SX-1080 What to know before diving in?

hopjohn

Silver Face
I recently purchased a SX-1080 (Thanks Dan) that I intend to restore. I've done some reading in other threads in preparation, but I've not seen any where a comprehensive restoration was in mind from the start. I've found threads involving recaps and general repairs of various things and even read the entire thread where MTF patiently guided a beginner through 13 pages before ultimately having them give up. A real heartbreaking thread.


Here's what I've come to know about the SX-1080 so far. Unobtanium output devices. A thermal resistor that should be checked. Power board a bit under built. One of a kind tuner ICs that can go bad.

Here's what I know about my unit in particular: It appears to be all original with FM and AM working, though I've yet to check the tape loops, aux or phono inputs. The initial DC offset was 1.2V & 1.1V (Yes, that's VOLTS!) yet the relays would still click on (worrisome). Initially the bias measured about 26mv with ideal at 30mv according the manual and that was reset to within 0.5mv. The offset has been set to under 5mv in each channel with a minimum 20 minute warmup. The offset pot sucks or I'd get it closer to 0mv. After setting the offset and bias I listened to the tuner with speakers connected and the sound seemed normal.

Okay to the point, I'd like to know some general weaknesses, areas for audio improvement (trannys included), pitfalls to avoid or common mistakes, and any other general advice on a full restoration of this unit in particular. Maybe even some replacement parts #'s for transistors that are commonly replaced or can be improved upon. Any specific areas where poly caps can make a marked difference. Any info like this at all really.
 
I was able sift through enough threads to come up with a pretty strong parts list for the power supply. I put in an order for those parts. I'll be forging on without much insight on this one I'm afraid.
 
What you asked was a pretty tall order there, aggravating the situation is the fact that I'm short on available posting time.

This thread holds pointers to many unit's lists:http://www.audiokarma.org/forums/showthread.php?t=457663

this is the 1080 list http://www.audiokarma.org/forums/showthread.php?t=322650

these are some of the transistors, as you can see I have not had enough time to update the lists, nor put them into a spreadsheet (which is why you heard crickets when you asked about transistors):

YOU could start up and post a spreadsheet / list using all of the above and greatly advance the cause... Then I would go through it and add in the rest as needed.

It is ALWAYS best to post the proposed purchase list BEFORE "pulling the trigger" so that old / outdated / obsolete recommendations can be weeded out.

These are my working notes text files:

power supply awr-152

q1 2sd712 to-220 bce
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54

q2 2sc1735 npn to-92 bce 100v 0.5a 0.8w 50-300hfe 130mhz
512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

q3 2sa850 pnp to-92 bce 100v 0.5a 0.8w 50-300hfe 130mhz
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

q4 2sb682 to-220 bce
512-KSA940TU pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54

Q5 2sd712 to-220 bce
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54

Q6 2sc945 to-92 ecb
512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

D8 mz140
512-1N5244B Fairchild 14 V, 0.5W Zener

d9 mz130
512-1N5243B Fairchild 13 V, 0.5W Zener

d10, d11 LZ230
512-1N4748A Fairchild 22 V, 1.0W Zener

c11,c12 220uf 100v 647-UPW2A221MHD 220uf 100v $0.80 ea
c13 220uf 35v 647-UPW1V221MPD 220uf 35v $0.22 ea
c15,c16 220uf 80v 647-UPW2A221MHD 220 100v $0.80 ea
c17,c18 47uf 16v 647-UPW1V470MED1TD 47uf 35v $0.10 ea
c19,c20 4.7uf 50v 647-UPW1H4R7MDD 4.7uf 50v $0.12 ea
c23 2200uf 35v 647-UPW1V222MHD 2200uf 35v $1.08 ea
c24,c25 47uf 25v 647-UPW1V470MED1TD 47uf 35v $0.10 ea

