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Leestereo's Restoration and Upgrade of a Sansui CA-3000

Leestereo

Leestereo

Super Member
At the request of AK member @greymatter, a very nice Sansui CA-3000 was the subject of a complete restoration and upgrade.

Part 1: F-2486 Equalizer (Phono) Circuit Board

In the CA-3000, the phono stage consists of a pair of F-2486 boards, one for each channel.

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Signal Path Components
The C01 capacitor, which is the high pass filter for the 75µs RIAA correction, was originally a 10µF/16V bipolar electrolytic type and was replaced with a 10µF/50V Nichicon Muse ES bi-polar audio grade type. The stock capacitor (C02) in the input low-pass filter was a 10pF garden-variety ceramic type; the replacement was a 5pF C0G type (the lower value eliminates any high frequency phase shift within the audible range due to the filter's F3). The stock C03 capacitor was a polarized 47µF/6.3V capacitor and was upgraded to 47µF/16V Nichicon ES type. The C04 capacitor, originally a 1uF bipolar electrolytic type, was upgraded to a WIMA MKS4 stacked film type. The C08 capacitor, originally a polyester film type, is part of the 75µs RIAA equalization and was upgraded to a polypropylene film type. The C09 capacitor, similar to C03, was replaced with a 47µF Nichicon ES type. The C10 is part of the output high pass filter and was originally a 10µF/50V bipolar type, the replacement was the same. The C14 capacitor, which is the high pass filter for the 3180µs RIAA correction, was originally a 22µF bipolar electrolytic type and was replaced with same.

Non-signal Path Components
The pass transistor (TR07) was the failure prone 2SC1313 and it was replaced with a KSC945C(G). The capacitor (C05) that filters the pass transistor output was replaced with a low ESR type and its capacity was increased to 220µF from 100µF. The capacitor (C06) on TR07's base was originally 33µF/50V and was replaced with a 100µF/50V low ESR capacitor. The local decoupling capacitors, C11 and C12, were originally rated at 220µF/50V; these were replaced with 470µF/63V low ESR types (note that it is advisable to increase the voltage rating of these capacitors since they are subject to 47 volts).

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Ben has done a incredible job on both the Ba / Ca 3000 . They are a beautiful sounding vintage Sansui that is just wonderful of listen to and look at. A HUGE Thank You to Ben and the love he put into these gems . Listening to them now on my NewForm Research V645s . What a match !
 
Part 2: F-2487 Volume & Muting Circuit Board

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Signal Path Components
The input high-pass filter capacitors (C01/C02), originally 1µF low-leakage electrolytic types, were upgraded to WIMA 1µF stacked film types. The 47µF capacitors (C03/C04) in the feedback loop high-pass filter were polarized electrolytic types and were replaced with Nichicon ES bipolar types. The output capacitors (C09/C10) were upgraded to 4.7µF WIMA MKS2 types from the stock electrolytic bipolar types. The feedback by-pass capacitors (C11/C12) were upgraded to C0G types from ordinary ceramic types. Similarly, the capacitors (C13/C14) in the input low-pass filter were upgraded to C0G types. The stock transistors in the differential pairs (TR01/ TR03 and TR02/TR04) were failure-prone 2SA726 types; these were replaced with hFE matched KSA992 transistor pairs. Similarly, the transistors TR05-TR08 were failure-prone 2SC1313s; these were replaced with KSC1845 types.

Note: the F-2487 schematic above contains a few corrections compared to the one in the Sansui service manual: the signal path for the S03 switch when at position "2" and the ground connections for R05, VR01a, R09, R11 and C13.

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Part 3: F-2495 Tone Amplifier Board

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Signal Path Components
Each channel of the Tone Amplifier circuit compromises of 2 differential amplifiers in series. The input high-pass filter capacitors (C01/C02 and C11/C12), originally 1µF low-leakage electrolytic types, were upgraded to WIMA 1µF MKS2 stacked film types. The 47µF/6.3V capacitors (C03/C04 and C13/C14) in the feedback loop high-pass filters were polarized electrolytic types and were replaced with 47µF/25V Nichicon ES bipolar types. The output capacitors (C09/C10 and C19/C20) were upgraded to 3.3µF WIMA stacked film types from the stock electrolytic bipolar types. The stock transistors in the differential pairs (TR01-TR04 and TR09-TR12) were failure-prone 2SA726 types; each differential pair was replaced with hFE matched KSA992 transistors. Similarly, the remaining transistors (TR05-TR08 and TR13-TR16) were failure-prone 2SC1313s; these were replaced with KSC1845 types.

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Part 4: F-2491 Headphone Amplifier Circuit Board
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Signal Path Components
The input high-pass filter capacitors (C01/C02), originally 1µF low-leakage electrolytic types, were upgraded to WIMA 1µF stacked film types. The 10µF polarized electrolytic capacitors (C07/C08) in the feedback loop were upgraded to 10µF 25V bipolar types. Similarly, the speed up capacitors (C09/C10) were upgraded to bipolar types. The 220µF output coupling capacitors (C11/C12) were upgraded to bipolar types from the stock polarized types.

Non-signal Path Components
The emitter bypass capacitors (C03/C04) were increased to 470µF from the 100µF stock value; the increased capacity extends their effectiveness to below 20Hz. The capacitor (C601) that shunts the zener on the regulator transistor's base was originally 33µF/50V and was replaced with a 47µF/50V low ESR capacitor. The capacitor (C602) that filters the regulator transistor output was replaced with a low ESR type and its capacity was increased to 220µF from 100µF.

