Marantz 2220B Receiver Restoration

Unit: AM/FM Stereo Receiver

Manufacturer: Marantz

Model: 2220B

SN: 31995J4

Today I'm showcasing a Marantz 2220B vintage receiver that came in for restoration. Marantz 2220B was manufactured from 1974 to 1977. It produces 20 watts per channel into 8 ohms with no more than 0.5% total harmonic distortion. The damping factor at 8 ohms is 20. The optional walnut veneer cabinet for this model is WC-122 or WC-22. 

Marantz 2220B is a service-friendly receiver because of excellent access to each PCB.

FM Tuner Section Troubleshooting

Initial evaluation of this unit revealed that in addition to the common problems found in almost all vintage gears such as scratchy/noisy controls, burned bulbs, intermittent sound, etc., this unit also has issues with FM stereo reception. Despite a strong signal from the local stations, the stereo indicator lamp doesn't light up. I checked the sound with my headphones but didn't notice the stereo separation either. Also, pressing the FM Muting switch would mute the sound completely, even when tuned to a station with a strong signal.

The first thing I did was check the stereo indicator lamp. The stereo lamp lights up when the Phono, Tape, or Aux input is selected. However, it turns off when switching to FM input. This means that the lamp has not burned out.

The second step was to test the stereo MPX decoding circuit. I connected a frequency counter to the R312 test point and checked for the 19kHz VCO output. It was slightly off at ~18.8kHz and I adjusted it exactly to 19.0kHz with the trimmer R304. It didn't change anything. The sound was clear and loud, but still only in mono.

The next logical step was to check the FM Front End tuner alignment. A quick test at 87 MHz and 109 MHz revealed no problems. 

I then cleaned up all the controls, paying particular attention to the FM Muting switch, and moved on to the FM IF amplifier board. I checked all voltage distributions on this board and compared them with those shown in the circuit diagram. At no signal condition, the measured voltage on each transistor was very close to that shown in the circuit diagram. However, when I applied a stereo signal, the measured voltage across the three transistors (H207, H208, and H209) did not match what was shown in the circuit diagram (see below).

Voltage distributions at no signal condition (ref. voltage from the schematic is in brackets):

H201: B - 3.3V (3.4V); C - 7.5V (7.7V); E - 2.6V (2.8V)

H202: B - 3.3V (3.5V); C - 7.7V (8.5V); E - 2.7V (2.8V)

H203: B - 3.0V (3.0V); C - 9.1V (9.4V); E - 2.4V (2.4V)

H204: B - 3.2V (3.3V); C - 9.6V (10.1V); E - 2.5V (2.7V)

H205: B - 2.4V (3.3V); C - 13.3V (13.6V); E - 2.0V (2.8V)

H206: B - 3.5V (3.7V); C - 12.2V (13.2V); E - 2.8V (3.0V)

H207: B - 0V (0.04V); C - 13.9V (14.3V); E - 0.05V (0.06V)

H208: B - 0.05V (N/A); C - 0.18V (0.27V); E - 0V (0V)

H209: B - 0V (0.02V); C - 7.3V (7.4V); E - 0V (0V)

Voltage distributions when the stereo signal is applied:

H201: the same as at no signal condition

H202: the same as at no signal condition

H203: the same as at no signal condition

H204: the same as at no signal condition

H205: the same as at no signal condition

H206: the same as at no signal condition

H207: B - 0.07V (1.77V); C - 13.9V (14.3V); E - 0.08V (1.18V)

H208: B - 0.08V (N/A); C - 0.2V (0.06V); E - 0V (0V)

H209: B - 0.08V (0.6V); C - 7.3V (0.06V); E - 0V (0V)

The DC voltage obtained by rectifying the sub IF output signal from the H206 is applied to the base of H207. The output signal must be above a specified level to turn on transistor H207. This level (muting threshold level) is adjusted by trimmer R253. 

When the H207 turns on, the muting switch transistor H208 is also turned on. It decreases the emitter-collector resistance and allows the emitter current path to the final IF amplifier H205. However, if the DC output obtained is smaller than the predetermined level, the H207 keeps its turn-off state. As a result, the switch transistor H208 also keeps its turn-off state and no emitter current is supplied to the transistor H205. The DC voltage obtained is also used to make the Auto-Stereo switching transistor H209 turn on and off.

So, the problem seems to be somewhere down in the circuit after transistor H206. The voltage measured on the base, collector, and emitter of H206 matches those on the circuit diagram. However, the DC voltage applied to the base of H207 is too small to turn it on. 

I tested the transistor H207 to make sure that it was okay. Then, I measured the voltage at the base of H207 while rotating the trimmer R253. The base voltage was very low (~0.05-0.07V) at any position of the trimming resistor. I thought that perhaps one of the 1N60 germanium diodes was faulty, but testing did not confirm this assumption. Finally, I checked the voltage on the anode of H217, and it was close to zero volts.

