Another SX-1010 this time a transformer

Discussion in 'Pioneer Audio' started by Bradbrews, Apr 5, 2017.

  1. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    First a bit of an introduction:
    My vinyl got sent to the basement many years ago, along with the PL-5 turntable, and the Dual 510. The cassettes also live down there with the TEAC V-850X. I have a second system down there that I use when I spend time on projects. I usually spin vinyl, but decided a while back to play a tape. The TEAC would not engage to play, and in an effort to fix it, I found you guys. The deck is fixed now - new belt- and I've been learning all about my old gear from the archives here.
    Now back in ~1990 I got an SX-1010 from a friend who knew I fixed things. He said the transformer was blown - apparently it had happened once before many years ago - and he was done with it. I verified the failed transformer, open primary I think, but 1990 was a long time ago. Anyway, I could not obtain a new one for a reasonable price then, and decided to bring the unit partially back to life with transformers I had in the stash. I found that with two units I could turn the SX-1010 into a functioning tuner, and phono preamp. It was my only tuner until HD radio started being broadcast, when it too joined the basement system.
    Now, with renewed interest in the SX-1010 I procured a transformer at a reasonable price, and I would like to see if I can't make it whole again. You can see the two transformers I used. IIRC the small one is just for the lights.
    IMG_2834.JPG IMG_2836.JPG IMG_2837.JPG IMG_2838.JPG IMG_2839.JPG IMG_2841.JPG
    I've read a fair amount on the importance of using a DBT, power supply rebuilds, tickling the dragon, and not rushing forth, so my question is how should I proceed to replace my old repair with the proper transformer?
    Should I just hook the new one up and power it on with a DBT? I know the non amp section of the unit functions today. I don't know why the transformer failed, but the thought was maybe lightning or power surge, but twice? I do know the two failures were years apart, not back to back, so that might mean two different causes.
    I'm no tech, but I've got a Fluke 87, an old B&K scope, and a few years of electronics classes in the 80's before everything went digital on me. I've only got wick for desoldering, but if I need to rebuild the power supply a few new tools are always fun to add to the collection.
     
  2. rcs16

    rcs16 Super Member

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    2,972
    Location:
    Baldwin, Ontario, Canada
    I do not see any reason why you could not hook up the new used transformer and fire it up on the DBT.
    First I would do some ohms measurements to determine if the big ecaps can take a charge/are not shorts and that the o/p bjts are not shorted. Also check all the regulated o/p's are not shorts either.
    So you had what powered up using those other transformers? Just the +13V for the tuner? You say you had the phono working, it needs +/-24V which is derived from the +/-56V regulated
    Does the sx-1010 has a soft-start ckt? no it does not.
     
  3. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    To determine what I did back when I 'fixed' the 1010, I measured the voltages on the power supply board AWR-053.
    pin 8 = 53.0 V
    pin 7 = 50.9 V
    pin 6 = 11.6 V
    pin 5 = 11.5 V
    pin 4 = 3.8 V
    pin 3 = 5.4 V
    pins 2 & 1 are not hooked to anything, as can be seen in the pic (the red wires twisted together)
    (these were measured with a cheap HF meter though, not the Fluke)
    Not exactly the correct voltages but its been working this way a long time. Why the phono works without the +/- 56 V to AWR-054 pin 10,I don't know, but it does.
    That big black transformer supplies the 50 V and 11.5 V and the 3.8 V. The second smaller one is for the 5.4 V lighting the display.
     
  4. rcs16

    rcs16 Super Member

    Messages:
    2,972
    Location:
    Baldwin, Ontario, Canada
    Makes no sense, +/- 56 V to AWR-054 pin 10
    The regulated DC voltages are as shown on p57 of the service manual.
    Sounds like you are okay to hookup the transformer and power up on the DBT with a 100W lamp. Did you check the resistance across the big ecaps with the power off and the ecaps discharged first?
     
  5. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    I checked the big ecaps and on both the resistance started low, and rose nicely until they were about 1.4K ohms in circuit. All 4 of the main diodes checked OK as well in circuit, so I installed the ATT-166 transformer. Using a 100W bulb in the DBT I plugged the unit in, and the bulb lit up too well, and stayed bright. It did not dim as hoped, and I measured only 5.4 volts across the line into the 1010. I lifted the fuses in the line level section to verify that the source of the current draw was in the amp portion, and the results were the same. Prior to hooking up the red wires, 1& 2 feeding the main caps and diodes, with the old transformer set up, the tuner display lights lit up and the bulb on the DBT was unlit.
    So am I correct in thinking that I have a problem in one or both of the AWH-032 power amp circuits?
    Is there a good thread to look at that covers the best next steps for me?
    Isolating which side is the problem would seem to be whats next..
     
