DIY Restoring a Pioneer RT-909 Reel-to-Reel

[pustelniakr]

Recap Capstan Motor Drive Board

While the motor plate is removed, if you are going to recap the unit, now is the time to recap the capstan motor drive board. Replace all the 'lytic caps, refresh all the circuit board solder joints, and clean off all the old flux (isopropyl alcohol). Also, put fresh heatsink compound under the heatsink'd motor driver.

Pics 1 & 2 show 'before' and 'after' views of the capstan motor drive board.





Enjoy,
Rich P

 

[pustelniakr]

Capstan Drive Work (cont)

1. Fill the bearing ball cups in the rear of each capstan shaft with white lithium grease, then push a nylon thrust bearing ball into each cup, to be retained by the lube (lube should overflow). Refer to pic 1.​

2. Install a new capstan drive belt ( http://www.vintage-electronics.net/pioneer-rt-909-belt-kit.aspx ). It simply goes around the capstans as seen in pic 1.

3. Install the motor plate, with the motor pulley coming down on the top of the belt, as shown in pic 1. Secure the motor plate with its 4 screws.​

Enjoy,
Rich P

 

[pustelniakr]

Reel Brake Work

While the brakes may work fairly well on these old units, the felt brake pads can be impregnated with lube and/or fine dust, and the brake pad adhesive can be quite weak. In order to ensure longevity after all this work, I strongly recommend replacing the brake pads (I have no current source. I'll update if I obtain one).

1. Remove the 4 screws (indicated in pic 1) securing the Control B mounting bracket to the front of the unit.​

2. Remove the single screw (indicated in pic 2) securing the Control B mounting bracket to the side of the unit.​

3. Remove the 2 screws (one at each end, on the back side) securing the top frame bracket, then rotate the Control B assy down, away from the reel motors, as indicated in pic 3.​

I will show the process of replacing the more complicated of the 2 brake pads. The other one will be pretty much the same thing...

1. Remove the single screw securing the motion sensor slit (indicated in Pic 3), and remove the motion sensor slit. Then, remove the 2 screws retaining the motion sensor, and hang the sensor by its wire bundle (as in Pic 4).​

2. Disconnect the brake spring from the motor assy.

3. Remove the c-clip and plastic washers ('A' in pic 4) from brake shaft. Be sure to capture both nylon washers (one one each side of the brake assy).

4. Remove 2 screws ('B' in pic 4) retaining the solenoid link to the brake, the slide the brake (& link) from the motor.

5. Mark the position of the brake drum on the motor shaft, then, loosen the setscrews retaining the brake drum to the motor shaft and remove the brake drum.

6. From the side of the unit, loosen the setscrews retaining the reel table to the front motor shaft and remove the reel table from the motor shaft.

7. Put 1-2 drops of Teflon lube (Tri-Flow, etc.) on each reel motor bushing (front and rear).

8. Reinstall the reel table, then, clean the brake drum braking surface with isopropyl alcohol and reinstall the brake drum.

9. Remove the brake band from its assy (2 screws). Carefully remove the old brake pad and its adhesive from the brake band. Be extremely careful in this process, not to bend or kink the brake band, or you will RUIN it. Please re-read what I just wrote. It is IMPERATIVE that you heed it!

10. Cut new pad to length with scissors & attach the new pad even with 1 side of the band. Then use a razor blade and trim the other side even with the band.

11. Reinstall the brake band, ensuring that it is square with its assy.

12. Lube the brake shaft with white lithium grease, install a nylon washer, then the brake assy (with its solenoid link), followed by another nylon washer and the c-clip. Then secure the solenoid link (2 screws).

13. Re-position the brake drum to center on the brake band.

14. Reinstall the motion sensor and the sensor slit.​

Enjoy,
Rich P

 

[pustelniakr]

Recapping the Control B Assy

While the Control B assy is rotated down for access, if you are going to recap the unit, now is the time to recap the Control B board. Replace all the 'lytic caps, refresh all the circuit board solder joints, and clean off all the old flux (isopropyl alcohol). Also, put fresh heatsink compound under the heatsunk drivers.

Pics 1 & 2 show 'before' and 'after' views of the Control B board.