R3 R8 2.2 ohm 1/4w series resistors(flameproof) 660-CFP1/4CT52R2R2J

*************** protection circuit **********

on the protection board, awm-120:

awm-120 q1 2sa733 to-92 ecb 512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
awm-120 Q2 2sc1438 to-92 ecb 512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40

awm-120 d1 mz-130 512-1N5243B Fairchild 13 V, 0.5W Zener
awm-120 d2 1s2471 = 512-1n4148
awm-120 d3 1s2471 = 512-1n4148

awm-120 c1 220uf 35v cea 220uf 35v 647-UPW1V221MPD $0.22 ea
awm-120 c2 100uf 16v cea 100uf 35v 647-UPW1V101MPD $0.26 ea
awm-120 c3 10uf 16v cea 10uf 50v 647-UPW1H100MDD $0.12 ea
awm-120 c4 47uf 16v cea 47uf 35v 647-UPW1V470MED1TD $0.10 ea
awm-120 c5 47uf 16v cea 47uf 35v 647-UPW1V470MED1TD $0.10 ea
awm-120 c6 1uf 80v cea 1uf 100v 647-UPW2A010MDD $0.16 ea


awr-152 d1 400v 1A 512-1n4004
awr-152 d2 400v 1A 512-1n4004
awr-152 d3 400v 1A 512-1n4004
awr-152 d4 400v 1A 512-1n4004
awr-152 d5 200v 10A/200A surge diode bridge 750-MP1004G-G
awr-152 d6 400v 1A 512-1n4004
awr-152 d7 400v 1A 512-1n4004
awr-152 D8 mz140 512-1N5244B Fairchild 14 V, 0.5W Zener
awr-152 d9 mz130 512-1N5243B Fairchild 13 V, 0.5W Zener
awr-152 d10 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener
awr-152 d11 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener

awh-071 amplifier transistor substitutions

Q1 2sa979 dual transistor pnp bcecb 100v 50ma 0.4w 250hfe 150mhz
two: 512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea (matched gain works a bit better)

Q2 2sc1775a npn to-92 ecb 120v 50mA 0.3w 160hfe 100mhz
512-KSC1845UBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

Q3, Q4 2sc1885 npn to-92 150v 0.1a 0.75w 150hfe 200mhz
512-KSC3503estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.28 ea

Q5 2sa912 pnp to-92L ecb 150v 0.1a 0.75w 150hfe 200mhz
512-KSA1381estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.27 ea


Q7 2sb536a pnp to-220 bce 120v 1.5a 20w 250hfe 40mhz
Q6 2sd381a npn to-220 bce 120v 1.5a 20w 250hfe 45mhz
863-MJE15033G pnp to-220 bce 250v 4a 50w 30mhz 100hfe $1.25
863-MJE15032G npn to-220 bce 250v 4a 50w 30mhz 100hfe $1.07
or if idle current too high use:
512-KSA940TU pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.62
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.66




Q8 2sc869 npn to-92 bce 50v 30ma 0.2w 35hfe 150mhz
512-KSC1845FTA (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

d1 & D2 (D6 & D7 too, but not needed??) 1s2471
512-1N4148 Diodes - Small Signal 100V Io/200mA

D3 & D4 SIB01-02
512-UF4004 ultra fast rectifier 1amp 400v $0.13 ea


Caps:
C1 & C2 2.2uf 25v low leakage:
647-UKL1H2R2MDDANA 2.2uf 50v
two to make non-polar 1uf cap, so:
667-ECQ-E1105KF is 1uf 100v poly cap non-polar


C11 0.22uf 25v low leakage, to stacked poly metalized film:
667-ECQ-E2224KF 0.22uf 250v


150k multi-turn trimpot - offset (like 1980's)
652-3296P-1-254LF Bourns Trimmer Resistors - Multi Turn
3/8" 250Kohms Sealed



100 ohm single turn trimpot - bias(like 1980's)
652-3386H-1-101LF Bourns Trimmer Resistors - Single Turn

2.7k 1w 5 % metal film resistor 594-5073NW2K700J $0.16 ea
 
I don't have a spreadsheet program installed on this computer. So this text file will have to do for now. Mark, I believe this is the format that you use so if not let me know and I'll correct it. All the recommendations are yours from previous posts and posts of those you were directly helping that I believe were approved. If there is obsolescence or improvements they'll have to be updated. Also if you could shed light on what the prefixes mean (CSZA, CEA etc.) that would be helpful.
 

