Bassman Build-up (a bit long)
Moderators: pompeiisneaks, Colossal
Re: Bassman Build-up (a bit long)
When a tube conducts current, there's a voltage drop across both the plate resistor and cathode resistor. If you're reading 3.3k resistance from the tube pin socket to ground and also reading essentially 0 volts when powered, then the tube can't be conducting. Check and see if you have the right plate resistor.
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JazzGuitarGimp
- Posts: 2355
- Joined: Mon Jul 23, 2012 4:54 pm
- Location: Northern CA
Re: Bassman Build-up (a bit long)
If you have an ohmmeter, you should measure the resistance from V1, pin 3 to GND. If all is well with the cathode circuit, it will measure 3.3K, but I have a feeling it's going to be 0 ohms. Okay, I've said it three times now, so I am goint to shut up. Good luck.
Lou Rossi Designs
Printed Circuit Design & Layout,
and Schematic Capture
Printed Circuit Design & Layout,
and Schematic Capture
Re: Bassman Build-up (a bit long)
And there it is. Jazzguitargimp & bcook, the only thing worse than making an error is repeating it multiple times. My inexperience at both measuring and reading resistors and DMM's.
3.3 won't get the job done. 3.3K will. I see it checked off on my Mouser BOM but can't be 100% that it made it onto the order, leastwise, I don't see any on my storage cards.
I tacked in a 3.3K wirewound and got 2.2 @ pin 3. Its late and I'm not going to plug in the guitar. I'll pick up the carbon film item.
I can only imagine the frustration when novices wade in, neck deep, and you guys keep throwing life lines that are not grasped, till the bitter end, (Honey, it was in the LAST place I looked), however the gratitude on this side is immense.
Thank you,
Gary
3.3 won't get the job done. 3.3K will. I see it checked off on my Mouser BOM but can't be 100% that it made it onto the order, leastwise, I don't see any on my storage cards.
I tacked in a 3.3K wirewound and got 2.2 @ pin 3. Its late and I'm not going to plug in the guitar. I'll pick up the carbon film item.
I can only imagine the frustration when novices wade in, neck deep, and you guys keep throwing life lines that are not grasped, till the bitter end, (Honey, it was in the LAST place I looked), however the gratitude on this side is immense.
Thank you,
Gary
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JazzGuitarGimp
- Posts: 2355
- Joined: Mon Jul 23, 2012 4:54 pm
- Location: Northern CA
Re: Bassman Build-up (a bit long)
Good job! And ...... Sorry I got a bit antagonistic there. I guess I was feeling like:
A) A broken record.
B) A bit blue in the face.
C) The child everyone loves to ignore at the dinner table
And of course I am just trying to be funny
it was clear from the voltages on each side of the anode resistor that the tube was passing current, so there had to be an issue with the cathode resistor / circuit.
Here is a mistake I've made more than once (and I am certain I am not alone here) at both the Digi-Key and Mouser sites: when you enter a specific resistor (or capacitor) value into the search engine, say 6.8K, if you're paying attention (I am usually asleep at this point), you'll notice that your decimal point as well as the 'K' designation are ignored. So you wind up with 6.8R, 68R, 680R, 6.8K, etc in your search results. I cannot tell you how many times I've been in the throws of assembling something (usually a breadboard for a client) and I've got all the packages of resistors in my hands, saying to myself "I know I ordered some 6.8K resistors!" when I finally realize I'm holding a bag of 68K and it occurs to me there are no 68K parts in the design!
A) A broken record.
B) A bit blue in the face.
C) The child everyone loves to ignore at the dinner table
And of course I am just trying to be funny
it was clear from the voltages on each side of the anode resistor that the tube was passing current, so there had to be an issue with the cathode resistor / circuit.
Here is a mistake I've made more than once (and I am certain I am not alone here) at both the Digi-Key and Mouser sites: when you enter a specific resistor (or capacitor) value into the search engine, say 6.8K, if you're paying attention (I am usually asleep at this point), you'll notice that your decimal point as well as the 'K' designation are ignored. So you wind up with 6.8R, 68R, 680R, 6.8K, etc in your search results. I cannot tell you how many times I've been in the throws of assembling something (usually a breadboard for a client) and I've got all the packages of resistors in my hands, saying to myself "I know I ordered some 6.8K resistors!" when I finally realize I'm holding a bag of 68K and it occurs to me there are no 68K parts in the design!
Lou Rossi Designs
Printed Circuit Design & Layout,
and Schematic Capture
Printed Circuit Design & Layout,
and Schematic Capture
Re: Bassman Build-up (a bit long)
Lou,
Thanks for keeping it light. The reading numbers tell a story and don't lie. Absolute and unyielding in an environment full of variables. Your persistence paid off.
I played this amp this evening for an hour. The clean side has a world of volume it didn't have before. My time was spent looking at the balance between the volume, drive, and master, while looking for a tonal balance across the pickup selection. (old parker deluxe). When I found myself a little disappointed in the balance, a tweak of the 3 tone controls brought things in line. I like the bright switch and the presence is definitely there, subtle but effective.
The 3.3K resistor needs to be upgraded and I'm looking for a 27K for the Bias resistor.
Is the bias difference due to the budget "National" 6L6's? (USSR), or symptomatic of something else internally?
I've got a 4.2K Ohm O.T., 50/60 watt, 4,8,16 ohm taps. Will I be able to try 6V6 tubes using my usual 4 or 8 ohm speaker box options? I'm sure the 6L6 are still too robust for my gig venues, BUT I do have a master volume control that I didn't have before.
