sbelyo

My money is on the stray magnetic field so I'm going to go in that direction. I'll try and find an example of both tones so I can make an educated guess on that. I believe my power is asymmetric, I'm in the US and use 120V power so there is one hot leg, one neutral, and one ground to earth. Did I answer that right?

I will measure the current possibly this weekend. I suspect there is a good amount of headroom. Is it a problem if there is too much headroom? No DC on the line. I ran a dedicated circuit for A/V equipment Signal grounds are isolated from ground. The E pin is in the front left corner of the case by the power switch. There is no ground loop breaker scheme.

I can't add space so I'll try re-orienting and some mu-metal. Didn't know there was plactic plate. I'll look for one

Electrical hum that I hear in the headphones.

So over the past two weekends I re-cased my original Dynahi. It's always had a slight 60 Hz hum from the transformer (my best guess). The amp boards, psu and tranny are all in one 16" x 12" x 4" case from par-metal. This time I put the transformer in it's own aluminum project box with a cover and then put that in the case. Then I put an aluminum barrier plate that runs the length of the case in between the amp boards and the power side. I used unshield twisted pair wire to hookup the input and output of the amp. The hum is still there as it was before without any of that. My guess is that aluminum project box is not a good shield and I should use shielded twisted pair with a drain wire for the input and the output. Can I improve the shielding of the transformer using this http://www.digikey.com/product-search/en?mpart=11.5X12-6-1181&vendor=1067 or this http://www.ebay.com/itm/152045122881?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT ? And for hookup wire, does anyone have a suggestion for shielded twisted pair with a drain wire? Like maybe this http://www.markertek.com/product/bl-8451-100/belden-8451-22-awg-stranded-microphone-cable-100-foot-black

If you're not going to use se out is 4 pin ok then?

What is the correct zip file for the latest tested dual supply board?

Now that I've re-read the thread and want to build this amp. Is this correct ? For alps quad rk27 8/7/2015 6:02 PM 34599 alpsquad3.zip Current Dynalo SS board with through hole for everything except for pzta56 and pzta06 2/6/2016 9:25 AM 325771 kgdynalobal9.zip Current working and tested Golden Reference board used with Dynalo 6/7/2015 1:30 PM 339289 goldenreference.zip

Yeah, I built it way back in the day. It's seen a ton of use. Honestly I have no idea how many hours it's been running. There's been at least three or four times in it's life where it's been left on for days at a time. I will replace the electrolytics. I'm guessing the standard grade Nichicon's are ok to use? That's all that'll fit and meets the specs and is stocked by mouser or digikey

does anyone have a pair of the through hole boards?

It's running fine now. I put a 1.6 amp slow blow fuse in it and it fired right up. I guess it needed that extra few seconds on startup to charge the caps and the current was popping the fuses. The amp lived it's whole life in the old case with a 1.0 amp fast blow in it. At least I don't have to build another one

good point, Nichicon is all that's available it looks like

My next step was to recap it. I'll try the slow blow fuse or maybe borrow my dad's variac to power it up slowly first. Then order some caps. I saw some nice mundorf caps but they're snapin. Can I just staighten them and dremel the leads to fit the through holes?

I'd say 1500 to 1800 hundred hours over a 9 year period. I took the amp apart about 6 months ago wanting to re-case it and in the process I got hit by a truck so it took me about 6 months to recover to the point where I could work on it again. It hasn't had power since October maybe. Ti suggests switching to a slow blow fuse so I will try that today. Could it be the caps are just dead from age?

Ok, so I tested the board in and out of the chassis and the results are the same. There's no short from the inputs to the chassis or ground, or to themselves There's no short from the outputs to the chassis When I measure resistance on the outputs I get a short (0 ohms) for a solid second on -V to GND but then the meter ranges. On +V to GND the meter just ranges. I also measured the voltage on each of the caps and they all read just a few millivolts.

Thanks Pars... I'll check this when I get home. I didn't drop anything on it that I know of.

Diodes all show 0.368 voltage drop and 0L in reverse. These appear to be good. The transformer checks out ok when not connected to the PSU board. Fuse blows immediately when powering on with no amp boards connected. What could be next, the electrolytics?

I got lazy and trusted the beeper. The transformer is fine and the rectifier diodes seem ok, my measurements on them are above. What should I check next?

ok, diodes all show 0.368 voltage drop and 0L in reverse. These appear to be good. What could be next, the electrolytics?

ok, the transformer is good. its back in the case and does not blow a fuse. So it's got to be something on the psu board. How do I test the rectifier diodes with the diode setting on the meter? What value should I expect?

oh ok, I had assumed it was shorted because I tested another Avel lindbeg transformer and it doesn't set off the continuity alarm. I'll put it back in the case and see if it blows a fuse when it's not connected

4.8 ohms between the primaries and 1.1 ohm between each of the secondaries

For the secondaries if I check for continuity between orange and yellow its positive, if I check for continuity between red and black it's positive. For the primary the gray and brown wires are twisted together and the violet and blue are twisted together for 115V operation. If I check for continutiy between them it's positive. I cant figure out how it got this way. I'm not sure where to start looking on the board

I'd agree... Both secondaries short to each other and the primary shorts to itself. The primary does not short to the secondary. I'm leaning towards the board. I get a momentary short from -30 to GND and again on +30 to GND on the output. The meter rings continuity for one second then shuts off. Is that normal?

Can I test the rectifier diodes on the circuit with a meter?