Attachments

  • sx-1080lparts.txt
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Re caps: read the tuning fork sticky at the top of the forum page. specifically the capacitors articles.

I was able to inhale it into a spreadsheet (with your name associated with it, credit where credit's due), but don't have time right now to look at it closely. That will be later...
 
Re caps: read the tuning fork sticky at the top of the forum page. specifically the capacitors articles.

Thanks for the heads up. Some very enjoyable reading.

EDIT: Here is the capacitor code chart that can be found in the Tuning Fork guide

s6JQ8Tr.jpg


I was able to inhale it into a spreadsheet (with your name associated with it, credit where credit's due), but don't have time right now to look at it closely. That will be later...

Grog deserves the credit, all I did was add transistors and diodes to his cap list.
 
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Initial impressions

Alright, let's have a look. The first thing that stands out is the large torodial transformer and the beer can girth of the 22000uf caps. Quite an impressive step up from the SX-980. Dusty, dingy, just what you'd expect vintage 1978.

Ec4SvpC.jpg


Eyeing the power supply, you can see where heat has changed the color of the PCB around the regulators and the diodes behind them. The glue around the caps provides a little more work, but it's nothing new.

dcwLxAq.jpg


Further observation shows the boards of these units have no part number identifiers on them. That sucks! Fortunately, the service manual will provide assistance, but it just means you have to be that much more careful replacing parts. Photos and notes will be vital.
 
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Indicator LED Conversion

Before the major surgery begins. I thought I'd try a LED conversion of the small indicator lamps. First, the voltages need to be determined. The phono, aux, AM, and FM, all read ~13.6V DC, the stereo indicator slightly less at ~13.2V DC.


erCKLUf.jpg


Next the specifications of the LEDs need to be known. I'll be using straw hat white 5mm LEDs which have a typical V drop of ~3.4v, and a current rating of 20ma. With that, I head to LEDCalculator.net and let the calculator do the math for me. Plug in the data values and click. Now we have the value of the necessary dropping resistor. 560 ohm 1/4W for Phono, Aux, AM, FM, and 510 ohm 1/4W for the stereo indicator.

CyDKDEz.jpg


Observing polarity, the existing bulbs are removed and in their place the dropping resistors and JST connectors are installed. The dropping resistors are soldered to the cathode side. Using the connectors allows easy removal of the meter holder bracket and LED replacement should that ever be necessary. I color code each connector with shrink tubing for easy identification.

ZW1HgoW.jpg


The stock housing holds the LEDs face forward with the help of a bit of sponge custom fit for the job. The LED leads are poked through the sponge and down the existing hole where the stock bulbs once were.

uCxDvZK.jpg


Parts used:
560 Ohm Resistors x5
JST connectors x5
Ebay store LED Wholesale World
White Straw Hat LED 5mm x4
Warm White Straw Hat 5mm LED x1 (Auxillary)

EDIT: As Mark points out in a later post, R18 120 ohm of the power supply effectively increases the overall resistance to 680 ohm (560 + 120) lowering the current draw of the LED to 15ma. Though unintentional, I found the brightness of the LEDs to be ideal. Depending upon the LEDs you use YMMV.
 
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Indicator LED Conversion contd.

The male end of the JST plugs are soldered to the LED leads and again color coded with shrink tubing to match their corresponding source. The housing is neatly reinstalled.

IKHdVPT.jpg


Even temporarily without the dial lighting, the crisp glow of the indicators are once again as well illuminated as the 1978 originals...and will be for MANY years to come.

iT89dwW.jpg
 
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Hello Hopjohn,

I have to ask why the JST connectors on LED's when they last so long.
Why no just solder them directly in?

I have a 1080 also and enjoy the progress you guys make restoring these fine units.
 
Hi Hopjohn,

Rebuilding your SX-1080 is really challenging, rewarding and a lot of fun. Mine has been working absolutely beautifully since I recapped it.

As you could see in my thread, I had a disaster that I overcame with MTF's help.

My thoughts and advice:

1) I didn't recap my tuner board. I decided not to touch it based on threads on the forum. It works perfectly anyway.

