Fisher 202 Receiver Restoration

Unit: AM/FM Stereo Receiver

Manufacturer: Fisher

Model: 202

SN: 22247

Another Fisher receiver (Futura series, model 202) came in for restoration. I restored exactly the same model a few months ago and one can read the restoration process in detail here: Fisher 202 receiver restoration. So, this post will be shorter than usual but I want to document what was done on this unit for future references. I hope it will be a good addition to my previous post about the Fisher 202 restoration.

Before I powered up this little receiver I checked the fuses on the back side to make sure that all of them have a correct rated current. There are three fuses on the back side: the main 2A slow blow fuse to protect the unit and two 2.5A slow blow fuses to protect the left and right channels. The fuse protecting the left channel was blown but someone bypassed it with a small piece of aluminum foil (!). Well, I was not surprised since you never know what can be found in these old units... Anyway, I replaced the blown fuse with a new one and powered the receiver up using my Dim Bulb Tester (DBT). The light bulb flashed for a second on bright and then dimmed out almost completely. So, this unit has no short circuit.

Blown fuse - bypassed with a small piece of aluminum foil

Power Amplifier Board

The Fisher 202 has two driver boards. These boards are very easy to service once removed from the slot. I didn't find any signs of overheating on these boards. All transistors and diodes have been tested and no bad components were found. So, I replaced only electrolytic capacitors. The original e-cap C01 installed in the signal path has a relatively high equivalent series resistance (ESR) of 2.6Ω (left channel) and 2.2Ω (right channel). I replaced it with a low leakage Nichicon UKL cap. The ESR of a new e-cap is only 1.5Ω which is lower in comparison to the original one. The lower ESR is always better, especially for e-caps installed in the signal path. The remaining three e-caps C02, C03, and C04 were replaced with low impedance and high-reliability Nichicon UPW capacitors. All original e-caps removed from the power amplifier board were tested with Atlas ESR70 capacitance meter and the results are below.

Test results on original capacitors removed from the power amplifier board:

C01-L: rated capacitance – 1uF, measured – 1.44uF, ESR – 2.6Ω, deviation: +44%

C01-R: rated capacitance – 1uF, measured – 1.36uF, ESR – 2.2Ω, deviation: +36%

C02-L: rated capacitance – 100uF, measured – 131uF, ESR – 0.05Ω, deviation: +31%

C02-R: rated capacitance – 100uF, measured – 131uF, ESR – 0.06Ω, deviation: +31%

C03-L: rated capacitance – 220uF, measured – 266uF, ESR – 0.15Ω, deviation: +21%

C03-R: rated capacitance – 220uF, measured – 270uF, ESR – 0.15Ω, deviation: +23%

C04-L: rated capacitance – 47uF, measured – 85uF, ESR – 0.19Ω, deviation: +81%

C04-R: rated capacitance – 47uF, measured – 77uF, ESR – 0.22Ω, deviation: +64%

Left and right driver boards - after servicing

Power Transistors

The original Hitachi power transistors 2SC1030 were removed, cleaned, and tested with Atlas DCA55 semiconductor analyzer. According to the datasheet, the DC current gain measured in each transistor was in spec. However, it should be noted that Atlas DCA55 semiconductor analyzer provides the accurate reading for DC current gain only on low-power transistors. A high-power transistor requires a much higher collector current and collector-emitter voltage to accurately measure its current gain. However, it is still a very useful device for comparing transistors of a similar type for the purposes of gain matching or fault-finding.

I replaced the old thermal pads with new Mica ones and refreshed the thermal compound.

Original power transistors with new pads and thermal compound

Power Supply Board

The power supply board has three electrolytic capacitors C01, C02, and C03. These were replaced with low impedance Nichicon UPW caps. The new e-caps have a maximum operating temperature of +105C which is a beneficiary in power supply circuits. The original e-caps installed in vintage gears from the 70's have a maximum operating temperature of +85C. All original e-caps removed from the power supply board were tested and the results are below. The ESR of the original e-cap C03 is elevated. The new e-cap installed instead of C03 has a lower ESR of 0.15Ω.

