Beschreibung
*This listing is fora Completely Overhauled, Burned-In, Tested, and Guaranteed Sansui1000A* Am besten persönlich abholenThis is not the average ebaythis has been serviced job where someone replaced only the clearlydefective capacitors with cheap parts to make it work. Youregetting a restored, completely rebuilt, world-class Sansui1000A!With this unit, I took my timeto test, clean, repair, replace, and upgrade everythingnecessary while using only the most appropriate high quality parts. Theattention to detail here is key. I strove to keep the unitas original as possible, replacing only what is necessary in the audiosections while maintaining original lead dress.While Im not muchfor superlatives, this unit does of course sound very good! Minimal distortion, fast and deep bass (especially with thepresence on), clean midrange, and clear high end. Basicallywhat anyone should expect from a decent piece of tube audio gear.With the exception ofrepair-in-progress photos, I took pains to slightly overexpose the photos tothe point where it shows random dust! I want there to be NO surprises for thenew owner, but do note that most small bits of dust, small defects, etc. cantbe seen under normal lighting conditions. Known IssuesThere are many knownissues concerning any potentially restorable Sansui 1000A. Those issues, aswell as any specific to the unit under repair, MUST be accounted for. The mostprominent include:1. All oil capacitorsmust be replaced. Like all Japanese oil caps of this era, they will be leaky,open, or shorted. 2. All electrolytics must be replaced. This unit was built in1971, and has sat unused for an indeterminate amount of time. Hum and highimpedance in the audio amp are not acceptable, especially given the FARsuperior replacement parts available today. 3. Heat. These units did not provide enough ventilation,especially in the area surrounding the left channel output tubes and powersupply resistors. This commonly leads to output tube and/or transformerfailure. 4. Switches. The rotary wafer switches (Mode, Band Selector,Selector) as well as the front panel rocker switches (Presence, Loudness, etc.)invariably come with a great deal of black oxide on the contacts. This causesproblems due to intermittent or open connections. 5. Output tube bias circuit. Many units come with a biascircuit that does not allow bias adjustment of individual tubes. This isunacceptable in a high-end piece of equipment. 6. No power supply soft-start. The 1000A comes up to over 500Vwithin seconds of turn-on...however the tube cathodes are not warmed up foranother 30 seconds! This causes unnecessary cathode stripping and temporaryvery high voltage on the B+ rail, stressing components. 7. Illumination. Fuse type dial face bulbs andStereo indicator bulbs are frequently burned out, and as theyrequire the disassembly of the faceplate, are difficult to replace. 8. Tubes! Many tubes may be marginal, bad, or simply noisy soall must be tested and auditioned. 9. Solid-state rectifiers. These units use solid staterectifiers from the 1970s which are of very poor quality in comparison toreplacement parts available today. 10. Input/Output connectors. The RCA jacks and speakerconnectors are of dubious quality and always arrive with some sort ofcorrosion, even if its very thin. 11. Flimsy 2-Prong AC cable. Any decent equipment mustinclude a high-quality, properly grounded AC cord. 12. Fuse. This should be replaced with a rating suitable tothe line voltage without taking into account the outlets on the rear whichare frequently left unused. 13. One AC input is 117VAC. There is a selector for input linevoltage, one of which is 117VAC, whereas the line voltage in many countries thehousehold line now averages between 120-130V. Using the unit at these voltages increaseshigh voltage and filament voltage, shortening the life of the tubes. 14. Physical condition. Being a vintage receiver isnt easy!They usually come with some wear and tear, and are many times quite dirty. Repairs and RestorationChassisChassis & knobs cleanedinside and out. Dust, dirt, corrosion, etc. removed.Top cover and base panelre-painted. Both covers were cleaned, primed, paintedwith two coats, then baked in an oven to harden. I used the nearoriginal color on top with flat black on the bottom. If you look at thetop panel with a certain angle on the light you can see deviations from theshape of the metal underneath; these are not normally visible. Bottom panel hasgrommeted bias adjustment access holes drilled, all mounting areas have beencleaned to provide a nice low resistance ground path, and the original mountinghardware has been replaced.Transformer coresrepainted. All three transformers were carefully removed,their bells taken off, windings and leads taped off, and their cores primedthen painted with flat black high heat paint.Faceplate, dial glass, andinside the dial were disassembled, cleaned, andreassembled. The bezel was professionally polished. There are small (basicallyunnoticable) blemishes on the panel and one on the bezel corner which Ihave taken photos of. Dial string was replaced, re-tensioned, and the dialindicator set correctly.New rubber feet installed. I didnot like the other set of hard plastic feet as it allowed the receiver to slidetoo easily and they tended to scratch surfaces!ElectronicsALL low voltage audio signalpath capacitors replaced. Many times overlookedwhen rebuilding these units due to their location/low voltage andtheir not being oil capacitors - theyre old mylar and ceramic! Theseinclude the audio premp input capacitors, audio section of the FMdemultiplexer, and Loudness switch to name a few. Theyare all now polystyrene, polypropylene, silver mica, and PIO (audio preampinput