Is img turned off?
Moderators: pompeiisneaks, Colossal
Re: Is img turned off?
If you have board-side connections for each pin, I'd check there rather than at the pin itself. I accidentally shorted two pins together and made some nasty looking sparks. If that's all you got, I guess just be careful.
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skyboltone
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Re: Is img turned off?
I'll second this.benoit wrote:If you have board-side connections for each pin, I'd check there rather than at the pin itself. I accidentally shorted two pins together and made some nasty looking sparks. If that's all you got, I guess just be careful.
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
*corrections made
Great suggestion in time. The voltage recording went flawlessly without sparks because I recorded at the other end of a wire when possible; and I predict that not all the voltages are ideal: * Corrections madebenoit wrote:If you have board-side connections for each pin, I'd check there rather than at the pin itself. I accidentally shorted two pins together and made some nasty looking sparks. If that's all you got, I guess just be careful.
V1 (12ax7)
P1: 213
P2: 0
P3: 2
P4: 68 AC (91 on standby)
P5: 68 AC (91 on standby)
P6: 234
P7: 0
P8: 2
P9: 68 AC (91 on standby)
V2 (12ax7)
P1: 250
P2: 0
P3: 3
P4: 68 AC (91 on standby)
P5: 68 AC (91 on standby)
P6: -1
P7: 0
P8: 0
P9: 68 AC (91 on standby)
V3 (6V6)
P1: 0
P2: 68 AC (91 on standby)
P3: 325
P4: 322
P5: 41
P6: 0
P7: 68 AC (91 on standby)
P8: 47
V4 (5Y3 GT)
P1: 0
P2: 353 DC (461 on Standby)
P3: 0
P4: 305 AC (331 on standby)
P5: 0
P6: 305 AC (331 on standby)
P7: 0
P8: 353 DC (461 on Standby)
Last edited by bcmatt on Sat Jul 26, 2008 5:34 pm, edited 2 times in total.
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skyboltone
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Re: Is img turned off?
We need to record the filament voltages as AC not DC readings. Do they glow normally?
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Re: Is img turned off?
Yes, they seem to glow properly.skyboltone wrote:We need to record the filament voltages as AC not DC readings. Do they glow normally?
V1 isn't as bright as V2 but that is likely due to it being Tungsol vs. the JJ in V2.
Thanks for the AC/DC correction. I have fixed it on the post above now.
So, are these pin voltages reading something somewhat believable everywhere that they should?
Re: Is img turned off?
(heheh, I love quoting myself)bcmatt wrote: So, are these pin voltages reading something somewhat believable everywhere that they should?
So, is the plate on the second valve on pin 6 supposed to be reading 0? Could my problem be around there somewhere?
Does that indicate a dead triode on the tube, or is it something that should be feeding into the tube from right before that should give it a voltage?
Unfortunately, I am at a different town right now because I am on holidays, and I didn't think to bring extra 12ax7s with me. I have a spare 6V6, but no immediate access to any 12ax7s. That tube was previously used for the tremolo circuit on the vibrochamp.
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skyboltone
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Re: Is img turned off?
It depends. If the plate is shorted to the cathode on V2b you might get that reading. On the other hand, if you pull that tube you'll then see near identical voltages at pins 1 and 6. Otherwise, you've found your problem. start working back through the circuit and find out where that pin is supposed to land on your layout, then find out why you have no plate voltage there.
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Re: Is img turned off?
It is fixed!
It was the 500 pF cap that also comes off pin 6. I had accidentally installed it blocking the B+ voltage to pin 6 after the 100k resistor. Of course, it wasn't obvious because my wires to the eyelet were underneath the board. I just had to alter a couple connections and voila!
My problem is that I changed the layout too many times in order to make it fit on the Vibro Champ eyelet board.
I learned that things would have been less confusing (and more aesthetically pleasing) if only I had managed to track down my own new eyelet board to build on, rather than adapting one from a different amp. Even if I couldn't get any board material, I would have been better to go straight Point to point with just terminal strips. I'd consider that next time.
Anyways, this is one great and versatile little amp that has some great manageable volume and heaps of gain on tap if I need it. Thanks for all your help, skyboltone! This is one cool little amp. I'm glad you posted the schematic. This is way more useful than my BF vibro champ clone with filament hum. The hum balance pot seems to be a great addition too.
I'm going to make and stain a wooden faceplate now to match my stained purpleheart strip on my cabinet. This is all practice for my first Liverpool that I plan to build in about a month.
So, now, if it seems to sound good, do you think it is running at fine enough voltages and won't cause any problems?
It was the 500 pF cap that also comes off pin 6. I had accidentally installed it blocking the B+ voltage to pin 6 after the 100k resistor. Of course, it wasn't obvious because my wires to the eyelet were underneath the board. I just had to alter a couple connections and voila!
My problem is that I changed the layout too many times in order to make it fit on the Vibro Champ eyelet board.
I learned that things would have been less confusing (and more aesthetically pleasing) if only I had managed to track down my own new eyelet board to build on, rather than adapting one from a different amp. Even if I couldn't get any board material, I would have been better to go straight Point to point with just terminal strips. I'd consider that next time.
Anyways, this is one great and versatile little amp that has some great manageable volume and heaps of gain on tap if I need it. Thanks for all your help, skyboltone! This is one cool little amp. I'm glad you posted the schematic. This is way more useful than my BF vibro champ clone with filament hum. The hum balance pot seems to be a great addition too.
I'm going to make and stain a wooden faceplate now to match my stained purpleheart strip on my cabinet. This is all practice for my first Liverpool that I plan to build in about a month.
So, now, if it seems to sound good, do you think it is running at fine enough voltages and won't cause any problems?
