2021-12-01
Recapping the whole QXHD
Happy Holidays.
Attached over two postings are all the documents and drawings I created to assist me in a complete recap of a Otari MX-5050 "Original Version" reel to reel tape deck. This is the version that had the tape transport and the electronics package separate from each other. I hope others may find these handy.
Notes:
- Capacitor C4 on the PM-872A Reproduce Amplifier was a big leaker on all four of my boards. I took a guess (I am not an engineer) that perhaps this cap's voltage rating was a tad low so I upped the voltage value from 16 to 25 volts.
- The other caps upped in voltage was done as that particular voltage/capacitance value was not stocked at either Digi-Key or Mouser in the ELNA RFS series capacitor family that I picked for this recap.
- A few other substitutions were made due to other non-stock situations.
- The PCB numbers were obtained from the actual PCB's in my unit (serial # 17712028H) circa late 1970's? This chart puts all these PCB numbers in one place:
Posting #1: PCB Photos w/ Caps Located:
- PB-0141 Capstan Servo Drive Capacitor Locator
- PM-817A Motherboard Capacitor Locator
- PM-822A Bias Buffer Amplifier Capacitor Locator
- PM-823A TT Motherboard Capacitor Locator
- PM-824 Master Oscillator + Power Supply Capacitor Locator (redrawn)
- PM-825B TT Logic Capacitor Locator
- PM-871B Record Amplifier Capacitor Locator
Posting #2: PCB Photos w/ Caps Located + Cap Lists:
- PM-872A Reproduce Amplifier Capacitor Locator
- PM-874 Sel. Rep. Amplifier Capacitor Locator
- PM-875A Capstan Servo Power Supply Capacitor Locator
- PM-878 Test Oscillator Capacitor Locator
- Cap Listing - PCB's
- Cap Listing - Matrix
- Cap Listing - Total
I also redrew the two large schematics and will create another posting if AudioKarma will let me. I'm not even sure my double posting idea for this posting will work. Let's find out.
From his notes
Started this project 12/2021. Made a bunch of lists. Posted them on AudioKarma forum. See whole separate section on this. BTW; after all the recapping was performed on one of the stereo sections of the record / reproduce electronics I was ready to test. I then discovered that during the move to Delaware I lost the interconnection cable. Great. UPDATE: I just misplaced the cables. All is good.
PM-872A Reproduce Amp: leaker cap (1)
PM-872A Reproduce Amp: leaker cap (2)
PM-871B Record Amp: jumper corrosion
Recap: old caps, channel 1 and 3