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Everything posted by Monkeyboi

  1. If you were pulling more than 3A, then the original diodes would be inadequate IMHO and IME most likely to fail prematurely. Nothing wrong with using large value capacitors with a lower ESR. Firstly they will have a lower loss and dissipation and the Nichicons are a good choice, and secondly they will most likely last longer than the "no name" types. The point of the whole exercise is does the unit effectively block any d.c. content present on the mains? IME, most Chinese designed devices have overly inflated specifications and at best achieve about 50% of what
  2. I'm not doubting you mate. Just the circuit makes no sense whatsoever. Cheers, Alan R.
  3. I think there's an error in the reverse engineering. The two 2200uF capacitors appear to be effectively across the mains and not in parallel with the diode arrays in a series configuration with the output, that is in series with the load . Also they are in aiding (+-+-) not opposing (+--+) polarities. Cheers, Alan R.
  4. What people spend their money on is of no concern to me mate. I just have a low level of sympathy for them when they get scammed with an amplifier that delivers half the output power the maker claims it's supposed to or is equipped with a transformer that's well below the required VA rating and with a 220v primary instead of a 240v primary which experiences a meltdown or blows up. 🤣 Likewise for other bits of kit with outrageous claims We live in a disposable society Andy. People aren't interested in real quality. What they want is lots of "gold" plated plastic bling. Things a
  5. #1 rule of diodes. Same way connected parallel diodes don't share the current equally. The one with the slightly lower forward voltage drop will start conducting more than the other and eventually sink most if not all of the current. If the maximum sustained current through the conducting diode is exceeds its rating it will fail. This same rule applies to zener diodes for the same reason except in a zener we are referencing the reverse avalanche breakdown voltage (the zener voltage in layman's terms). Now when the first diode fails due to excessive current it will most probably
  6. This unit is more like the business. Beefy diodes with a 10A continuous current rating. Personally I would have mounted them with a bit of clearance above the PCB as they will get hot with a full 10A load. The electrolytics are rated at 15.1A @ 60 deg C. Aluminum electrolytic capacitors - Snap-in capacitors - B41231 (tdk.com) Cheers, Alan R.
  7. Sure it can pass 10A if it is designed correctly and it will do this with minimal volt drop within the device. A d.c. blocker with piddly 2200uF caps won't pass 10A safely. Most 2200uF / 50V electrolytics aren't rated to pass 10A, more like under 2A even for low ESR electroytics. Just check the ripple current ratings of a typical 2200uF / 50V. Most are rated at about 1.7A maximum. Sustained currents exceeding the ripple current rating of the capacitors will eventually result in their failure due to inrush currents at switch on. Whilst the inrush current will be brief it will eventua
  8. Good to read that you resolved the problem. 👍 IMHO, there's nothing more annoying than a buzzing transformer. It really detracts from the lower level listening enjoyment IME. 😟 It's a possibility that you have more than 1.2 - 1.4 volts of d.c. on your mains supply in which case a d.c. blocker with just 4 diodes in it won't fully eliminate the d.c. If you have a digital multimeter that is capable simultaneous a.c. and d.c. voltage measurements you can quickly determine the magnitude of the d.c. voltage present on your mains supply. If your step-down transformer is on
  9. Absolutely. The Australian made units have to pass electrical certification and safety test before they can be legally sold here in Australia. Exactly the reason why some bits of hifi kit aren't retailed here. It's either because it doesn't meet Australian Electrical Safety Standards or the manufacturer / distributor doesn't want to pay for the certification testing. When you personally import a bit of electrical equipment (in this case a d.c. blocker on a PCB or in kit form) it's probably going to slip through Customs without much problem. However, connecting it directly to t
  10. BTW, as a matter of interest, what are the capacitance and voltage ratings on those two electrolytics? Cheers, Alan R
  11. Hmmmm...... Just looking at those two pissie little electrolytic capacitors at the mains input side. 2000W capacity at 240v = 8.33A. Unless they have very large capacitances with a very high ripple current rating I seriously doubt if they could sustain that current flow without one hell of a voltage drop or for very long before the magic smoke escapes with a loud bang. There's only one way to find out. Hook it up to a 2kW bar heater and stand back. Oh, and BTW wire a fuse or circuit breaker in the mains input side just for safety and piece of mind. I sure as hell would be
  12. I saw that too. Same pictures. Same serial number. Maybe the sale fell through? 🤔 Cheers, Alan R.
  13. What type of output connector does it need to have? USB Type A, USB-C, round barrel jack? Does it need a single output or multiple outputs? Something like the above pictures but with USB or d.c. barrel jack connector(s) instead of the one shown? Cheers, Alan R.