Its time for me to find my dovetail jig and think about a cabinet. A proper faceplate or laminate will finish off this non-standard layout as well.
Attached is a 3rd voltage reading.
Thanks for keeping it light. The reading numbers tell a story and don't lie. Absolute and unyielding in an environment full of variables. Your persistence paid off.
I played this amp this evening for an hour. The clean side has a world of volume it didn't have before. My time was spent looking at the balance between the volume, drive, and master, while looking for a tonal balance across the pickup selection. (old parker deluxe). When I found myself a little disappointed in the balance, a tweak of the 3 tone controls brought things in line. I like the bright switch and the presence is definitely there, subtle but effective.
The 3.3K resistor needs to be upgraded and I'm looking for a 27K for the Bias resistor.
Is the bias difference due to the budget "National" 6L6's? (USSR), or symptomatic of something else internally?
I've got a 4.2K Ohm O.T., 50/60 watt, 4,8,16 ohm taps. Will I be able to try 6V6 tubes using my usual 4 or 8 ohm speaker box options? I'm sure the 6L6 are still too robust for my gig venues, BUT I do have a master volume control that I didn't have before.
Its time for me to find my dovetail jig and think about a cabinet. A proper faceplate or laminate will finish off this non-standard layout as well.
Attached is a 3rd voltage reading.
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Re: Bassman Build-up (a bit long)
Since the Bassman chassis I used doesn't actually FIT a Bassman cabinet, and having 4 gigs coming up, I really want to take the amp out. I'm waiting for a finger joint template to be delivered, and then have to figure out what wood and finish I'm going to use. In the meantime I had some 3/4 birch ply available and put it to use. Mitered corners, drilled, glued, and screwed in both directions its a tank at 22 1/8" long. just a spit longer than a Bassman, but in 3/4 instead of 5/8.
I've got an etched stainless faceplate (black graphics) coming, and for now,will be playing it through a 2-10 (generic 100W Celestions), closed back, ported speaker cab I have. (also home built, the white mica beast in the picture)
3 hours later:
[img:640:384]http://i294.photobucket.com/albums/mm81 ... 829fe8.jpg[/img]
[img:640:384]http://i294.photobucket.com/albums/mm81 ... 4275db.jpg[/img]
The amp sounds great at every setting.
I must again offer sincere thanks for all the support, patience and guidance through the bumpy parts. Each time I flip the toggles on this amp, it's truly exciting. I hope the feeling lasts.
Gary
I've got an etched stainless faceplate (black graphics) coming, and for now,will be playing it through a 2-10 (generic 100W Celestions), closed back, ported speaker cab I have. (also home built, the white mica beast in the picture)
3 hours later:
[img:640:384]http://i294.photobucket.com/albums/mm81 ... 829fe8.jpg[/img]
[img:640:384]http://i294.photobucket.com/albums/mm81 ... 4275db.jpg[/img]
The amp sounds great at every setting.
I must again offer sincere thanks for all the support, patience and guidance through the bumpy parts. Each time I flip the toggles on this amp, it's truly exciting. I hope the feeling lasts.
Gary
Re: Bassman Build-up (a bit long)
I use these chassis and order them in two different sizes to accommodate either mojotone size head cab (20.5) or custom sized 1-12 combo cab (20 3/16). I trim the front edge so I can get to the pots better. Nothing wrong with making your own cab. Glad you are using your amp looks great.My Bassman chassis has a sloped front with a bit of a lip return to the inside. This is making front controls a little more tedious than they might be ordinarily.
Mark
Gig report
I worked with my country quartet last night. Instead of my massive 2-10 tank cabinet, I grabbed my sons Carvin 1-12 cabinet http://www.carvinguitars.com/products/112AG and packed off to the gig.
Immediately the cleans were full and expressive off my Nashville style Partscaster. (all 3 PU's are rails). Just a little tweaking of the amps tone, all three knobs almost @ 12 OC, a little boost on the bass. Bright switch off, presence midway, as well as input and master volumes.
I got brave and flipped the OD switch, drive @ midpoint give or take, set the level as needed and it was definitely "ON".
Once I realized I didn't have to go searching for a "perfect" setting, the tone was already there, I personally relaxed and could play without wondering if my expression/touch/nuance would make it through.
Got compliments on the sound, playing (always a plus), and craft work. This great experience might just be the difference between my TM-60 and any old tube amp, but I'm certain this build was just more than any old tube amp. That's my story and I'm stickin' to it.
So that's pretty much a wrap from beginning to end. It was and will remain, my pleasure.
Dez
Faceplate:
[img
141]http://i294.photobucket.com/albums/mm81 ... 5148e4.jpg[/img]
Immediately the cleans were full and expressive off my Nashville style Partscaster. (all 3 PU's are rails). Just a little tweaking of the amps tone, all three knobs almost @ 12 OC, a little boost on the bass. Bright switch off, presence midway, as well as input and master volumes.
I got brave and flipped the OD switch, drive @ midpoint give or take, set the level as needed and it was definitely "ON".
Once I realized I didn't have to go searching for a "perfect" setting, the tone was already there, I personally relaxed and could play without wondering if my expression/touch/nuance would make it through.
Got compliments on the sound, playing (always a plus), and craft work. This great experience might just be the difference between my TM-60 and any old tube amp, but I'm certain this build was just more than any old tube amp. That's my story and I'm stickin' to it.
So that's pretty much a wrap from beginning to end. It was and will remain, my pleasure.
Dez
Faceplate:
[img
141]http://i294.photobucket.com/albums/mm81 ... 5148e4.jpg[/img]