Found issue with the voltage regulator, repaired it and began more debugging

TEMPORARY 22 OHM RESISTOR OF SMALLER WATTAGE PUT ON CARD FOR TESTING

I didn't have a large 22 ohm resistor on hand, but could install a couple of 1/2 W 47 ohm resistors instead while I figure out what is causing the overload. Once that is resolved and I buy the proper resistor, the card can be restored to original condition.

BINARY SEARCH OF CARDS USING 35V TO SEE WHICH IS OVERLOADING REGULATOR

There are five cards that are supplied with the +35V produced by the voltage regulator card. I decided to test card by card to figure out which is overloading the regulator. The first card I inserted, D2, worked just fine. I would then insert E2, H2, J2 and K2 in turn, with the other cards out of the compartment.

FOUND A DEAD SHORT ON CARD E2

When I powered on the electronics with card E2 inserted, there was a big puff of smoke since my tiny substitute resistors blew faster. I checked the resistance of the 35V input pin B09 to ground and found it to be zero volts!

I was pretty sure that the tantalum filter capacitor for that voltage on the card had shorted. I pulled it off the card and confirmed that it had failed with a dead short, as these types of capacitors will do. I grabbed another capacitor from one of my spare/junk cards, after testing it for a short of course. With the capacitor replaced, the voltage regulator was happy with E2 installed as well as when D2 was installed.

Rather than iterate through puffs of smoke, I decided to test all the tantalum capacitors on the remaining cards - H2, J2 and K2. Another was shorted on H2 but the other two cards were okay. The same process was used to repair this card - grab a good part from a donor card and swap it into the card. 

To be extra cautious, I checked all the tantalums on all the cards. They filter the +3, -3, +6, +48 and +35 voltages when they enter a card. In addition one card had a slew of tantalums used for various timing circuits, so I checked all of those while I had the cards out. 

The components used by IBM were rated at 60V and I have never found one fail when used with the main logic voltages +3, -3 and +6, nor the +12V rail. However, the same parts are installed on 48V lines where they have failed and now I found two that were installed on a 35V rail but somehow failed in spite of a very large voltage margin. 

MACHINE COMES UP AND NO SMOKE NOW THAT THE CARDS ARE REPAIRED

I was now able to bring up the voltage rails and work with the drive without smoking resistors on the voltage regulator card. Much seemed to be working well so I moved on to test the emergency retraction to Home, the spin up to Ready status, and then some access movements. 

EMERGENCY RETRACTION TOGGLED THE DETENTS BUT NO MOVEMENT OF THE ARM

When I manually moved the arms out from the Home position (track 0) before turning on the 48V, the logic in the drive attempted to retract the arm back. It does this by setting the detent for 20 mil movement and pulling the voice coil in reverse, iterating this until the arm reaches track 0 and switches on the Home microswitch. 

I heard a buzzing from the detent solenoids but there was no movement of the voice coil at all. When I pushed it back myself to Home, the buzzing stopped (as it should). 

MAINTENANCE MANUAL SUGGESTS VOLTAGE CHECKS - WHICH FAILED

The maintenance manual suggests to try to emergency retract and to verify four voltages on the backplane that indicate it is trying to do the right thing. They were all out of spec compared to what was expected. 

ATTEMPTED TO SPIN THE CARTRIDGE FOR 90+ SECONDS TO SEE HEADS TRY TO LOAD

When the motor is turned on to rotate the platter inside the cartridge, a timer is started. After 90 seconds it should switch a signal which tells the drive to activate the Head Load solenoid. When that solenoid pulls in, it turns on a microswitch that indicates successful head loading. The drive should then turn on its File Ready signal indicating it is ready to accept commands. 

The switch never activated. When I restored my own 1130, I found that the timer relay was defective, yielding the same symptom. I bought a substitute timer switch as a fix. I will need to do the same here, but will pull out the relay and verify its failure, just in case there is a wiring issue instead. 

NEED TO STUDY THE LOGIC AND CIRCUITS FOR VOICE COIL MOVEMENT

In order to troubleshoot this, I need to dig through all the material and ALD pages so that I understand exactly what should be happening. I can then find deviations and from that hunt down malfunctioning components.