I have been acquiring a few 1970s receivers and I want to recap where appropriate. What should I prioritize? My main concern is the challenge of getting into tight spaces to replace the smallest electrolytics. I’ve fried one unit and I don’t want to make the “perfect the enemy of the good” kind of thing.
How to prioritize recapping.
- Thread starter Myshkin
- Start date
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- recap solid state
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start with the cheapest unit that you don't care about and master your skills.
learn to take stuff apart for easier access. again, refer to above.
The power supply.
If the power supply isn't working properly, it will affect the function of the receiver in general. This could include illumination, amplifier boards, reception, or any protection built into the receiver etc.
Refurbing a power supply is rather straight forward and includes replacing any caps, rectifier diodes, Zener diodes, resistors, transistors or any other items which show signs of stress or failure. Once rebuilt, the power supply will again put out reliable voltages as specified in the service manual.
Unfortunately,it is usually the small, low voltage caps that will go high in ESR first.
Continuing....
After the power supply, I'd be looking at signal path caps such as might be in the preamp section, then tuner section (some will say don't mess with the tuner if you can't do an alignment) then display or other caps associated with unobtanium type parts, because if these caps short open, you could lose something that really matters. That would all be after caps where the sleeves have shrunken due to heat exposure, etc.
After the power supply, I'd be looking at signal path caps such as might be in the preamp section, then tuner section (some will say don't mess with the tuner if you can't do an alignment) then display or other caps associated with unobtanium type parts, because if these caps short open, you could lose something that really matters. That would all be after caps where the sleeves have shrunken due to heat exposure, etc.
p4spooky
Active Member
I take a more detailed approach when it comes to refurbishing my own equipment.
1. PSU gets a full restoration - all zeners, capacitors, series pass transistors and power resistors are replaced.
2. Small signal transistors (especially if they are in the "noisy" AK list gets changed (exception tuner) - in Preamp/Power amp boards
3. Preamp/Poweramp - Replace all capacitors using film/PP/Nichicon KL/UES where appropriate
4. VD1212 replaced to 2X1N4148 in series along with Zeners in Preamp and Driver boards
5. Replace protect relay and capacitors in protect circuit
6. Replace relay driver transistor for reliability in protect circuit. If IC is used leave it alone if it is working
7. Regrease all transistors mounted on heatsinks (PSU/Driver boards and power amp HS)
8. Inspect for any HOT resistors - replace with higher wattage (next step higher 1W -> 2W for example)
9. Remove all glue around capacitors - replace any component contaminated with glue
10. Replace fusible resistors MF same value and wattage
11. Replace tuner capacitors only (generally does not require a realignment) as long as SAME values are used
12. Inspect main filter caps - replace as needed if ESR/Capacitance is out of spec
1. PSU gets a full restoration - all zeners, capacitors, series pass transistors and power resistors are replaced.
2. Small signal transistors (especially if they are in the "noisy" AK list gets changed (exception tuner) - in Preamp/Power amp boards
3. Preamp/Poweramp - Replace all capacitors using film/PP/Nichicon KL/UES where appropriate
4. VD1212 replaced to 2X1N4148 in series along with Zeners in Preamp and Driver boards
5. Replace protect relay and capacitors in protect circuit
6. Replace relay driver transistor for reliability in protect circuit. If IC is used leave it alone if it is working
7. Regrease all transistors mounted on heatsinks (PSU/Driver boards and power amp HS)
8. Inspect for any HOT resistors - replace with higher wattage (next step higher 1W -> 2W for example)
9. Remove all glue around capacitors - replace any component contaminated with glue
10. Replace fusible resistors MF same value and wattage
11. Replace tuner capacitors only (generally does not require a realignment) as long as SAME values are used
12. Inspect main filter caps - replace as needed if ESR/Capacitance is out of spec
Power supply / regulator, amp driver boards and then any in signal on tone or preamp boards. In that order