
- (Using a voltage setpoint type of servo, all the tracks should be accessable, but linearity may be a challenge. Use a table of correct setpoints? Using HOME position to be slightly above 1 count would possibly work, but very slow recovery from servo overshoot on seek to HOME.)
Head Cable A,B,C,D,E,F,H - missing G - Relates to the ReadWrite heads, top and bottom Joe Feng - which is which?
from "Senior Design Project Report-Phase2" - page19
Track Pot Corrections, from Dave Bennet, Oct 24, 2006 - Diagram by Ed Thelen
Good news, Bad news
Al, Joe and I removed the track pot today. First of all the students did not number the connector pins correctly, most probably because they did not remove the pot as we did. When you do remove the pot and use the connector pin designations it becomes much more logical and it is obvious what we have. The connector is laid out as follows:C A B F D E K H J M LThe students numbered M as pin 1, K as pin 2, F as pin 3, C as pin 4, J as pin 5 and so on. They were on the right track and if they had known the connector pin designations it would have been as obvious to them as it is to us. Pin A is not "home" as they thought, but is rather the + node. There is no "home" tap. As Al quotes the Wes Dickinson paper, home is derived from an external adjustable network. This accounts for the fact that there are only 9 wires in the pot interface, whereas if there were a home tap, 10 wires would be required.
New fact number 2, there is only one open tap, not 2 or 3 as the students thought. The open tap is track 80. They did not mention anything for pin H, that they called pin 9, but it is connected and it is track 100.
Here's what we have:
At least this is a logical pin numbering system as you would expect.
A is positive node B is track 00 C is track 20 D is track 40 E is track 60 F is OPEN, should be track 80 H is track 100 It is GOOD J is negative node K is the wiper L and M are not used
Readings from pin A are as follows:A to B 4.67K A to C 8.53 K A to D 12.35 K A to E 16.19 K A to F OPEN A to H 23.72 K A to J 24.40 K A to B 4.67 K B to C 4.14 K C to D 4.10 K D to E 4.10 K E to F OPEN F to H OPEN H to J 954 ohmsSince my meter does not seem to be completely accurate and to check the linearity in a way to include pin H, I checked resistances accross two nodes:B to D 7.97 K C to E 7.94 K E to H 7.82 KSo I think we are good except that one tap is open.
Now for the bad news:
The potted "arm" that connects the back of the pot to the 11 pin connector appears to be potted in place. I took out the 3 screws apparently holding it in place and it did not budge. Consequently, I believe that servicing the pot, no matter who does it, would require destroying the potted arm and the wiring inside it. I'm sure that we could find someone who could make us a mold BEFORE we destroy the old potting so that it could be replaced after the pot is repaired, but I think it would be a lot harder to do after the existing potting is destroyed, probably resulting in an appearance issue.
Then Dave gave some task assignments relative to the above findings.