Happy New Year!
Have you worked with tube voltages before?
If I understand your post you are getting 270VAC instead of the 210VAC before the B+ diode and ground
What are you measuring the voltage with? RMS or peak to peak?
If that is correct you most likely getting greater than 20VAC before the heater diode bridgeAlso if the AC voltage drops from 270VAC to 110VAC something is loading the B+. Is this with a microphone connected? It reads like you have added resistance to ground loading the B+ rail or something(s) else wrong.Is this the transformer? http://catalog.triadmagnetics.com/Asset/VPT230-110.pdf
if the 15VDC zener burned Is this the schematic? https://dl.dropboxusercontent.com/u/43869772/U67/Du67-PCB%20PSU.pdfI am surprised it was not modernized
Was the zener heatsinked?
Are you testing the power supply without a heater load? This can be an issue.
1) check you have 20VAC before the heater power supply diodes if much higher this can be a problem2) check R2 22ohms 2watts.
The Zener in this circuit is a shunt regulator. In this case R2 22ohms is part of what sets the current in the zener with the heater load connected when the load is disconnected the current shunts to the zener
The total current is the current in the zener and the current in the tube heaterIf there is no tube heater connected max current will flow in the zener and the zener will be dissipating the max amount of heatIt is a balancing act to build a simple zener shunt regulator that can survive without a having the load connected
HELP! First of all I'd like to point out that I am a novice but do have a basic understanding of schematic and component reading. I know how to use a DIMM and I'm trying to better my knowledge on a day to day basis. I've built a total of 5 mics so far, 3 of which were kits on PCB and 2 of which were point-to-point. I'm pretty good at following directions and all my mics are working. That's why I'm stumped on this one.I'm having such an issue with the PSU of this build... First the 15V Zener died on me and I've replaced it (I mean it really burnt out). When I hook up the Triad (VPT230-110) to AC power (without connecting it to the PCB) I get a reading of about 270 VAC. Seems normal I would say... *at this point I guess I should point out that I'm living in Germany where we have 230 V*. When I connect it to the PSU and measure the VAC at the "AC in" on the PCB (terminal connectors) I get a reading of 110VAC and the unit is humming relatively loud. I've noticed that the Triad is getting hotter than I remember them getting. I've tried turning the Rtrimplate with no difference. I've doubled and triple checked the values of the components and I'm sure that all is correct.Any help would be greatly appreciated Thanks!Dennis
When you are ready with your PSU first test it with load resistors, for heater 33ohm/2W(pin 3-4), and for B+ approx 480kohm/0,6W (pin5-7 as the ground points 3-7 are connected) if your can set your voltages with this way according to the descriptions(-6,3V heater,and 210V B+) then it will be also fine with mic connected.
A buzzing transformer is a sign the circuit is drawing too much current. Could be a leaky capacitor (almost easier to just replace all of them vs looking for the faulty one)
"No, I'm getting 270VAC from the Triad Tranny when it's connected directly to 230V and I measure the black and yellow wires. As soon as I hook it up to the PCB of the PSU I measure 110V. It should be ~270VAC as stated in the build guide here: http://www.vintagemicrophonepcbkit.com/D67B/D67B/D-67%20Build%20Guide.html"I'm not sure you should be reading 270VAC on a naked Triad VPT230-110 transformer.The build guide says:"Apply power to the PSUCheck voltages at the AC input of the PSU PCB~270VAC at the HT input"This implies that the transformer is attached/installed in the PSU (has load).
But you are measuring a naked transformer, not connected to anything but the AC mains and the multimeter, right?
According to the data sheet here: http://www.mouser.com/ds/2/410/media-1067313.pdfInput Voltage: Series: 230VAC, 50/60HzParallel: 115VAC, 50/60HzOutput Voltage: Series: 230VAC CT @ 0.11A Parallel: 115.0VAC @ 0.22A4. Voltage Regulation: 12% TYP from full load to no loadGetting 270VAC on what should be a 230VAC output is a 17% jump. That seems wrong.Also, double-check your jumpering (series vs. parallel) of the transformer's windings. This quote may be important:"Primary and secondary windings are designed to be connected in series or parallel. Windings are not intended to be used independently."If I understand you correctly, you have 230VAC input, so you MUST set up the primaries in series:Input1: Series – BLUE and BROWN, Jumper GRAY to VIOLET
Perhaps the problem of the secondaries dropping down from 270VAC (still way over the 230VAC) to 110VAC is due to some problem with the jumpering of the secondaries.
If I understand the U67 PSU Build Guide correctly, the intended output of the transformer is 210VAC, so you would run the output secondaries in series too:Output : Series – BLACK and YELLOW, Jumper RED to ORANGE230VAC in, 230VAC out, right? This is basically a "unity" transform.
What is your AC mains voltage? It should not be 270VAC at the wall, so it is weird that you are getting 270VAC on the output of a naked transformer set up for unity transform.
I know you're trying to do switchable 115VAC/230VAC input, but for now, it is probably best to remove any switches on the input side and just go with 230VAC input.
I have the exact same toroidal transformer (VPT230-110) for the build I'm doing (poctops D-47) and I get 260VAC from the secondary. So that is also off I guess!(?) Have not connected it to the PCB or anything...havn't even tried so far....Hooked it up the exact same way, i.e. Grey to Violet in series, Blue and Brow to mains (which is about 220V here in Sweden) then on the secondary Red-Orange i series, measuring from Yellow and Black./Johan