So, the faulty component appears to be the coil L202. I swapped the suspect L202 with a spare coil from another Marantz 2220B and the stereo reception was restored. Now, the voltage at the anode H217 is 1.4V, the stereo indicator lamp lights up, and I can hear the stereo separation between the left and right channels. I double-checked the voltage across the three transistors (H207, H208, and H209) and it is also very close to that shown in the circuit diagram.

Voltage distributions after the faulty coil L202 was replaced (stereo signal is applied):

H207: B - 1.56V (1.77V); C - 13.8V (14.3V); E - 0.95V (1.18V)

H208: B - 0.68V (N/A); C - 0.08V (0.06V); E - 0V (0V)

H209: B - 0.6V (0.6V); C - 0.05V (0.06V); E - 0V (0V)

Power Supply Board (P800)

The regulated power supply has 6 aluminum e-caps C803, C804, C805, C808, C809, and C810. All of them were replaced with low-impedance and high-reliability Nichicon UPW caps. Those e-caps are designed for switching power supplies and can operate in the temperature range from -55 to +105 C. The original e-caps installed in vintage gears from the 70s have a maximum operating temperature of +85C.

The original e-caps were tested with an Atlas ESR70 capacitance meter and the results are below.

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

C803: rated capacitance – 470uF, measured – 448uF, ESR – 0.29Ω, deviation: -5%

C804: rated capacitance – 470uF, measured – 306uF, ESR – 0.44Ω, deviation: -35%

C805: rated capacitance – 100uF, measured – 93uF, ESR – 1.68Ω, deviation: -7%

C808: rated capacitance – 3.3uF, measured – open

C809: rated capacitance – 470uF, measured – 519uF, ESR – 0.52Ω, deviation: +10%

C810: rated capacitance – 1000uF, measured – 1166uF, ESR – 1.52Ω, deviation: +17%

Both transistors (H805 & H806) and one rectifier diode H808 installed on this board were also replaced to improve the reliability of the power supply. The original transistor 2SD330 installed in position H805 was replaced with a new ON Semiconductor MJE15030G. Transistor 2SC945 installed in position H806 was replaced with a new Fairchild KSC945CYTA. The rectifier diode SIB-01-02 installed in position H808 was upgraded to a fast recovery rectifier UF4005.

The original trimming resistor R808 was replaced with a new Bourns potentiometer.

The DC voltage between pin J812 and ground was adjusted to +35V with the trimming resistor R808.

DC voltage between pin J812 and ground under no signal condition

Power supply board - before and after

Phono Amplifier Board (P400)

The phono amplifier board has two solid tantalum capacitors (C401, C402), two low leakage e-caps (C407, C408), and three aluminum electrolytic capacitors (C411, C412, C421). The solid tantalum capacitors installed in the signal path were replaced with modern low-leakage Nichicon UKL caps. The original low-leakage capacitors were also replaced with modern low-leakage Nichicon UKL caps. The remaining aluminum e-caps were replaced with low-impedance Nichicon UPW/UPM caps.

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

C401: rated capacitance – 2.2uF, measured – 2.2uF, ESR – 6.8Ω, deviation: 0%

C402: rated capacitance – 2.2uF, measured – 2.2uF, ESR – 6.4Ω, deviation: 0%

C407: rated capacitance – 22uF, measured – 22uF, ESR – 0.71Ω, deviation: 0%

C408: rated capacitance – 22uF, measured – 21uF, ESR – 0.88Ω, deviation: -5%

C411: rated capacitance – 47uF, measured – 56uF, ESR – 1.61Ω, deviation: +19%

C412: rated capacitance – 47uF, measured – 55uF, ESR – 1.14Ω, deviation: +17%

C421: rated capacitance – 100uF, measured – 102uF, ESR – 1.05Ω, deviation: +2%

Phono amplifier board - before and after

Tone Amplifier Board (PE01)

The tone amplifier board has six low leakage e-caps (CE05, CE06, CE19, CE20, CE21, CE22), two bi-polar capacitors (CE23, CE24), and three aluminum e-caps (CE03, CE04, CE25). The original low-leakage e-caps CE19 and CE20 were replaced with film polyester WIMA caps. The other low leakage e-caps with higher rated capacitance were replaced with modern low leakage Nichicon UKL caps. Two bi-polar e-caps were replaced with film polyester WIMA caps. And, the remaining aluminum e-caps were replaced with low-impedance Nichicon UPW caps.

