Fisher TX55 restoration
- Thread starter paul_ral
- Start date
paul_ral
Well-Known Member
Picked up my Fisher today, so it has a painted wood case, no original knobs (I pus some Marantz ones), a lot dirt inside. The front panel is in good condition
Before
After a good bath
Powered on, no AC voltages after transformer. Check the voltage after power switch no voltage again. So I put another power switch and amplifier runs. I repaired OEM switch and installed inside. I check DC output voltages and BIAS, all are OK. With speakers connected the right channel is weak. I plan to do a total recap.
Before
After a good bath
Powered on, no AC voltages after transformer. Check the voltage after power switch no voltage again. So I put another power switch and amplifier runs. I repaired OEM switch and installed inside. I check DC output voltages and BIAS, all are OK. With speakers connected the right channel is weak. I plan to do a total recap.
Fred beat me to it. I make a habit of raising them 1/4" off the board for airflow. If you've ever seen a fried PIONEER SX-1010 power supply board you'll understand why.
The SX-1010 also has the POWER SUPPLY on the bottom of the unit and the board is Upside down, and has little to no natural ventilation either, due to the design of the unit. So the heat from the P.S. gets trapped and pretty soon stuff starts overheating and boards get brittle. The boards can be re-populated, even totally black boards as long as the traces are in decent condition, and best practice now is to raise diodes off the board, along with power resistors (which incidently do more damage to the board than the diodes). There is even a special tool to put a crimp in the leads so they stay up away from the boards while you are positioning and soldering.
I would replace the rest of the caps on the power supply at minimum. Once the voltages are stable and reliable, the rest of the unit should follow suit.
I would replace the rest of the caps on the power supply at minimum. Once the voltages are stable and reliable, the rest of the unit should follow suit.
paul_ral
Well-Known Member
Thanks for reply Larry.
The power source is very simple as you can see: 1 filter cap, 4 diodes and 1 resistor. I am planning to do a total recap and I placed my order to Mouser. Most of capacitors are Nichicon KL in signal path, Nichicon KA for the others and KG for coupling. I used KA series in my SX-440 and I like how it sounds. These caps are smaller so I have well-ventilated boards inside. I'll change all carbon resistors with Dale ones too.
The power source is very simple as you can see: 1 filter cap, 4 diodes and 1 resistor. I am planning to do a total recap and I placed my order to Mouser. Most of capacitors are Nichicon KL in signal path, Nichicon KA for the others and KG for coupling. I used KA series in my SX-440 and I like how it sounds. These caps are smaller so I have well-ventilated boards inside. I'll change all carbon resistors with Dale ones too.
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I'd go with the KG's as they tend to work best with other Nichicon's. But if they're too tall, go with the Mundorf's.
paul_ral
Well-Known Member
Today my order came from Mouser and I finished my amplifier. Some pictures with final result:
For amp section I use Nichicon KL and Nichicon KA series and Mundorf M-Lytic for outputs. All carbon resistors were replaced with Vishay/Dale new ones. I replaced old mica with silicone pad on outputs transistors.
In preamp section I use Elna Silmic II, Nichicon KL, Nichicon KA and Nichicon ES caps and I keep all transistors on boards.
Adjust DC balance potentiometer VR601 and VR603 for equal clipping and set BIAS from VR602&VR604 to obtain 7,5mV across R614 and 612. Both channels works great, no hum, so I am thinking to keep all low signal transistors on boards.
Thanks for watching!
For amp section I use Nichicon KL and Nichicon KA series and Mundorf M-Lytic for outputs. All carbon resistors were replaced with Vishay/Dale new ones. I replaced old mica with silicone pad on outputs transistors.
In preamp section I use Elna Silmic II, Nichicon KL, Nichicon KA and Nichicon ES caps and I keep all transistors on boards.
Adjust DC balance potentiometer VR601 and VR603 for equal clipping and set BIAS from VR602&VR604 to obtain 7,5mV across R614 and 612. Both channels works great, no hum, so I am thinking to keep all low signal transistors on boards.
Thanks for watching!
Nicely Done. How does it sound???
paul_ral
Well-Known Member
For me it sounds warm but it is a little difference between Pioneer SX-440 and TX-55, Pioneer has more bass at low volume. Increasing the volume the bass become more present, like my Marantz 1060 works. Overall I like how it sounds. Maybe because I recapped my old Sansui SP-70 using the capacitors which you recommended to me. Thanks again
Next step is to order 6 knobs from Mouser, I found these:
https://ro.mouser.com/ProductDetail/450-2225
https://ro.mouser.com/ProductDetail/450-3225
Then I'll send the wood cabinet to the carpenter because it was painted in black.
Next step is to order 6 knobs from Mouser, I found these:
https://ro.mouser.com/ProductDetail/450-2225
https://ro.mouser.com/ProductDetail/450-3225
Then I'll send the wood cabinet to the carpenter because it was painted in black.
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Sounds like a plan both for the knobs and the speakers.
