jamesmking

your dn2540 looks to be in backwards compared to the silkscreen.... the hashed section on the silkscreen indicates the metal tab... perhaps this could be because your silkscreen is wrong or maybe the builder has modified the pcb?? have you checked which pin is connected to what compared to the schematic? and looked at the dn2540 data sheet to confirm the orientation?

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el84? - the spec sheets says thats 0.76A per valve for the heater.... http://www.r-type.org/exhib/aaa0028.htm T2 and most of kevins designs are EL34. EL34 is around 1.5A to 1.6A heater per valve. http://www.r-type.org/exhib/abv0058.htm As craig says its around 3A for a pair and separate heater windings for each channel... I use transformer windings rated at 4.5A and the extra 1.5A is simply a safety margin. Heater current draw will be higher when the heaters are cold (less resistance) but the current draw will decrease within a minute or as the heaters heat up and reach steady state. I aim for 50% margin on the transformer heater windings. I like to run the el34 heaters at 6V rather than 6.3 for longer life.

personally I use cal test silicon test lead wire. Its cat IV rated at 1KV , very flexible and can withstand 180C. Its also just copper strands with no plating. (I find almost anything silver plated to be bright sounding and have banned anything silver or silver plated from hifi). I also arrange the wiring to the plugs and sockets so that + voltages go in the top half, grounds and zero volts in a line through the middle and - voltages in the bottom half. This keeps the potential difference between any two pins to a minimum. when possible I leave unused pins around any especially high voltages. I also test with a insulation tester. At 1000V the insulation resistance must be off the scale and there must be >50Gohms resistance at 2500V between all adjacent wires. https://www.uni-trend.com/html/product/tyyq/Electrical/UT510_Series/UT513A.html

another possibility is to either change the voltage set resistor or parallel it so that the voltage is lower. I do this on initial testing of high voltage rails. I generally parallel to get about 50 - 100V output, use a variac and check it regulates close to the expected output voltage. This reduces the voltages and if something does go wrong there is more chance of more components surviving... but as I say each to their own problem solving style.

You can and I have/do. I agree its not 100% reliable in circuit and I know it was not designed to be used testing in circuit. In some cases it will not be consistent when identifying a transistor because the circuit puts it close to the edge case for a recognition and probably has zero input protection but I still have and do find it useful in circuit. Its useful when you have two identical or near identical circuits. You can make comparisons and it at least narrows down what you might have to desolder. In some cases the circuit around the transistor effect the behaviour of the transistor so its miss identified or is right on the border of identification (as stated in the post above). But quite often it will identify correctly and I have never had it identify a bad transistor in circuit as good... its just another tool to be used on special occasions when you know what you are doing and you have to think about the results. For example when testing one of two individual transistors wired as a Darlington pair can identify the single transistor as a darlington. But again if it does the same identification with similar gain on both the good and bad rails then those transistors are likely to be good etc etc. I prefer testing this way than desoldering all the transistors and checking them all. But different people go about problem solving and troubleshooting in different ways. When I know it identifies a transistor correctly and consistently in one circuit and identifies the corresponding transistor in the other rail as two back to back diodes or says the gain in the good rail is say 100 and the gain on the other transistor is 2 then that transistor is suspect and a candidate for pulling and further testing.... (all of which I have experienced) Its more limited when you can't make comparisons between known good and known bad, but if it correctly identifies a transistor type and pin out then a quick look at the schematic for possible other transistors nearby it could be identifying instead then you can be reasonable certain that transistor is ok.

I mean just for the -260V / 300V rail. I entirely agree the rest of the psu looks like its working including the -560V rail the +300V rail sits on.