Enjoy,
Rich P

 

[pustelniakr]

Torque Adjustments

The brake and motor torque adjustments are adequately covered in the service manual. However, here are a few considerations:

• Use a 7" reel with a hub diameter of 60mm, and a push-pull tension meter with a 0g - 500g range. Tie a string to the tension meter and wrap it in the direction of reel rotation opposite the torque being measured.
  
  
• Pic 1 shows how to simulate tape presence, so that the unit will attempt to drive tape. The frame front panel has tabs, intended to tie rubber bands to pull the tension roller guide pins off of their shut-off points.

• Brake torques are adjusted via brake spring tension.
  
  
• Pic 2 shows the pots on the Control B board, for adjusting the various reel motor torques. The pots are clearly labeled on the board.

• Brake torques should only be measured after the brake has been electrically lifted then freshly released (preferably, several times).

• Pic 3 shows the tension meter, wound for the following measurements: Secondary supply side brake torque

• Pic 4 shows the tension meter, wound for the following measurements: Supply side brake torque, forward play back-torque, fast forward back-torque, reverse play take-up torque, rewind take-up torque.

• Pic 5 shows the tension meter, wound for the following measurements: Take-up side brake torque, reverse play back torque, rewind back-torque, forward play take-up torque, fast forward take-up torque.

• Pic 6 shows the tension meter, wound for the following measurements: secondary take-up side brake torque.

Enjoy,
Rich P

 

[pustelniakr]

Counter Board Recap

The Counter board is accessed for recapping, by removing the 2 screws securing it to the front panel, and lifting it out of its retainer. Replace all the 'lytic caps, refresh all the circuit board solder joints, and clean off all the old flux (isopropyl alcohol).

Pics 1 & 2 show 'before' and 'after' views of the Counter board.





Enjoy,
Rich P

 

[pustelniakr]

VU Drive Board Recap

The VU Drive board is accessed for recapping as follows:

1. Remove the single screw holding the drive board to the bottom of the frame.

2. Disconnect the connector to the VU Meter board.

3. Pull up on the Drive board, releasing it from the 3-pin connector on the Mother board.

4. Replace all the 'lytic caps, refresh all the circuit board solder joints, and clean off all the old flux (isopropyl alcohol).​

Pics 1 & 2 show 'before' and 'after' views of the VU Drive board.

Note: Leave the Drive board uninstalled while recapping the Mother board (next).





Enjoy,
Rich P

 

[pustelniakr]

Mother Board Access

Now it gets really hairy/scary for a bit...

The Mother board is accessed for recapping as follows:

1. Remove the 2 screws securing the VU Meter & remove the VU assy (cable was connected to the Drive board).

2. Remove the grounding spring from the pitch pot ('B' in pic 1).​

3. Remove the panel nut and washer from each of the 3 level pots ('A' in pic 1).

4. Remove the 13 screws securing the lower chassis face (indicated in pic 1). Pic 2 shows the VU assy and lower chassis face removed.​

5. Remove the ground screw ('A' in pic 3), the screw ('B' in pic 3) retaining the signal panel to the rear panel, the 2 screws ('C' in pic 3) securing the voltage selector to the rear panel, and the 3 screws ('D' in pic 3) retaining the lower rear panel. Then, remove the lower rear panel, as shown in pic 4.​

6. Remove the 2 screws ('A' in pic 4) to free the chassis to rotate open.​

Enjoy,
Rich P

 

[pustelniakr]

Mother Board Access (cont.)

1. Remove the screw ('A' in pic 1) securing the corner of the Control A board to the bottom right chassis side.​

2. Rotate the unit onto its right side.

3. Remove the 3 screws securing the left chassis side frame to the upper front chassis face.

4. Remove the screw securing the pre-amp board mounting frame to the left chassis side frame.

5. If the top rear frame brace is installed, remove the 2 screws retaining it to the frame and remove it.

6. Remove the screw securing the left chassis frame side to the chassis center brace, and remove the left chassis frame side, as seen in pic 2.​

Enjoy,
Rich P

 

[pustelniakr]

Mother Board Work

Now that you can access both sides of the Mother board, perform the following operations:

• Replace all the 'lytic caps
  
  
• Refresh all the circuit board solder joints (except those in thermal contact with any Styrol caps)
  
  
• Clean off all the old flux (isopropyl alcohol).
  