  6. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    I checked the output transistors today and am quite sure that Q3 and Q4 are shorted. I checked in circuit, and got zero volts on all 6 measurements for them. On the others I measured B to E in both directions. This is what I got in circuit with the Fluke in the Diode function:
    Q1 pins 10- 5 = 1.332V and 0.511 V
    Q2 pins 10-14 = 1.333V and 0.512V
    Q5 pins 13-16= 0.454 V and 1.252v
    Q6 pind 13-17= 0.455V and 1.251V
    Q7 pins 13-16= 0.536V and 1.444V
    Q8 pins 13-17= 0.536 and 1.444V

    I should have checked that first, but with the DBT I hope no harm was done.
    Should I disconnect Q3, and Q4 and try again on the DBT, or is it time for replacing them and known problem transistors or more in the amps?
    I'll go look at the parts list for rebuilds..
     
  7. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

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    Best to pull them and check.
    A shorted output will check with very low resistance between two of the three contacts of the TO-3 output (check all three against each other).
    Mostly the Collector will be shorted to the Emitter.
    The output case is the collector and should be insulated from the mounting heatsink. If the outputs check good then make sure the outputs are mounted correctly, in the correct positions and the paste is non conductive. After mounting the good outputs make sure with the DMM that there is no continuity between the output and chassis ground.

    EW has a sticky that explains testing a BJT transistor:
    http://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

    I'm not really following the thread and am a little confused to the troubleshooting sofar.
    Did the set work with the makeshift transformer? It worked as a preamp only?
     
    Last edited: Apr 10, 2017
  8. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
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    Location:
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    If you find that any of the outputs are shorted then check the corresponding driver transistors and if these are shorted or have leakage present then check the pre-drivers and so on, get the schematic and work back from the outputs.
     
    WE6C likes this.
  9. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    Thanks - I will go ahead and pull the outputs off the heat sinks and check them out of circuit.
    Besides being very careful not to bend the leads to the "horse shoe" shaped diodes near the diode body when disconnecting them from the heat sink are there any other things to watch out for?

    To clarify the units condition; It worked fine as a tuner and phono preamp (tape out jacks used to feed another amp) before installing the new, used correct transformer. With the new transformer installed, and only pins 1 & 2 connected (to the diodes and main ecaps, and amps, etc..) I have a bright 100W bulb on the DBT that won't dim.
    The e caps and diodes checked OK in circuit, and I suspect shorted Q3 & Q4 output transistors.
     
  10. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

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    You are on the right path.
     
  11. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    I pulled the outputs and checked them. I found 2 that were shorted, and one of the '679's (a PNP?) measures 2.25V e+ to c- which I think should read OL.
    If I interpret that correctly, 3 outputs on the Left heat sink (left channel I think) have failed.
    Of the rest, 4 of them measured OK in the ranges of 0.551V to 0.511V, and OL in the rest.
    The last one, a NPN? measured 0.510V b+ to e- and 0.477V b+ to c-. Does the lower voltage mean its getting weak, or do they just vary?
    I have not yet progressed onto checking the transistors on the amp boards, left first I assume. Is that the next step? To do that will I have to remove them from the board?
     
  12. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

    Messages:
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    Location:
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    Your using the "V" which means volts.
    Your meter is setup for resistance which would be readings in ohms. The Omega symbol.
    The four that measured high .551 .511 probably measure in mega ohms which is means their good.
    The last one is good but you should replace all of them anyway.

    The amp board you found the bad outputs on will have be checked over. Its best to replace all the all the silicon (Transistors) on the boards. So you will need to check the diodes and replace the caps. Check all the resistors for correct value.
    The 1010 has a fragile amp circuit when the components get old. Some are time bombs so replacing the lot is wise.
    It's going to cost $70 dollars or so in parts and shipping.

    There's alot to do so don't rush it. You will be happy in the end.

    Mouser part numbers:
    You will need two of each for both boards
    Power Amp Assembly (AWH-032-0) (Times two) (Check board number, the D version does not have the 1.5uF cap.) (Q1 and Q2 should ideally be gain matched, this is optional though)

    AWH-032-0: C1: .68uF 25v CSSA: 505-MKS20.68/63/5 .68uF 50v
    AWH-032-0: C2: 1.5uF 25v CSSA: 647-UKL1H1R5MDD1TA 1.5uF 50v (CHECK FOR THIS BEFORE ORDERING!!)
    AWH-032-0: C4: 10uF 16v CEA: 647-UPW1E100MDD 10uF 25v
    AWH-032-0: C8: 330uF 6.3v CEA: 647-UPW1A331MPD 330uF 10v


    awh-032 C1 0.68 25 cssa 667-ECQ-V1H684JL (obsolete) use 505-MKS2.68/50/10
    awh-032 C2 1.5 25 cssa 647-UKL1H1R5MDD1TA
    awh-032 C4 10 16 cea 647-UPW1E100MDD
    awh-032 C8 330 6.3 cea 647-UPW1A331MPD

    awh-032 Q1 2SA726 512-KSA992FBU
    awh-032 Q2 2SA726 512-KSA992FBU
    awh-032 Q3 2SA726 512-KSA992FBU
    awh-032 q4 2sb528 ksa1220 / ksa1381
    awh-032 Q5 2SC1451 512-KSC3503DSTU / KSC2690?
    awh-032 Q6 2SC1451 512-KSC3503DSTU
    awh-032 q7 2sd358 ksc2690
    awh-032 q8 2sb528 ksa1220
    awh-032 q9 2sc1448 ksc2073
    awh-032 q10 2sa740 ksa940
    awh-032 q11 2sc945 512-KSC1845FTA
    awh-032 q12 2sa733 512-KSA992FBU

