9941 mit Relais?

      Good evening everyone,
      here the photo of the repair of the power supply of Saba 9941. The great bridge rectifier is 100v/10a type and was coupled with the cooling radiator. The capacitors are large 10.000MF/63V protected by silicone hat. The fuse holders are protected in plastic case. The capacitor 220Mf is 100v, as recommended to me. Resistance 2.2 ohms is the type fused integrated. The bridge rectifier square D in 1427 was replaced as recommende to me: I was able to find the same square type, but 1.5 Amp type. The bridge D1414 is placed between the two fuses ( 2 amp ), using " sterling " tube to prevent short circuits. All voltages are correct . The ripple voltage of + -35 volts is 5% for 5 Amp absorption: very good! Now we have to see what happens when we turn-on the machine! Greetings to all, see you soon. Giuseppe.






      Today is Sunday, hello everyone.....well, after the repair of the power supply, a proper check of the voltage and a first clean from dust inside, I reinstalled the power supply module and I checked the remaining circuits of the UHC 9941 :

      The FM radio does not receive for nothing. The left tape vu meter goes to the middle value while the right tape VU meter does not work. The other bands seem to recieve something;

      the cassette deck goes into play, but after a while ( 10 seconds) goes in stop and its sound is very low; during the short time of play his two VU meters go to maximum and there they remain ;

      i have not tried the turntable, but the phono stage seems work ( " buzz " by touching the connector phono board pins ) .

      Anyway, there is a general problem of audio amplification, which is relevant to all sources. Aside from the noise of the switches and potentiometers, I see that the regulator bass right channel works little. I will try to solve these problems of general amplification before, then i will pass to analysis of the individual sources problems.

      Has anyone had the same problems i described? Can anyone talk about the specific defects of radio, of tape low sound and bass regulator sound? In the meantime i go back to work on my beautiful UHC 9941, enjoying a good cup of coffee. Greetings all, thank you! Giuseppe Mazzilli.

      Good morning to all, as I said here I am again for the news.

      I said that the work would continue repairing the problems of preamp audio. I cleaned the switches and potentiometers with contact cleaner before ( just a little, of course), then with the help of the oscilloscope I found the cause of the fault to the right channel bass controller. The two in the photo marked Philips capacitors have a low value (1.3 MF left channel, 0.7 MF right channel !!).

      Yes, i must replace them.

      During my technician life work , I noticed that many Philips defective capacitors in equipments Revox mounted are of the same type as those in this Saba tone controller board. So i will change all the capacitors (number 8) with good tantalum capacitors. The tantalum capacitors have excellent low-noise characteristics during the charge and discharge, and good heat resistance, also their value remains stable over time. Their use is designed on the lines of very small signal. I have calculated that the value of the capacitors in the signal path in this controller board is a good right size, then I will confirm the same values ​​chosen originally. In these days of continuous reading of the wiring diagram, during my train journey to the place of work / home, I have to confirm what has already been said by all of you: the SABA UHC 9940/41 is just an electronic honest hifi compact and well done. Here is a photo of the two capacitor discharges, soon I will make a picture of the board with all the capacitors replaced with the tantalum type. See you soon ! Giuseppe Mazzilli

      Here are the two capacitors responsible for the incorrect adjustment of the bass tone.

      Hello Giuseppe,

      interresting fact, that you too have experienced the problems with the Philips capacitors. Long time one thought that they would last very long.
      Perhaps you could replace them not with tantal-types, but instead with MKS4 from Wima. The low voltage types are still small enough to fit in the pcb. Achim made best experiences with this capacitors in signal line. I don't really know how the quality of today's tantal elkos will be, but in the older Saba sets like the 8100 or older many tantals get faulty with short circuits.
      Gruß, Gunnar

      Hello Gunnar,

      I show you a picture of new tantalum capacitors, which i normally replace in Revox equipment, instead of the original Philips electrolytic.

      In a technical bulletin official Revox is specifically asked to replace the faulty capacitors Philips of small capacity with " Tantalum capacitors." The report is dated eighties, when perhaps the Wima capacitors were too " bulky " to be mounted on the PCB.

      But i'm not sure that it was the " real " reason.

      The capacitors, such as transistors and all active components, " slightly " add tonal timbre to the system's final voice. I prefer tantalum capacitors because they give the sound a characteristic emphasis on notes from medium-acute to up, but with no special skills on the extreme detail. Several technical Revox bulletins say this, for it is sought to officially replace the tantalum capacitors in their products, which are known everywhere for their tone slightly " hot " on the middle frequencies. If you' ve noticed, even Hi-fi products such as Grundig, Saba and Telefunken from the same era have used tantalum capacitors in large quantities for their timbre, even accepting the increase in the final price of the equipment.
      The short-circuit with tantalum capacitors, in my experience, often occur in the dc power supplies, because it is used the capacitor voltage as close to the working circuit voltage and this so because, physically, the capacitors perform better their duties.

      But rarely i've found tantalum capacitors in short-circuited in audio lines of low dc voltage, maybe they were slight loss, this yes, but because of old age.

      However, i think to mount tantalum capacitors instead of electrolytic capacitors Philips least in this tone control, where the negative feedback signal is greatly used, and then, where the signal is strongly tonally colored by the type of capacitor used. I believe, so, to respect the real sound value of 9941, in the idea with which it was engineered.

      An affectionate greeting to Gunnar, thanks for explaining your opinions. Giuseppe Mazzilli from Rome, Italy.