Test results on original capacitors removed from the power supply board:

C01: rated capacitance – 100uF, measured – 134uF, ESR – 0.09Ω, deviation: +34%

C02: rated capacitance – 100uF, measured – 132uF, ESR – 0.07Ω, deviation: +32%

C03: rated capacitance – 220uF, measured – 368uF, ESR – 0.32Ω, deviation: +67%

Power supply board - before and after

Pre-amplifier Board

I replaced all electrolytic capacitors on this board. The e-caps C1 and C2 installed in the signal path were replaced with low leakage Nichicon UKL caps. The original e-cap C1 installed in the right channel has a very high ESR in comparison to C2 in the left channel. The ESR of the Nichicon UKL capacitor is about 1.80Ω. The low ESR is critical for e-caps installed in the signal path. The remaining e-caps were replaced with low impedance Nichicon UPW/UPM caps.

Test results on original capacitors removed from Pre-amplifier board:

C1: rated capacitance – 10uF, measured – 12uF, ESR – 11.6Ω, deviation: +20%

C2: rated capacitance – 10uF, measured – 15uF, ESR – 1.84Ω, deviation: +50%

C9: rated capacitance – 100uF, measured – 152uF, ESR – 0.50Ω, deviation: +52%

C10: rated capacitance – 100uF, measured – 148uF, ESR – 0.46Ω, deviation: +48%

C16: rated capacitance – 100uF, measured – 154uF, ESR – 0.04Ω, deviation: +54%

Pre-amplifier board - before and after

Control Amplifier Board

All electrolytic capacitors on this board are installed in the signal path. The exception is only the e-cap C525.  I replaced e-caps C503/C504, C511 thru C514, and C517/C518 with low leakage Nichicon UKL caps. The e-cap C525 was replaced with a low impedance Nichicon UPW cap. 

This board also has four noisy 2SC458LG transistors and I replaced them with modern low noise Fairchild KSC1845. The new transistors were carefully matched by current gain and base-emitter voltage within 1%. Watch the pinout on replacement transistors. The original transistor is BCE and the new one is ECB.

I tested all original 2SC458LG transistors from this board with Atlas DCA55 semiconductor analyzer. One transistor TR501 from the left channel was found leaky. The measured collector leakage current was 0.026mA which is substantial for Si transistor. A leakage current is expected to be less than 0.001mA for the Si transistor.

Test results on original capacitors removed from Control amplifier board:

C503: rated capacitance – 10uF, measured – 19uF, ESR – 2.5Ω, deviation: +90%

C504: rated capacitance – 10uF, measured – 17uF, ESR – 2.6Ω, deviation: +70%

C511: rated capacitance – 4.7uF, measured – 6.9uF, ESR – 2.2Ω, deviation: +47%

C512: rated capacitance – 4.7uF, measured – 6.9uF, ESR – 2.2Ω, deviation: +47%

C513: rated capacitance – 1uF, measured – 1.7uF, ESR – 2.7Ω, deviation: +70%

C514: rated capacitance – 1uF, measured – 1.3uF, ESR – 2.2Ω, deviation: +30%

C517: rated capacitance – 1uF, measured – 1.2uF, ESR – 3.0Ω, deviation: +20%

C518: rated capacitance – 1uF, measured – 1.3uF, ESR – 2.2Ω, deviation: +30%

C525: rated capacitance – 220uF, measured – 268uF, ESR – 0.04Ω, deviation: +22%

Faulty transistor TR501 from the left channel - substantial leakage current

Control amplifier board - before and after

Dial, Dial Pointer, and Stereo Indicator Lamps

The dial pointer and two stereo indicator bulbs burned out in this unit. I replaced them with new white LED lamps. The new LED lamps will virtually last forever. I also replaced the original incandescent bulbs with cool blue LED lamps to decrease heat and improve the illumination. I found that the cool blue LED lamp makes the illumination of the dial scale more uniform in this model.

Burned original dial pointer bulb

New white LED lamp installed

Burned original stereo indicator bulbs

New white LED lamps installed

New cool blue LED lamps installed

Center Voltage Adjustment

The center voltage adjustment is a straightforward procedure and is clearly described in the service manual. The DC voltage between pin 5 of the left/right channel driver board and the ground should be adjusted to ~31V. I adjusted the center voltage at pin 5 to ~30.7V on each channel since the voltage measured at pin 3 was 61.4V. In general, the DC voltage at pin 5 should always be half of the voltage at pin 3.

Center voltage adjustment - left channel

Center voltage adjustment - right channel

Voltage measured between pin 3 and the ground

All the knobs and the faceplate were gently cleaned in warm water with dish soap. Also, all pots and switches have been cleaned with DeoxIT 5% contact cleaner and lubricated with DeoxIT FaderLube 5% spray.

The final result can be seen in the photos below. Please watch a short demo video at the end of this post. Thank you for reading.

Fisher 202 - after restoration

Demo video after repair & restoration