I hate to be a stickler, but I think the amp will sound much better running as it's intended to, at the proper plate voltage and current on the output stage, which should be 130mA. Personally I would revert to the original 5U4 rectifier.
cosme
New Member
One of the monoblocks had a good run. Started hearing a slight hum and then it started blowing fuses. Checked connections and components and couldn’t find anything amiss. I feared a short circuit within the power transformer, and long story short, it started smoking and crackling. Took the ends off, visually inspected and one of the leads broke off with the slightest of touches.
RIP
RIP
albusark
Dynaco Fan
To me that means it frayed apart from the solder point to the internal wire, and with just a few strands left it essentially became a fuse that broke apart (the hum). This should absolutely be repairable by making a new bond to the coil wire.
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cosme
New Member
Not my cleanest work but I made an attempt to dig out a bit more of the wire that snapped off (and the neighboring wires while I was at it).
First image is the exposed wire. I believe my amplifiers are from the first (or at least very early) run. The cloth wrap flakes completely off very easily and the metal wire itself is very brittle.
Second image is my attempt to bandage the connections up and give additional insulation.
I was able to get it up to 120 VAC on the Variac with no illumination from my dim bulb tester. Lasted a solid 30-40 seconds before it went awry again and dim bulb tester glowed super bright.
May try again tomorrow. Tried to be conservative with my excavation attempt but may be a bit more aggressive tomorrow. Not much to lose at this point.
First image is the exposed wire. I believe my amplifiers are from the first (or at least very early) run. The cloth wrap flakes completely off very easily and the metal wire itself is very brittle.
Second image is my attempt to bandage the connections up and give additional insulation.
I was able to get it up to 120 VAC on the Variac with no illumination from my dim bulb tester. Lasted a solid 30-40 seconds before it went awry again and dim bulb tester glowed super bright.
May try again tomorrow. Tried to be conservative with my excavation attempt but may be a bit more aggressive tomorrow. Not much to lose at this point.
albusark
Dynaco Fan
Reminds me of these decware zen triode kits I built for a friend (monoblocks). It was my first time working with Edcor transformers, they are very well made. The paint on them smelled fresh when I received them, so I guess they're made to order? Anyway I like the blue aesthetic on the Mark III with the new boards.
cosme
New Member
Looks great! I’ve heard nothing but positive things about Edcor.
I had meant to ask what driver board set up are you running?
Edcor output transformers are hit and miss unfortunately. The SE models seem to have more consistency. The CXPP models are the ones more concerning. If you buy any CXPP models, be sure to test them for frequency response (if you can) because they can vary wildly from great to horrible in a feedback amplifier.
This has been my experience and not just with one pair, but 5 or six pairs of CXPP's.
This has been my experience and not just with one pair, but 5 or six pairs of CXPP's.
albusark
Dynaco Fan
Well since there's basically zero information about these zenkit builds, I will add that I was told by Deckert to add a couple drops of super glue into the holes where the windings come out of each transformer as he had issues with Edcor wires just ripping out while building. I did that and had two smooth builds. Never heard a decware amp and not personally interested, but these DIY boards do have a high quality sound. If building consult the forums or call the company because the instructions for the kit are trash.
Now that we're on the conversation, I hear often that Dynaco transformers are legendary to "ok/good/great" depending on the person. So to the vets here, what companies and brands made the greatest power and output transformers?
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albusark
Dynaco Fan
For sure try again, but it may be an internal short between windings.
Was the rectifier tube removed for this? If there is a short somewhere on the DC side of the rectifier, ~30 seconds before it goes full bright might be about how long it takes for that to show up.
If its bright without the rectifier then I agree it sounds like something within the transformer. Unfortunate but at least power transformers are easier and cheaper to get than outputs.
If its bright without the rectifier then I agree it sounds like something within the transformer. Unfortunate but at least power transformers are easier and cheaper to get than outputs.
cosme
New Member
Yes, this was with the primary leads hooked up to the variac and all other windings disconnected.
The P782 is out of stock at Dynakit and Triode Electronics has theirs at $399. Quite the jump in price in the past year or so.