      The new Revox tantalum capacitors:




      http://saba-forum.dl2jas.com/bildupload/Rexox%20tantalum%20capacitors.JPG


      Edit: Big picture now smaller, DL2JAS

      Hello everyone,

      well, after having repaired the general problems of audio amplification I passed the review of the tape deck.

      I had to completely disassemble the mechanics, clean, wash it. ( photo 1)

      The reel motor gave electric spikes during rotation and so I had to open it and clean from oxide the engine manifold and brushes. The direct drive motor was very hard to spin and dry. I think that all the equipment has been used in a very smoky places, because the mechanical parts are slightly sticky. But it is not old grease, it's just smoke residue. A good cleaning is what we want!

      For engine DD lubrication I used a specific oil for REVOX direct drive capstans, used in several models such as the B 215, B225, B 710. This type of oil is very expensive! ( photo 2 )

      I had to glue the magnet of the automatic stop and replace the belt, because after the play the tape was to stop after a few seconds. ( photo 3 )

      I managed to find a new head rec / play which is the re-edition of the original, identical to the electrical characteristics for which I have to change anything, nor equalization rec / play, nor the bias. The need is to leave all the electronic project as the source. ( photo 4 )

      I had to replace the damping oil of tape loading, with a new oil for tape deck, also used to slow the lowering of the arm of the turntable. I had to wash the circuit rec / play, full of dust and cigarette smoke. ( photo 5 )

      I had to replace several electrolytic capacitors with new tantalum, because the sound was very low, marked in the photo. ( photo 6 )

      Next step: the calibration.
















      http://saba-forum.dl2jas.com/bildupload/New%20damping%20oil%20Photo%205.JPG





      Edit: Rework of one photo, DL2JAS

      Hi Giuseppe,

      nice job you're doing here! Very consistent in all steps. I did not disassemble my recorder in the set to that level...
      One sees that you are familiar with the service-work in the mechanical parts.

      I made the experience with sets from smoky environments too. The greased or oiled bearings or surfaces now are sticky and have to be overhauled. And often the transmission belts and wheels with rubber surfaces get really nasty sticky, almost like glue and the belts loose every tension, like chewing gum.

      But fortunately this stage of "pollution" is rare.
      Gruß, Gunnar

      To Tapeworm 664: thank you for what you say. The value of 9941 deserves all this attention. I have noticed that some of the settings ( tape, tuner ) do not appear in the service of the database. But these settings are quite intuitive and will be executed. Now as I write this I have not yet finished the job closing the tape deck because I noticed that a shielded cable that connects the head rec / play the circuit is faulty. Sometimes the signal disappears. It is damaged at the point where the form "elbow". it is evident that the tape deck has been much used. I will keep you informed. Thank you for your attention and appreciation. Greetings and see you soon.

      Hi Guiseppe,

      I only read the thread now -- interesting aspects, and good work !
      I had the same problem with the Philips axial electrolytics a couple of
      times now. I have tried Wima MKS 4 with spacing 15 mm with success.
      I must say that I prefer these over a replacement with Tantalums. The
      "timbre" (as you call it) is an effect that is still being used by certain
      manufacturers today, such as Naim Audio. But if you are listening carefully
      into complex music from acoustic instruments, and voices (including chorus),
      I think you might prefer the MKS, too. A touch "cooler", but more transparent.

      Since there are lots of other aspects in the SABA electronics that limit
      transparency, I think the MKS is a good solution (plus one where you never
      have to care about again ...).

      Best regards,

      Michael

      To Michael (kugel-balu ) :

      hello and thank you for your interest. Yes, you are right when you say that the performance of Wima capacitors are better than tantalum. Doing authorized service representative to brand Revox, I really many tantalum capacitors to be used. Currently I'm getting good results with tantalum capacitors and sound very convincing to me. I have to make a count of the values ​​of the capacitors and I have to take into account the physical compatibility of Wima capacitors for their assembly. For now I have to go ahead with the repair because the 9941 Saba has very many problems. Ciao ! Giuseppe.

      Dear Giuseppe,

      for your concrete question with the tape deck, I can't help -- but I'm sure Gunnar or
      some other member will know the answer.

      As to the Wima issue: The series "MKS 2" has a spacing of just 5 mm, and fits in
      most places. Then, there is also the "MKS 02" series, with spacing 2,5 mm -- but
      I think that is already too small for most cases at hand. The common values are
      1 uF (where I often use 1,5 uF, as they tend to have smaller values, while the
      electrolytics tend to have larger ones), 2,2 uF and 4,7 uF. For the latter, one
      might want to add some smaller cap in parallel, as the 4,7 uF Wima are often
      _significantly_ smaller in value (more then 10 %). I rarely use the 10 uF from
      that series -- there, a tantalum might still be the better choice.

      Best regards, and good luck,

      Michael

      Dear Micheal good morning,

      yes, i'm in agreement with you when you speak of the values ​​of Wima capacitors smaller than the values ​​of the electrolyte. Thank you for introducing me to the different types and sizes of Wima capacitors. This will help me choose calmly the number I need.

      I will use the e-bay, because in Italy is complicated to do this. I do not know why (perhaps the crisis is the cause ) in Italy going worse and worse, the distributors of electronic components have lost the desire and passion in their work.
      The old commercial providers, now retired, they sold the business to people who do not do their job with the same passion as previous sellers.
      They think only about making money so easy, because the taxes are really high. So they haven't a good variety of sales of electronic components.

      In the meantime, I realized that the tape deck could be improved in performance mode recording ALC (Auto Level Control), which I will explain in the next post.

      Thanks Michael for your help.

      I wish you a good day. Giuseppe, from a sunny Rome ( gasp!)