Evan's Audio: Repair and Sale

I will be going to peoples houses to use my UMIK2 and RoomEQ Wizard to help set up their stereos. Also, if you are interested in learning more about stereo repair, dm me and I can point you to some valuable resources

I use Wima polyester capacitors for all values below 10μF, 105C Nichicon KL for all polarized coupling capacitors, Nichicon ES or EP for all bipolar capacitors, Nichicon HE or PM for all small filtering capacitors, and Kemet, Panasonic, Nichicon, Vishay, Kemet and Epcos for all larger capacitors. For axial capacitors I use vishay and F&T. For higher voltage film capacitors I like Vishay, Panasonic, ICEL, and Solen.

I have taken up a Technican II job out of state and will be Technician III in early 2024. If you’d like me to work on your stuff still, dm me and I will respond with the name of the business and the lead time.

The repair side of Evan’s Audio is no more. I will only be doing sales and consulting from now on. Thank you for your patience

I am willing to work on what you have. I charge 60 dollars an hour, 1 hour minimum and billed in half hour increments. I use Audio Precision, Fluke, Rohde and Schwarz and Sencore test equipment and have been repairing consumer hifi for 6 years off and on.
I also have lots of serviced stereo equipment for sale. Summer class is almost over and I leave town for good in a month.

Quad ESL63 stereo loudspeakers (needs repair) $650
Pioneer VSX53 HDMI receiver $50
Technics SA828 100W stereo receiver $400
DBX 400X program route selector $75
Shure M97xE JICO SAS stylus $225
Kenwood C2 stereo preamplifier $170
EAW close coupled electronic crossover $80
Fisher 210t stereo receiver parts or repair $40
Yamaha M60 stereo power amplifier (new relay with glow removed) $300
Bose 201 series II $50
JBL 5306 6 mic mono preamplifier with VU meter
$200
Apt Holman rackMount stereo preamplifier recapped $600
Kenwood KA7300 stereo integrated amplifier $325
Dynaco FM1 $125
Sansui AT15L audio program timer $75

McIntosh MA6100 repair. Had low frequency oscillation when phono stage was selected. Found to be bad orange bipolar capacitors in the preamp stage. Replaced all orange capacitors in the amp and it’s ready to go. One measured 17uF when it should be 10uF, indicating DC leakage. Sounds great Now.

Worked on an SX950 with intermittent protection issue. Replaced bad transistors in power supply. When I turned it back on it wouldn’t come out of protection, which would be fine if not for the customer watching me while I work. Embarrassing! He left and I continued working on it. Didn’t take long for me to find out one of the solid core wires broke off the post, which I told him might occur. He drove right back after I soldered it back on and took the receiver. An easy 56 dollars.

Due to summer classes and a backlog of items that need to be fixed before being sold, I will not take in any new repairs or restorations beyond simple servicing and diagnoses. I have about 30 listings on marketplace so if you want something stereo related, DM me with what you want and I’ll give you a description of what I have. Thank you for your patience.

-Evan

Pioneer SX1080 came in with excessive distortion in both channels. Oxidized controls and relay with pitting on the contacts were the causes. All controls cleaned and lubed and the speaker protect relay replaced. Replaced the 2SA726 as a preventative maintenance. Sounds great now.

All this heathkit aa1600 needed was new emitter resistors in the left channel. Gave it a recap and replaced the output device thermal pads anyways. Ready to sing for years to come.

Marantz 2500 balance control contact cleaning with DeOxit F5 faderlube. Sounds really good and even has an oscilloscope

Visual representation of A weighting filter. Commonly seen on signal to noise measurements of audio equipment, it shows the human ear’s range of sensitivity to pink noise

Harman Kardon HK6200 repair, muting at 30W instead of max power of 45W was occurring. Reflowing the bias transistor boards solved the issue. Also the main board and phono boards needed many cold joints to be reflowed. One electrolytic capacitor was found to have high ESR. Two small value electrolytic capacitors near the main heat sinks were replaced with film. Clips at about 55W at 1kHz 8ohms.

.5Vrms 1kHz square wave fed into Harman Kardon HK770 (with Rload at 8ohms) compared to input signal square wave from Wavetek 395

New cards

Current view of the workspace. Getting a PC and DCA75 soon too, for more intense semiconductor analysis.

Deciding to step up my repair game. Soon I will be a lot faster at fixing equipment due to increased knowledge base. Only then will I bump up my hourly rate.

I have decided to still take in repairs and restorations of power amplifiers, receivers, preamplifiers, integrated amplifiers and speaker crossovers for the foreseeable future.

Shop space is limited due to many items for sale taking up space so come by as soon as you can to get your item in the queue. One thing to note is everything will take one month or longer to get done. If I can fix it while you watch, great. If I can fix it in a week, great. But don’t expect work done sooner than one month. Still have a lot of jobs to juggle at Evan’s Audio.

