Hi, Checked the output transistors mn2488 and mp1620 and they are fine. Was recommended to replace the 0.22 ohm resistor (OK) and the 180 ohm resistor as well. Trouble is the current resistor is 220 ohm (original) so is it possible that this is the norm for 240V Australian models? Would it make any difference? Thanks a lot (love your site)
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Re: Sony resistor values?
It is recommended to use the same value due to the function of the resistors and their values.
A lower value will let the current flow a bit faster and the higher value will slow it down according to their design.
Try installing the same value of 220 ohms.
Hope this helps.
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I would also replace 2sa992 (2pcs) and 2sc1845 on preamp board- sometimes they look ok when you test them by regular meter. Check 1.2 kOm and 4.7ohm resistors at preamp pcb. Check diodes on output pcb (could be smd type, connected from base of output transistors to emitter i think)
Initially, the displayed message "PROTECT" is as it implies, the STR-DE185 has gone into auto-protect mode. The built-in auto diagnostics has sensed a fault and kicked in to prevent further damage to the Sony unit. In most instances, this is brought about by a faulty speaker (should be 8~16 ohms), loose/disconnected speaker wiring, strands of speaker wires inadvertently touching its opposite, overheated, ventilation holes covered, played with the volume level high for an extended period of time or a localized fault in the internal electronics of the amp circuitry. Offhand, since DIY (do-it-yourself) repair is being done and assuming that you are comfortable working with electronic components & circuitry, use of a DVM/VOM, a soldering iron/station and safe practices with electrically powered devices, access to a Service Manual or at the very least, a schematic diagram would be a necessity.
consider doing a RESET. Turn off the STR-DE185, press and hold the POWER button for 5 seconds or more or till "INITIAL" message is displayed. This would force the Sony to revert to factory defaults removing any glitches, errors in settings & configurations, presets, memories and user preferences;
hi please check the wiring of the output it could be short or the speaker would be short or it could be the diode at the secondary supply that had short or capacitor disconnect the power supply ans check the OHMS of the transformer .or check the transistor could be stort
When replacing output transistors on amplifiers it is generally a good practice to replace the output capacitors as well as the biasing resistors.
Just because one transistor is bad does not mean that that is the whole problem.
Look for what caused the problem.
Bad speakers,bad wires,defective traces on circuit board,poor soldering.
Also when mounting the transistor make sure it is insulated and grease it with a dab of silicone heat sink compound.
Whenever I service a board I examine all components for tolerance as well.
A resistor marked at 1% tolerance,example 1k ohm + or - 1% should read no less than 990 ohms and no more than 1010 ohms. Anything else your asking for trouble.
Another point is that some amplifiers use matching pairs.
Pairs complement each other in an output stage and must be replaced in pairs.
I repaired a Sansui Amplifier a while back and it looked as if a power output resistor was burned.
Comparing the two channels I figured the matching value from the other side and replaced all of them and the system has worked flawlessly for years now.
I am a retired electrical engineer and have worked in a few areas of electronics for over 35 years.
Hope this information helps you.
Hi John. It can be fixed, and most probably relates to the power supply. There is a Sony repair doc that lists low or no display, but also associated with no audio.
Here is the information regarding the problem.
The power supply is the main culprit for most of the TA-E9000ES failures. Symptoms of this are no sound and a very dim or no display. Apparently the power board has several weaknesses which have caused Sony to supply a modified version in later production units.The circuit around transistors Q108 and Q109 are prone to oscillation, which will cause one or both transistors to break down, as well as resistor R124. This resistor is originally a surface mounted device capable of 1/10 watts of heat dissipation. The modification suggested by Sony is to replace this 4.7 k ohm resistor with a 1 watt rated version. Also, to prevent further oscillations a 100 pF capacitor is added in parallel with R153. (Some suggests that also transistor Q110 is a candidate for replacement.) The US issued service bulletin from Sony suggest that this fault may occur with units having a serial number in the range 800001 - 802746.
If you still have sound, then there may well be a problem elsewhere. It is a great Preamp, and I recommend you get it fixed. A Sony Authorised service center would be the best place to take it. They supply good inside information about this most problems that occur on their gear. There is good info on your preamp controller here
Thanks for the clarification. From the fuse behavior and feeding the amp into another amp (generally a no-no) it almost certainly is in the output section. If the amp used output transistors (numbered something like Axxxx/Cxxxx where xxxx=0000-9999) there will be some white three-legged low value (.47 ohm or less) resistors that are probably open. FYI the full part numbers for the transistors would be 2SA/2SC so a part marked C3281 would need a 2SC3281. B+D Enterprises (Google them) has most Japanese semiconductors and they have never sold me a fake transistor.
OOPS-forgot to mention if your bias turns out ok after replacing any blown outputs, turn it off and resolder the collectors (center) pins of all 4 output transistors and turn it back on-should work but you'll need to recheck bias and dc offset. They appear to both be adjustable on the board sticking up on the top side-it's right in the middle and has 4 trim pots on it......
bring data sheet of this ic from the net-check supply voltage(vcc or vdd)-check ground.apply audio signal and test if it is present in input pins after that check your signal in output pins.have a visual inspection around the ic for burnt resistors or bad capacitor. if every thing is fine replace the IC.
I'd suspect that one of the two output transistors on that channel has gone bad. If you are unsure how to test or troubleshoot this, then you might try replace both the NPN and PNP outputs and catch the bad one that way. If your amp uses an output module then you would of course have to replace the module which would replace all the output transistors on both channels. Good luck. Another thing to look out for, is the emitter bias resistors. They are the large white ceramic ones near the outputs. Sometimes one of those will open up too. They will be of a very small resistance value like .5 ohms (point five ohms) or something in that general ballpark, and have a wattage value of typicaly 5 watts. So they are pretty big resistors. Be sure to check them all even if you do find a bad output transistor. They will often go out with the transistor. Good luck.