2) Be really careful to use leads and tools that have insulators right down to the tips, so you don't inadvertently short out things like transistors by touching them.

3) If you look at your photo showing the top of the unit you can see the massive black heats sinks for the output transistors and you'll see a little brown do-dad attached to the top of each side of the heat sink with a couple leads coming out of each one. These are the STV4H Bias Diode listed under Semiconductors on page 56 of the service manual on the Parts List of Power Amplifier Assembly AWH-071. They are unobtainium, fragile, and don't like to be handled. Do not tighten the screw too tight on these as the little legs that hold them on will break off. They are vital to the receiver. I broke one of the legs off one of mine, but it seems to be working fine.

Good luck!

Grog
 
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Hello Hopjohn,

I have to ask why the JST connectors on LED's when they last so long.
Why no just solder them directly in?

I have a 1080 also and enjoy the progress you guys make restoring these fine units.

Just a personal choice and certainly not necessary.

Hi Hopjohn,

Rebuilding your SX-1080 is really challenging, rewarding and a lot of fun. Mine has been working absolutely beautifully since I recapped it.

As you could see in my thread, I had a disaster that I overcame with MTF's help.

My thoughts and advice:

1) I didn't recap my tuner board. I decided not to touch it based on threads on the forum. It works perfectly anyway.

2) Be really careful to use leads and tools that have insulators right down to the tips, so you don't inadvertently short out things like transistors by touching them.

3) If you look at your photo showing the top of the unit you can see the massive black heats sinks for the output transistors and you'll see a little brown do-dad attached to the top of each side of the heat sink with a couple leads coming out of each one. These are the STV4H Bias Diode listed under Semiconductors on page 56 of the service manual on the Parts List of Power Amplifier Assembly AWH-071. They are unobtainium, fragile, and don't like to be handled. Do not tighten the screw too tight on these as the little legs that hold them on will break off. They are vital to the receiver. I broke one of the legs off one of mine, but it seems to be working fine.

Good luck!

Grog

Grog, I enjoyed reading your thread.

1) I will likely recap the tuner board, despite the dangers.
2) I have a plastic tool for adjusting the bias/offset. I have the clip on leads and also capped leads to minimize the risk, but nothing is fool proof of course.
3) That's good information and thanks for sharing.
 
Power Supply Pt.1

REFER TO PARTS LIST ATTACHMENT IN POST#4
Key:
Green= Installed part that was not included in parts list.
Blue = Optional, uninstalled part that was not included in parts list.
Red = Part included in parts list that was not installed
()= Part # Used instead of listed part either because the listed part was out of stock or no longer available.

<AWR-152 Power Supply Assembly>

AWR-152 C11 220 100 CEA 220 100 647-UPW2A221MHD (647-UHE2A221MHD6)
AWR-152 C12 220 100 CEA 220 100 647-UPW2A221MHD (647-UHE2A221MHD6)
AWR-152 C13 220 35 CEA 220 35 647-UPW1V221MPD
AWR-152 C15 220 80 CEA 220 100 647-UPW2A221MHD (647-UHE2A221MHD6)
AWR-152 C16 220 80 CEA 220 100 647-UPW2A221MHD (647-UHE2A221MHD6)
AWR-152 C17 47 16 CEA 47 16 647-UPW1C470MDD (647-UPM1C470MDD)
AWR-152 C18 47 16 CEA 47 16 647-UPW1C470MDD (647-UPM1C470MDD)
AWR-152 C19 4.7 50 CEA 4.7 50 647-UPW1H4R7MDD (647-UPM1H4R7MDD)
AWR-152 C20 4.7 50 CEA 4.7 50 647-UPW1H4R7MDD (647-UPM1H4R7MDD)
AWR-152 C23 2200 35 ACH-060 2200 35 647-UPW1V222MHD (647-UHE1V222MHD6)
AWR-152 C24 47 25 CEA 47 25 647-UPW1E470MDD (UPM1E470MED1TD)
AWR-152 C25 47 25 CEA 47 25 647-UPW1E470MDD (UPM1E470MED1TD)