Nothing overly mechanical. No turntables, CD players, cassette decks or reel to reels. No RF work as I lack a FM generator and RF spectrum analyzer and 200MHz oscilloscope. So only the amp and preamp sections of a receiver I am comfortable doing. And no audio video receivers either. No point to point restorations either, just repairs. Can caps I can replace but many P2P film caps and resistors and even bad wires? No to that.

Nothing worth less than 100 dollars used is worth repairing in my shop as well.

Photo is of a Heathkit AA1600 power amplifier I am doing a partial restoration on.

Hafler 9505 DPDT switch and main filter replacement. All the philips can caps we’re doing real poorly, some bulged. 320W at 8 ohms with below .2% THD+N at 1kHz and 20kHz

Yamaha M60. Near zero distortion at all power levels. Immeasurable. I’m going to need a cleaner oscillator to get to the bottom of this. For sale, serviced with new relay (15A vs original 7A). Speaker selector switches cleaned with deoxit F5. Class A feature lowers THD by a db or two. The noise is -125db for left channel and -127db for right channel. Impossible to measure that as well. This is truly a remarkable amp. If only it had a beefier power supply, but that’s what the M80 is for.

500 dollars. Services and tests within spec.

Partial restoration of parasound HCA1200II. The plated through board combined with capacitor leads bent around the board made this partial recap of the amp a bit tricky to do… I did eventually get both amp boards recapped with Nichicon PW and MKS2 for the one bipolar cap. Bias set to 10mV across each channel emitter resistor. IMD. Signal to noise ratio. And THD+N checked as well as 120kHz and 1kHz output ratio (down only -2.6db at 120kHz from 1kHz)

Input board solder reflowed and relays polished. DeOxit F100L applied to input attenuators. RCA jack of left channel needed to be worked with RCA plug to reduce the jack distortion. Lookin nice. Here is a THD graph showing the levels of the 1KHz harmonics. .008% THD+N of 1kHz at 8ohm at 250mW ain’t bad

Yamaha c65 and the caps I replaced and it’s phono stage THD+N spectral content.

Parasound HCA-1200II audio amplifier distortion, prior to a small electrolytic (non name brand) capacitor replacement. These FR4 plateed through hole boards can be hard to remove parts from if the cap is bending the leads around the bottom of the board. Note how the 2H (second harmonic) dominates. Even order harmonics dominating is a sign of lower crossover distortion than other, more “pro audio” models like the low bias Crown XLS602. All of this is on purpose. Makes for a more natural sound with certain loudspeakers

Here is another Yamaha p2200 driver board before restoration. I used bipolar caps for the input and feedback stages as well as low ESR caps for the rest of the electrolytics, save the tantalum caps which I replaced with Wima MKS2 for better sound and reliability. Next pic is a Yamaha A1000 parts unit as the design is too complex for my taste, proper replacement parts are hard to find, and it isn’t worth so much (though the engineering is impressive). I also changed the fuse resistors on the p2200 to yageo MFR metal film resistors of correct wattage.

Replaced the protect circuit caps as first step in troubleshooting protect circuit issue, when I found out it was indeed the protect circuit. Before that point I found close to zero DC on the outputs of each channel prior to the speaker protect relay. Found out the two new caps didn’t cut it. Traced missing voltage and high AC to a shorted half wave rectifier diode for a protect circuit supply. Still no drive for the protect circuit clamp. Changed out the likely suspect transistors one by one till the amp was made reliable and stopped parts replacement as soon as I could in this area. Transistor choice is not so crucial in non audio areas.

A message I wrote to a customer of mine: basically I want to get to know you at some level before taking your money!

Yamaha C65 phono stage almost lacks any measurable harmonic distortion. Also extremely high overload margin for pops and clicks being less audible. Fine design. 4th job in a week is a C65 (will soon find the time to make posts about a Phillips receiver, Yamaha p2200 and Pioneer SX650 protection circuit repair real soon). Still got some time for time, parts and mental energy intensive projects for others to complete during the winter but simple stuff like this is fun. Also recapping another C65 for a customer who’s buying one from me soon, not a wholesale electrolytic replacement but replacing certain caps with bipolar: some ES series, some EP series (both Nichicon) since ES is sold out till 2024 in some sizes. Having a rough time personally but finding solace in small jobs. Also my -140db THD 1kHz and 20kHz oscillators came in. Excited to feed them into my UPL and stress it out in a good way. Will be useful for extremely low distortion gain stages. And for personally finding out that banana plugs are inferior to speak-on.

And of course please inquire about what is for sale

Finishing up an old job on this Hafler 9505. Needed to get all 4 can capacitors replaced. Couldn’t find any screw terminal ones that fit, after a really long time searching. So I had to make do

Sansui 9090. Replaced a fuse and it was fine. Went ahead and gave it a full service. Many things done. Not mentioned is me cleaning the driver board contacts with 91% alcohol

Fully restored Yamaha P2200 (well, except for the two meter board trimmers but they are not exactly critical for sound nor unreliable). All fuse resistors, bias trimmers, electrolytic caps replaced with 105 C Nichicon replacements, bipolar used for input and feedback caps and low impedance used elsewhere. Main filters are Epcos.

