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Hi all, I was advised by some head-fi members to inquire about the technical aspects of this amplifier here. Do let me know if I'm failing to follow any rules; just trying to avoid any catastrophes! Here are the photos of my amp: https://imgur.com/a/sshHA7B The amp is an 8FQ7 SRM-007t rated for 100v 50/60hz outlets. I have a step down transformer (PowerBright) rated for 120v to 100v, and my outlets are, I believe, 120v at 60hz (American). The transformer works fine with my Japanese SRM-252S, but the fuse has blown 3 times now when turning on the 007t (always the 2nd time it turns on; the first time seems to be working). I've tried debugging this for a bit, hence the 3 blown fuses, but I'm not too sure why since the 007t is rated for 100v in and the transformer is rated for 100v out. Birgir kindly helped me debug this somewhat and believes that the most likely culprit is a short somewhere on the board, but I'm fairly inexperienced with more complex circuit boards and having investigated every individual trace on the board could not find anything that looked like a traditional short. If I'm being honest, the board looks relatively pristine if a bit dusty, which I'm trying to clean myself; could anyone help me figure this problem out? The fuses are 1 Amp / 250V 5x20mm, unbranded. I've since bought a handful of extras from a different brand but haven't yet tried them with the 007t. The tubes look to be vintage GE 8FQ7 / 8CG7 tubes, which are apparently the original tubes the amplifier came with, so I am fairly certain that they're not the problem, but I might have to rebias them as it's quite old. There are 3 red lights in the case and the power button is red; I'm not too sure if the lights indicate anything out of the ordinary. Thanks in advance! E: As far as I can tell, the wiring is for 100v; the fuses are in the 1,3,6 positions. I'm not entirely sure about the colored wires coming from the transformer inside the amplifier, though.
Hi y'all, Got my entry ticket into the Stax world in the beginning of 2018 with a Lambda Signature SR-407 earspeakers / SRM-T1S energizer combo. Got them from a Japanese seller and therefore I'm having to use a 100V step-down transformer for Japanese electronics here in Brazil (power outlets at home are 127V, 60 Hz). Only recently got the nerve to open the energizer to remove some dust and check the components (a bit scared of touching those big-ass 100 uF caps, but an anti-static brush and a lens cleaning blower sort of did the job). As far as I could see, all components seem original: The tubes are Gold Aero 6CG7's, Stax Signature selection. I understand that Gold Aero is not really a tube brand, but they rather select NOS tubes from various different brands. The only info I could get from the tube rear is that they are 6CG7's (not the equivalent 6FQ7) made in USA. (Edit) Comparing the remaining original lettering's shape in the tube rear with pictures from Ebay tube listings pointed to the tubes having in fact been made by Sylvania, most likely in the 1950's. For example, this 1956 6CG7 tube made by Sylvania for Zenith looks exactly the same (apart from the Zenith red print replaced in my case with the Gold Aero print, of course), particularly on the inside: https://www.ebay.ca/itm/1956-Sylvania-Zenith-6CG7-Test-NOS-Grey-Plates-Silver-Shield-Serious-Tubes-L398/174307174026 The tubes have grey plates with a silver center shield and a copper grid. The four, big 100 uF caps at the bottom right are Hitachi (CE W 85oC, 400V), but they baffle me somehow - the exact same cap brand / model looks very different in other people's SRM-T1S's pictures (usually black with aluminum / black top, unlike the bronze "unibody" ones in mine), so I wonder whether there is something special about them or if the different looks are only due to the period they were made. I've noticed that the Alps potentiometer is sometimes mounted in the opposite orientation elsewhere (with the PCB facing up instead of down as in mine). My listening so far showed nothing wrong with the combo (apart from a grounding issue - see 5. below) and I've really enjoyed the experience so far - my only previous contact with electrostatics was listening to Martin Logan ESL's, but the technology has always fascinated me. However, I worry about the long-term maintenance of the energizer, considering its age and my distance from the manufacturer, so I eventually need to learn to fix it myself. I may also consider modding the energizer in the future to improve it if it stops working properly. This leads me to the following questions: How do I identify tube / cap failure, apart from the glowing of the tubes? I have no experience at all in that (in due time: all 4 red LED's inside the energizer are glowing, including the one beneath the Alps potentiometer); Should I need to replace the tubes in the future, which brands are most recommended for my combo? I've seen several people here in the forum recommending prioritizing Japanese brands for a better match - how do they compare to my Gold Aero (Sylvania)s? Should I need to replace the electrolytic caps in the future, which brands are most recommended for my combo? Do I need to worry about the long-term wearing of other components (resistors, diodes, input MOSFETs)? Most likely due to the use of the step-down transformer and the fact that my apartment's power outlets are not grounded (sorry, old building), the energizer suffers from occasional humming when no signal is being fed (I use the balanced XLR inputs from a Fiio X7II DAP, which happens to have balanced output). Any ideas? Would modding the power supply help?