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

CE03: rated capacitance – 10uF, measured – 11uF, ESR – 1.61Ω, deviation: +10%

CE04: rated capacitance – 10uF, measured – 9uF, ESR – 1.44Ω, deviation: -10%

CE05: rated capacitance – 4.7uF, measured – 4.4uF, ESR – 2.6Ω, deviation: -6%

CE06: rated capacitance – 4.7uF, measured – 4.7uF, ESR – 2.8Ω, deviation: 0%

CE19: rated capacitance – 1uF, measured – 1uF, ESR – 4.2Ω, deviation: 0%

CE20: rated capacitance – 1uF, measured – 1uF, ESR – 4.4Ω, deviation: 0%

CE21: rated capacitance – 3.3uF, measured – 2.9uF, ESR – 2.8Ω, deviation: -12%

CE22: rated capacitance – 3.3uF, measured – 3.1uF, ESR – 3.2Ω, deviation: -6%

CE23: rated capacitance – 1uF, measured – 0.8uF, ESR – 3.3Ω, deviation: -20%

CE24: rated capacitance – 1uF, measured – 0.8uF, ESR – 3.8Ω, deviation: -20%

CE25: rated capacitance – 220uF, measured – 181uF, ESR – 0.43Ω, deviation: -18%

Tone amplifier board - before and after

Main Amplifier Board (P700)

The main amplifier board has 4 low-leakage capacitors (C701, C702, C705, C706) and 4 aluminum electrolytic capacitors (C709, C710, C719, C720). I replaced the original low-leakage e-caps with modern low-leakage Nichicon UKL caps. The remaining aluminum e-caps were replaced with low-impedance Nichicon UPW caps.

The protection circuit is also assembled on this board and has 2 aluminum electrolytic capacitors C721 and C722. I replaced them with low-impedance Nichicon UPW caps.

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

C701: rated capacitance – 3.3uF, measured – 3.1uF, ESR – 6.1Ω, deviation: -6%

C702: rated capacitance – 3.3uF, measured – 3.1uF, ESR – 5.2Ω, deviation: -6%

C705: rated capacitance – 47uF, measured – 46uF, ESR – 1.04Ω, deviation: -2%

C706: rated capacitance – 47uF, measured – 46uF, ESR – 0.96Ω, deviation: -2%

C709: rated capacitance – 47uF, measured – 50uF, ESR – 0.98Ω, deviation: +6%

C710: rated capacitance – 47uF, measured – 53uF, ESR – 1.09Ω, deviation: +13%

C719: rated capacitance – 220uF, measured – 242uF, ESR – 0.91Ω, deviation: +10%

C720: rated capacitance – 10uF, measured – 11uF, ESR – 5.6Ω, deviation: +10%

C721: rated capacitance – 47uF, measured – 54uF, ESR – 1.08Ω, deviation: +15%

C722: rated capacitance – 220uF, measured – 245uF, ESR – 0.84Ω, deviation: +11%

The first stage of the main amplifier circuit is a differential amplifier consisting of two amplifying transistors with a common emitter: H701/H703 and H702/H704. The original PNP transistor installed in these positions is 2SA763. This transistor is not on my list of infamous transistors that are prone to failure. However, testing each pair of transistors installed in the differential amplifier always makes sense to ensure they are still well-matched. 

As can be seen from the test below, the mismatch of each pair of original transistors in the left and right channels is ~45% and ~13%, respectively. I prefer to keep the mismatch between the two transistors in a differential amplifier as small as possible since it is critical to the correct operation of this circuit. So, I replaced each pair of the original 2SA763s with a closely matched pair (within 1%) of modern Fairchild KSA992 low-noise transistors.

Test results on original 2SA763 transistors

H701 (left channel): hfe - 161, Vbe - 0.744V 

H703 (left channel): hfe - 234, Vbe - 0.754V

H702 (right channel): hfe - 202, Vbe - 0.748V 

H704 (right channel): hfe - 228, Vbe - 0.751V

Test results on new KSA992FBU transistors

H701 (left channel): hfe - 419, Vbe - 0.760V

H703 (left channel): hfe - 422, Vbe - 0.761V

H702 (right channel): hfe - 417, Vbe - 0.762V

H704 (right channel): hfe - 417, Vbe - 0.763V

The original relay driver transistor on this board is 2SC1318. It usually degrades over time and I replaced it with a new Fairchild KSC2383. The new transistor has the same pinout as the original one.

Each original MV-13 diode installed in positions H705 and H706 was replaced with two 1N4148 diodes connected in series.

Finally, the original protection relay was also replaced with a new Omron relay to improve overall reliability.

Power amplifier board - before and after

Dolby FM Set (PC01)

The Dolby FM set has four solid tantalum capacitors (CC01, CC02, CC03, and CC04). I replaced them with film polyester WIMA caps.