You may have done some of these tests already but for the -260V output (i.e. 300+ above the -560V rail, -1 inspect carefully for solder shorts, joints missing solder etc. 0. I would check the AC voltage going in is what is expected. 0.5 check dc voltage after bridge rectifier and smoothing cap is what is expected. 0.6 check the input side of the pass transistor Q19, if Q19 only has say 145V on the input side then it cant be expected to output 300V... 1. I would connect to a variac and see if the psu is actually regulating at 134V or if it varies with input voltage 2. I would check the voltage reference is outputting the correct voltage 3. If the op amp is in a socket I would swap it out for a known good one 4. I would check the voltage drop across the zeners diodes and check the value of the resistors in the voltage divider that sets the output voltage 5. if you have a peak dca75, de-solder the transistors and run an identify on each. I have found that most of the failed transistors I have tested on the dca either show up as back to back diodes, shorts or open, or crazy low gain compared to the spec. 5.1 although not as reliable, you can use the dca in circuit without desoldering the transistors first. Make sure the circuits are not powered and the reservoir caps are fully discharged before running any in circuit tests. if you run dca75 identify tests on the transistors on a known good rail and compare to the corresponding transistors in the bad rail. Any major differences may identify that component as a possible issue, since the rails have identical topology and the low voltage behaviour of all the transistors in the rails should be approximately the same. Do expect some identification fails (device not recognised or no device connected) since you are testing in circuit. But at least it gives you a point of comparison and can be quicker and safer than desoldering... good luck I have not used the DY294 in circuit, I certainly would not advise using any of the breakdown modes in circuit because the voltages used could easily over volt components. The peak dca75 identify function seems to be quite "gentle" and I have used it in circuit on various golden reference lv and hv boards, blue hawaii amp boards etc with no ill effect. Diode testing the transistors is also an option but I have found transistors that have failed but pass the multimeter diode check because they have failed in such a way that they now act as diodes with zero gain. In this respect peak dca75 identify is better. But multimeter diode check is better than nothing. NOTE any depletion mosfets may diode test as shorts or near shorts since depletion mosfets are fully on by default unlike enhancement mosfets...

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fair enough, sounds like you are well prepared. good luck with your build and finding the remaining transistors.

yep and make sure the silicon you have got is not fake.... This is why I chose to build a modern T2 - which I can highly recommend, I have not compared it to an original T2 but at least I know I all the transistors are from mouser with the exception of the 2sk216 and 2SJ79 which I sourced from a reliable forum member. I know members who have built an original T2 had issues and lost hundreds of $ in burnt NOS transistors... for me the modern T2 makes more economic and practical sense.

Seriously! OMG how many more bad spec sheets can we find in a week.... ok here's another spec sheet for the 2sa1968 (dated September 1998).. also says NPN... Sanyo datasheet (September 1998) also says NPN for the 2sa1967.... Hitachi datasheet (unknown month 1991) for the 2sa1960 says NPN.... looks like many of the 2sa196X sheets are wrong then...

Hi Kevin, I did not realise they where all the same company. 😞 The spec sheet I have (dated 1995 September) says the 2sa1968 are NPN: However we already have a specsheet which can't even get the pinout right for the G3R450MT17D so who knows anymore... Every single 2sa1968 they sold me (54 of them) all tested on the peak dca75 as PNP rather than NPN and broke down at around 200V instead of 900V utter junk.

Maybe the seller was just lazy and use a photo from elsewhere? yep my dy294 says around 1520V breakdown into an open circuit, so that's good evidence your transistors have a breakdown exceeding that. Also given the markings look correct I would say you have a winner and the price is not crazy low either. (I don't understand why the 294 displays a 1 in the left most column on the 200V range into an open circuit but does not do this on the 1500V range...). its possible the seller sells a mixture of fakes and non fakes. For example I purchased some 2sk216 and 2sj79 from littlediode on ebay and the sk216s where genuine and the 2sj79s where obviously fake, wrong markings, leads wrong, crazy low breakdown voltage. Returned them. Seller is still selling the same fakes years later. nikko on ebay also sells fakes. For example their 2SA1968 are fakes. they are not even NPN transistors....

time to get out the dca75 and dy294. Your photos look consistent with my known good from mouser. If they are fakes they are extremely good.