    These diodes are cheap and you may not need them.
    If you have the time a capability replace them.
    awh-032 D1 1S2473 512-IN4148
    awh-032 D2 1S2473 512-IN4148
    awh-032 D3 1S2472 512-UF4004
     
    Last edited: Apr 10, 2017
  13. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    Thanks!
    What are the recommend replacements for the output transistors? Should I just search here for a list?
    Also, in one of the threads on 1010's replacing the trim pots on these boards was mentioned as well. Is that recommended?
    Should I just get parts and start replacing, or should I first try to keep identifying failed parts and just concentrate on getting it working before I start replacing parts?
     
  14. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

    Messages:
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    For the 1010 I like the MJ21195 and MJ21196's
    Eight of these
    567-175-6-310P

    It's easier to replace the components. The transistors that survived were heavily damaged and will not be reliable.
     
  15. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    Alright - I'm going to take on the challenge of rebuilding the amp boards!
    I'll update my progress once I get some solder melting.
     
  16. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,200
    Location:
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    I think you have made the right decision, esp since you know you already have some bad transistors and then there will be the 2SC1451's and the 2SA726's and their complements that will need doing so you might as well replace them all along with the caps while you are in there.

    As zebulon said also check the resistors and diodes.

    All the best with it.
     
  17. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    Going over the part numbers above with my schematic I noticed I have a few differences.
    I was lucky enough to get the schematic along with the 1010 and still have it, and found it - a small miracle!
    On the Diodes, I don't have D1, (or C1) on my schematic.
    However, my D3=1S1886 and D4=1S1886.
    I also have D7 & D8 both = 1S1885. What part numbers should be used to replace these diodes?
    The other difference, if it matters is that my Q1 and Q3 are 2SA726S but Q2=2SA726 as listed above. Does the 'S' at the end of the part number mean I need a different part to replace it Q1 vs. Q2?

    Should I post a picture of the schematic with these nuances or are all the variants up here already?
     
  18. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

    Messages:
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    Location:
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    Check this quote from Mark:

     
  19. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

    Messages:
    4,093
    Location:
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    awh-032 C1 0.68 25 cssa 667-ECQ-V1H684JL Obsolete, use 505-MKS2.68/50/10
    awh-032 C2 1.5 25 cssa 647-UKL1H1R5MDD1TA
    awh-032 C4 10 16 cea 647-UPW1E100MDD
    awh-032 C8 330 6.3 cea 647-UPW1A331MPD

    awh-032 Q1 2SA726 512-KSA992FBU
    awh-032 Q2 2SA726 512-KSA992FBU
    awh-032 Q3 2SA726 512-KSA992FBU
    awh-032 q4 2sb528 ksa1220 / ksa1381
    awh-032 Q5 2SC1451 512-KSC3503DSTU / KSC2690?
    awh-032 Q6 2SC1451 512-KSC3503DSTU
    awh-032 q7 2sd358 ksc2690
    awh-032 q8 2sb528 ksa1220
    awh-032 q9 2sc1448 ksc2073
    awh-032 q10 2sa740 ksa940
    awh-032 q11 2sc945 512-KSC1845FTA
    awh-032 q12 2sa733 512-KSA992FBU

    awh-032 D1 1S2473 512-IN4148
    awh-032 D2 1S2473 512-IN4148
    awh-032 D3 1S2472 512-UF4004
    awh-032 D4 1S2472 512-UF4004
    awh-032 D5 STV-3H X
    awh-032 D6 STV-3H X
    awh-032 D7 1S1885 512-UF4004
    awh-032 D8 1S1885 512-UF4004

    awh-032 VR1 2.2K multi T 652-3296P-1-202LF
    awh-032 VR2 470 ohms 1T 652-3386H-1-501LF
     
  20. Bradbrews

    Bradbrews New Member

    Messages:
    33
    Location:
    Near Ann Arbor MI
    There are two transistors that are on back order at Mouser.
    awh-032 Q1, Q2, Q3 and Q12 512-KSA992FBU and
    awh-032 q11 512-KSC1845FTA
    are there others I can substitute for these?

    The first one has two other suffix KSA992's which I assume would be OK, but the KSC1845 does not, so I thought it best to ask here..
    In fact quite a few of them I need to get with suffixs other than those listed.
    Is that a problem?
    Should I post whats available here before I go ahead and use them?
    For example, for Q4 I chose KSA1220AYS as the KSA1220 without the AYS suffix was not available.
     

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