  
• Replace the old heatsink compound under all heatsink'd drivers.
  
  
• DeOxit all pots and switches on the mother board. Note: You will have to remove the shield from the 'REC Mode' switches before you can DeOxit them, remember to put the shield back on when done.
  
  
• DeOxit the contacts of the connector to the Control A board, then treat them with Pro-Gold.

Pics 1 and 2 show 'Before' and 'After' views of the Mother board...





Enjoy,
Rich P

 

[pustelniakr]

Pre-Amp Board Work

While you have the Mother board accessible, the pre-amp board is also accessible. Remove the 2 screws securing the pre-amp mounting bracket, and maneuver the bracket free (twist latching tab), then perform the following operations on it:

• Replace all the 'lytic caps. Note that there are a few special low-leakage 'lytics (orange ones, replaceable by Xicon LLRL series).
  
  
• Refresh all the circuit board solder joints (except those in thermal contact with any styrol caps)
  
  
• Clean off all the old flux (isopropyl alcohol).

Pics 1 and 2 show 'Before' and 'After' views of the pre-amp board...





Enjoy,
Rich P

 

[pustelniakr]

Control A Access & Work

1. Reassemble the left side, up to but not including the installation of the lower chassis faces (front and rear).

2. Rotate the unit onto its left side.

3. Remove the 2 screws (bottom) securing the Control A assy to the frame.

4. Remove the 2 screws securing the switch assy and switch array to the Control A riser.

5. Disconnect the 2 connectors from the Control A assy. DeOxit the contacts of each connector, then treat with Pro-Gold.

6. Protect the solder side of the Mother board, and hang the Control A assy for work, as in pic 1.​

Now that the Control A is accessible, perform the following operations on it:

• Replace all the 'lytic caps. Note that there are a few special low-leakage 'lytics (orange ones, replaceable by Xicon LLRL series).
  
  
• Refresh all the circuit board solder joints (except those in thermal contact with any Styrol caps)
  
  
• Clean off all the old flux (isopropyl alcohol).

Pics 1 and 2 show 'Before' and 'After' views of the Control A board...





Enjoy,
Rich P

 

[pustelniakr]

Switch Assy Work

While the Control A Assy is accessible, the Switch assy is also accessible. Perform the following operations on it:

• Replace all the 'lytic caps. Note that there are a few special low-leakage 'lytics (orange ones, replaceable by Xicon LLRL series).
  
  
• Refresh all the circuit board solder joints (except those in thermal contact with any styrol caps).
  
  
• DeOxit the slide switches.
  
  
• Clean off all the old flux (isopropyl alcohol).
  
  
• DeOxit the contacts of both connectors, and treat them with Pro-Gold.

Pics 1 and 2 show 'Before' and 'After' views of the Switch assy...

Note: Do not DeOxit the snap dome switches of the Switch Array. DeOxit is not compatible with snap dome switches, and the only recourse to a faulty snap dome is replacement.





Enjoy,
Rich P

 

[pustelniakr]

REC/PLAY Alignment/Calibration

Reassemble the unit, up to but not including installation of the cosmetic parts, faceplate, knobs and bonnet.

The REC/PLAY alignment/calibration of the unit is covered quite adequately in the service manual (head alignment, bias, EQ, levels, etc.). Here are a few considerations for this task:

• While working with the powered unit, be sure to wear adequate eye protection. 'lytic caps, installed backwards or over-voltage'd, tend to explode or go off like bottle rockets.
  
  
• While working with the powered unit, be sure to remove all conductive items from your hands and arms. There are some dangerous voltages in there.
  
  
• Before loading the very expensive calibration/alignment tape, run a few expendable tapes through, to make sure that the transport is assembled and operating correctly. Calibration tapes are over $100 each, so you really don't want to trash one.
  
  
• When it is time to put the calibration tape on, make sure you first thoroughly clean and demagnetize the transport. A magnetized transport will damage your calibration tape. I highly recommend a big Han-D-Mag de-magnetizer (https://www.splicit.com/Tape-Head-Demagnetizer-p/thd.htm).
  
