SAE Mark Four C replacement Pwr transistors

Discussion in 'Solid State' started by hgriffin1, Aug 1, 2013.

  1. hgriffin1

    hgriffin1 New Member

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    Hello,

    Can anyone recommend a replacement for SAE 701 power transistors in the Mark Four C power amplifier? I checked the SAE refernence chart on Wardsweb.org and there is nothing showing for these devices... It also appears the the replacements for the SAE 202 and SAE 11 devices are now obsolete...

    Thanks,
    Hugh
     

     

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  2. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    What do the ACTUAL transistors say on them???
     
  3. hgriffin1

    hgriffin1 New Member

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    They are imprinted "SAE 701". The other imprinted numbers are: 466 7325 (printed with red ink) & 466 7330 (printed in black ink) I assume the color designates NPN and PNP.

    "SAE 11" M(otorola) 0063 7439 (in red ink) M(otorola) 0063 7426 (in black ink)
    "SAE 202" M(otorola) 7413 (in red ink) M(otorola) 7339 (in black ink)
     
  4. hgriffin1

    hgriffin1 New Member

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    BTW they are all T0-3 cases
     
  5. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Did you try contacting him directly? He may have data that is not on the site.

    The On-Semi mj21193 and 94 should be heavy duty enough to handle to handle the Mark 4C. Physically check the polarity on them then match the new ones to them.

    What are the the 11 and 202 devices?? I don't see them listed in the tables on wardsweb

    On the #'s you gave for the "11" the 1st 3 should be the part # and the last four are the date manufactured. And for the 202 they are the date codes. ie:7439 = 1974 39th week

    Please take some pictures of the Mark4C, 11, & 202 output's that are clear and legible. Might be able to discern something from them. Also some specs for all 3.

    Thanks

    Larry
     
    Last edited: Aug 2, 2013
  6. elnaldo

    elnaldo Addicted Member

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    Do you have a schematic? The schematics I've seen from SAE were very clear about this things.
     

     

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  7. hgriffin1

    hgriffin1 New Member

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    Pics of Output Transistors

    Here are the pictures of the output transistors. I don't have a full schematic. Just a block diagram of the amp showing the configuration of the outputs. No values for these components unfortunately.
     

    Attached Files:

  8. llwhtt

    llwhtt Super Member

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    Are you working on a 4C or 4D? The schematic you posted is for a 4D which is a completely different circuit from the 4C. Can you post a picture of the PCBs? If it is truly a 4C then you will want 2N3773 output devices. The 4D uses Darlington output devices.

    Craig
     
  9. hgriffin1

    hgriffin1 New Member

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    PCB pics

    Here's a pic of one of the boards, and internal shot and the face plate with the model name...
     

    Attached Files:

  10. electrohifi

    electrohifi Active Member

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    those look like old motorola devices, you need to cut a dead one open and post a pic so we can see if it is hometaxial or not. those tops pop off quite easy with decent size wire cutters just go hard and slow so you dont wreck the insides.
     
  11. petehall347

    petehall347 the brandy coffee man Subscriber

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    here you go .. i see one reference "0063"..i will leave it up you to see if the others are there ..
     

     

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  12. llwhtt

    llwhtt Super Member

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    Go to "SAE Talk" for the schematic in the files section, you'll have to join but no big deal. Mouser has the 2N3773s and the 2N4036s in the differential if needed. Check your DC offset and swap the socketed 2N4036s around if needed. Also check the big carbon comp resistors (2.7K and 1.5K) they are usually out of tol. Might want replace all of the axial electrolytic while you are at it, Mouser carries Nichicons, that what I use.

    Once you are on the SAE Talk site you'll see many different "Marks", your amplifier may or may not match the schematic exactly. I've been thru a bunch of the Mark IIIs and IVs, not many were exact matches. I chased the true output devices for hours and Mark at Absolute Sounds had answer, 2N3773s. He was one James Bongiorno's "designated" repair guys. This amplifier is before the Bongiorno era though, the "D" was his. You can tell by the dual diffs in the front end.

    Craig
     
  13. sregor

    sregor AK Subscriber Subscriber

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    At wardsweb the 11-0063 is listed as MJ802 (also SAE 101) The 202 is also listed as 11-0069 and is MJ4502 ,
     
  14. hgriffin1

    hgriffin1 New Member

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    I DL'd the schematic from SAE Talk. Thanks! Yes, the output devices are different on mine. The schematic shows SAE 601's... I will be ordering some 2N3773's. Already have the caps on order. The comp resistors were out of tolerance as well so they will be replaced. Thanks for all the help!
     
