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Stunning Accuphase E-303 Amplifier Repair & Overhaul

For those who haven’t heard an Accuphase E-303, they really are one of the sweetest sounding integrated amplifiers ever made. Come with me as I repair and overhaul one.

Given everyone’s sitting at home dealing with the Coronavirus, I decided to finish this Accuphase E-303  article, for your reading pleasure. I started writing this one 18 months ago, that’s how many articles I have in the pipeline. I’ve clearly got a bit of catching up to do.

Accuphase E-303

The Accuphase E-303 is a heavy, full-featured integrated amplifier with MOSFET output devices, superb sound and robust construction. I listen to every piece of equipment I work on and, out of hundreds of integrated amps I’ve heard, a well-sorted E-303 like this is one of the sweetest sounding integrated amps you’ll find.

Accuphase E-303

Accuphase released the E-303 integrated amplifier way back in 1978. Back then it cost 245,000 Japanese Yen, roughly equal to $3750 AUD or the price of a new small car, 40 years ago. You can imagine the equivalent cost now, allowing for inflation. I calculated it an eye-watering roughly $20K AUD…

Whatever the price, Accuphase really hit it out of the park with this model and the E-303 and E-303X  remain incredibly popular. They change hands for around $1500 – $2000AUD and at these prices, compared to new gear, they are an absolute bargain.

By the way, if you like Accuphase articles and equipment, make sure you read about my Accuphase E-202 and Accuphase M-60 restorations. I also have Accuphase E-206, E-301, P-20, P-300, T-105, T-100, DC-330, C-200L, C-230 stories in the pipeline.

Accuphase E-303

Accuphase E-303 Specifications

As usual, specs come courtesy of HiFi Engine:

Power output: 130 watts per channel into 8Ω (stereo)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.08%
Damping factor: 80
Sensitivity: 0.125mV (MC), 2.5mV (MM), 160mV (line)
Signal to noise ratio: 72dB (MC), 86dB (MM), 100dB (line)
Output: 160mV (line), 1.3V (Pre out)
Load impedance: 4Ω to 16Ω
Semiconductors: 113 x transistors, 2 x IC, 18 x FET, 39 x diodes
Dimensions: 445 x 160 x 370mm
Weight: 20kg

Problems With This Accuphase E-303

This E-303 had many issues, mostly due to neglect and poor quality previous work. Here’s a summary of what my inspection revealed:

  • She’d been neglected and had sat in a shed somewhere for a long time.
  • She’d been dropped at some point and many of the back panel connectors had been epoxied back in place.
  • Someone had attempted to repair a broken mute relay, failed and then taken the mute relays out of circuit by cutting the power wires to the board.
  • She was filled with dust, dirt
  • There were several bad connectors and many dry joints
  • Many capacitors needed replacement
  • All adjustments were way out with massive DC offsets in both channels
  • Some intermittent popping sounds in one channel

Clearly this E-303  needed significant TLC. Note though that each job is different and this one had a budget limit. The brief was repair and overhaul as necessary. It was not a full restoration and therefore many good original parts remain.

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The first look inside. You’ll note the usual dust, dirt and neglect.
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Good cable management isn’t a new thing!
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A closer look at this board. Note that with Accuphase gear, there are trimmers on most boards, usually for DC offset adjustment.
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Work is needed here, both amplifier modules must come out for overhaul.
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We’re looking at the tone and buffer amp board, mid-frame, with filter capacitors behind.
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Here is the whole power supply including transformer, with the power supply and protection board to the right of frame.
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Here, we can see some of the heat damaged capacitors on the amplifier modules. I replaced all these small caps

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Overhaul

As usual, I start with the low hanging fruit and work from there. I replace bad caps, look at switches and controls, connectors, soldering, relays and so on. As I work through each ‘fruit’, performance improves and I can focus on remaining problems.

Amplifier Modules

Let’s start with the amplifier modules, seeing as these get the hottest of any of the boards and are under the greatest ‘load’ shall we say.

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Modules removed for inspection and repair
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Board separated from heatsink assembly, ready for washing.
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As usual, I replaced mica thermal pads and paste with silicone thermal pads. There are sound engineering reasons for doing so. Yes, THIN mica and fresh thermal paste make for a better thermal interface, but thick mica and/or old paste is much worse than silicone. Silicone is less messy and maintains performance over a longer timeframe.
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Cleaning MOSFETs and heatsink

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Original Hitachi MOSFETs mounted on new thermal interfaces. This setup will last well.
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The other channel

Turning attention to the boards, I repaired dry joints and replaced small capacitors. Note that this is not a full restoration, so many larger capacitors that measure well remain in place.

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All the small heat-damaged capacitors have been replaced in this shot
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Here is one of the finished, washed and overhauled amplifier modules

Tone and Buffer Amplifier

This board is an important one as all signals pass through it on the way to the power amplifiers.

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I tested electrolytic capacitors, reworked many dry joints, serviced trimpots etc.
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Look at this mess – someone left the board like this for me to find!
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Same area after re-work and cleaning

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The finished, re-worked and cleaned tone and buffer amp board

Power Supply

The power supply is one of the most import, if not the most important parts of any electronic device. It’s no different with this E-303.

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The black connector in the middle of this board was a real problem. It took a while to resolve issues associated with this connector. Can you see the two flying wires…?
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Yes, this black connector and these two cut wires really sucked b#%ls…
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See these lifted traces and burned flux? I repaired all this damage and more.
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The repaired areas, with flux gone, pads seated and joints re-worked.
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Other dry joints and damage
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More overheated pads…

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Note the bulging plastic top on one of these larger capacitors. If you spend time in forums, you’ll perhaps have read that this means the capacitor must be replaced, but like many things, it’s not so simple. The only way to know if a capacitor must be replaced is to test it and these capacitors all tested perfectly. All the bulging plastic really tells us is that this capacitor has been exposed to heat. Heat can damage plastic and the component inside can remain electrically perfect. On a job like this, where the customer has requested an overhaul and repair, rather than a full restoration, it’s important to make sensible economic decisions that work within the customer’s budget. Other improvements can be discussed once the unit is back up and running.

