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  1. jeromach

    Adjustments JVC 4-DD5 Quadrophonic demodulator?

    I have rebuilt a JVC 4-DD5 demodulator, but encounter the problem that the right channel seperation of front and rear speakers is not working correctly. The left channel front / rear seperation works fine. There is a service manual for this demodulator showing several test points and trim pots...
  2. jeromach

    Sansui AU-20000 balance potmeter

    I did a full rebuild on a Sansui AU-20000 and encountered a lot of issues. Fortunately, after ages of time, I managed to solve everything, but there's one thing that really gives me a headache. Unfortunately this amp apparantly had been "treated" in a butchery, since a lot of things were a big...
  3. jeromach

    AC on chassis Sony STR-6060F

    I changed the mains switch of a Sony STR-6060F for a new one, together with the safety capacitor (Y2/X1, since it's line-to-line). It all works fine, but there is a 125V AC voltage when I measure between mains (both leads!) and the chassis ground. Touching the receiver generates the feeling of...
  4. jeromach

    Technics SU-VX920, voltage problem

    Perhaps someone with some higher technical skills than I have could help me walk this through? This amplifer had a blown right channel. Four power outputs and a number of resistors (normal ones and emitter resistors) needed to be replaced. After the repair the amp in fact is working ok, all...
  5. jeromach

    Marantz 4230 + JVC 4-DD5

    I was wondering, is it possible to hook up a JVC 4-DD5 to a Marantz 4230 and would it work? My knowledge of Quadraphonic equipment does not go so far that I know if SQ and CD-4 can be combined, or is the output of the JVC just some kind of AUX output fed into the Marantz 4-channel AUX inputs?
  6. jeromach

    Preventively replacing VD1212 and similar diodes, why?

    In so much repair and rebuild topics I notice these diodes are being replaced because they are "known bad". It's only that I not yet have come across someone explaining WHY they are known bad. When I started rebuilding amps a couple of years ago I blindly replaced all these diodes, but I also...
  7. jeromach

    Destroyed filter caps

    Anyone ever seen something like this? These filter caps come from a Sansui BA-2000, they should measure 12k uF, but all four actually are between 5 and 6k uF. It seemed to still have been working. Bizarre, never seen anything like it;
  8. jeromach

    Sansui 350A strange "clipping" problem

    I bought this receiver from a guy that recapped it, but could not get it to work. Well, I need to say it's not an easy one indeed. The issue is that when fed a plain 1kHz sine wave the lower part of the sine is fine, but the upper part is rounded off, not exactly like clipping, but in that...
  9. jeromach

    Pioneer M-22, 2SD356 and 2SB526, why matched?

    I am working on a Pioneer M-22 which doesn't come out of protection and I am considering a full rebuild. I noticed the service manual mentions the 2SD356 and 2SB526's need to be matched. Does anybody know why that is?
  10. jeromach

    SA-9900 repair issue

    Hi folks, I'm working on this SA-9900, given it a full recap and done a repair on the power supply section, but I now came across a thing I somehow seem not be able to solve. Before the repair to the power supply section the amp came out of protection and ik worked, but it had an enormous loud...
  11. jeromach

    Sansui G-22000, can the pre-amp work without the power amp?

    I'm working on the pre-amp of a G-22000 which has intermittent channel drop outs (I suspect one of the reed relays), but I cannot test it, since it will not go out of protection without the power amp (and that one is not nearby). I just wonder if somenone knows of a work around to get it to...
  12. jeromach

    Technics SU-8080, dancing voltages

    I have a Technics SU-8080 integrated amp that I rebuilt some time ago, but put it in a corner due to a problem I could not solve. In the main amp section somewhere there is an issue with voltages that are incorrect and they really dance, sometimes even from + to - (at least, that is what the...
  13. jeromach

    Sansui AU-5900 voltage issue

    Hi, Some months ago I worked on a Sansui 5900, gave it a full recap, but also a change of all small signal transistors. Everything ok, exept for one nagging issue, there is something wrong at the F-2604 tone control board. It is fed from pin 24 with 22 volt DC and none of the transistor...
  14. jeromach

    Cyrus two (2) rebuild

    Interesting rebuild, this one. I got it as "broken", both internal fuses blown and after some investigation also two (of the eight) outputs. It was a customer amp, but the customer decided it would be cheaper to buy a second hand "mor" amp than to go for the rebuild and I could keep it. Since...
  15. jeromach

    Sansui AU-505 (uit z'n) hum

    Good morning fellow Sansui lovers, I bought an AU-505 recently with a continuous hum on the right channel. Rather loud, not volume pot related, it sounds like the 50/60Hz hum when the mains frequency gets into the signal path. Now I thought it would be solved after a recap, so that's what I...
  16. jeromach

    Cryogen treated fuses

    Can this be bought in the US too?
  17. jeromach

    DIY 70's Technics switches cleaning

    Most of the 70's Technics amps have issues with the switches, causing scratchy channels, dropouts or even no channel at all. We know deoxit might work nicely for potentiometers, but switches are a different story. Unlike potentiometers that have a brass slider moving over a carbon element, the...
  18. jeromach

    Announcement: Technics SU-8600 rebuild

    I have a weak spot for the Technics SU-8600. I already did a "refresh" on one once (repair + recap "light") and I know it's not an amp for the fainthearted, nevertheless I got myself one yesterday as a project successor to the Technics SU-8088 I recently finished. The 8600 has been produced...
  19. jeromach

    Yamaha M-50 power supply voltage adjustment

    I got this amp at my bench with just the question of giving it a check. I already learned from here the issue with the infamous c607 cap, but there's still some thing that made me wonder; DC offset at right was ok 1,4mV, but at left 62,3mV. I could correct that without a problem. The...
  20. jeromach

    Technics SU-8099 oddity

    I was in the good fortune of obtaining a Technics SU-8099 yesterday, but what really surprised me was the "engine hood" that was different from any other 80xx I have see so far. Normally the grid is integrated in the metal of the cover, but in this case the grid consists of three seperate...
  21. jeromach

    Technics SU-8088 satisfactory rebuild

    (as a follow up of this thread) I already have done repairs and recaps on a couple of SU-8088's and SU-8099's, but the 8088 I just finished is the first one I gave a rebuild all the way. Where in the past I did not exchange the large filter caps or transistors and diodes, in this rebuild...
  22. jeromach

    Relay takes 15 seconds to disengage

    I am working on a Technics SE-9060 and came to this strange problem; Upon switching on main power the speaker relay switches on without the regular delay. Upon switching off power the relay takes appr. 15 seconds to switch off. The speaker switches main and remote do switch the relays on...
  23. jeromach

    Technics SE-9060 filter cap replacement

    I think this is going to get tough; is there any capacitor of 18.000uF 63v+ with a height of 2" / 5 cm. max? The only one I could find was a CDE at Mouser. Then there used to be a Panasonic, but it's obsolete. We're talking these caps btw; I'm looking to place new ones in the...
  24. jeromach

    AU-719; capacitor (of the exploding kind)

    I'm doing an AU-719 rebuild, very nice amp (it's getting). The driver boards have been done and I now just finished the PSU and protector board together with new large filter caps (12000uF/100V). That didn't go without some excitement :). Of course I used a dbt on the first test run; bright...
  25. jeromach

    Luxman SQ-507x rebuild (questions)

    Luxman SQ-507x rebuild I'm preparing the rebuild of a 507x, which isn't particularly easy, because apparently there is no service manual available. All I could find was a schematic that in fact isn't readable and/or is not according to the amp as I have it here. For the rebuilt it doesn't...
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