Left channel differential pair of 2sa750 got noisy, replaced with ksa992fta on both channels to be safe. Relay polished as it was not pitted, shrinking sleeve capacitor replaced, controls cleaned, dc offset and bias adjusted. Quick job. Owner is looking to sell it so if you’re interested I can put you in touch with him. Has broken speaker system 2 switch that I could not find a direct replacement for.

Crossover distortion. That’s the distortion this amp is putting out. With only a slight 300kHz low pass filter (just the bandwidth of my AP P1+ analyzer) here is what the distortion looks like on a scope. Also heres the A weighted 30W noise. And the distortion spectra. Note how it’s odd order harmonics.

After replacing the 4 MJE15024G output transistors and both driver transistors (original drivers tested good but some of the outputs shorted to base and I wanted to be safe), I get lower distortion at 200W into 8 ohms at 1kHz on the repaired channel. My method of replacing only the suspect half of the complementary output pairs works. Now is this amp sellable? I will have to burn it in for the next few days to find out. If I get no faults after running at 200W continuously for a while, I will sell it for around 250 dollars. If this were a customer unit I would not have skimped on replacing the MJE15025Gs but I decided against it as they test fine out of and in circuit as well as the amp not being worth a whole lot.

Reflowed solder joints on front channels output board as customer had issue 2 entire years ago with the unit shutting off after warm up. Afterwards, 1/3 of max power was applied to my loads from front channels at 1KHz, loads set at 8 ohms. Cover off then on, for 30 minutes time and no issue was found. I had to assume front channels were to blame, since so many more cold solder joints were found on that output board. With limited information (customer was bringing it in for the owner and owner was unavailable) I did limited testing, to save money as the unit can be easily found on online marketplace for 185 dollars shipped. Distortion was very low, below .006% midband into 8 ohms.

Relay replacement of Onkyo P-3090, customer had issues with noise out of both channels during warmup process but issue was never seen during testing. Excessive distortion was traced back to two relays, 6 of which were changed out with close matches. 190ohm coil resistance for originals and 268ohm coil resistance for new ones, G5V type by Omron. Same voltage, type, and footprint. Output and input jacks were also causing some distortion, customer decided to clean them himself. Total time was 2.16 hours for testing before and after and relay replacement. Met spec at 1kHz, needed to use Rohde and Schwarz UPL to check THD+N against spec as Audio Precision analyzer had too high a residual.

Apt Holman Preamp. No right channel output, issue traced to IC6. No repair completed, only diagnosis as owner elected to go with Audio Proz Apt Holman preamp refurb which i helped suggest, after learning my refurb would only be 150 dollars cheaper.

Finally a spectral analysis of Chris Lewis’ beyond excellent TA100WA replacements in this Kenwood KA9100. Left channel has been redone as well as right channel. Both test amazingly well.

Kenwood KA9100 repair. 2 black leg 2SC1775 transistors were replaced along with the relay and output IC. pre out/main in switch was also repaired. original TA100WA module was unavailable so i used Chris Lewis’ Pyramid Audio replacement module (i may have even tested this one myself when i worked for him over the summer). Excellent engineering on display, a very linear output IC, certainly much lower distortion than the module it replaced (a faulty Sony module) and even better than the working left channel Sony module which has much higher crossover distortion. Before ordering the most expensive part i made sure to swap transistors between amplifier channels to determine the faulty part.

Partial restoration of Yamaha CA1010. 90% of what needed to be replaced was replaced. I decided against replacing 10 of the fusible resistors in the power amp section due to both time constraints and testing of similar parts. All pulled fusistors were within spec.

Some of the tantalum capacitors in the phono stage were replaced with Nichicon KL, all other capacitors replaced with Nichicon HE and PM and KG for main filters and VP for bipolar. Values below 5.6uF replaced with polyester Wima MKS series. Relays replaced with same type Omron brand and fusistors replaced with Yageo and Dale metal film type. All trim pots except for meter trim pots replaced.

The -3db down point was 100khz and the unit is within 1db from 12.5hz to 40khz and within .2db in the audible band. Distortion was well below the .02% spec… except near 100W where it rose to the .02% spec. Clipping point at 1khz for THD+N was about 98W. IM distortion started to clip at 71/73W. A weighted noise was -101db for both channels but that’s with 40 ohm termination. None of the pots or switches required contact cleaner save the speaker selector switch. Working the balance and volume pots back and forth did reduce 20khz distortion.

Repair and service of Pioneer SX950, also recapping the phono preamp due to suspecting all those caps to be bad due to their type, one of which actually tested bad for leakage, improving THD+N by a small amount in that channel. Also all problematic transistors such as 2sc1318 and 2sa720 and 2sa725 and 2sc1313 in phono preamp and power supply were replaced with correct substitutes. This not only fixed the noise issue that was present in both channels of the phono preamp but ensured reliability of the power supply. ksa1013 and ksc2383 and ksa992 and ksc1815 were used. bias and dc offset were adjusted. performance was checked for both phono preamp and the rest of the amplifier. total time: about 2.5 hours.