Low Heater Voltage on Herzog Clone

[The New Steve H]

I got my Herzog deal wired up and tried it out. No output yet. The heaters on the preamp and output tube are only getting about 3.5V AC.

Posting the schematic again. I used the lower drawing. As you can see, there is a footswitch relay on the same circuit as the heaters. I tried to do it the way the schematic shows it. I found a very small Fujitsu relay with a 6V coil (817-FTR-F1CA006V), and I used a 1N4007 for the diode. Of course, it was not possible to find out what kind of relay was in the original Herzog.

The footswitch circuit appears to work, except for not getting the heaters warm. The resistance on the switches goes to below one ohm when I use the manual switch to turn on the relay.

I don't know of any other problems with it. No smoke, no obvious shorts. I admit, I have not made a detailed study of all the voltages, but it's pumping plenty of DC into the amplifier circuit.

The current limiter isn't doing anything weird. Not flashing or getting extremely bright.

I'm tempted to find some other way to power the relay, or to remove it until I get the rest of the amp working.

[M Fowler]

I have to ask why you open so many threads on the same subject all concerning you building a Herzog?

Keep it under one so all reference to the build is available as one read.

[diagrammatiks]

the coil should be dc. the heaters should be ac.

the coil should not be ac.

[The New Steve H]

I talked to some other people about this, and the conclusion was that the diode and capacitor supply negative DC to the coil.

[marcoloco961]

I talked to some other people about this, and the conclusion was that the diode and capacitor supply negative DC to the coil.

One side tied to ground the other to -6 DC or more should work the relay. Just bypass the mute circuit, dis-connect the relay and try it again.

The heaters to the tubes should be wired off the secondary before the diode that goes to the relay, using the AC voltage. You don't have them wired on the other side of the diode do you? That would be feeding DC to the heaters, although that should heat them IIRC. You might try opening the contact on the man. switch to see if it is drawing so many milli-amps that it doesn't leave enough to heat the tubes. Does the PT have enough amps on the 6.3 to power the tubes and the relay?

Have you tested to make sure you have 6.3 VAC on the heater filaments directly off of the secondary winding before the diode?

[ChrisM]

I have to ask why you open so many threads on the same subject all concerning you building a Herzog?

Keep it under one so all reference to the build is available as one read.

+1

You need to do way more reading before you jump in on projects!

[Firestorm]

What does the 6.3VAC winding of your PT look like? You haven't accidentally used the center tap AND grounded one end of the winding have you?

[The New Steve H]

One side tied to ground the other to -6 DC or more should work the relay.

The relay works fine; the heaters are the problem.

You need to do way more reading before you jump in on projects!

Trust me; reading up on Herzog builds takes about 5 minutes. There is practically no information out there. I've looked.

What does the 6.3VAC winding of your PT look like? You haven't accidentally used the center tap AND grounded one end of the winding have you?

I have to admit, given some of the things I've done, this is a reasonable question. I will post the transformer diagram again. As you can see, it's two green wires with a green/yellow center tap, which I grounded. I put a trimmer between the wires to diminish hum, but I removed it just to make sure it wasn't causing the voltage problem.

Does the PT have enough amps on the 6.3 to power the tubes and the relay?

That's my concern. I'm wondering if the relay I chose dissipates too much energy. It's very tough to get info on this aspect of relays. At least for me.

I have not looked at the amp yet today, but I'm sure the 3.5V reading was AC, not DC. I will double-check, but my meter won't read DC when it's in AC mode, so I don't think this is a problem.

Have you tested to make sure you have 6.3 VAC on the heater filaments directly off of the secondary winding before the diode?

No. Time to rip my nice shrink wrap apart and measure, I guess.

[The New Steve H]

I just checked. The combined filaments on a 12Ax7 draw 300 mA. The filament on a 6V6 draws 450 mA. The transformer says it will do 2A.

Maybe I should measure the resistance of the relay coil?

