SABA 9241 digital repair information

      SABA 9241 digital repair information

      Hallo !

      Sorry but this is almost the limit of my knowledge of the German language ! :)

      I'm starting to repair a sick (no, very sick !) SABA 9241 digital. The output and driver (TREIBER) module closer to the power transformer are dead, looks like this thread : Saba 9241 - noch einer zur Überholung. The other channel is OK.

      The other problem is the digital display that only displays garbage, like these threads :

      Saba 9241 wie Frequenzanzeige Platine ausbauen

      Digitalanzeige, RDS etc. beim 9241 und 9260

      My questions :

      The BD417 and 418 are unobtainium here; even the NTE replacement is no longer available. The only available current production ones I found are these ones from Toshiba :TTA006B,Q (DigiKey 264-TTA006BQ-ND) and TTC011B (DigiKey 264-TTC011BQ-ND). Would these be suitable replacement ? What would you suggest for the BC557B, the BC447, the BC560 and the BSW 39/6 ? Is the circuit very critical or there is some tolerance on the parameters ? For the output amplifier, I was able to purchase the BD245C and BD246C from BG electronics but they are not of the same brand (Bourns for the 245 and Power Integration for the 246) When I was a young student in electronics school I leaned that a complementary pair should be of the same brand, so should I hunt to get same brand or again the circuit is not that critical ? I have access to a well equipped lab, so I can match parameters if required, as long as I know what I should be looking for !

      For the display, can I replace both the AO808 and AO810 display drivers using this technique :

      Digitalanzeige, RDS etc. beim 9241 und 9260

      Danke !

      Claude
      Bilder

      • 9241displayrep.jpg

        130,38 kB, 500×726, 46 mal angesehen
      Dateien

      Hello Claude,

      BD417 ---> BD139 (different pin-out, need to cross pins) Digi-Key
      BD418 ---> BD140 (different pin-out, need to cross pins) Digi-Key


      different pin-out also for the following substitutes, check pin-out in data sheets:

      BC557 ---> 2SA733(P)
      BC560 ---> 2SA733(P)
      BC447 ---> 2N5551 (yes, its a BC447)
      BSW39/6 = BC639 ---> 2N5551

      Or this list:


      AO808 and AO810 are available as a nice new rebuilt here: kettronik.de/
      Write him an email (email address in the "impressum" of his web page).

      Regards
      Reinhard

      Ersatzteil for SABA 9241

      Hallo Oldifan and DL2 JAS.

      Thank you both for this information, I will contact kettronik for the AO808 and 810 rebuild modules. He also has an interesting loudspeaker relay replacement with inductors, same for the power relay. Have you tried these ? He may also have in stock the AY-5-8100 counter in case I need a spare part.

      A few years ago through hole European transistors were easy to find here, same for Japanese parts. Today most are "Obsolete", even the BC447 and BC547... and the 2SA733; unless I purchase 252 pieces ! Of course there is Ebay, but I am always uncomfortable to purchase from unknown sellers; I had some bad experiences with fakes.

      The general purpose transistors here are the 2N2222 or 2N3904 (NPN), 2N2907 or 2N3906 (PNP), though I would suspect they may be more noisy for audio work.

      With the information you provided I'm more comfortable to search for replacement. The 2N5551 is available, same for BD139 and 140. To replace the 2SA733 would MPSA56 or KSP2907 be good choices ? These are easy to get.

      Also, should I try to get the same brand of output transistors or a mix is OK (Bourns for the BD245 and Power Integration for the BD246) ?

      To be safe I will also replace the electrolytic capacitors and the 22uF tantalum on both driver boards. Would you suggest I also replace all the electrolytic capacitors on the "NEITZTEL" module and C2301, C2302, C2311, C2312 and C2322 on the main board ?

      Thank you very much for helping me on this project !

      Vielen Dank euch beiden ! (is that a good translation for "thanks to both of you ??)

      Regards and 73 from Claude VA2 HDD
      Bilder

      • BC447.png

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      • BC547.png

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      • 2SA733.png

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      Dieser Beitrag wurde bereits 3 mal editiert, zuletzt von „va2hdd“ ()

      Dear Claude,

      can't you get the transistors from Mouser ?