capacitors). ALL Oil capacitors replaced. I installed NOS Aerovox CP04, GudemanXFHS, & Sprague CP08/196P paper in oil (PIO) glass hermetically sealedmil-spec parts. In the chassis pictures, many of these have heat shrink overthem (this is to cover the metal case to avoid possible shorts) or wiressoldered to the case (shorting the case to ground providing shielding andeliminating the possibility of feedback from case). I used theseparts to maintain the vintage tone that is associated with units fromthis era.ALL Electrolytics replaced. MainB+ capacitors are NichiconPW. Secondary B+ capacitors are NichiconCA. Screen decoupling electrolytic replaced with two 47uF in series with 220kequalizing resistors as that is the only part of the power supply that reachesabove 450V during normal or high line conditions (higher voltage rated qualityelectrolytics are no longer available). All other electrolytics arePanasonic EB, ED, or EM. All types are rated at 105C with very low impedanceand all but the PW are rated for at least 10,000Hrs.Fresh heat shrink and nylonbraid around external power resistor wires. Theold braid was cracked and hardened.Audio amplifier hum pots. Theleft and right channel of the audio amplifier have independent DC biasedfilament supplies. Each has a 100 ohm hum adjustment pot, which was adjustedfor lowest output hum.Phono/Mic preamplifier. Theelectrolytics and output coupling capacitors were replaced, but no othermodifications were performed. I used the mic and phono inputs and found thenoise not to be objectionable at all! Judging by the current draw, this couldbe replaced with a simple JFET preamp for lower noise and higher quality, but Ichose not to do this as most of the people I know use separate phono preampsanyhow.Some items disabled. Theseinclude: 1. The 5-pin DIN tape input connector, as these are rarelyused and it would have been more work to re-attach after the RCA inputrebuilds. 2. The speaker phase switch (see below) 3. The headphone jack and speaker on/off switch, as they were poorquality, superfluous functions that relied on a dummy load that wasremoved. This enabled me to add a line filter and IEC socket to the powersupply! ControlsALL pots cleaned with Deoxit. Noisefree is the way to be.Speaker phase switch disabled. Originalswitch contacts were pitted from hot switching, and this seemed only tocause trouble as a high-resistance contact in the speaker circuit. For me,theres plenty of other ways to reverse phase if need be.Speaker impedance switchreplaced. When disassembled, I found the contacts pitted beyond repair. It wasreplaced with a near-identical manufacture switch of the same era that wasdisassembled and had its contacts cleaned and polished before installation.ALL eight front panel rockerswitches and ALL three rotary disassembled and cleaned. Thiswas, without a doubt, the most time-consuming part of the job! With thewafer and rocker switches in the 1000A (and most wafer switches in general!),due to the type of oxidation on the contacts (read: thick, black, sometimesmixed with hardened lubricating grease, and possibly non-conductive)the best method is to clean each contact mechanically with a trusty pencileraser. Even then, some contacts needed to be pre-cleaned with naptha to removesome very thick oxide/grease. All contacts were tested after repair using a4-wire digital ohmmeter to check contact resistance. TubesALL tubes havebeen precision tested. Any tube testingmarginal, bad, or noisy was discarded. Pins have been cleaned on all miniaturetypes. The tubes installed are as follows: Audio 12AX7 preamp tubes replaced with RCA short plate. 6AN8A phase inverter tubes are NOS Motorola branded Tung-Sol 7591A power output tubes replaced with new manufactureTung-Sol. Tuner 6AU6 are original Matsutshita. 6BE6 replaced with NOS RCA. 6AQ8 are original Matsutshita. 6CW4 were replaced with NOS RCA. 6BA6 are original Matsutshita. 6BL8 are original Matsutshita. Upgrades:Adjustments & MeasurementsFilament voltage. Filamentvoltage was measured at the pins during operation and found to be within 2% oflisted value.High voltage. Highvoltage measured at all points in the power supply during operation andfound to be within 5% of listed value (depending on how heavily the outputtubes were biased).Bias and solid state preampvoltage. Measured during operation and found to be within 5% of stated valueon the preamp, with the bias range having an upper end at approx -27V.Output tube bias. Outputtube bias was set initially, then after a week of listening adjustedto final resting point of 35mA +/-100uA per tube at 117VAC line. If youplan to operate this unit at nominal 120-130VAC line voltage, for longevity ofthe tubes I strongly suggest using a line voltage adjustment transformer todrop the incoming line voltage.Resistor values. One3k in the feedback loop was out of tolerance, so I replaced the 3k feedbackloop and the 3k & 5k L+R summing resistors in both the leftand right channel for symmetry using Dale RN60 metal film resistors.Resistor values were tested before installation to within 0.2%. Allothers were found to be within +/-5% of stated value.Tuner. AM/FMtuner and demiltiplexer was checked for proper operation and adjusted wherenecessary.Burn-in. Thisunit has been my main workshop amplifier for over a month. This allowed timefor all of the parts to stabilize and any defects to make themselves known.BiasOutput tube bias circuitcompletely rebuilt. It now has four easilyaccessable adjustments for each output tube. I installed a schottky rectifierfor low noise, Panasonic EB long-life capacitos, Dale RN60 mil-spec metal filmresistors, and Dale mil-spec 10-Turn wirewound miniature trimmers for precisionadjustment. This is mounted and assembled point-to-point on FR-4 material.Bias tubes without removingbottom cover! Gold pin-probe sockets installed nextto tubes so you can make plate current measurements using only a voltmeter.Between each probe socket is a precision 1 ohm, 0.1% non-inductivewirewound plate current sense resistor for absolute accuracy. Grommeted accessholes on the bottom of the amp allow for flathead adjustment ofindividual tube bias current. Tubes and their corresponding adjustment holesare all labeled.