Test results on original capacitors removed from the Dolby FM set:

CC01: rated capacitance – 1uF, measured – 1uF, ESR – 10.6Ω, deviation: 0%

CC02: rated capacitance – 1uF, measured – 1uF, ESR – 19.7Ω, deviation: 0%

CC03: rated capacitance – 1uF, measured – 1uF, ESR – 9.6Ω, deviation: 0%

CC04: rated capacitance – 1uF, measured – 1uF, ESR – 15.3Ω, deviation: 0%

Dolby FM set - before and after

FM IF Amplifier, Detector, Muting Control Board (P200)

The FM IF amplifier control board has 7 aluminum electrolytic capacitors: C218, C223, C224, C226, C231, C232, and C233. 

The original e-cap C231 was replaced with a film polyester WIMA cap. The remaining e-caps were replaced with low-impedance Nichicon UPW caps. 

Test results on original capacitors removed from the FM IF amplifier control board:

C218: rated capacitance – 10uF, measured – 12uF, ESR – 2.8Ω, deviation: +20%

C223: rated capacitance – 10uF, measured – 11uF, ESR – 4.6Ω, deviation: +10%

C224: rated capacitance – 10uF, measured – 11uF, ESR – 4.1Ω, deviation: +10%

C226: rated capacitance – 100uF, measured – 116F, ESR – 1.28Ω, deviation: +16%

C231: rated capacitance – 1uF, measured – 1.1uF, ESR – 3.8Ω, deviation: +10%

C232: rated capacitance – 33uF, measured – 38uF, ESR – 1.22Ω, deviation: +15%

C233: rated capacitance – 10uF, measured – 9uF, ESR – 3.4Ω, deviation: -10%

The faulty coil L202 was replaced with a spare coil from another FM IF amplifier board.

FM IF amplifier, detector, muting control board - before and after

MPX Stereo Decoding Amplifier Board (P300)

The MPX Stereo decoding amplifier board has 3 bi-polar electrolytic capacitors (C305, C306, C307), 4 solid tantalum capacitors (C321, C322, C323, C324), and 3 aluminum electrolytic capacitors (C301, C308, C325).

All original bi-polar and solid tantalum capacitors were replaced with film polyester WIMA and Kemet caps. The remaining aluminum electrolytic capacitors were replaced with low-impedance Nichicon UPW caps. 

Test results on original capacitors removed from the MPX Stereo decoding amplifier board:

C301: rated capacitance – 10uF, measured – 12uF, ESR – 3.1Ω, deviation: +20%

C305: rated capacitance – 0.47uF, measured – 0.38uF, ESR – N/A, deviation: -19%

C306: rated capacitance – 0.22uF, measured – 0.16uF, ESR – N/A, deviation: -27%

C307: rated capacitance – 0.22uF, measured – 0.16uF, ESR – N/A, deviation: -27%

C308: rated capacitance – 220uF, measured – 270uF, ESR – 0.98Ω, deviation: +23%

C321: rated capacitance – 0.22uF, measured – 0.21uF, ESR – N/A, deviation: -5%

C322: rated capacitance – 0.22uF, measured – 0.22uF, ESR – N/A, deviation: 0%

C323: rated capacitance – 1uF, measured – 1uF, ESR – 5.6Ω, deviation: 0%

C324: rated capacitance – 1uF, measured – 1uF, ESR – 5.1Ω, deviation: 0%

C325: rated capacitance – 220uF, measured – 201uF, ESR – 0.56Ω, deviation: -9%

MPX Stereo decoding amplifier board - before and after

FM Front End & AM Tuner Board (P100)

The FM Front End & AM tuner board has one solid tantalum capacitor C141 and 5 aluminum electrolytic capacitors (C127, C135, C136, C140, C143).

The original solid tantalum capacitor was replaced with a film polyester Kemet cap. The other two capacitors with a nominal capacitance of 1uF were replaced with film polyester WIMA caps. The remaining aluminum electrolytic capacitors were replaced with low-impedance Nichicon UPW caps.

Test results on original capacitors removed from the FM Front End & AM tuner board:

C127: rated capacitance – 47uF, measured – 57uF, ESR – 0.74Ω, deviation: +21%

C135: rated capacitance – 10uF, measured – 13uF, ESR – 1.57Ω, deviation: +30%

C136: rated capacitance – 1uF, measured – 1.1uF, ESR – 1.75Ω, deviation: +10%

C140: rated capacitance – 100uF, measured – 109uF, ESR – 0.82Ω, deviation: +9%

C141: rated capacitance – 0.22uF, measured – 0.22uF, ESR – N/A, deviation: 0%

C143: rated capacitance – 1uF, measured – 0.9uF, ESR – 3.4Ω, deviation: -10%

FM Front End & AM tuner board after servicing (sorry, I forgot to take a picture before servicing)

Power Transistors

The original power transistors were removed, degreased, and tested with Atlas DCA55 semiconductor analyzer. According to the datasheet, the measured DC current gain on all transistors was in spec. 