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Part 5: F-2494 Regulated Power Supply Board (Low Voltage)

In the CA-3000, the Low Voltage Regulated Power Supply consists of a pair of F-2494 boards, one for each channel.

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The initial DC filtering capacitors (C01/C07) were replaced with 680µF low ESR types. The capacitors C02/C08 on the bases of the pass transistors were increased to 120µF from the 47µF stock value. The ceramic capacitors (C03/C09) were upgraded to high-stability C0G types. The zener shunt capacitor (C04) was increased to 33µF from the stock 10µF value. The low-leakage capacitors at C05 and C10 were replaced with 105°C low-leakage types. And the capacitors (C06/C11) that filter the regulated DC output were replaced with 1000µF 35V low ESR types. The 0.5W voltage dropping resistors at R01 and R09 were replaced with 1W metal film types. The stock transistors at TR02 and TR03 in the positive regulator circuit were failure-prone 2SC1313 types; these were replaced with KSC945C(G) transistors. Similarly, the stock transistors at TR05 and TR06 in the negative voltage rail were failure-prone 2SA726 types; these were replaced with KSA733C(G) transistors. The trimmer at VR01 was upgraded to a 5kohm cermet multi-turn type.

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Part 6: F-2494 Regulated Power Supply Board (High Voltage)

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The initial DC filtering capacitors (C01/C07) were increased to 270µF from the 100µF stock value. Similarly, the capacitors C02/C08 on the bases of the pass transistors were replaced with 270µF low ESR types. The ceramic capacitors (C03/C09) were upgraded to high-stability C0G types. The zener shunt capacitor (C04) was increased to 33µF from the stock 10µF value. The 10µF low-leakage capacitors at C05 and C10 were replaced with 105°C low-leakage types. And the capacitors (C06/C11) that filter the regulated DC output were replaced with 470µF 63V low ESR types. Although the stock C06 capacitor appears intact, the glue used during manufacture had corroded the leads and electrolyte had leaked onto the board. The 0.5W voltage dropping resistors at R01 and R09 were replaced with 1W metal film types. The stock transistors at TR03 and TR06 were the failure-prone 2SC1313 and 2SA726 types, respectively; these were replaced with KSC945C(G) and KSA733C(G) transistors. The trimmer at VR01 was upgraded to a 5kohm cermet multi-turn type.

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Part 7: F-2493 Power Supply Circuit Board

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On the Power Supply Board (F-2493), which filters the mains AC, all of the voltage dropping resistors were upgraded to higher wattage/low TCR metal film types: R01, R02 and R06 were increased to 1W resistors; R03-R05, R08 and R09 were replaced with 3W resistors; and R07 was replaced with a 0.5W resistor. All new fuses were installed; the fuse elements may fatigue over time which diminishes their capacity. The capacitors C01-C04 were retained since they still measured as "as new" for capacity, ESR and %vloss.

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Part 8: F-2492 Meter Circuit Board

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The input high-pass filter capacitors (C01/C02), originally 1µF polarized electrolytic types, were upgraded to WIMA 1µF stacked film types. The 22µF capacitors (C05/C06) in the feedback loop high-pass filter were polarized electrolytic types and were replaced with Nichicon ES bipolar types. The 10µF capacitors (C07C08) at the TA7136P output were upgraded to Nichicon ES bipolar types. The bi-polar capacitors at C11/C12 were upgraded to WIMA 1µF film types. Similarly, the tantalum capacitors at C13/C14 were upgraded to WIMA film types. The capacitors C15/C16, which suppress the push-button switch noise, were also replaced with film types. Note that these capacitors were a production-run change (along with a board revision) and are not shown in the service manual schematic (nor in the F-2492 board illustration). The 47µF filtering capacitors (C601/C602) were replaced with 100µF low ESR types. The failure-prone VD1212 diodes at D01-D04 were each replaced with a pair of 1N4148 diodes in series. The stock transistors at TR05-TR08 were failure-prone 2SC1313s and were replaced with KSC1845 types (the transistors TR07/TR08 were also a production run change). The stock 0.5W 15V zener diodes at ZD601/ZD602 were upgraded to 1.3W variants.

When the CA-3000 was initially bench-tested, the left channel meter was non-operational; the VD-1212 diodes and/or the 2SA1313 transistor were presumed to be the culprits. However, following the aforemention F-2492 restoration/upgrade, the left meter remained non-operational: a previous tech's solution to the malfunctioning left channel meter was to disable it via its adjustment trimmers. Following re-calibration, the left meter functioned properly.

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I enjoy reading them all so . Don't understand much , but it's never to late to learn how the pro do there thing .

The System is just amazing Ben . The best move I ever made having you do your great work on these babies Ben . Just beautiful . Thx again buddy.
 
peterott said:
Is TR07 a typo and TR09 meant instead?
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I don't think so, I think I can see what you are saying, the board marking under TR07 looks a bit like TR09 - but it isn't if you look carefully. ;)

Compare other '7's marked on the board with '9's - clearly a curly tail on the '9' - but a sloping upright on the '7' :)
 
Hyperion said:
I don't think so, I think I can see what you are saying, the board marking under TR07 looks a bit like TR09 - but it isn't if you look carefully. ;)

Compare other '7's marked on the board with '9's - clearly a curly tail on the '9' - but a sloping upright on the '7' :)
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You're right. Very "confusing" in the picture from that angle and basically no other "7" or "9" to compare with close by :)
It just immediately stuck my eye somehow.
 
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