  15. RoveronMars

    RoveronMars New Member

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    Hello. I found this thread a little bit confusing. I am trying to find replacements for the SAE 701 transistors. The thread started off promisingly referring to SAE 701 but subsequently changed to SAE 601 for which supposedly is the 2N3773 equivalent. I am hoping someone can tell me the equivalent for the SAE 701. I am a bit curious as to why on the SAE Mark 31 power amp, the SAE 701 are green inked on the "b" channel versus blacked inked on the "a" channel. All of the SAE 701's are NPN BJT type. I am currently recapping this power amplifier and would appreciate any comments as well as answers. Thanks, Roveronmars
     
  16. sregor

    sregor AK Subscriber Subscriber

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  17. llwhtt

    llwhtt Super Member

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    My 4C schematic has MJ802/4502, SAE101/202, SAE0063/0069 for the drivers and SAE601 for the outputs. My personal 4C has those drivers with SAE701 outputs. When I rebuilt my MKXXXIM (mono) it originally had SAE601 outputs and I used the 2N3773s as replacements. All of these transistors are relatively slow as are all of the ON Semi TO-3s so shouldn't be a problem to use the latest and greatest MJ211xx types.

    Just going thru my SAE schematics and found the schematic that covers the MKIIB, MKIII, MKIIIA and MKIVB. In the notes section it says SAE601 was 2N3773.

    Craig
     
    Last edited: Dec 8, 2018
  18. RoveronMars

    RoveronMars New Member

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    My thanks to sregor and llwhtt for their replies. Right now I am in the midst of writing my synopsis of the problems found with the SAE Mark XXXI power amp that I owned. I will include results from the PEAK Atlas DC Pro testing of the output transistors and hopefully will resolve whether it should be 2N3773 or MJ21194. This synopsis I hope to include in this thread tomorrow night. RoveronMars
     
  19. RoveronMars

    RoveronMars New Member

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    Currently I am repairing a SAE Mark XXXI power amp that is capable of 50 watts RMS per channel (can go up to 70 watts RMS before clipping, however this is unobserved by me with the use of a sine wave generator, an oscilloscope and a load). I hope to at a later date to find the benchtest graphs of this amp, if they exist among my voluminous files. A few months ago, I overdriven the amp playing Pink Floyd "Wish you were here" CD and the 2.5 A slo-blo fuse blew. I replaced the fuse and powered it up and the fuse blew promptly. I opened up the chassis and looked around, didn't see any problems except for two electrolytic capacitors with melted plastic coverings splitting off their metal cases. I unsoldered these from the PCB and checked both capacitor ratings and esr with a PEAK Atlas esr meter. Both capacitors were originally rated 64 microfarads at 64 V. The top capacitor on the PCB was found to be 68.20 microfarad with an esr of 0.20 ohms. The bottom capacitor was found to be 82.14 microfarad and an esr of 0.14 ohms. The top half of the pcb is judged to be the A channel with the bottom half judged to be B channel, both being on the component side. The component side is towards the front of the amp.

    Let's describe the age of the amp and how the amp was obtained by me. I went to college from 1972-1977, at one point during a summer vacation, I built a Dynaco tubed power amp and solid state preamp from kits. And during that period people from the Mcintosh company came by a local stereo shop to benchtest any amp the public brought in to that store. Their way of convincing the public that their amps were state of the art, I guess. So I had the Dynaco amp benched tested against the McIntosh amp and to everyone's surprise, the Dynaco was found to be virtually the same level as the McIntosh standard. The owner of the stereo store made an offer that I could not refuse, namely the SAE MARK XXXI power amp. Apparently I bought the kit for around a hundred bucks and the owner told me the SAE was retailing for 200 bucks, and it was brand new and boxed (more on that later). At the time, I was a poor student, so gaining an amp worth twice the value of the Dynaco was a steal. Of course many years later I rued the loss of the Dynaco simply because it was a tubed amp (plus the fact that Dynaco no longer sell these kits and if you wanted a Dynaco, you can probably find these on EBAY but selling for many times what I paid for in kit form) and I now realized that tubed anything of auditory nature are to be prized and never parted with. So given the years I attended college, I'd say the amp was probably made in those years. Further research of the internet discovered a brochure for SAE components (wardsweb.org) saying the Mark XXXI sold for 200 bucks around the years 76-81 and a copy of the Mark XXXIb schematic (wardsweb.org) shows the amp was probably in its second iteration as of 9/30/77 (the schematic doesn't match what I can observe of the amp I am working on now, to wit, the amp I have doesn't have a biasing transistor, a time-delayed relay circuit, a thermal fuse, a choke after output transistors (Darlington'ed on the PCB) that the Mark XXXIb has. Other differences of note,on the Mark XXXI the output transistors are all NPN and ganged together with low ohm wirewound resistors feeding into the output terminals whereas the Mark XXXIb have same number of output transistors but half are PNP's and the other half are NPN's with half the number of low ohm wirewound resistor feeding into a choke circuit and passing through a time-delayed relay circuit on its way to the output terminals, and further the power supply is sized about 4 farads higher than the Mark XXXI.

