Project: SX-1250 (2nd Take)

[knownman]

Wow,

this is a great find. I can’t thank you enough for being so generous with your time and efforts. I’ll definitely use this as inspiration.

Matt

 

[Oleg LED]

AWE-068 (TUNER)
AWE-068: C4: 220uF 16v CEA: UKA1E221MPD1 220uF / 25v
AWE-068: C10: 0.47uF 50v CEA: MKS2D034701E00JI (WIMA) 0.47uf / 100v
AWE-068: C23: 10uF 16v CSZA: UKL1E100MDDANA 10uF / 25v
AWE-068: C25: 470uF 16v CEA: UKA1C471MPD1 470uF / 16v
AWE-068: C26: 4.7uF 25v CEANL: MKS2C044701M00KO00 (WIMA) 4.7uf / 63v
AWE-068: C28: 10uF 16v CSZA: UKL1E100MDDANA 10uF / 25v
AWE-068: C29: 10uF 16v CSZA: UKL1E100MDDANA 10uF / 25v
AWE-068: C32: 100uF 16v CEA: UKA1E101MED 100uF / 25v
AWE-068: C33: 1uF 50v CEA: MKS2C044701M00KO00 (WIMA) 4.7uf / 63v
AWE-068: C35: 0.1uF 35v CSZA: MKP2C031001F00JS (WIMA) .1uf / 63v
AWE-068: C36: 1uF,25, CEANL: MKS2C041001F00JC00 (WIMA) 1uf / 63v
AWE-068: C38: 1uF,25, CEANL: MKS2C041001F00JC00 (WIMA) 1uf / 63v
AWE-068: C41: 1uF,10, CSZA: MKS2C041001F00JC00 (WIMA) 1uf / 63v
AWE-068: C42: 3.3uF,10, CSZA: MKS2C043301K00KSSD (WIMA) 3.3uf / 63v
AWE-068: C43: 0.22uF,25, CSZA: MKS2C032201B00JA00 (WIMA) .22uf / 63v
AWE-068: C48: 47uF 16v CEA: UKA1E470MDD 47uf / 25v
AWE-068: C56: 10uF,16, CSZA: UKL1E100MDDANA 10uF / 25v
AWE-068: C59: 0.1uF,35, CSZA: MKP2C031001F00JS (WIMA) .1uf / 63v
AWE-068: C60: 220uF 16v CEA: UKA1E221MPD1 220uF / 25v
AWE-068: C10: 0.47uF 50v CEA: MKS2D034701E00JI (WIMA) 0.47uf / 100v
AWE-068: C61: 47uF 16v, CEANL: UKL1V470KPDANA 47uF / 35v

It's a very nice work and very well documented! Did it require any adjustments for FM tuner after recap? I have never changed capacitors on tuner board since there is always a chance that it would require some adjustments. Thanks.

 

[Super Noob]

I re-cap tuners only = have done 15 or so. If the tuner & alignment was working well before the re-cap, the tuner will work well or better after the recap. (no exceptions).

 

[Oleg LED]

I re-cap tuners only = have done 15 or so. If the tuner & alignment was working well before the re-cap, the tuner will work well or better after the recap. (no exceptions).

I see. Thank you for reply and comment. I should try it on my next project.

 

[knownman]

POWER AMP (AWH-048) – Quantity 2
AWH-048: C2 10uF 16v CEANL: UKL1E100MDDANA 10uF / 25v
AWH-048 C5 220 16 CEANL: UKA1E221MPD 220uF / 25v
AWH-048: C11: .22uF 10v CSZA: MKS2C032201B00JA .22uF / 63v
AWH-048: C15: 470uF 80v CEA: UPW2A471MHD 470uF / 100v
AWH-048: C15: 470uF 80v CEA: UPW2A471MHD 470uF / 100v

AWH-048: Q1 2SA750: KSA992FBU (HFE Matched)
AWH-048: Q2 2SA750: KSA992FBU (HFE Matched)
AWH-048: Q3 2SC1439 : KSC3503DSTU
AWH-048: Q4 2SC1439: KSC3503DSTU
AWH-048: Q5 2SA858: KSA1381ESTU
AWH-048: Q6 2SA858: KSA1381ESTU
AWH-048: Q11: 2SC869: KSC2310YBU

AWH-048: VR1 500 Ohm: 25 Turns = 3296P-1-501LF
AWH-048: VR2 500 Ohm: 1 Turn = 3386H-1-501LF

AWH-048: D3: 1S1886: 1N4004
AWH-048: D4: 1S1886: 1N4004
AWH-048: D5: 1S2473: 1N4148
AWH-048: D6: 1S1886: 1N4004
AWH-048: D7: 1S1886: 1N4004
AWH-048: D8: 1S2471: 1N4148
AWH-048: D9: 1S2471: 1N4148
AWH-048: D10: 1S1886: 1N4004
AWH-048: D11: 1S1886: 1N4004

Supernoob,

I noted that you don't or didn't replace Q7,8,9 or10? Is there a specific reason for this or was it done and just not noted?

