Hey ya all! New to the forum so howdy! Pat here from Olympia WA. I have an old Firstman Vanguard 200 that I'm rebuilding. Before I make any real moves I'm wondering if anyone can lay some eyes on the power transformer and take some best guesses as to the taps. I think I know what I'm dealing with but am not sure. In the picture from top left to bottom right I'm pretty sure the taps are as follows, yellow neutral from power switch, center unknown, right yellow line from fuse holder, bottom left white rectifier, black ground with capacitor to neutral yellow, white rectifier, black ground, yellow heater. The yellow and black wires going off to the left are to an indicator light. Gray cord on top is power, neutral going to power switch, the other line side is to fuse. Last, lower right yellow wire is going to heaters.
Can anyone confirm these assumptions?
Two questions, the yellow heater wire is only attaches to half the tube sockets heater turrets, in series. The other half of the heater turrets are series wired together to ground. Does this sound correct?
Next, how would I wire a tube rectifier given there appears to be no rectifier heater taps?
That's it for now!
Thanks for the looks,
Pat
Can anyone confirm these assumptions?
Two questions, the yellow heater wire is only attaches to half the tube sockets heater turrets, in series. The other half of the heater turrets are series wired together to ground. Does this sound correct?
Next, how would I wire a tube rectifier given there appears to be no rectifier heater taps?
That's it for now!
Thanks for the looks,
Pat
Hi Pat, and welcome.
There is a diyAudio group for instrument amplifiers, where somebody may have more specific knowledge, but I'd add a comment about this scary looking device: that capacitor looks like what's now called a "death cap", meaning one with the ability to kill as it ages and fails. The several flying unconnected wires don't instill confidence. Please be very very careful playing with this contraption; it can absolutely, positively kill you or someone else using it. Heads up!
All good fortune,
Chris
There is a diyAudio group for instrument amplifiers, where somebody may have more specific knowledge, but I'd add a comment about this scary looking device: that capacitor looks like what's now called a "death cap", meaning one with the ability to kill as it ages and fails. The several flying unconnected wires don't instill confidence. Please be very very careful playing with this contraption; it can absolutely, positively kill you or someone else using it. Heads up!
All good fortune,
Chris
Ah yeah! Was planning on removing the death cap and adding three wire plug/chassis ground. Thanks for the heads up!
Quite worried about this post and your safety.
1) mains and most tube voltages are DEADLY. Serious.
2) NO GUESSING ALLOWED, you NEED the proper schematic and/or have a qualified Tech measure voltages.
Again: no guessing.
3) you have no clue, you shouldn´t be inside that chassis at all.
For starters, you confuse/mix series with parallel wiring, that alone disqualifies you, sorry.
You have a vague idea abut adding a tube rectifier for which you find no windings.
Please get a qualified Tech to deal with that amp.
1) mains and most tube voltages are DEADLY. Serious.
2) NO GUESSING ALLOWED, you NEED the proper schematic and/or have a qualified Tech measure voltages.
Again: no guessing.
3) you have no clue, you shouldn´t be inside that chassis at all.
For starters, you confuse/mix series with parallel wiring, that alone disqualifies you, sorry.
You have a vague idea abut adding a tube rectifier for which you find no windings.
Please get a qualified Tech to deal with that amp.
Sounds correct. So the top row is the primary, and the bottom row are HV1-CT-HV2 and HEATER1 HEATER2
So all the heaters are grounded on one side. Not uncommon, but if you upgrade the amp it would be better to wire them conventionally, and add an artificial centre tap.
You can't. Well maybe if you used a rectifier with an isolated heater like the EZ81, or add a separate heater transformer, but frankly I would just abandon the idea of a tube recto.
Hey all! Thanks for all the warnings and concern.
The Firstman amps have no schematics available online. I did get the amp a decade plus ago and it was a functioning unit. I wasn't into the sound and stripped it with the intention of rewiring it. Never got around to it so here we are now. The amp had a duel EL84 a power section, ECC83 driver, ECC83 termolux, and ECC83 preamp and Diode based rectifier. Both transformers are in a state as I found them.
The real question is can I add a tube rectifier, looks like no as Merlinb stated. There are no rectifier heater taps. But EZ81 was what I was thinking as I was going to model after a Marshal 18watt. No biggie, diodes it is!
Merlinb, to the artificial center tap mod, is there a schematic you could reference? I've googled around and have an idea but, picture worth a bunch of words! Hahah!
Thanks all!