    Upon closer look of the components used and seeing telltale rosin deposits, I noticed things that are not consistent with my first belief that I had gotten a brand new amplifier in the box from the owner of the stereo store. To wit, most of the diodes on the A channel side between the pre driver(?) transistor (M SJ5262) and the driver(?) transistor (M SJ5261) which are obvious due to the black cases with white bands being replaced with glass cases with black bands and resin deposits left behind on the trace side of the PCB. The B channel diodes are original and clean. Additionally the pre driver (?) and driver (?) transistors were also obviously replaced (rosin deposits) on the A channel only. In the area close to the middle of the PCB close to the M SJ5262 transistors, there are 4 discrete diodes in a bridged formation (original black cases with white bands and rosin deposits on the traces). A teardrop capacitor is not consistent with the original rectangular capacitors and is found on the A channel side between the M SJ5262 and M SJ5261 transistors (again rosin deposits). Two capacitors were found on the trace side of the PCB and the lack of rosin deposits leads me to believe they were modifications made by the SAE manufacturing process. As best I can tell, the ceramic disc capacitor runs from the collector side of the 2N3738 to the base side of the 2N4036, being on the B channel side. The other capacitor (teardrop type) being on the A channel side runs from the base side of 2N4036 to the base of the M SJ5262. Further signs of repairs are found on the A side output transistors all marked 466 above the SAE701 above the 7330 (marked in black ink on the cases). Looking at the back of the amplifier with the heatsink covers removed. the A channel ouput transistors are exposed and from the bottom left transistor (A1) moving to the top left transistor (A2) to the top right transistor (A3) to the bottom right transistor (A4). A1, A2, A3 are marked by someone's hand with black slashes. On the A4, it appears to be written as 1-28-75. I surmised that around that time, it has been repaired and probably predates my receipt of this amp. On the B channel output transistors from the bottom right transistor (B1) to the top right transistor (B2) to the top left transistor (B3) to the bottom left transistor (B4) are found to be unmarked and probably original to the amp. There are differences among these though and are intriguing little mysteries. B1,B2, and B4 are marked 466/SAE701/7242 (green inked) but B3 is marked 466/SAE701/7251 (black inked).

    PEAK Atlas DC Pro results are as follows: A1 NPN silicon BJT hFE=6 at Ic=5.00mA; Vbe=0.575V at Ib=5.00mA; Ic leak=0.000mA, A2 NPN silicon BJT hFE=5 at Ic=5.00mA; Vbe=0.567V at Ib=5.00mA; Ic leak=0.000mA, A3 NPN silicon BJT hFE=6 at Ic=4.99mA; Vbe=0.572V at Ib=5.00mA; Ic leak=0.000mA, A4 NPN silicon BJT hFE=5 at Ic=5.01mA; Vbe=0.567V at Ib=5.00mA, Ic leak=0.000 mA, B1 NPN silicon BJT hFE=11 at Ic=5.00mA; Vbe=0.571V at Ib=5.00mA; Vce sat=0.09V at Ic=5.00mA and Ib=1.00mA; Ic leak=0.000mA, B2 NPN silicon BJT hFE=13 at Ic=5.00mA; Vbe=0.572V at Ib=5.00mA; Vce sat=0.080V at Ic=5.00mA and Ib=1.00mA; Ic leak=0.000mA, B3 NPN silicon BJT hFE=13 at Ic=5.01mA; Vbe=0.582V at Ib=5.00mA; Vce sat=0.05V at Ic=5.00mA and Ib=1.00mA; Ic leak=0.000mA, B4 NPN silicon BJT hFE=12 at Ic=5.12Ma; Vbe=0.563V at Ib=5.00mA; Vce sat=0.079V at Ic=5.00mA and Ib=1.00mA; Ic leak=0.000mA. At first glance it appears the transistors are ok due to no leak results but I am bothered by the doubling of hFE's from the A side to the B side and that the B side shows Vce sat results, which I need to do some further research on. I would appreciate comments on which is the better replacement transistor (2N3773 versus MJ21194 or other) for these already in place.

    I plan to unsolder from the PCB the M SJ5261's, M SJ5262's, and 2N3738's for testing by the PEAK Atlas DC Pro at a later date. I would also appreciate an actual schematic (free source or not).

    I am planning to recap all of the electrolytic caps (Holland brand, blue plastic see throughs with dark blue spirals, not made anymore except for NOS on EBAY, probably taken over by Phillips) with Mundorfs for the following old values, new values: 1) 10 mF 63 V; 10 mF 100 VDC, 2) 64 mF 64 V; 68 mF 100 VDC, 3) 220 mF 16 V; 220 mF 63 VDC, 4) 330 mF 63 V; 330 mF 63 VDC, 5) 470 mF 40 V; 470 mF 63 VDC, 6) 6000 mF 50 VDC GE brand; 6800 mF 100 V Nichicon brand (esr meter shown positive rail can was at 5760 mF esr of .03 ohms, negative rail can was at 5964 mF esr of .03 ohms). The Sensitron bridge (SLA-200-28; ~200 V 3 A rated) will be replaced by a Vishay 400V 8 A bridge. In the process of rebuilding the power supply, I will check voltages of the transformer output to verify whether it is 45 volt rails or whatever (schematic for SAE XXXIb says 45 volt rails). And the last thing will be to check all resistors and replace if necessary. Any comments would be appreciated. RoveronMars
     
    Last edited: Dec 12, 2018
  20. sregor

    sregor AK Subscriber Subscriber

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    Last edited: Dec 12, 2018

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