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I’ve replaced the smaller electrolytic capacitors on this board. That’s because the bigger ones test well. Remember, this is a budget-limited overhaul, not a restoration.
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The finished E-303 power supply and protection board, re-worked, cleaned, repaired and overhauled.
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And from the top…

Preamplifier Board

The preamplifier board is a critical one because all signals pass through it unless the amp is operated in power amp bypass mode. The E-303 has an especially nice FET based phono preamp and there were massive DC offsets through this area, so she needed some extensive work. Someone who previously worked on this E-303 had also damaged a trace to the extent that it was almost destroyed.

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Looking at the right-hand end of the E-303, with the preamplifier board removed.
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And here it is. Many smaller capacitors and dry joints needed attention on this board. You might also notice the balanced, symmetrical circuit configuration. It’s a very nice preamp.
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Wow and yes, lots to attend to here
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Dual FET packages and thermally bonded small signal bipolar transistor pairs. Note the offset trim adjustment right next to these devices.

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All joints like these need repair

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They are always worst with the higher current devices, as is the case here. They dissipate more heat, so the joints degrade more quickly.
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Detail shot showing small electrolytic capacitor replacements and the now washed and cleaned board.
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Can you believe this ground trace was just left like this? This must be repaired.
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For repairs like this, I bare fresh copper and solder in a wire jumper.
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The overhauled preamplifier board

Mute Relay Board

There was one very strange problem that I simply had to resolve for my customer. Someone had attempted to repair a mute relay problem but decided it was too difficult. So, they gave up, cut power to the board and lifted pins on both relays, effectively hobbling the whole board and circuit.

Now, these mute relays are there for a reason. They are partly why Accuphase equipment is so quiet in general operation and the board really needs to be working.

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When you know there’s a problem: two flying power wires cut and flapping around inside an Accuphase amplifier…
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A closer look at this mute relay board and I could see where they should be connected. Note the lifted relay pins – the mid pin in each group of three you can see. Note also the cut power wiring.

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I first tried repairing the relay pins and wiring, just to see who this thing would behave. It didn’t help. I then removed and tested the relay. It was dead.
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Luckily I was able to obtain a replacement. Yep, that’s a brand new old stock, virtually unobtainable Fujitsu mute relay for an Accuphase E-303. Don’t ask me how I got it…!
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Mute relay power wiring reattached to the board and new relay installed. This relay-controlled mute circuit now works very well.

Testing and Adjustment

This is the last but one step before cleaning. With the amp on the bench, I run power-on testing, set quiescent current draw and DC symmetry at the various stages of the amplifier. From the service manual, there are 8 separate adjustments in an Accuphase E-303.

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The E-303 back together and looking much cleaner
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Here the E-303 is hooked up to two DC mV meters as I set quiescent current draw. These amplifiers run warm and there is a useful amount of class-A power.
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I think the Accuphase E-303 looks especially pretty with those power meters and understated design aesthetics.

Final Cleaning and Results

Finally, we come to the end of this epic write-up. The last stages for me are always to clean the chassis exterior, knobs, connectors and so on, followed by a final test and photo-shoot.

After all the work, this lovely old Accuphase E-303 sounds amazing and runs very well. She’s had somewhat of a hard life and I spent a little more time on one or two of the connectors and switches, but I know her owner is very happy with her. He paid very little for her due to her slightly unloved condition. I think you’ll agree, she looks great now!

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Hasn’t she cleaned up well!
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A missing balance knob is now really the only cosmetic issue with this old girl

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I Love the power meters on the E-303

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It’s business as usual @ Liquid Audio, despite Coronavirus, so if you’d like my assistance with your Accuphase E-303, or any other Accuphase piece, don’t hesitate to get in touch.

Liquid Mike

As a kid, I cherished my Tandy 200-in-1 electronics project lab, Dick Smith electronics kits, my Dad's hi-fi and my own first proper system. Later, I created Liquid Audio to help keep classic hi-fi gear alive and well. Our mission: to deliver TLC for classic Japanese, American and European hi-fi stereo equipment.

This Post Has 8 Comments

  1. Ben Bourke

    Hey Mike I have a fully restored e303 that sounds amazing, it does tend to get quite warm, not hot though, if you put your hand on the top cover. Is this normal? I suppose it’s a hard question to answer but just thought I’d ask.

    1. Liquid Mike

      Hi Ben, these do run quite warm when correctly set up and that part really is critical. You definitely don’t want anything sitting on top of one!

      1. Ben Bourke

        Thankyou for replying Mike. I suppose these run in class A up to a point… certainly sound like it.
        Absolutely gorgeous sonics!!!

        1. Liquid Mike

          No problem and actually all conventional amplifiers run in class-A up to a certain point, the E-303 just has a wider class-A envelope than many integrated amplifiers. They sound great even unrestored and can sound even better, depending on precisely what is done, what parts are used and how they are set up.

          1. Ben Bourke

            Hey mike I emailed you just to let you know what the tech said upon completion of the work he did.
            Totally understand if you haven’t the time to read it, but if you do then great.
            Thanks

            1. Liquid Mike

              Hi Ben, where are you and who was the technician you used here? I haven’t received an email.

              1. Ben Bourke

                Ah just emailed you then!
                I am in qld. Unfortunately!!

                1. Liquid Mike

                  No problem, I’ve replied via email. It’s hard without seeing the work but most work I see is unfortunately not standard necessary for equipment like this.

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