AWR-152 D1 10E2 400v 1A 512-1n4004
AWR-152 D2 10E2 400v 1A 512-1n4004
AWR-152 D3 10E2 400v 1A 512-1n4004
AWR-152 D4 10E2 400v 1A 512-1n4004
AWR-152 D5 KBPC10-02 200v 10A/200A surge diode bridge 750-MP1004G-G
AWR-152 D6 10E2 400v 1A 512-1n4004
AWR-152 D7 10E2 400v 1A 512-1n4004
AWR-152 D8 MZ140 512-1N5244B Fairchild 14 V, 0.5W Zener
AWR-152 D9 MZ130 512-1N5243B Fairchild 13 V, 0.5W Zener
AWR-152 D10 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener
AWR-152 D11 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener

AWR-152 Q1 2sd712 to-220 bce
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe

AWR-152 Q2 2sc1735 npn to-92 bce 100v 0.5a 0.8w 50-300hfe 130mhz
512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe (512-KSC2383YTA)

AWR-152 Q3 2sa850 pnp to-92 bce 100v 0.5a 0.8w 50-300hfe 130mhz
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe (512-KSA1013YTA)

AWR-152 Q4 2sb682 to-220 bce
512-KSA940TU pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe

AWR-152 Q5 2sd712 to-220 bce
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe

AWR-152 Q6 2sc945 to-92 ecb
512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe (512-KSC2383YTA)

AWR-152 R1 10K 2w -> 660-MOS2CT52R103J
AWR-152 R2 10K 2w -> 660-MOS2CT52R103J

AWR-152 R3 2.2 ohm 1/4w series res.(flameproof) 660-CFP1/4CT52R2R2J
AWR-152 R4 1.5K 1/4 -> 660-SPR1CT52R152J 1w
AWR-152 R5 1.5K 1/4 -> 660-SPR1CT52R152J 1w
AWR-152 R6 1.5K 1/4 -> 660-SPR1CT52R152J 1w
AWR-152 R7 1.5K 1/4 -> 660-SPR1CT52R152J 1w

AWR-152 R8 2.2 ohm 1/4w series res.(flameproof) 660-CFP1/4CT52R2R2J
AWR-152 R9 10 ohm 2w -> 660-MOS2CT52R103J 2w
AWR-152 R10 8.2K 1/2w -> 660-SPR2LT521R822J 2w
AWR-152 R11 4.7K 1w -> 660-MOS2CT52R472J 2w
AWR-152 R12 47K 1/4w -> 660-SPR2CT521r473J 2w
AWR-152 R13 15K 1/4w -> 660-SPR3CT631R153J 3w
AWR-152 R14 15K 1/4w -> 660-SPR3CT631R153J 3w
AWR-152 R15 51K 1/4w - > 660SPR2LT521R513J 2w
AWR-152 R18 1/2w -> 294-120-RC 1/2w
AWR-152 R19 6.2k 1/4w -> 660-CF1/2CT52R622J 1w


The foil side of the power supply. Not exactly ideal access, but it'll have to do.
TpQAzrQ.jpg
 
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Power Supply Pt. 2

The larger caps are removed allowing the glue left on the PCB to be dealt with. Capacitors C11 and C12 were according to the parts list 220uf 100v. Those pulled from the board however, were 100uf 100v. The black 2200uf cap has an unused third middle pin that should be noted during removal. The silkscreened polarities of these 6 capacitors all appear accurate.

fltCmxm.jpg
 
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Gee that all looks familiar!

I re-capped my power supply board but never did do anything with those original hot voltage regulators. I don't have the heat discoloration on my board like yours did so I think my receiver has seen light duty over its years. I'd like to replace the parts just for preventive maintenance though.

I need a modern parts list for that board.
 
Power Supply Pt. 3

Yes, Grog this unit has seen some use. Discoloration on the supply around the regulators is evidence of that. I'm sure Mark will go over the parts list in post #4 when he has time. For now, I'm going to use the regulators previously recommended.

Here we have the pads of D10 and D11 of the power supply. They've nearly desoldered themselves from the board. Photographic proof that restoring vintage units is a good idea even when they are still working.

sT6SMxJ.jpg
 
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