  14. Yes, you will get slugged 10% GST on both the item and the shipping cost. Cheers, Alan R.
  15. Not off topic IMHO. In fact quite related. The often overlooked solution to the problem. I sometimes find it amusing and saddening all at the same time that someone would spend thousands of dollars on a pair of interconnects only to realise that the only person who benefited from the "upgrade" was the retailer who sold them. Now please don't misinterpret my words. I'm not anti-cable or a person who doesn't believe in worthwhile improvements, but I'm with @rockeater on this one. Take care of the room acoustics and try different loudspeaker positioning first before pointing the
  16. IMHO the most influencing factor in any given system is the frequently overlooked or simply ignored listening room acoustics. Obviously this doesn't apply to headphone listening, but for the majority of us with a system with loudspeakers IME cables costing a quadzillion $$$$ make a very small difference (if any) in a listening room that is acoustically poor. Cheers, Alan R
  17. Hi Roger, Yes, those extended range VU meters, whilst it's a great idea implementing both peak and average in the one display aren't completely without their issues. If you can't get the two meters to track accurately check the audio input to the VU meters is the same on each board for various positions of the master level control. If the signal input voltages are the same, adjustment of the input sensitivity is achieved by trimpot RV1. If you don't have access to the ETI magazine article instructions on how to set up the VU meters the following may be of assistance.
  18. Failing tantalum capacitors were my same observations with the ETI 5000 series Control Preamplifier I have built a couple of these. The first one was lost in a house robbery and I came upon a partially assembled kit many decades later on Ebay. The 2nd kit functioned well for about six months before the power supply decoupling tantalums (the circa 1980s ones supplied with the kit) started going short circuit. Strangely taking them out of circuit and testing them with a LCR meter they appeared to be normal however leakage testing them revealed otherwise with them failing before the rated vol
  19. This cartridge and some other models came about primarily due to the JVC CD-4 / RCA Quadradisc discrete 4 channel records which requires the cartridge to be able to reproduce frequencies to 45kHz and beyond. The extended frequency response was normally only achieved by the use of stylii with special profiles like the Shibata and other makers using similar profiles. Conical stylii are simply incapable of accurately reproducing the 45kHz signals as were many elliptical profiles in the mid 1970s, hence the development of the Shibata and compatible profiles. I still have my Shure V15
  20. My comment was a generic observation of the internet and not specifically aimed at anyone (I've yet to name) or about jfets. Indeed I have used jfets in pre-amps and the front end of power amps as well as RF gear dating back to the 1970s so they are devices that I would like to think that I have some degree of familiarity with. In many decades working in the industry I'm yet to find a datasheet or reference book from a semiconductor manufacturer with blatantly obvious technical data errors beyond the odd spelling or grammatical errors that somehow slipped through the p
  21. Hmmm.... 3% distortion is IMHO pretty high. Easily audible to most. I guess it just goes to prove that measurements do matter. Cheers, Alan R.
  22. Hmmmm... there sure is some fugly gear pictured here. Perhaps better listened to in a dark room or with the eyes closed? Cheers, Alan R.
  23. The internet is an amazing source of information. Unfortunately not all of it is true. There's one hell of a lot of misinformation being thrown around with zero accountability for potential consequences. Like some of the electronics channels where the vloggers / presenters have a very distorted and erroneous view on basic established electronics concepts. However no matter how often you bring the errors to their attention the BS continues. Dare to challenge their assertions and risk incurring their wrath. Hey but 100k+ subscribers can't be wrong - or can they? 🙄
  24. Apologies guys. I got side tracked with a few other projects and a number of repairs for some SNA members. Nothing to really add since the d.c. offset mod, but expect if you are building from an original kit of parts to have tantalum capacitor failures. The best solution is to simply buy new ones and heave those old ones out. The old ones fail short-circuit but may trap a few players as some of these old tag tantalums will test okay out of circuit on your LCR meter but will fail the leakage test when a voltage approaching their working voltage is applied. Happy to an
  25. It depends mostly on the type of resistor. In the ESP05 improved PSU the 10 ohm resistors shown are cracked carbon film 1W types. When overloaded but not to the point of total destruction the thin layer of carbon can develop microfine fractures which can alter the resistance when the resistor is hot and dissipating heat. This can potentially introduce minor changes in the resistance thus creating additional noise when current flows through it. These carbon film resistors have brass end caps which are mechanically attached to to the carbon film which is bonded to the ceramic
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