However, it should be noted that the 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 applied fresh thermal paste and replaced the old thermal pads with new Mica ones, which is always a good idea when working with any vintage receiver. The old grease can frequently dry, causing the transistors to suffer from poor heat dissipation. This can lead to overheating and failure of the device.

Dial and Meter Lamps

The original dial and meter lamps in this unit were replaced with new warm white LED lamps.

DC offset and Bias Adjustments

Be aware, that the service manual has an error for bias adjustment. The correct procedure is described below.

The Bias on the left channel is measured across two emitter resistors R759 and R761. So, the voltmeter should be connected between J714 (+) and J716 (-). On the right channel, the bias is measured across two emitter resistors R760 and R762. So, the voltmeter should be connected between J715 (+) and J717 (-). The Bias should be adjusted to ~20mV on each channel with the trimming resistors R733 and R734.

The DC offset on the left channel is measured between J723 and J722 (ground). On the right channel, it is measured between J724 and J722 (ground). The DC offset should be adjusted as close to zero volts as possible with the trimming resistors R711 and R712.

Bias on the left and right channels after restoration

DC offset on the left and right channels after restoration

Output Power Test

The final output power test was performed at the end of my restoration. The amplifier was loaded with a low inductance 8Ω/100W dummy resistor for each channel. The oscilloscope was connected across the speaker terminals and a sine-wave signal of 1kHz was applied to the AUX jacks. The output sine-wave signal was perfectly symmetrical on both channels with no clipping up to 13.71 VRMS (left channel) and 13.67 VRMS (right channel). It corresponds to the output power of 23.5W on the left channel and 23.4W on the right channel.

Output power test

As usual, all the knobs and the face plate were gently cleaned in warm water with dish soap. All controls 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. The receiver looks and sounds great again. Please watch a short demo video at the end of this post. Thank you for reading.

Marantz 2220B - after restoration

Demo video after repair & restoration

Marantz 2265B Receiver Restoration

Unit: AM/FM Stereo Receiver

Manufacturer: Marantz

Model: 2265B

SN: U130304

Today I'm showcasing a Marantz 2265B vintage receiver that came in for restoration. Marantz 2265B was manufactured from 1977 to 1979. It produces 65 watts per channel into 8 ohms with no more than 0.05% total harmonic distortion. The damping factor at 8 ohms is 55. The optional walnut veneer cabinet for this model is WC-122.

According to the factory stamp on the chassis, this receiver was manufactured in June 1978.

Power Supply Board (P800)

The power supply board has 14 aluminum electrolytic capacitors: C801, C802, C803, C804, C806, C809, C810, C812, C813, C815, C817, C818, C819, and C820.

I replaced all capacitors on this board with low-impedance Nichicon UPW/UPM caps.

The original e-caps were tested with an Atlas ESR70 capacitance meter; the results are below.

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

C801: rated capacitance – 470uF, measured – 447uF, ESR – 0.32Ω, deviation: -5%

C802: rated capacitance – 330uF, measured – 271uF, ESR – 0.75Ω, deviation: -18%

C803: rated capacitance – 100uF, measured – 115uF, ESR – 0.56Ω, deviation: +15%

C804: rated capacitance – 47uF, measured – 52uF, ESR – 0.73Ω, deviation: +11%

C806: rated capacitance – 10uF, measured – 12uF, ESR – 0.77Ω, deviation: +20%

C809: rated capacitance – 330uF, measured – 372uF, ESR – 0.31Ω, deviation: +13%

C810: rated capacitance – 470uF, measured – 466uF, ESR – 0.38Ω, deviation: -1%

C812: rated capacitance – 10uF, measured – 9uF, ESR – 0.95Ω, deviation: -10%

C813: rated capacitance – 100uF, measured – 111uF, ESR – 0.69Ω, deviation: +11%

C815: rated capacitance – 100uF, measured – 78uF, ESR – 0.56Ω, deviation: -22%

C817: rated capacitance – 4.7uF, measured – 4.5uF, ESR – 3.6Ω, deviation: -4%

C818: rated capacitance – 47uF, measured – 49uF, ESR – 0.88Ω, deviation: +4%

C819: rated capacitance – 220uF, measured – 211uF, ESR – 0.67Ω, deviation: -4%

C820: rated capacitance – 470uF, measured – 492uF, ESR – 0.34Ω, deviation: +5%

All transistors and two Zener diodes on this board were also replaced to improve the reliability of the power supply. Below is a list of original and replacement parts that I have used.

