[FarisElek]

Yeah I just used random pots. I have a bunch laying around from previous projects where I got the wrong pot. I'm not too worried about them sticking out a little. I think it looks kind of cool.

What fuse are we supposed to use with the SS Psu? I'm also going that route due to the possibility of smoke.

Also, are you sure we used the unregulated side of the PSU? I know we are not supposed to use regulators but it's very confusing. I haven't gotten any real advice on the PSU from Gregory.

Ryan

[mikeij]

The goal is to protect the transformer from a short/over current condition, and it's rated at 550VAC at 230mA.  I got 600VAC rated 500mA slow blow  fuses.   I would have preferred a lower mA rating or a fast blow, but I couldn't find anything.  I'll probably keep a current probe on one of the legs for a while to be safe.

No, I'm not 100% sure about anything with this PSU.  I've done some continuity tests to see where everything is routed, but haven't done any math to see if values and expectations are correct.  I followed what he said to not populate, and am assuming that since the regs aren't on there we're not supposed to use the regulated output - but that's just a hypothesis.  I need to double check my layout a little more.

[FarisElek]

Damn that stinks! I didn’t think the resistors and caps in the lower right of the psu went to the unregulated side. But I didn’t check. Just assumed. So I installed SMA into the regulated side. I guess I better look into that.8’ wiring the output transformers tomorrow and was planning on testing voltages tomorrow. I’m nervous tho!!!

[FarisElek]

Wiring output transformer not as straight forward as I thought it would be.

Gregory's inputs for the transformers are labeled primary high, primary low, secondary high, secondary low, 300v CT, and then there is a spot for the secondaries to join.

In my Edcore transformer I have Plate, screen, B+, screen, plate.

My instinct is to:

Connect the two secondaries at "secondary hi" and "secondary lo"

"Primary h"i being the  first Plate according to continuity, so I'd connect "plate" to that one there.

"primary lo" I'd image is the second "plate" wire on the transformer?

B+ = 300v CT


But that leaves me with the two "screen" wires on the transformer. Do I attach the plate and screen together?


Here is the 9185 datasheet that the circuit is designed for
https://www.sowter.co.uk/colours/9185.pdf

and here is the edcor transformer datasheet:
https://www.edcorusa.com/content/images/thumbs/0005883_cxpp10-8k_100.png

[scott2000]

But that leaves me with the two "screen" wires on the transformer. Do I attach the plate and screen together?

Sounds like you don't need to worry about using the screen wires from the Edcor in Gregory's circuit .

[FarisElek]

Thank you Scott2000 for the reassurance. I've isolated the un-used screen wires and have them hooked up and ready to go. I tried turning it on today but my fuses zapped right away. No smell or smoke, just insanely underrated fuses.

The original Gates manual as well as the Zayance Sta level use a 2 amp slow blow. I used a 500ma slow blow and watched voltages as it turned on. It didn't even make it on for a a second. I got 1V lol. I imagine since this is a Dual it might need closer to 4amp. I bought some 2, 3, and 4 amp fuses.

Ryan

[mikeij]

This is what it looks like to me:

550VAC - the transformer is rated at 230mA.  The fuses are only on this secondary winding.   If you're blowing fuses, I'd check your load resistance first before upping the fuse value.  Also, make sure your fuses are rated for 600VAC.  I had to order new ones.  It looks like the Gates only has a fuse on the 110AC wall input side, which the dual STA has as well.  That's where I would expect the 2A to 4A slow blow to be- the one that's similar to the Gate's schematic. 

5VAC - It's not fused, and doesn't look like this is needed since it only powers the rectifier tube screen.

6.3VAC - This is a high current secondary for tube heaters.  This is also unfused.

According to the Gates schematic, it's fused on the 110VAC wall which takes into account all secondary winding currents.  The Gates PSU is significantly different than this PSU.

Again, just my observations.  Hopefully I'm looking at this correctly.  I just got a Mouser order with xfrmr and choke, and the case should be arriving this week.  I made a visio block diagram of the PSU, but I need to double check that and probably make a schematic.  I installed KiCAD over the weekend so will probably try and do that this week.

My assumption was that the regulated high voltage output was for when the regulators were stuffed and the tube rectifier was used, and that the unregulated high voltage is when the diodes are used instead of the tube and the regs are not stuffed (per the big red 'X' in the errata). 