      As to capacitors: If you look into the older descriptions here, you will see which capacitors are worth replacing, and which are not. It is more important to inspect the solder points etc. carefully, as they are often degraded. Check the "9241 rework" by nightbear for a start (I hope you can translate it well enough).

      Best regards,

      Michael

      Dear Claude!

      The translation is good.
      I tried to find suppliers in Canada.
      First idea mouser, Michael wrote.
      It seems to be not the same product line as Europa and USA.

      Then there is RS Components
      ca.rs-online.com/transistors-modules/bipolar-transistors/

      Try Dönberg (Donberg), too:
      donberg.co.uk/
      They ship worldwide and have many special parts for radio, TV, video...
      For the German members, Dönberg is something like ASWO.

      You can often use 2N2222 and 2N2907 as good replacement for BCxxx.
      But be carefull, they seem not to be low noise.
      In stead of BC546 ... BC560 you can use BC846 ... BC860.
      It is the same but housing SMD.

      For BD245/246 I would use the same brand if possible.
      TIP33/34 is the same, only stamped with TIP.

      Do not replace every electrolytic capacitor, normally unnecessary.
      Little capacitors and tantalum I would replace.

      73 es 55 de DL2JAS
      Was bedeutet DL2JAS? Amateurfunk, www.dl2jas.com

      Hallo to all members.

      I'm starting to really measure how old these receivers are becoming; it is almost easier to find parts for vacuum tubes radios... Almost ! ;)

      Thanks to kugel-balu for suggesting Mouser as a local source, of the six big suppliers here (DigiKey, Newark, Arrow, Mouser, Future, Allied (which is now RS) and Electrosonic (Master)) Mouser always had a better choice of euro parts. I will follow your advice and read "9241 rework" by nightbear"; translating will be part of the fun !

      I tried to order TIP33 and TIP34 for the output pairs, but Mouser, Newark and Digikey obsoleted the TIP34 ... I found that New Jersey semiconductors ( njsemi.com/) is a small USA company that specialize in reissuing obsolete semiconductors and they sell BD245/BD246. Mouser has the 2N5551 (BC447 and BSW39 replacement suggested by Oldifan), the BD 139/140 and the BC557. So I'm all set, now it is time to order my spare parts and warm up the soldering iron :) ! (and also the desoldering gun ... ;) )

      Vielen Dank euch beiden !

      Regards and 73 from Claude VA2 HDD

      Dieser Beitrag wurde bereits 1 mal editiert, zuletzt von „va2hdd“ ()

      Hallo to all members.

      kugel-balu I started translating and reading "9241 rework" by nightbear". :D I laughed very loud reading the description of the odour that emanated from the poor receiver. <X
      Mine has been carelessly worked on by an unqualified repairmen, but at least it is complete, clean and odourless !

      Regards and 73 from Claude VA2 HDD

      Hallo to all members !

      I'm working hard on my 9241. I received most part for repair; most important I got the output transistors. I have access to a transistor tester (Peak DCA75) that measures Vbe and static gain ( ᵦ       ). Should I match the output pairs for ᵦ or Vbe or try to find best compromise for both parameters ?

      I attached a photo of the almost completed module.

      Danke !

      Best regards and 73 from Claude VA2 HDD
      Bilder

      • SABA 9241 output module_tn.jpg

        622,01 kB, 3.765×1.484, 38 mal angesehen

      Hi Claude,

      matching is not strictly necessary due to the 0.22 and 0.27 resistors in each branch. The 0.27 resistors distribute current evenly under medium and high load conditions. However, I always try to find the best combination for the pairs, connected to the same driver transistor. Here Ube is more interesting than Beta, as long as the gain differs not extremely. Ube should differ only some single mV.
      Keeping Ube differences small ensures, that the quiescent current will be split evenly to both transistors of one branch.

      Matching PNP and NPN is not necessary. The .22 resistors and the possibility to adjust for 0 V dc at the output make life simple here.