Q801: NPN, 2SC1567 (original), replaced with a new Fairchild KSC2690AYSTU

Q802: NPN, 2SC1318 (original), replaced with a new Fairchild KSC2690AYSTU

Q803: PNP, 2SA794 (original), replaced with a new Fairchild KSA1220AYS

Q804: PNP, 2SA684 (original), replaced with a new Fairchild KSA1220AYS

Q805: Zener, 19.2V/0.5W, WZ-192 (original), replaced with a new Fairchild 1N5249BTR

Q806: NPN, 2SC1384 (original), replaced with a new Fairchild KSC2690AYSTU

Q807: PNP, 2SA684 (original), replaced with a new Fairchild KSA1220AYS

Q808: NPN, 2SD313 (original), replaced with a new Fairchild MJE15030G

Q809: Zener, 14V/0.5W, WZ-140 (original), replaced with a new Fairchild 1N5244B

Q810: NPN, 2SC945 (original), replaced with a new Fairchild KSC945CYTA

Q811: NPN, 2SC1318 (original), replaced with a new Fairchild KSC2383YTA

Q812: NPN, 2SC1318 (original), replaced with a new Fairchild KSC2383YTA

The original protection relay in this unit was already replaced with a new Omron relay.

Power supply board - before servicing

Power supply board - after servicing

Main Amplifier Board (P700)

The main amplifier board has 8 low-leakage e-caps (C701, C706, C716, C717, C751, C756, C766, C767) and 6 ordinary aluminum electrolytic capacitors (C710, C722, C723, C760, C772, C773).

The original low-leakage e-caps were replaced with modern low-leakage Nichicon UKL caps. The remaining aluminum e-caps were replaced with low-impedance Nichicon UPW caps.

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

C701: rated capacitance – 4.7uF, measured – 4.7uF, ESR – 5.7Ω, deviation: 0%

C706: rated capacitance – 47uF, measured – 46uF, ESR – 1.04Ω, deviation: -2%

C710: rated capacitance – 47uF, measured – 48uF, ESR – 0.56Ω, deviation: +2%

C716: rated capacitance – 10uF, measured – 11uF, ESR – 1.87Ω, deviation: +10%

C717: rated capacitance – 10uF, measured – 11uF, ESR – 1.76Ω, deviation: +10%

C722: rated capacitance – 220uF, measured – 225uF, ESR – 0.34Ω, deviation: +2%

C723: rated capacitance – 220uF, measured – 222uF, ESR – 2.1Ω, deviation: +1%

C751: rated capacitance – 4.7uF, measured – 5.2uF, ESR – 5.1Ω, deviation: +11%

C756: rated capacitance – 47uF, measured – 44uF, ESR – 0.94Ω, deviation: -6%

C760: rated capacitance – 47uF, measured – 49uF, ESR – 0.76Ω, deviation: +4%

C766: rated capacitance – 10uF, measured – 11uF, ESR – 1.63Ω, deviation: +10%

C767: rated capacitance – 10uF, measured – 11uF, ESR – 1.95Ω, deviation: +10%

C772: rated capacitance – 220uF, measured – 239uF, ESR – 0.35Ω, deviation: +9%

C773: rated capacitance – 220uF, measured – 219uF, ESR – 0.47Ω, deviation: -1%

The four original capacitors installed on this board were secured at the factory with glue. Before installing the new capacitors, I removed the old glue but noticed that two resistors (R709 and R759) located next to capacitors C723 and C753 were also covered in old glue. I decided to replace them with new KOA Speer metal film resistors to prevent possible degradation in the future.

The first stage of the main amplifier circuit is a differential amplifier consisting of two amplifying transistors with a common emitter: Q701/Q702 and Q751/Q752. The original PNP transistor installed in these positions is 2SA722. This transistor is not on my list of infamous transistors that are prone to failure. However, testing each pair of transistors installed in the differential amplifier always makes sense to ensure they are still well-matched. 

As can be seen from the test below, the mismatch of each pair of original transistors in the left and right channels is ~14% and ~16%, respectively. I prefer to keep the mismatch between the two transistors in a differential amplifier as small as possible since it is critical to the correct operation of this circuit. So I replaced each pair of the original 2SA722s with a closely matched pair (within 1%) of modern Fairchild KSA992 low-noise transistors. I put a slight smear of new thermal paste on one face of KSA992 and pressed both transistors together. Heat shrink tubing was used to hold them together mechanically.

Test results on original 2SA722 transistors

Q701 (left channel): hfe - 373, Vbe - 0.786V 

Q702 (left channel): hfe - 426, Vbe - 0.787V

Q751 (right channel): hfe - 397, Vbe - 0.786V 

Q752 (right channel): hfe - 342, Vbe - 0.787V

Test results on new KSA992FBU transistors

Q701 (left channel): hfe - 407, Vbe - 0.761V

Q702 (left channel): hfe - 407, Vbe - 0.763V

Q751 (right channel): hfe - 404, Vbe - 0.762V

Q752 (right channel): hfe - 405, Vbe - 0.761V

Each original MV-13 diode installed in positions Q703, Q704, Q753, and Q754 was replaced with two 1N4148 diodes connected in series.

All original trimming resistors were replaced with new Bourns potentiometers.