[Biasing should only be performed by a qualified technician asthe pin probe sockets can have up to 500VDC present!] ConnectorsALL RCA connectors replacedwith quality gold connectors. This was NOT an easy jobto do well, but I think it is well worth it! Original RCA connectors werecarefully removed. Then the RCA holes in the phenolic were reamed slightlylarger to accomodate the new connectors. Next, the opening in the chassis waswidened slightly so the new ground terminals would not contact the chassis (thetool did slip twice, but it is not noticable). They were then installed,rewired, and continuity checked.Repaced speaker terminals withmodern connectors. Same method used as with theRCA jacks. New terminals are suitable for use with wire, spades, and bananaplugs.Heat IssuesOutput tube heat sinks. Customaluminum finned tube heatsinks have been fabricated and added to theoutput tubes, doubling their average life and removing heat more quickly in theprocess.Input tube shielded heatsinks. Retrofitted with a tube shield base and added very high qualityMil-Spec IERC heat-sinking tube shields. These units typically reduce bulbtemperatures to 115°C for extra long life.Phase inverter heat sinks. The6AN8A gets surprisingly hot. Retrofitted with a tube shield base and addeda custom modified Mil-Spec IERC heat sink type unit. These units remove heatfrom the bulb more effectively than ANY other type of chassis mount tube heatsink or shield, typically acheiving bulb temperatures as low as 104°C. Forreference, a common silver shield will RAISE temperature upwards of180-200°C!DC fans installed. Thesehave been positioned to remove excess heat from the power tube areas first.Powered from the main heater winding, their power circuitry is installedso that NO noise from the fans enter the audio stages. The have their own heavyduty barrel-type power connector (next to the power cable connector). Thisallows for for easy disconnection and removal of the top cover, or todisable them during critical listening as they do make a little noise.Incandecent lamps. Dialillumination lamps and stereo indicator lamps have been replacedwith LEDs so you dont have to replace them again! They look great,eliminates bulb heat contribution, and frees up current on themain heater winding allowing the installation of the DC fans. The tunersensitivity meter and mono indicator lamps were left incandescent -the face plate would look awful with the cold, harsh glow of leds inthese positions!High VoltageHigh voltage power supplyrectifiers replaced. Here Iinstalled Cree silicon carbide schottky rectifiers to eliminateswitching noise. These are miles above the iffy60s/70s rectifiers that comes stock in these receivers.High Voltage time delaycircuit. This circuit uses a heavy-duty 30 second 120VAC time delay relaycoupled with a 120VAC coil 4PDT relay to connect the power transformerhigh voltage secondary directly to the rectifiers, shorting out a high valueresistor. This designhas several advantages: The relay coil and the delay relay heater both operate from the 117V tap on the transformer primary, eliminating any extra load on the power transformer and delivering 117V to the relay coils regardless of the actual line voltage. The 4PDT relay is arranged with three of its 5A contacts in series for higher standoff voltage while switching approx 180V AC. Series connection and AC switching increase lifetime of the relay significantly! The delay relay only controls the relay coil voltage; it should therefor last a lifetime. Both relays are socketed for easy replacement. The two relays are arranged such that when the 4PDT relay turns on, the time delay relay turns off. That means that if the stereo is quickly turned off and on again, the time delay relay will be cool, allowing the time delay function to still operate!AC Power InputComplete EMI/RFI Line Filterwith IEC power plug. Three stageinductive/capacitive design eliminates both common mode and differential modenoise from entering or exiting the line connection! Constructed using 250VACX or Y rated capacitors, 3A rated 100uH and 1.7mH inductors, anda high quality IEC plug, the filter was assembled point to point onFR4 board and rigidly mounted to the chassis both using the IECplug and steel standoffs. The IEC plug was installed so I had to makethe minimum amount of modification to the chassis.The whole line filterassembly is still (relatively) easy to remove for servicing.Fully grounded. 12 gaugesolid copper wire connects directly to the ground terminal of the IEC plug,traverses the line filter, then connects directly to chassis at the center ofthe power supply to serve as a star ground. Safe AND low noise!High quality Power Cord. 14-3shielded mil-spec cable with the shielding terminated to ground only at thehospital grade power plug.New fuse holder & Fuse. Theold fuse holder had a missing cap. The original fuse was sized totake into account the current draw from the AC outlets on the rear which havebeen removed. I will provide one installed and two additional fuses of thecorrect value for the country it is sent to (3.2A, 2.8A, or 1.5A for 100V,110-130V, or 220-240V respectively). Now THAT is arestoration. Enjoy!
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