[mikeij]

I also wanted to show the Voltage/Current target from a Gates schematic.  This is for 1 unit, and this is on the high voltage output just after the choke (L1).  It looks like the target we're shooting for is 300V and 80mA per load, so 160mA for both boards.

So,  if you're popping 500mA 600VAC fuses, I'd strongly suggest reviewing your boards.  They're more than likely popping for a reason.

[FarisElek]

I popped 240v fuses at 300ma. I bypassed the fuses on the PCB so I was blowing the ones off the IEC. I probably should have used the fuses on the PSU board but at the time I made that decision the build seemed very straight forward 

I'm installing the fuses after the secondary windings just in case. Getting the fuses you recommend.

Can you do me a favor and let me know how much resistance between 6.3v low and ground you have? I have just under 1ohm (1.5 ohm and slowly moves down to 0.8 ohms) and I can't find out if that's normal...

[mikeij]

I don't have tubes or audio transformers yet + a couple of components that just arrived today, so I'm not quite ready to measure yet.

Heating elements in general can be tough - and I think the same holds true to tube heating elements.  They usually have a low resistance, so it can be hard to tell vs a short to ground - which is why they have a significantly higher current rating. 

I'm still learning about this as I go as well, and you're a little further along than I am, so I'm looking forward a bit, but when I get to the point of applying power, (just thinking out loud) I would expect that if the transformer is rated for 6A, I would expect both boards to draw 3A max - hopefully closer to 2A for working headroom.   In that case, if you measured a minimum of 3 ohms per board, you should be ok for the transformer.  This is really close to continuity on a lot of meters, so if you're just checking for continuity to ground, it might give a false positive.

[FarisElek]

Perfect! Your response is what I figured but I also am too new to this to feel certain about any of it. Honestly, I was extremely careful with selecting parts and have put too many hours thus far into wiring, checking diode direction, asking Gregory stupid questions, etc. I think everything is probably good.

I'll receive the fuses and be able to test by the end of the week. I'll report any findings.

Best,
Ryan

[mikeij]

Sounds good.  I finished the schematic of the high voltage section, just thought I'd share.  If you or anyone else find any errors, let me know and I'll revise and re-post.  But, I think it solved the questions of what the regs did and which outputs to use - unreg v regulated.

It looks like you're right, we should still use the regulated output.   I'm not sure why he added the unregulated dropping resistor, but it looks like he left it out of the errata for a reason. 

[FarisElek]

Got the fuses and installed them. Flipped her on. No smoke, no smell. All of the pots on the PSU appear to do almost nothing...

I was able to max out the 300v voltage on the mainboards to 286. 6.3v heater maxes out at 6.1. Getting 109v at the resistor in front of the input transformer that says 105v. Getting 2.6v on R20.

I seem to have less than 1ohm...maybe even less than 0.5ohm on "6.3v LO" Thus when it's on I'm getting no voltage on it.
Meters don't work and it seems that the center pin of the SMA for VU is 70ohms. It's not getting any or little voltage too.

Using Ecore output transformer and am 75% sure they're hooked up right as I'm using the plate wires, the secondary wires, and the CT wire and not using the screen wires.

I'm not using all the PCB mounting screw areas. Is there any that are completely necessary?

Left channel works but is thin sounding. Control panel for channel one works too.

Right change has sound but control panel doesn't do anything. Weirdest thing is that the moment I turn it off and the tubes are powering down, the control panel will work like normal for that couple seconds before its completely powered down. A grounding issue?

Not using LED dropping resistor or LED. Is it necessary?

Edit: Still not getting anything at 6.3vlow, but I swapped the control board ribbon cables and was able to control output with one panel and input with another and get nice full sounding audio. Think something is up with my ribbon cable connectors...Think I'm going to just buy a whole bunch of sma cables and connectors just in case.


Edit #2: removed control board and 300v has become 300v when I put the trimmer to least resistance. 6.3v with least resistance too. Swapping control boards made a difference. Something is up my with them. I still think it has something to do with the ribbon cable/header.

Still don’t know if “6.3v low” is messed up or something. No voltage there. Are we supposed to jump the fixed resistor or the capacitor that the eratta says to remove on the control board? If I wasn’t told specifically to jump something then I just left it blank.