Pat
The Firstman amps have no schematics available online. I did get the amp a decade plus ago and it was a functioning unit. I wasn't into the sound and stripped it with the intention of rewiring it. Never got around to it so here we are now. The amp had a duel EL84 a power section, ECC83 driver, ECC83 termolux, and ECC83 preamp and Diode based rectifier. Both transformers are in a state as I found them.
The real question is can I add a tube rectifier, looks like no as Merlinb stated. There are no rectifier heater taps. But EZ81 was what I was thinking as I was going to model after a Marshal 18watt. No biggie, diodes it is!
Merlinb, to the artificial center tap mod, is there a schematic you could reference? I've googled around and have an idea but, picture worth a bunch of words! Hahah!
Thanks all!
Pat
Looked into it a little more. Given the PT windings, looks like the heaters are what they are, same with the rectifier. Much like an old Fender. I'll just go with it as is! The ACT will help with hum so will add that as well.
Thanks again for the looks all!
Thanks again for the looks all!
What do you intend? If it's an audio amplifier, I'd stop thinking of a tube rectifier. If it's a geetaar amp, well, maybe...
Best regards!
Best regards!
To find what tap is what on an unknown transformer it's a good start to use a digital multi meter (DMM) or other volt/resistance meter to find what wires, what taps join to another tap. With the meter set to ohms/resistance measure the DC resistance between each lug/wire, all wires should be unsoldered for this, just take a picture and make a drawing and or label each wire first before unsoldering. Primary windings usually have a resistance of a few hundred ohms or the low kilo ohm range. Heater windings and low voltage wndg's a resistance of a few ohm's or the low tens of ohm's.
To be certain one would usually connect what you think is the primary to a low voltage, say 10v AC. You can use another tfmr for this with a low voltage secondary, connect that to the mystery primary and measure what voltages you get at the other windings.
One thing that's a bit concerning about the transformer is that the taps/lugs look very close to the chassis hole. It's be a good idea to insulate them with shrink tubing. That or at least gently bend them out of reach of the chassis.
Good luck, Andy.
To be certain one would usually connect what you think is the primary to a low voltage, say 10v AC. You can use another tfmr for this with a low voltage secondary, connect that to the mystery primary and measure what voltages you get at the other windings.
One thing that's a bit concerning about the transformer is that the taps/lugs look very close to the chassis hole. It's be a good idea to insulate them with shrink tubing. That or at least gently bend them out of reach of the chassis.
Good luck, Andy.
Hey all, thanks for the info!
Merlinb, I appreciate the link! It's pretty much the info I need for the heaters! Looks like best I can do is a more effective heater line layout.
Kay, yeah, guitar amp. I was one to begin with, something like a 15watt EL84 amp. Real simple but I wasn't into the sound so I stripped it down and am rebuilding similar to a Matchless Spitfire. Given the PT I have to work with seems a diode rec with a sag resistor is the only way to go.
Andy, I appreciate the the walk through on identifying the taps! Also, yeah, the camera angle is pretty misleading but, I'm going to do as you say and insulate or better isolate them!
Merlinb, I appreciate the link! It's pretty much the info I need for the heaters! Looks like best I can do is a more effective heater line layout.
Kay, yeah, guitar amp. I was one to begin with, something like a 15watt EL84 amp. Real simple but I wasn't into the sound so I stripped it down and am rebuilding similar to a Matchless Spitfire. Given the PT I have to work with seems a diode rec with a sag resistor is the only way to go.
Andy, I appreciate the the walk through on identifying the taps! Also, yeah, the camera angle is pretty misleading but, I'm going to do as you say and insulate or better isolate them!
A sag resistor is a possible substitution of a vacuum tube rectifier. Anyway, I don't know if it is an adequate one. Remember a vacuum diode doesn't behave like an ohmic resistor. Try it, it's DYI fun!
OTOH, if the power transformer is apt, get an EZ81, whose heater can be fed from the same winding as the other tubes', and it easily copes with the plate current draw of an EL84 PP pair plus the small signal tubes. The EZ81 cathode to heater voltage rating usually is also sufficient. There are/were many industrial made devices with this layout.
Best regards!
OTOH, if the power transformer is apt, get an EZ81, whose heater can be fed from the same winding as the other tubes', and it easily copes with the plate current draw of an EL84 PP pair plus the small signal tubes. The EZ81 cathode to heater voltage rating usually is also sufficient. There are/were many industrial made devices with this layout.
Best regards!
Hey Kay! Thanks for the info! I wasn't sure about sharing the heater tap but there ya go! I'll give it a shot. The EZ81 was the tube I was thinking of trying to rectify with. As far as the number of tubes the transformer would be working with I'll drop the 12AX7 tremolo stage and place the EZ81 power draw there. Love tube amps DIY flexibility!