starcat THE EBAY TRANSISTORS LOOK FAKE the sellers negative feedback is also full of warnings of fake transistors, not as described, measured and out of spec, arrived not working etc etc. and many many cases of just not shipping anything at all. My known genuine have: 1. numbers and letters inside the circular indents. there should be left circular indent moulded words china and a single letter code, right circular indent a three digit code again moulded in my case 1 letter followed by 2 numbers. 2. all text should be moulded not printed or etched 3. the manufacturers logo is different 4. the main writing on the lower half of the body should be inside a indented rectangle. All of which agrees with the photos in the posting from John just above and is significantly different from the ebay listing you link to. Production may have changed over the years but I highly doubt the ebay devices are even cree. To attempt to determine if genuine. least reliable visual inspection of case, markings, <- some what reliable but production markings change over the years and some are easier to fake than others. However some fakers are so lazy simple things like the length of the pins, shape of the case are wrong. But the more practiced fakes will take another device with the same case and legs and rub off any markings and print new markings or laser etch new markings. I don't think many if any fakes would go as far as to remould cases. better visual inspection and then transistor identifier like a peak dca75. can identify pin out and type but not breakdown voltage which is important for power supplies and valve amps etc. I have received fakes that don't even have the correct pin out or are not even the correct type e.g. npn when they should be pnp etc etc. But again the more experienced and more prolific fakers will at least provide a fake with the correct type and pinout even if the breakdown voltages, wattages etc are very different. even better a device capable of testing breakdown voltages like a DY294... can provide breakdown voltages but not characteristic curves but this would not necessarily spot a fake that has similar pin out and breakdown voltages but wildly different characteristic curves. even better proper high voltage curve tracer and measure against spec sheet curves and or a known genuine parts P.S. I have reported multiple serial transistor fakes to ebay and ebay do not give a damn. I have tried explaining that not only is it fraud but the voltages involve constitute a potential risk to life and fire hazard... ebay don't give a damn. I went to pay pal... don't give a damn. The issue is many people don't realise about fakes and if they buy and don't test or use them they will probably leave good feedback about the transaction reinforcing the sellers reputation.... I fell into this trap myself when I first started I just did not know about fakes. As an experiment I even purchased over a period of more than a year a few transistors of the same type from the same seller and every time they were fakes. I used ebay returns each time providing evidence from the DCA and DY294 that they where fakes and the seller continued to sell the same fakes year in year out with no problems. I bet they even resold the ones I returned.

heads up, more parts (this time SMD) being deleted the 2sc3324 is going the way of the dodo - both the BL and GR grades. its used in joamats mini T2 mouser has plenty of stock of BL but no GR radio spares no stock farnell no stock digikey no stock of BL grade. but has stock of GR grade MMBT5962 is also going. Its used in Mr Carlsons capacitor leakage tester... mouser no stock digikey no stock farnell 3 left in stock radio spares has stock

I thought I was going insane. Here's the data sheet from mouser: source and drain are reversed compared to your datasheet for the same product also the current ratings are different WTF GeneSic..... https://www.mouser.co.uk/datasheet/2/169/G3R450MT17D-1919148.pdf

The pin out is NOT the same... G3R450MT17D is G S D looking from front left to right C2M1000170D is G D S looking from front left to right. don't worry the C2M1000170D will be back in stock in a few months... maybe.... Update: well I though I had derped but it turns out there are at least two versions of the G3R450MT17D datasheet and they don't even agree on the printout or current handling...

the smd version is at https://www.head-case.org/forums/topic/12733-balanced-to-unbalanced-board/page/2/ intermixed with the balanced to unbalanced board discussion. It looks like it is based on the 2017 through hole and does not have adjustment pots for dc offset. The 2018 through hole version has extra circuitry for controlling the dc offset and adjustments pots. I built the through hole version 2018 and found that with a 10K tkd pot on the input it had some high frequency instability with the volume control almost all the way up. I also got some dc offset with varied as the buffered heated up. The transistors gain seems to be very temperature sensitive and although I matched the pnp transistors and matched the npn transistors I could not get a good match between the npn and pnp - the slope of the curves were too different. I don't know if a smd version of the 2018 was released.

rather than create an adapter I soldered clip leads onto the pcb and ran the leads through the existing holes in the plastic case: The clips also allow me to use adapters for sot23 etc etc. (the same adapters I also use with my peak dca75 transistor tester and identifier)

I agree a lot comes down to how much you are going to build and your budget... however sometimes solderwick cant cut it. I once soldered an octal socket on the wrong side of a 2mm 2oz copper board.... solderwick that out 😱 desoldering station to the rescue, board and socket survived. the socket was ptfe round pin with tight pcb holes. 😬