  
• I know that folks fawn over the old Maxell tapes, but there are new tapes being manufactured today, which can be purchased at good prices. I highly recommend RMGI-Emtec LPR35 (https://www.splicit.com/LPR35-Reel-to-Reel-Audio-Recording-Tape-p/lpr35.htm). It is a +6db tape with most excellent results. Although it is a +6db tape, I do not recommend trying to record to the full +6db, as you are likely to saturate the heads rather than the tape. I would recommend recording to +4db, but not to mis-calibrate the VU meters to read 0db at +4db, as some do. Calibrate the meters to an accurate 0db level, but record to +4db on the meters.
  
  
• I highly recommend calibrating the unit to the tape you will actually record on. That way you have optimum response, period. That is also another good reason to use modern tape. With old tape, you never know what condition the tape is going to be in, and it is very hard to optimize the machine to allow for the wide variation you will get with old tapes.
  
  
• For a calibration tape, I highly recommend the MRL 21T204 ( http://www.usrecordingmedia.com/caltap.html ). It has all the tones you need for playback EQ adjustment, playback level adjustment, speed adjustment, and playback frequency response testing.
  
  
• The input signal is not listed in the service manual for the 'Level Meters 0db Adjustment'. It should be 1kHz at -10db (316mV). The input level is then adjusted for the correct internal voltage level, and the meters are then adjusted.

The following lists a few web sites for good info on R2R calibration/alignment:

• https://www.barryrudolph.com/greg/align.html
  
  
• http://www.usrecordingmedia.com/whcataareall.html

Enjoy,
Rich P

 

[pustelniakr]

Cosmetic Detailing

Before putting on the knobs and panels, be sure to clean them up and polish them.

Do not use harsh chemicals on the brushed aluminum. Limit your chemicals to a soft toothbrush and dish soap (not dishwasher soap).

For polishing, I suggest a good quality automotive wax. I use Meguiar's 'Cleaner Wax'.

Good luck on your own machine. Be careful. The results can make you cry (one way or the other)...

Enjoy,
Rich P

 

[pustelniakr]

Supplemental Info:

Setting Pinch Roller Pressure

What you do is to manually raise the rollers to contact the capstans. Verify that both rollers contact the capstans at the same time (roller diameter is in question if not). Measure the play left until the capstan solenoid is bottomed out. That is the solenoid gap we are talking about adjusting. It is not critical, but get it as close to center of the range as possible.

The pinch roller pressure is actually governed by little springs in the pinch roller arms, and is not really adjustable, except by changing the springs. If your gap is good and your springs are good, you will have good roller pressure. The roller pressure measurement is a verification, not feedback on adjustment. The pressure will either be right or not. If not, bad springs, or sticky lube in the mechanism.

You adjust the solenoid gap by moving the solenoid, itself. Make sure that the solenoid remains square to its plunger travel, also.

Wow is an indication of off-center, or out-of-true rollers, or capstan belt that is too tight, too thin, or stretched, or a capstan motor with a bent shaft or some other damage. Insufficient roller pressure will usually manifest by overall tape slow-down towards the end of tape play. Adjust your gap, verify synchronous roller-to-capstan contact, and see what issue(s) remain...

Enjoy,
Rich P

 

[pustelniakr]

Supplemental Info

Equipment Needed To Do a Proper Tape Deck Calibration and Alignment

You will need a good test tape, specified up-thread. It will cost you in the neighborhood of $150.

You will need a good, dual-channel, milli-voltmenter, graduated in dbV, to measure stimulus input and deck response (record and playback).

You will need a good sine-wave signal source, with output graduational control, in dbV, to produce the necessary input stimulus.

You will need a good wow/flutter meter, and/or frequency counter, to set tape speed.

You will be able to use a good distortion analyzer, to help in adjustment of recording bias.​

Here's what I use:

Leader LMV-185A 2-Channel AC Millivoltmenter

Leader LFM-39A Wow & Flutter Meter

HP 8903A Audio Analyzer

Sound Technology 1700B Distortion Measurement System

Leader LAG-126S Audio Signal Generator

Fluke 8060A True RMS Multimeter

MRL 21T204 Multifrequency Calibration Tape (Must be new and fresh)

Chatillon DPP-.5Kg Push/Pull Tension Meter​

Enjoy,
Rich P