Main amplifier board - before and after

Pre and Tone Amplifier Board (PE01)

The pre and tone amplifier board has 14 low-leakage capacitors (CE01, CE02, CE03, CE04, CE09, CE10, CE31, CE32, CE39, CE40, CH11, CH12, CH15, CH16) installed in the signal path, and 4 aluminum electrolytic capacitors (CE35, CE36, CE43, CE44).

Four original low-leakage capacitors (CE01, CE02, CE31, CE32) installed in the input signal path were replaced with high-quality film polyester WIMA caps. Other original low-leakage e-caps were replaced with modern low-leakage Nichicon UKL caps. The remaining aluminum e-caps were replaced with low-impedance Nichicon UPW caps.

Pay attention to capacitor CE40. The polarity of CE40 is shown backward on the circuit board silkscreen. The negative lead of CE10 must be connected to pin JE10.

Tip: Disconnecting the solid white/black wire from the pre and tone amplifier board will give you more room to work with. Just remember to solder it back when you're done with this board.

Test results on original capacitors removed from the pre and tone amplifier board:

CE01: rated capacitance – 1uF, measured – 0.9uF, ESR – 4.1Ω, deviation: -10%

CE02: rated capacitance – 1uF, measured – 1.0uF, ESR – 4.2Ω, deviation: 0%

CE03: rated capacitance – 33uF, measured – 38uF, ESR – 1.41Ω, deviation: +15%

CE04: rated capacitance – 33uF, measured – 41uF, ESR – 1.34Ω, deviation: +24%

CE09: rated capacitance – 4.7uF, measured – 5.3uF, ESR – 3.4Ω, deviation: +13%

CE10: rated capacitance – 4.7uF, measured – 4.8uF, ESR – 4.3Ω, deviation: +2%

CE31: rated capacitance – 1uF, measured – 1.0uF, ESR – 4.0Ω, deviation: 0%

CE32: rated capacitance – 1uF, measured – 1.0uF, ESR – 3.6Ω, deviation: 0%

CE35: rated capacitance – 3.3uF, measured – 3.6uF, ESR – 2.1Ω, deviation: +9%

CE36: rated capacitance – 3.3uF, measured – 3.8uF, ESR – 1.6Ω, deviation: +15%

CE39: rated capacitance – 4.7uF, measured – 5.3uF, ESR – 3.4Ω, deviation: +13%

CE40: rated capacitance – 4.7uF, measured – 5.6uF, ESR – 4.8Ω, deviation: +19%

CE43: rated capacitance – 100uF, measured – 121uF, ESR – 2.4Ω, deviation: +21%

CE44: rated capacitance – 100uF, measured – 118uF, ESR – 1.4Ω, deviation: +18%

CH11: rated capacitance – 2.2uF, measured – 2.0uF, ESR – 5.1Ω, deviation: -9%

CH12: rated capacitance – 2.2uF, measured – 2.0uF, ESR – 5.3Ω, deviation: -9%

CH15: rated capacitance – 10uF, measured – 9uF, ESR – 1.24Ω, deviation: -10%

CH16: rated capacitance – 10uF, measured – 9uF, ESR – 1.51Ω, deviation: -10%

Six NPN transistors (QE05, QE06, QE07, QE08, QH03, QH04) installed on this board are Hitachi 2SC1345. This transistor is on my list of transistors that are prone to failure. I replaced all original 2SC1345s with new Fairchild KSC1845 transistors. Watch the pinout on replacement transistors. The original transistor is BCE and the new one is ECB.

Pre and tone amplifier board - before and after

Monitor & Filter Switches Circuit Board (PS01)

The monitor & filter switches circuit board does not have electrolytic capacitors but contains three prone-to-failure transistors: 2SA720 (QS01), 2SC1345 (QH01 and QH02).

The original Panasonic 2SA720 was replaced with a new Fairchild KSA1013YBU transistor. The replacement transistor has the same pinout as the original one.

Both original Hitachi 2SC1345s were replaced with new Fairchild KSC1845 transistors. Watch the pinout on replacement transistors. The original transistor is BCE and the new one is ECB.

Monitor & filter switches board - before and after

All switches on this board can be easily cleaned and lubricated during the servicing. However, the "Tape Copy" and "Tape Monitor" switches are located between this and another small board, as seen in the photo below. The small top PCB must be removed to access all hidden switches for cleaning. This can be a challenging task for those who don't have the right tools. For this purpose, I used my Hakko FR301 desoldering tool, which greatly helped.

"Tape Copy" and "Tape Monitor" switches are sandwiched between two PCBs

The small top PCB and extension shaft are removed - now it is easy to clean and lubricate

Phono Amplifier Board (P400)

The phono amplifier board has 6 low-leakage e-caps installed in the signal path (C401, C402, C409, C410, C417, C418) and two aluminum electrolytic capacitors (C423, C424).