      Best regards,
      Christian
      **************************************************
      2 + 2 = 5 (für extrem große Werte von 2)

      Hallo to all members.

      Thank you Christian and Andreas, I followed your advice. I tested all the NPN for Vbe at 5 mA and selected the four closest ones and then I retested for Beta and selected the two winners. I redid the same for the PNP's.

      Michael I will swap 1N4151 for the 1N4001; thank you for the suggestion.

      I added a picture of today's.

      Danke ! :)

      Best regards and 73 de Claude VA2 HDD
      Bilder

      • SABA 9241 output module with BD246 BD246_tn.jpg

        557,11 kB, 3.930×1.613, 33 mal angesehen

      Dieser Beitrag wurde bereits 2 mal editiert, zuletzt von „va2hdd“ ()

      Excellent !! I have one other (tiny) suggestion: Since the BD 140, unlike the BD 418, has no fin, I'd add a small piece of aluminium, about the size that connects the two BD 139. This transistor does get rather hot when you run the amp a bit louder ...

      In any case, with these modifications, this is a heck of a power amp, and the sonic performance is pretty damn good ! If you follow the advice on the wiring (replace the green wire with a slightly thicker one, and add bridges on the track side of the big PCB in parallel to the thin wires for the right channel), you'll also get a very decent bass control.

      Also, you might want to take a look at the recent discussion concerning C 1157 (22 nF). It seemed a little better to use small capacitors (15 nF) between base and collector of T 1156 and of T 1163. This is discussed in the thread on: SABA 92xy, 914x und 7140 Endstufen-Revision

      Best regards,

      Michael

      Dieser Beitrag wurde bereits 5 mal editiert, zuletzt von „kugel-balu“ ()

      Hallo to all members.

      Thank you Christian, I used to teach electronics, I try hard to work cleanly; and I don't want to create extra troubles...

      Hi Michael, I will look at the tread on base coupling capacitors (between base and collector of T 1156 and of T 1163), swapping 15 nF and 22 nF is not very difficult ; and I will add a small heat-sink to the transistor.

      I plan to leave one channel original and I will upgrade the other one. After I will go to a friend's lab and test with an Audio Precision analyzer to quantify any improvements.

      I found something strange on my "TREIBER" modules. C1101, marked on the plan as 2.2uF was 0.22uF on one and 22uF on the other one. The soldered joints looked original, both were Tantalum drops ( <X I don't like drop Tantalums; I saw too many short in Tektronix and Fluke equipment). I replaced these with 2.2uF 63V Film. Have you seen something similar ?

      Best regards,
      Claude

      Dear Claude,

      the C 1101 is marked as 2,2 uF in the circuit diagram, but on most modules, you will find 22 uF tantalum. I normally replace them with fresh ones (22 uF, 35 V), and never got a problem afterwards.The original ones are mostly 22 uF, 16 V, and some are indeed faulty. You can safely use a 22 uF or 47 uF electrolytic here, which should have high quality. A 2,2 uF film capacitor, in my opinion, is not recommendable here, this capacitor is for smoothing out the voltage and reducing noise and ripple.

      Check out the other suggestions on how to modify this module. C 1106 should be bipolar, and I prefer 47 uF there, with a 1 uF film capacitor in parallel. I use matched transistors for T 1112 and T 1114, check the data of the others, and usually replace T 1108 (BC 639). C 1111 should be a good film capacitor, which is no problem as there is enough space on the PCB.

      In any case, if the two cards differ, make them equal ... the value for C 1101 you report must be an outlier, or a mistake. So far, I have never seen anything except 22 uF here (though I know some deviations occur).

      Best regards,

      Michael

      Halo to all members.

      I just received the parts I ordered from Ketronics. I was putting back together the frequency counter box (Anzeinge-Modul) 21, and I found that I made a very silly mistake when I started the repair. I have no picture of the cable between the module 21 and the LED display to know if the white cable goes on the left or the right side ? Can someone send me a picture of the connector where it connects to the front panel ?

      Thank you and best regards,

      Claude