good soldering technique and understanding what is going on when you solder: (a little wordy, somewhat dated and slow paced but the latter part of the video has lots of useful info). I heartily agree a good quality temperature adjustable soldering iron is essential and it will make soldering easier, more consistent and you will get better joints. Something along the lines of the hakko fx888d (although the use interface is horrible) that has descent power and is reliable and has repeatable temperatures. also good quality solder and good quality flux I would add a good quality multimeter, one that will not blow up in you hand if say by accident try to measure a 400V psu rail when the meter is in resistance mode... and yes I am speaking from experience here.... I was tired had already lecturer for 9 hours that day. its not cheap but I really like the brymen BM869s. - or one of the lower end models they seem to be very well made and robust. If the multimeter supports temperature probe(s) all the better for verify transistor case temperatures are not excessive etc. joe smith one you tube has done some excellent videos comparing and torturing multimeters for reliability and high voltage tolerance. for proper verification of stability, checking for clipping, etc a signal generator and scope are necessary. For a signal generator the bare minimum would be the analog output of a sound card on a pc and some software to generate sine waves, triangle and square. given the high voltage outputs and rails the scope needs to have switchable x1 and x10 probes (x10 is actually divide by 10 so you can get 400V down to a more manageable 40V). Scopes can be dangerous to use since the ground wire on the probes is actually earth referenced and is clipped to something in the circuit which is not at earth potential you get the possibility of a short to ground.... Some form of desordering to 1. fix mistakes, 2 make repairs. The cheap option is solderwick or a spring loaded desoldering pump. The far more expensive option is a desloldering station. For me using a soldering iron and solder wick has resulted in to many lifted tracks and is too slow and clumsy. something like this works well and is worth its weight in 2sj79s. There are many similar types out there. it is temperature controlled and has a vacuum pump to suck out the solder. For safety a variac is also very useful it allows you to slowly increase the voltage going into the psu so that if there is an issue it would hopefully manifest at lower voltages and hence reduce the collateral damage once you get more serious a transistor tester and identifier can be very useful especially to check for bad components or to post mortem when the "magic smoke comes out". It can also do small signal transistor and led matching. if you are going to do any surface mount soldering there are multiple ways to do it. fine tip soldering iron, hot air station, reflow oven. Magnification is useful - . The cheap ones can be really uncomfortable and can slide off your head easily but if your eyesight is not 20/20 I find them essential for surface mount and for generally inspecting joints etc. now some "luxury" items to make life easier etc The duoyi allows you to test high voltage zeners and also aids in detecting fake old stock transistors by providing non destructive transistor breakdown voltage testing. The instruction manual is crap and the sockets are junk. But with some modifications it works well. another luxury is an LCR meter - this can allow you to match capacitors and inductors and also can measure lower capacitances e.g. a few PF than a multimeter can manage. It can also measure the effective series resistance of caps and other parameters so you can compare caps and identify worn out caps in old equipment. super luxury items because you are addicted to building: distortion analyser super luxury? ultrasonic cleaner. flux residue can result in joints degrading over time and at the voltages some stax amps work at e.g. the T2 the residue can conduct and cause failures. super luxury: sometimes the provided gerbers are the wrong shape, don't fit your style and you wish you could change them. Sprint allows you to import gerbers, modify and re-export. Its relatively cheap. https://www.electronic-software-shop.com/lng/en/electronic-software/sprint-layout-60.html?language=en super luxury: sometimes you want to make your own schematics: https://www.electronic-software-shop.com/lng/en/electronic-software/splan-70.html super luxury: hands free thin probes for smd or when you don't have 3+ hands available. (The same company also sells hands free multimeter probes). disclaimer, all items shown here I own personally and use regularly. However, other builders may have their own favourites and peoples priorities and build styles vary. So these are suggestions and nothing more.

GR78xx and gr79xx are surface mount versions of the golden reference LV without the input or output smoothing capacitors. In general the golden reference LV come in dual (both positive and negative supplies on one pcb) or separate plus and minus pcbs. The gerbers can be found at: https://drive.google.com/drive/folders/0B_iJFfZStuVhSE5nOHBVdTByR1k the latest dual golden reference that I know about is goldenreference6D.zip this is marked on the pcb as version 0.45: the dual output board has provision for 25mm diameter input smoothing cap and optional output on led. https://drive.google.com/file/d/0B6JqIzEX9jZ0LTQ4ZG9HTDE2U0k/view?usp=sharing the individual rail pcbs are goldenreference6minus.zip and goldenreference6plus.zip: https://drive.google.com/file/d/0B6JqIzEX9jZ0ejFrM2lQZnFMa0U/view?usp=sharing https://drive.google.com/file/d/0B6JqIzEX9jZ0R1NpaDNuSzl4NHM/view?usp=sharing there is a goldenreference7plus.zip and minus but the pcb markings for them say 0.43 and do not have an option for a led showing the output is on, however the board allows for a larger diameter input smoothing cap at ~35mm diameter. https://drive.google.com/file/d/0B6JqIzEX9jZ0UFRaQzJSd1UwOTQ/view?usp=sharing and https://drive.google.com/file/d/0B6JqIzEX9jZ0YksyazZ0QXZ5djg/view?usp=sharing