All original low-leakage e-caps were replaced with modern low-leakage Nichicon UKL caps. The remaining aluminum e-caps were replaced with low-impedance Nichicon UPW caps.

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

C401: rated capacitance – 4.7uF, measured – 4.8uF, ESR – 2.4Ω, deviation: +2%

C402: rated capacitance – 4.7uF, measured – 5.0uF, ESR – 2.1Ω, deviation: +6%

C409: rated capacitance – 33uF, measured – 38uF, ESR – 2.2Ω, deviation: +15%

C410: rated capacitance – 33uF, measured – 37uF, ESR – 1.41Ω, deviation: +12%

C417: rated capacitance – 4.7uF, measured – 4.2uF, ESR – 2.8Ω, deviation: -11%

C418: rated capacitance – 4.7uF, measured – 4.2uF, ESR – 2.6Ω, deviation: -11%

C423: rated capacitance – 47uF, measured – 46uF, ESR – 0.44Ω, deviation: -2%

C424: rated capacitance – 47uF, measured – 48uF, ESR – 0.52Ω, deviation: +2%

I also replaced the original Hitachi 2SA872 transistors installed in the differential amplifier circuit with modern Fairchild KSA992 low-noise transistors. Each pair of new transistors is closed-matched within 1%. The replacement transistor has the same pinout as the original one.

Test results on original 2SA872 transistors

Q401 (left channel): hfe - 354, Vbe - 0.776V 

Q403 (left channel): hfe - 318, Vbe - 0.776V

Q402 (right channel): hfe - 355, Vbe - 0.779V 

Q404 (right channel): hfe - 316, Vbe - 0.781V

Test results on new KSA992FBU transistors

Q401 (left channel): hfe - 409, Vbe - 0.760V

Q403 (left channel): hfe - 410, Vbe - 0.761V

Q402 (right channel): hfe - 412, Vbe - 0.761V

Q404 (right channel): hfe - 414, Vbe - 0.763V

Phono amplifier board - before and after

Power Transistors

All power transistors were removed, degreased, and tested with an Atlas DCA55 semiconductor analyzer. According to the datasheet, the measured current gain on all transistors was in spec. 

However, it should be noted that the Atlas DCA55 Semiconductor Analyzer provides accurate DC gain readings 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 handy device for comparing transistors of a similar type for gain matching or fault-finding.

I applied a fresh thermal compound and replaced the old thermal pads with new Mica ones which is always a good idea when working on any vintage receiver. The old grease can frequently dry, causing the transistors to suffer from poor heat dissipation. This can result in overheating and the destruction of the device.

Original power transistors

With new Mica pads

Main Filter Capacitors

Two main filter capacitors were tested with an Atlas ESR70 capacitance meter.  Both caps are still within the factory capacitance tolerance and have low ESR. So, I didn't change them. In general, the filter capacitors rarely fail in vintage gears, and I usually don't replace them unless their ESR is high.

Test results on the original filter capacitors:

C003: rated capacitance – 10000uF, measured – 10180uF, ESR – 0.22Ω, deviation: +2%

C004: rated capacitance – 10000uF, measured – 10140uF, ESR – 0.26Ω, deviation: +1%

Dial and Meter Lamps

The old incandescent lamps were replaced with warm white LED lamps to maintain the original look and decrease heat. The original incandescent lamps behind two meters were also replaced with warm white LED lamps. I have described this procedure many times in my previous posts (see for more details here). Note, that there is no vellum paper behind the dial scale in Marantz 2265B.

Dial scale removed - original incandescent dial lamps

Dial scale removed - warm white LED lamps

DC offset and Bias Adjustments

The DC offset on each channel is measured across speaker terminals (no load connected). It should be adjusted as close to zero volts as possible with the trimming resistors R710 and R760, respectively.

The bias is measured across two emitter resistors (wire wound type, 0.47Ω/5W). The voltage between pins J717 and J718 should be adjusted to ~20mV DC with the trimming resistor R716. This is a bias on the left channel. The voltage between pins J767 and J768 on the right channel should be adjusted to ~20mV DC with the trimming resistor R766.

DC offset on the left and right channels after restoration

Bias on the left and right channels after restoration

Output Power Test

The final output power test was performed at the end of my restoration. The receiver was loaded with a low inductance 8Ω/100W dummy resistor for each channel. The oscilloscope was connected across the speaker terminals and a sine-wave signal of 1kHz was applied to the AUX jacks. The output sine-wave signal was perfectly symmetrical on both channels with no clipping up to 24.72 VRMS (left channel) and 25.06 VRMS (right channel). It corresponds to the output power of 76.4W on the left channel and 78.5W on the right channel.

Output power test

As usual, all the knobs and the face plate were gently cleaned in warm water with dish soap. All controls 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.

Marantz 2265B - after restoration

Demo video after repair & restoration