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skyboltone
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Re: Is img turned off?
Well I think you did a super job. Especially for a guy just starting out. Now get yourself a chassis and a couple of transformers and build one for a 6L6 or EL-34 
Then you'll be the resident expert on the Class Act.
Dan
Then you'll be the resident expert on the Class Act. Dan
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Re: Is img turned off?
Hey thanks!skyboltone wrote:Well I think you did a super job. Especially for a guy just starting out. Now get yourself a chassis and a couple of transformers and build one for a 6L6 or EL-34
Dan
It was lots of fun and great practice working with the schematic. I'm loving the amp and am tempted to try new ones with the appropriate transformers.
Thanks for all the help.
Allen Class Act
I wanted to build one of these for sometime. After following this thread and readings Brandon’s comments about the amp I decided to give it a go.
It’s made mostly from reclaimed parts from past projects. The chassis is hand made from .082” aluminum. They are the same size as a 5E3 Tweed Deluxe. My brother-in-law works in a shop that does fabrication so a few years ago He helped me make up 15 of these. I used them for 5E3 style builds and 18 watt Lite style amps. This was the last chassis I had and it had been used for an AX84 P1 built for my nephew. He lost interest in guitar and amp projects and so it became the donor for this project. The turret board was from the P1 also. I removed any unnecessary turrets and added in a few after working up a layout. Tube sockets, pots, transformers, pilot light, switches also all used items. All of the small components are new.
The pictures show it with an EL-34 but I have used KT66 and 6V6 power tubes. All sound great, each with their own individual tonal character. I like the EL-34 for that classic rock thing. The KT66 in the high-gain channel with the controls down a little produces some of the sweetest/creamiest sustain for blues. And the 6V6 touches on all the areas above with it own 6V6 character. All in all I was surprised that it worked so well with each tube without changing the bias resistor. I did take the time to find a value that let me run all the tubes with out melting the paint off the 6V6. That means the EL34 and the KT66 are running cooler than optimum but the tone is still good. The 6V6 is right at 100% dissipation but I use a JJ and they seem to be able to take the punishment.
I have it in a black tolex cabinet that is the same size as a tweed super with 5E3 cutout and Vintage30 speaker.
All in all I think every one should have/build one of these. It would be a great amp for a project studio. You can get just about any sound out of it you want from clean to mean at levels you can live with. That’s not to say it doesn’t get loud. You could do small club gigs with it as is or mike it for larger venues.
Oh and last but not least I want to express my gratitude for this forum. There is so much generosity and knowledge here that it boggles the mind. My heart felt thanks to those who support this forum and make so much available to others.
RB
It’s made mostly from reclaimed parts from past projects. The chassis is hand made from .082” aluminum. They are the same size as a 5E3 Tweed Deluxe. My brother-in-law works in a shop that does fabrication so a few years ago He helped me make up 15 of these. I used them for 5E3 style builds and 18 watt Lite style amps. This was the last chassis I had and it had been used for an AX84 P1 built for my nephew. He lost interest in guitar and amp projects and so it became the donor for this project. The turret board was from the P1 also. I removed any unnecessary turrets and added in a few after working up a layout. Tube sockets, pots, transformers, pilot light, switches also all used items. All of the small components are new.
The pictures show it with an EL-34 but I have used KT66 and 6V6 power tubes. All sound great, each with their own individual tonal character. I like the EL-34 for that classic rock thing. The KT66 in the high-gain channel with the controls down a little produces some of the sweetest/creamiest sustain for blues. And the 6V6 touches on all the areas above with it own 6V6 character. All in all I was surprised that it worked so well with each tube without changing the bias resistor. I did take the time to find a value that let me run all the tubes with out melting the paint off the 6V6. That means the EL34 and the KT66 are running cooler than optimum but the tone is still good. The 6V6 is right at 100% dissipation but I use a JJ and they seem to be able to take the punishment.
I have it in a black tolex cabinet that is the same size as a tweed super with 5E3 cutout and Vintage30 speaker.
All in all I think every one should have/build one of these. It would be a great amp for a project studio. You can get just about any sound out of it you want from clean to mean at levels you can live with. That’s not to say it doesn’t get loud. You could do small club gigs with it as is or mike it for larger venues.
Oh and last but not least I want to express my gratitude for this forum. There is so much generosity and knowledge here that it boggles the mind. My heart felt thanks to those who support this forum and make so much available to others.
RB
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skyboltone
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Re: Is img turned off?
Wow, resurection of a dynosaur thread but what a great story and pictures. Good job man! Still haven't done mine but thanks for the encouragment.
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Re: Is img turned off?
If you don't mind, i have a question about the schematic. The grid load resistor on the last preamp stage is connected to the cathode of the previous stage. I've seen this in a few high gain preamps and have been wondering what the connection does. My guess is that it's a negative feedback source and smooths out the distortion??????
Learn me somethin', please
Learn me somethin', please
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skyboltone
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- Joined: Wed May 10, 2006 7:02 pm
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Re: Is img turned off?
I wonder if we ignore for a moment that it is grid connected to the following stage and few it as a high pass filter with a cutoff frequency of 28hz. Kinda like a fart snubber for that "previous stage". That's a wag for me.stevlech wrote:If you don't mind, i have a question about the schematic. The grid load resistor on the last preamp stage is connected to the cathode of the previous stage. I've seen this in a few high gain preamps and have been wondering what the connection does. My guess is that it's a negative feedback source and smooths out the distortion??????
Learn me somethin', please
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Re: Is img turned off?
So the coupling cap + the two resistors form a type of snubber? Hmmm...
gonna have to ponder that whilst staring at the schem for a bit.
Thank you.
gonna have to ponder that whilst staring at the schem for a bit.
Thank you.