[tubeswell]

Disconnect the heater winding wires from the circuit for a moment and (carefully) measure the VAC across that (just to check if its a winding problem). And don't let the windings short to anything when you have them floating around for this test.

[martin manning]

You need to do way more reading before you jump in on projects!

Trust me; reading up on Herzog builds takes about 5 minutes. There is practically no information out there. I've looked.

All the more reason to think the project through before you start!

[The New Steve H]

Really, I made a good effort on the Herzog. You can go back and see all the questions I asked (here and elsewhere) while I was trying to figure out the relay circuit. The schematics are full of holes, and no one builds these things, so I couldn't find anyone who had already solved the problem.

Eventually I reached the point where I had to start building and worry about the problems as they arose.

I guess I could email Garnet Amps, but I don't know how they'd feel about that.

[ToneMerc]

Eventually I reached the point where I had to start building and worry about the problems as they arose.

No, you chose to take that path. You are a self sadist, you love pissing into the wind uphill. Before you order parts or pick up a soldering iron you need to do more due diligence in order to prevent yourself from kicking your own butt.

TM

[Firestorm]

What does the 6.3VAC winding of your PT look like? You haven't accidentally used the center tap AND grounded one end of the winding have you?

I have to admit, given some of the things I've done, this is a reasonable question. I will post the transformer diagram again. As you can see, it's two green wires with a green/yellow center tap, which I grounded. I put a trimmer between the wires to diminish hum, but I removed it just to make sure it wasn't causing the voltage problem.

Okay. Take a look at the second Herzog schematic (actually the first one, chronologically) and see how you have wired your 6.3VAC supply different from that. Your DC supply for the relay is half-wave: one end or the wiring is grounded, the other one goes to the diode. Before the diode, that same end of the winding (the up arrow on the schematic) should go to pins 4 & 5 of your 12AX7 and pin 2 of your 6V6. Pin 9 of the 12AX7 and pin 7 of the 6V6 are grounded. This is the old-style heater wiring used in 50's amps; it gives then heaters a ground reference because one side of the heater supply is connected to ground and it works here because you need to ground one side of the winding to make the half-wave rectifier work. What (I think) you've done is grounded one leg AND the center tap, which shorts out half the winding. Heaters won't work, but the relay may be flexible enough to actuate on the 3.5ishVDC you're likely getting.

[The New Steve H]

No, you chose to take that path. You are a self sadist, you love pissing into the wind uphill. Before you order parts or pick up a soldering iron you need to do more due diligence in order to prevent yourself from kicking your own butt.

I enjoy posting here and getting valuable input on building and understanding amplifiers. I am polite to everyone here. I acknowledge response and thank people for their time. I haven't done anything to justify hostile or insulting comments. You will never see me posting an obnoxious comment about anyone else. I am an easygoing person. I don't bully people or harp on their mistakes. I don't flip out over trivia. I think my way is the right way to go through life.

I tried to understand this circuit before I built it. I scoured the web for schematics, and I came up with the half-baked drawings I have posted here. I asked question after question. I searched for and downloaded documents related to similar 5-watt single-ended amps. Really, there is a limit to what I can do, short of hiring an electrical engineer. Even experienced builders do not understand this schematic; their opinions on it conflict drastically. This is my fourth amp, and I have no training apart from a basic electronic course I took in college. I'm doing my best. I am not proactively trying to fail.

I could have chosen something easy, like a kit. But that's just soldering practice. I'm always going to look for projects that are more interesting.

If you have helpful advice, I'm glad to hear it. If you're just irritated because I chose a confusing project, why not ignore my posts instead of posting personal remarks? I'm sorry I made you angry, but I don't think there is anything I can do to prevent it from happening in the future. Truthfully, I think the mods should delete this whole exchange, in order to preserve the atmosphere of the board. I want to discuss amps, not personalities.

I'm going to take a break from posting. I don't want to cause a breakdown of civility. I'll figure this amp out on my own. If anyone wants to send advice via PM, I will be very grateful.

Thanks for the help, Firestorm. I'll poke around in the amp and try to apply what you told me.