[FarisElek]

So good-ish news. I got ahold of Gregory and it seems "6.3v lo" is supposed to be grounded, So my 6.3vlo being grounded is good and all my voltages are within 5 volts across the board. I think maybe the eratta data on the PSU was for the old PSU as for some reason my 6.3v is 6.3v with the pot turned completely off and the same goes with my 300v. It's more like 296-298v completely turned off. I can live with this. I don't really want to swap out any resistors in hopes to be to bring it exactly to 300v.

I've also figured out the problem with the control board. I'm fairly certain it's poorly crimped ribbon cables. I'm opting for SMA cables on every connection to avoid this. My meters weren't working but they were connected to the control board so hopefully that will be fixed as well.


Ryan

[FarisElek]

I got one channel working perfectly and another is thin sounding and has voltages jumping up and down on pin 3 and 5 of the 6v6, the primary high and low (plate voltages), the input transformer, and R19, R20, and R33. Probably more places but those were the ones I found.

Swapped tubes, output transformers, control panels, and cables on both channels to try to find the culprit and came out with nothing. Worried it might be the input transformer.


Ryan



Edit: I’m still working on it but I think my biggest realizations are that you should probably opt for SMA connectors on the entire build and that you should clean the heck out of the PCB’s. It seems like there is plenty of space and the flux isn’t that big of a deal as long as you do a minor clean, but I think I’ve found that the build is extremely sensitive and “optional” means extremely important.

[FarisElek]

Just a heads up that I have one channel working perfectly. Like PERFECTLY. Sounds amazing. 1ma Simpson meter with changed faceplate and everything.

Second channel is NO GO. Voltages on both sides of resistors are the same on both sides. Had to reach the tube pins so I've only checked some.

HOWEVER, I found that one side of the 27k resistor on the main board regulator circuit is way off from the working channel. One side says 7vdc. The working channel is closer to 27vdc. That resistor however is totally reading fine when I pulled one leg out. After that it looks like it goes to the 5k pot. Maybe the pot is bad? If anyone had any ideas that would be great. I'm working on a song right now and would love to use it on master bus. I've got other stuff but I'm super impressed by the working channel.

Ryan

[Bowie]

Just a heads up that I have one channel working perfectly. Like PERFECTLY. Sounds amazing. 1ma Simpson meter with changed faceplate and everything.

Second channel is NO GO. Voltages on both sides of resistors are the same on both sides. Had to reach the tube pins so I've only checked some.

HOWEVER, I found that one side of the 27k resistor on the main board regulator circuit is way off from the working channel. One side says 7vdc. The working channel is closer to 27vdc. That resistor however is totally reading fine when I pulled one leg out. After that it looks like it goes to the 5k pot. Maybe the pot is bad? If anyone had any ideas that would be great. I'm working on a song right now and would love to use it on master bus. I've got other stuff but I'm super impressed by the working channel.

Ryan

Check your solder joints, particularly at your grounds and areas where wires attach.  Not just visually, but with a meter to see if there's continuity from one component to another (don't read it from the board or the solder itself if possible). Cold joints can sometimes look great so don't go by appearance.

[FarisElek]

Yeah. I already went through the entire board and resoldered every point just in case and then cleaned it super well. It turns out that voltage that was off was because I forgot to change the trimmer resistor after altering voltages to see if it made an impact on the sound of the unit.

Channel 2 appears to have perfect voltages and I still have no explanation. Just no low end at all. Feeling at this point it has to be the input transformer. It's the only thing I haven't swapped between the two channels.

[FarisElek]

Welp. I carefully removed the Lundahl transformer from the PCB and began testing the leads. The Primary Low pin came right out from hooking up an aligator clip. No pulling. Just gravity from attaching it. I believe this was my missing low end problem. Does Lundahl or K&K audio offer warranty for this sort of thing? is it possible to open up a Lundahl and just reattach the pin. This has been a headache.

Ryan

[FarisElek]

Saw somewhere else on here someone had a similar problem and lightly pushed the pins of the lundahl in while heating with a soldering iron. Fixed my transformer. My Sta Level is 100% functional.


Ryan

EDIT: threw it into my rack and now both channels don't work right. Completely high passes tinny sound. Output brings volume up and then down and then up again and you turn to the right. both channels,. Why me?

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