Thank you,

Matt

 

[Super Noob]

sx-1250,awh-048r,q7,2sc1904,,,,,,512-KSC3503dstu
sx-1250,awh-048r,q8,2sa899,,,,,,512-KSA1381ESTU
sx-1250,awh-048r,q9,2sd610,,,,,,512-KSC2073TU
sx-1250,awh-048r,q10,2sb630,,,,,,512-KSA940TU

It’s likely I was out of stock on those medium sized transistors.

 

[calman46]

I'm using this thread on my SX1250 and have a question on the voltage bump up on two caps on the protection board . The caps are C1 and C2 ,they're both 470uf 6.3v , Why the voltage bump up to 25v,does it really mater here .The schematic has 0 volts ..

 

[MIJ_Pioneer]

There are many reasons why the voltage may be bumped - it not is necessarily a forward engineering choice. Could be availability or just a simple rule of thumb - The 25v will be fine there. Assuming there is not error in the schematic so would a 16v, 10v, and 6.3v - Just don't put a 0v rated capacitor in there

Excellent choice in restore thread, @Super Noob 's restore threads are top notch

 

[zebulon1]

And if you notice they form a bi-polar cap.

 

[calman46]

Maybe the voltage is not as critical when the caps are back-to-back . Yes Super Noob's restore threads are top shelve . Thanks guys

 

[merlynski]

Sometimes a newer cap that fits the lead spacing is a higher voltage. No point in spending a lot of time and money finding an exact replacement when a bit higher voltage won't hurt any thing, anyway.

When the caps are back to back the effective maximum dc blocking voltage is just the voltage of one of them. A reversed voltage electrolytic will leak current and be damaged, but back to back like that the forward biased one blocks the dc current, so it cannot hurt the 'reverse' biased one. It is the reverse dc current flow that damages the 'backwards' cap.

The resulting series capacitance is half the capacitance of just one of them.

 

[calman46]

What do think about using one 220uf(or closer to 235uf) bipolar cap here ? There are mixed opinions on how much bumping up the cap's working voltage .especially in the signal path .

 

[rcs16]

It’s fine if it fits

 

[merlynski]

What do think about using one 220uf(or closer to 235uf) bipolar cap here ? There are mixed opinions on how much bumping up the cap's working voltage .especially in the signal path .

While an audio signal does go through these caps, it is not in the 'signal path' that goes from an audio input to an audio output,

 

[calman46]

While an audio signal does go through these caps, it is not in the 'signal path' that goes from an audio input to an audio output,

Are you sure ? I'm looking at the large schematic and that relay goes right to the speaker switch.

 

[merlynski]

Are you sure ? I'm looking at the large schematic and that relay goes right to the speaker switch.

Yes, the full power signal comes out of the power amps, goes to the protection board pins (3, L; 9, R), then goes to the relay through a direct copper trace path, basically zero impedance through the protection board, the direct signal path to the speakers (8Ω, low impedance). It gets to the DC offset detection circuit through 75kΩ resistors (high impedance) before it comes to the bases of Q2 (dc coupled) and Q1 (AC coupled by C1, C2). Compared to the 8Ω load of the speaker at the output, the parallel load of the 75kΩ is insignificantly small, and cannot affect the signal quality. The detector IS connected to the signal path, but the audio does not go through the detector and onward to more circuitry that processes the signal that gets to your ears. The detector circuit samples a tiny bit of the signal for dc, but does not alter it.

 

[calman46]

Thank you kindly for the explanation. I'm feeling kind of foolish now because its explained in the SM . Really feeling the effect of Covid when ordering parts .

 

[merlynski]

You are welcome!
While I have usually read them, I don't always remember what is in the SM, I just interpolate the schematic. That sometimes leads me to make errors because I don't have eyes on the unit.

 

[calman46]

Your explanation clarifies the SM circuit description . I can do the work but have no electronic background.

 

[calman46]

The equalizer board in my SX1250 has 2.2uf Mylar caps at C1,C2 the SM has them as 1uf . I have some Panasonic ECW(metal polypro) 1.5uf and 1.2uf . I was thinking about using the 1.5uf ? the rest of the board appears to be the same as the SM. Please advise ,thanks